Technical and Economic Feasibility of Using Waste Wood for Small Scale Boiler and CHP in Solway Precast, Scotland

Technical and Economic Feasibility of Using Waste Wood for Small Scale Boiler and CHP in Solway Precast, Scotland
Department of Mechanical Engineering
Technical and Economic Feasibility of Using Waste Wood as
Biomass Fuel for Small Scale Boiler and CHP in Solway
Precast, Scotland
Author:
Setta Verojporn
Supervisor:
Professor John Counsell
A thesis submitted in partial fulfilment for the requirement of the degree
Master of Science
Sustainable Energy: Renewable Energy Systems and the Environment
2011
Copyright Declaration
This thesis is the result of the author‟s original research. It has been composed by the author and
has not been previously submitted for examination which has led to the award of a degree.
The copyright of this thesis belongs to the author under the terms of the United Kingdom
Copyright Acts as qualified by University of Strathclyde Regulation 3.50. Due acknowledgement
must always be made of the use of any material contained in, or derived from, this thesis.
Signed: Setta Verojporn
Date: 9 September 2011
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Abstract
Renewable energy has been widely used in power generation and household applications, its use
in industry is way more concerned in terms of its stability and reliability to meet the
manufacturing process energy demand according to the uncertainty of renewable technologies.
Manufacturing industries are considered the major energy consumption sector in Scotland.
Therefore it is important that this sector is developing in a sustainable way in emerging
economies to reduce greenhouse gas emissions and the use of conventional fuels.
The objective of this work is to investigate technical and economic feasibility of using waste
wood as biomass fuel in precast concrete site. This study looks at the precast concrete process
and its energy use with particular focus on Solway Precast. A review of small scale biomass
boiler and CHP that would be suitable for the case study was undertaken. And a tool was created
to analyse the economic and environmental performance between selected wood waste boilers
and CHPs for this case study and other type of manufacturing processes. This tool allows the
user to quickly calculate the economic and environmental performance using the thermal and
electrical demand profile, boiler or CHP technological specification, the operation mode, the
costs, financial incentives and other financial factors.
Different wood boilers and CHP that can be applied in this case study were analysed using the
tool. This study indicates that suitable biomass boilers or CHP can demonstrate economic and
environmental benefits. Wood fuel CHPs can give more long term profit than wood fuel boilers
in this analysis but with longer payback period. The quantity of CO2 emission reduction from
biomass CHP is also more than boilers in this analysis. However, the initial cost of the biomass
CHP is much more expensive than boilers of the same size. Therefore investing in biomass CHP
obviously has more risks than boilers due to the higher initial cost of the CHP.
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Acknowledgements
I would like to thank Prof. John Counsell for his valuable advice, support, and guidance to me
throughout the duration of my project.
I would also like to thank Dr. Paul Strachan, he has been kindly helping, supporting, and
advicing me from the beginning to the end of this MSc course.
To Ali Sheikh. Mark Young, Andy Gillon, and everyone at Solway Precast for their friendly
support and assistance getting the data and information throughout the duration of this project.
My classmates and friends who have been supporting me directly or indirectly to overcome any
problems during this MSc course and this project.
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Table of Contents
ABSTRACT .............................................................................................................................................................. II
ACKNOWLEDGEMENTS ......................................................................................................................................... III
TABLE OF CONTENTS............................................................................................................................................. IV
LIST OF FIGURES...................................................................................................................................................VII
LIST OF TABLES ..................................................................................................................................................... IX
1. INTRODUCTION.................................................................................................................................................. 1
1.1 BACKGROUND .........................................................................................................................................................1
1.2 RESEARCH FOCUS.....................................................................................................................................................3
1.3 OVERALL RESEARCH AIM AND INDIVIDUAL RESEARCH OBJECTIVES .....................................................................................5
2. LITERATURE REVIEW .......................................................................................................................................... 7
2.1 INTRODUCTION ........................................................................................................................................................7
2.2 PRECAST CONCRETE..................................................................................................................................................8
2.2.1 Introduction .................................................................................................................................................8
2.2.2 Precast Concrete Process ...........................................................................................................................9
2.2.3 Energy Use ................................................................................................................................................11
2.2.4 Environmental Impact in Precast Concrete Production ...........................................................................12
2.3 BIOMASS ..............................................................................................................................................................14
2.3.1 What is Biomass ........................................................................................................................................14
2.3.2 Wood Waste as a Biomass Fuel ................................................................................................................16
2.4 SMALL SCALE WOOD FUEL CONVERSION TECHNOLOGY .................................................................................................24
2.4.1 Combustion ...............................................................................................................................................25
2.4.2 Gasification ...............................................................................................................................................30
2.5 SMALL SCALE WOOD FUEL POWER GENERATION TECHNOLOGY ......................................................................................33
2.5.1 Internal Combustion Engine .....................................................................................................................34
2.5.2 Stirling Engine ...........................................................................................................................................34
2.5.3 Organic Rankine Cycle (ORC) engine .........................................................................................................35
2.5.4 Micro-turbine ............................................................................................................................................35
2.6
FINANCIAL INCENTIVES ........................................................................................................................................36
2.6.1 Renewable Heat Incentive (RHI) ...............................................................................................................36
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2.6.2 Feed-In Tariffs (FITs) ...............................................................................................................................37
2.6.3 Renewable Obligation Certificates (ROCs) ..............................................................................................37
2.6.4 Other Grants and Support Schemes ..........................................................................................................39
3. THE BIOMASS BOILER AND CHP TOOL .............................................................................................................. 40
3.1 INTRODUCTION ......................................................................................................................................................40
3.2 AIMS AND OBJECTIVE..............................................................................................................................................41
3.3 LIMITATION...........................................................................................................................................................42
3.4 CELL COLOUR CODING ............................................................................................................................................43
3.5 THE BIOMASS BOILER AND CHP TOOL STRUCTURE .......................................................................................................43
3.5.1 Energy Demand .........................................................................................................................................43
3.5.2 Wood Fuel .................................................................................................................................................48
3.5.3 Biomass boiler and CHP Specification .....................................................................................................50
3.5.4 Comparing Biomass Boiler and CHP .......................................................................................................52
3.5.5 Results .......................................................................................................................................................57
3.5.6 Results comparison ...................................................................................................................................58
3.6 DETAIL CALCULATION AND ANALYSIS OF THE TOOL .......................................................................................................60
3.6.1 Energy demand .........................................................................................................................................61
3.6.2 Wood fuel ..................................................................................................................................................63
3.6.3 Biomass boiler and CHP specification .....................................................................................................66
3.6.4 Comparing Biomass Boiler and CHP .......................................................................................................71
3.6.5 Results .......................................................................................................................................................84
3.6.6 Results comparison ...................................................................................................................................85
4. THE CASE STUDY .............................................................................................................................................. 87
4.1 INTRODUCTION: BACKGROUND OF SOLWAY PRECAST ....................................................................................................87
4.2 ENERGY DEMAND ..................................................................................................................................................88
4.2.1 Electrical Energy Demand ........................................................................................................................88
4.2.2 Thermal Energy Demand ..........................................................................................................................90
4.2.3 Fuel consumption and CO2 Emissions ......................................................................................................92
4.3 WOOD WASTE AT SITE............................................................................................................................................93
4.4 BIOMASS IN SOLWAY PRECAST..................................................................................................................................94
4.4.1 Thermal Demand Profile ...........................................................................................................................94
4.4.2 Electrical Demand Profile ........................................................................................................................98
4.4.3 Wood Fuel .................................................................................................................................................99
4.4.4 Biomass Boiler and CHP Specification...................................................................................................103
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4.4.5 Financial Incentives and Parameters......................................................................................................113
4.4.6 Results and Analysis ................................................................................................................................115
4.5 OVERALL RESULTS AND ANALYSIS ............................................................................................................................123
5. CONCLUSION ................................................................................................................................................. 124
5.1 CONCLUSION .......................................................................................................................................................124
5.2 FURTHER INVESTIGATION .......................................................................................................................................126
REFERENCES....................................................................................................................................................... 127
APPENDIX 1: FINANCIAL RESULTS ...................................................................................................................... 133
APPENDIX 2: MONTHLY BIOMASS CONSUMPTION ............................................................................................ 147
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List of figures
Figure 1: Basic precast concrete production process .................................................................................... 9
Figure 2: The effect of moisture content on the lower heating value of wood (kWh/kg)
(ELECTROWATT-EKONO (UK) LTD , 2003) ........................................................................................ 19
Figure 3: Main Biomass Energy Conversion Routes (Turkenburg, 2000) ................................................. 24
Figure 4 : Basic Process Flow for Biomass Combustion (Knoef et al., 1999)............................................ 25
Figure 5: The typical efficiency of the CHP compared to traditional heat and power generation (Self
Energy UK, 2009) ....................................................................................................................................... 33
Figure 6: Input and Output Cells................................................................................................................. 43
Figure 7: Choosing demand characteristic .................................................................................................. 43
Figure 8: Manually enter the hourly demand data ...................................................................................... 44
Figure 9: Generating hourly energy demand profile ................................................................................... 44
Figure 10: Result of the first step of generating hourly demand profile ..................................................... 45
Figure 11: Result of the second step of generating hourly demand profile ................................................ 45
Figure 12: Result of the third step of generating hourly demand profile .................................................... 46
Figure 13: Example of hourly demand profile result in January................................................................. 46
Figure 14: Input area for existing energy information ................................................................................ 47
Figure 15: Input area for wood waste information...................................................................................... 48
Figure 16: Wood waste summary table....................................................................................................... 49
Figure 17: Input area for extra wood needed to purchase information ....................................................... 49
Figure 18: Input area for biomass boiler and CHP information.................................................................. 50
Figure 19: Wood fuel choosing area ........................................................................................................... 52
Figure 20: Biomass boiler and CHP choosing area .................................................................................... 53
Figure 21: Choosing operation mode area .................................................................................................. 53
Figure 22: Choosing operation mode and operation time area ................................................................... 54
Figure 23: Results in choosing biomass boiler and CHP subsection .......................................................... 55
Figure 24: Tool Methodology ..................................................................................................................... 60
Figure 25: Thermal efficiency at range of operating capacity .................................................................... 72
Figure 26: Heat to power ratio at range of operating capacity .................................................................... 76
Figure 27: Solway Precast (Barr Ltd, n.d.) ................................................................................................. 87
Figure 28: Moulding Workshop (Barr Ltd, n.d.) ........................................................................................ 87
Figure 29: On-site Batching Plant (Barr Ltd, n.d.) ..................................................................................... 87
Figure 30: Cement Silo ............................................................................................................................... 89
Figure 31: Conveyor Belt............................................................................................................................ 89
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Figure 32: Vibrating Process ...................................................................................................................... 89
Figure 33: Kerosene tank ............................................................................................................................ 91
Figure 34: Kerosene heaters in the factory ................................................................................................. 91
Figure 35: Kerosene heater in the office ..................................................................................................... 91
Figure 36: Wood waste at Solway Precast site ........................................................................................... 93
Figure 37: Thermal demand settings of the tool for Solway Preacast ........................................................ 96
Figure 38: Hourly thermal demand profile of pre-stressed beds in Solway Precast for one year ............... 96
Figure 39: Thermal Energy Usage by Type of Demand (kWh).................................................................. 97
Figure 40: Thermal Energy Usage by Type of Fuel (kWh) ........................................................................ 97
Figure 41: Electrical demand settings of the tool for Solway Preacast....................................................... 98
Figure 42: Hourly electrical demand at Solway Precast site for one year .................................................. 98
Figure 43: Data entered in the wood fuel section for the 1st case ............................................................ 100
Figure 44: Data entered in the wood fuel section for the 2nd case ........................................................... 101
Figure 45: Wood waste summary for both cases ...................................................................................... 101
Figure 46: REFO 80 (Teisen Products Ltd, n.d.) ...................................................................................... 104
Figure 47: REFO 80 composition (Teisen Products Ltd, n.d.) ................................................................. 104
Figure 48: HT boiler with accumulator tank (Teisen Products Ltd, n.d.) ................................................. 107
Figure 49: HT boiler composition (Teisen Products Ltd, n.d.) ................................................................. 107
Figure 50: BG 25 CHP (Talbott‟s Biomass Generators Ltd, n.d.) ............................................................ 108
Figure 51: Example day of 1st operation method for HT 50 and HT 80 boilers with accumulator tank.. 110
Figure 52: Example day of 2nd operation method for HT 50 and HT 80 boilers with accumulator tank 111
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List of tables
Table 1 : Carbon emissions of different fuels per unit of energy (Biomass Energy Centre, 2003) ............ 14
Table 2 : Fuel prices per kWh (Biomass Energy Centre, 2011) ................................................................. 15
Table 3: Estimate of total wood waste arisings in the UK (The Waste & Resources Action Programme,
2005) ........................................................................................................................................................... 16
Table 4: Wood Fuel Lower Heating Value (ELECTROWATT-EKONO (UK) LTD, 2003; Biomass
Energy Centre) ............................................................................................................................................ 18
Table 5: Ash content from wood fuel (Eleotrowatt-ekono (UK) ltd, 2003) ............................................... 20
Table 6: Table of tariffs support for biomass in renewable heat incentive ................................................. 36
Table 7: Banding provision (Office of Gas and Electricity Markets, 2011) ............................................... 38
Table 8: Monthly electricity consumption in kWh ..................................................................................... 90
Table 9: Monthly quantity of kerosene ordered in litres ............................................................................. 90
Table 10: Monthly quantity of gas oil ordered in litres .............................................................................. 90
Table 11: Wood fuel characteristics............................................................................................................ 99
Table 12: Thermal energy demand-supply matching results .................................................................... 116
Table 13: Electrical energy demand-supply matching results .................................................................. 119
Table 14: Financial results ........................................................................................................................ 120
Table 15: Equivalent CO2 emission results for one year .......................................................................... 122
Table 16: Table 15: Equivalent CO2 emission reduction results for 30 years .......................................... 122
Table 17: 1st case financial result .............................................................................................................. 133
Table 18: 2nd case financial result ............................................................................................................. 135
Table 19: 3rd case financial result.............................................................................................................. 137
Table 20: 4th case financial result .............................................................................................................. 139
Table 21: 5th case financial result .............................................................................................................. 141
Table 22: 6th case financial result .............................................................................................................. 143
Table 23: 7th case financial result .............................................................................................................. 145
Table 24: Monthly biomass consumption in kg ........................................................................................ 147
Table 25: Monthly biomass consumption in m3 ....................................................................................... 147
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1. Introduction
1.1 Background
Renewable energy has been targeted to meet an equivalent of 100% electricity demand and 11%
of heat demand by 2020 in Scotland. Besides, the greenhouse gas emissions also have been
targeted to reduce at least by 42% by 2020 (The Scottish Government, 2011). Increasing
renewable energy and reducing greenhouse gases in the growing economy are a huge challenge.
Involving sectors are obliged to contribute in terms of technology, economy, politic, social
characteristics as well as our way of life.
There are four main end demand sectors which are domestic, transport, industry and services
sector in decreasing level of energy consumption in Scotland.
Manufacturing industries use approximately 35% of total energy used by all sectors in Scotland
in 2002. Industrial energy usage was mainly linked to production of food and drink, paper,
chemical and engineering in Scotland. Meanwhile, mineral industries such as cement counts for
a smaller proportion of the total industrial energy usage (AEA Technology, 2006). On the other
hand, the cement industry produces large amount of CO2 emissions, of which 50% is from the
chemical process, 40% from burning fuel, and the rest are from electricity and transport uses
(World Business Council for Sustainable Development, 2002).
Despite the fact that renewable energy has been widely used in power generation and household
applications, its use in industry is way more concerned in terms of its stability and reliability to
meet the manufacturing process energy demand. The lack of electricity or heat during the
ongoing process can the increase in cost of production and affect the machines in dysfunctions
the process. Moreover, the production operation, management and scheduling may need to be
changed according to the uncertainty of renewable technologies in order to maintain reliability
and efficiency of the process.
Precast concrete is the ready-made concrete product produced by casting and curing it under
controlled environment. It is formed into certain shapes and transported to the construction site.
The precast concrete plant uses electricity and heat depending on the process. Due to the closely
1
monitoring in the manufacturing site, the precast concrete has been well strengthened than
construction site-casting.
Barr limited incorporating Solway Precast Concrete is committed to keep improving the
environmental performance and minimizing the impact of their activities. They approached the
University of Strathclyde in order to develop in a sustainable way by reducing the CO2 emissions
while maintaining or improving economic benefit. Renewable technology had been using at Barr
Limited prior to this thesis focusing on the usage of landfill gas. This thesis will propose and
compare biomass technologies to generate electricity and heat that would be suitable for Solway
Precast Concrete (Concrete Manufacturing Site) energy demand. Which it will also reduce the
CO2 emissions and fossil fuel consumption at the site. Return on investment, capital costs,
maintenance costs, grid connection costs will also be analysed.
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1.2 Research Focus
Nowadays, renewable energy interests public, private and government sectors due to its
potentiality to reduce greenhouse gas emissions and replacement of conventional fuels. It is
important that industrial sectors are developing in a sustainable way in emerging economies.
Renewable energy can be applied in industrial as long as industrial sectors are encouraged to
take this step and prepared to take on the long term commitment to renewable and climate
friendly technologies. However, it would only be possible if firms have the financial capacity or
support to invest in the particular renewable technologies. Moreover, the knowledge and state-of
the-art technologies need to be well established. Firms that have financial capacity should set
examples to others to follow the steps.
The main focus of the study of this thesis is to look at the feasibility of wood waste biomass
technologies for a precast concrete plant. Scalable framework for biomass boiler, and combined
heat and power in precast manufacturing process will also be made to be adaptable for other type
of industrial manufacturing process.
Wide range of wood waste biomass conversion technologies will be considered to be able to
sufficiently supply heat and electricity for the precast concrete manufacturing process and an
office building of Barr Limited Solway Precast Concrete at Barrhill, Scotland. The decision of
biomass technologies would be based on costs, financial and reduction of CO2 benefits, and more
importantly, applicable of the particular technologies at the site. To make the best use of
proposed biomass technologies, the process energy demand must be reduced as much as possible
to reduce unnecessary costs for oversize the renewable energy options. Nonetheless, this thesis
will not focus on this issue due to the time limitation and numerous options to improve energy
efficient at this site.
Since the precast concrete process have a lot of wood waste products from shuttering used for
concreting and moulding process, it can be used as an important fuel source instead of being
disposed of at a cost to the company. It is significant to know that the landfill option is also
available for wood waste. However, the cost of sending waste wood or any other materials to the
landfill site are increasing every year. And it is also involved with fuel in transportation which it
would increase the CO2 emission to the atmosphere. These issues make the alternative uses of
wood waste becoming more attractive and interested. The efficient use of this by-product is a
3
basic essential for industrials (Action Renewables, n.d.). Therefore, in this thesis, wood waste is
taken into account in the calculation of the renewable energy potential. Due to the need of heat
and electricity at the site, the comparison between wood waste boiler and wood waste CHP will
be analysed to compare energy performance, energy savings, capital costs, maintenance costs
and applicability to install. Also the benefits from renewable incentive schemes for heat and
electricity would be analysed.
This thesis will set out the tool not only for precast concrete manufacturing process, but also
other type of industrial manufacturing process to use renewable energy. Reduction in the amount
of electricity imported from the grid, conventional fuels and CO2 from renewable technologies
will financially benefit the industries and the country itself due to the reduction of power
generated as a whole. This case study would also set the example for other small industrials that
want to use wood waste as a biomass fuel to make long term profit and improve environmental
performance.
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1.3 Overall Research Aim and Individual Research Objectives
The overall aim of this research is to integrate wood waste biomass technologies into precast
concrete manufacturing process without impact on the quality and delivery of the precast
concrete product. However, in order to understand energy demand for precast concrete
manufacturing process it is really important to gain an insight into understanding the process
itself and the heat and electricity required for the process as well as the office at the site. The heat
and electricity demand will be matched with range of biomass boiler and CHP technologies
regarding to energy performance, demand-supply matching, financial benefits and environmental
impacts. Further, this research will assess the biomass boiler and CHP technologies that would
be suitable for the case study (Solway Precast). The wood waste boiler at the site would be the
first thing to be analysed following by biomass combined heat and power technologies. The case
study chapter contains the details of research strategy, the energy demand data collection at the
site, techniques to be used to analyse that energy demand data and strategy for renewable energy
generation in Solway Precast.
Specifically, within the background of higher education, the objectives of this research are to:
1. Understand the precast concrete process and energy used in this
2. Investigate the feasibility of using waste wood as a biomass fuel for heat and combined
heat and power (CHP) in this precast concrete plant case study
3. Evaluate the potential financial benefits and CO2 reduction of biomass in the case study
4. Create a scalable tool for precast manufacturing process which can be adapted for other
type of manufacturing processes
For the purpose of each of the above objectives, objectives 1 focus on the existing technology of
the precast concrete process for the case study and heat and electricity use in each of the process.
Objectives 2 and 3 will make the key comparisons to biomass energy technologies for the precast
concrete process, especially in wood waste boiler and wood waste CHP. Objective 4 will make
this thesis be useful for other type for industries.
This research work will contribute the establishment of wood waste energy production
technologies not only for precast concrete industries, but also other industries. Firstly, by
reducing the CO2 emissions in to the atmosphere and the electricity import from the grid for the
5
case study. Secondly, by critically examining existing wood waste boiler and wood waste CHP,
allowing a meaningful comparison in performance, capital costs, operating costs, maintenance
costs and long-term financial benefits. Thirdly, by providing a tool that can be adapted to
implement to other industries.
The next chapter will be issues and related literature review, beginning with an investigation of
precast concrete manufacturing process.
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2. Literature Review
2.1 Introduction
This literature review section will observe the main issues surrounding renewable energy for the
industrial sector, especially in the precast concrete process. The outline of this literature review
will focus on objectives 1 and 2 as set out in the introductory chapter. However objectives 1, 2
and 3 will be met again in the case study chapter for collecting energy data and it will compare
many aspects in wood waste energy technology for the Solway Precast. While the final objective,
objective 4, will be derived from the results and conclusions of objective 1, 2 and 3:
1. Understand the precast concrete process and energy use in this
2. Investigate the feasibility of using waste wood as a biomass fuel for heat and combined
heat and power (CHP) in this precast concrete plant case study
3. Evaluate the potential financial benefits and CO2 reduction of using biomass in the case
study
4. Create a scalable tool for precast manufacturing process which can be adapted for other
type of manufacturing processes
By discovering the above areas of literature, the background information of precast concrete
process and biomass fuel for boiler and CHP will be extensively studied. Typical precast
concrete manufacturing processes will be explored in order to understand the energy used in each
process. Similarly, the existing technologies of renewable energy will also be explored to find
the most suitable technologies for the case study. Importantly, the number of key parameters that
influence the decisions of choosing renewable energy technologies will be studied and analysed.
At the end of the literature review chapter, it is hoped that an in-depth understanding of the
mentioned issues will be demonstrated. The reader will have a better understanding of the
precast concrete process and renewable technologies that would be suitable for this process.
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2.2 Precast Concrete
2.2.1 Introduction
Precast concrete is concrete that is casted and formed into a particular shape, then allowed to
become solid by curing process in a controlled environment before being delivered to a
construction site. On the contrary, on-site casting concrete is being done on construction sites.
With precast concrete production, the concrete is well casted, formed, and cured because of the
close monitoring process and the controlled environment in the precast plant. Moreover, the
mould that is used in precast concrete can be reused again for a certain amount of time before
they have to be eliminated. The strength of the precast concrete can be improved by reinforced
concrete (casting concrete with reinforcement of steel), or pre-stressed concrete (high-strength
pre-stressing tendons are used instead of steel). In practice, the process predominantly depends
on the type and shape of the concrete product. Therefore the process has to be managed to
optimize the product. Nevertheless, the main process consists of mixing, casting, curing, storing
and transporting. The basic materials in the precast concrete process are Portland cement, water,
aggregates, admixtures, reinforced steel, and woods (Elhag et al., 2005).
The precast concrete industry has existed for more than 150 years and has largely reduced the
costs of the construction site, and also construction time which therefore improves the quality
and performance of the construction site (Chen et al, 2009 cited in Elhag et al, 2005, p.10). As a
result, precast concrete products are used in a wide range of constructions from houses and
buildings with big infrastructures such as bridges, football stadiums, etc.
The precast concrete industry is more sustainable than on-site casting in the sense that it takes
less input, such as concrete and mould, for the same amount of concrete product (The Concrete
Centre, 2009). The process can be more sustainable if recycled and reused materials are being
applied. The by-product of the process, for instance, wood waste from unusable moulds can be
used as a biomass fuel to create heat or electricity.
Following this first introductory section, the remainder of this chapter will describe the
production process, the energy used, and the environmental impact of the precast concrete
product.
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2.2.2 Precast Concrete Process
The basic production process of precast concrete in the plant consists of mixing, mould making,
casting, curing, de-moulding, storing and transporting. These processes are illustrated in the
figure below.
Figure 1: Basic precast concrete production process
Mixing
The mixing or batching of concrete includes factors such as the ratio of the mixtures and the
speed of the mixers. Concrete mixtures consist of Portland cement, water, sand (fine aggregate),
small stone or gravel (coarse aggregate), and admixtures. The ratio of these mixtures depends on
the application of concrete product. In the precast concrete plant, mixing machines (concrete
mixing plant) are used. These mixtures are then transported and batched in a large concrete
mixing plant before casting them into moulds (Elhag et al., 2005).
Mould Making
Precast concrete moulds can be constructed of various materials but mainly from concrete, steel,
wood or fibreglass. The type of material depends on their frequency of usage. The amount of
time that steal mould can be reused is more than that in wood and fibreglass moulds. Wood and
fibreglass moulds can be reused approximately 40 to 50 times, while steel and concrete moulds
can be used almost ceaselessly (ASCENT, 2007).
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Casting
The casting process involves the pouring, compacting and levelling of concrete into moulds (Hu,
2006). After placing the concrete into the moulds by hopper or crane, the concrete is then
vibrated by a vibrator to consolidate and to make the concrete compact. The reinforcement steel
and pre-stressing tendons have to be inserted before pouring the concrete, if such strengthening
technologies are needed.
Curing
The curing process is to prevent water evaporating from the concrete too quickly. Since water is
the most important element for the hydration reaction, it will directly affect the strength of the
concrete. This hydration reaction can take days or weeks therefore the curing process must be
conducted at an appropriate time in order to achieve concrete strength, water tightness, abrasion
resistance, volume stability and durability (Cement Concrete & Aggregates Australia, 2006).
Only during the period when concrete is gaining strength does it need to be cured. The typical
process is to prevent loss of moisture from the concrete by covering the concrete with an
impermeable membrane or continuously wetting the exposed surface of the concrete. However,
the concrete in the precast process can gain compressive strength by accelerating the curing
process. The methods of accelerated curing are physical processes (conduction/convection,
electrical resistance curing, or pressure steam curing), mineral admixture (silica fume or fly ash),
and chemical admixtures (calcium, super plasticizers or self-consolidating concrete)
(Vollenweider, 2004).
De-moulding
The de-moulding process is the process of stripping the moulds or the frame and removing the
concrete. Concrete has to reach the strength required in the curing process before it removed
from the mould and is strong enough to prevent the concrete product from being damaged,
overstressed or distorted with regards to the de-moulding equipment used (CONSTRUCT, n.d.).
10
The method of de-moulding depends on the size and the shape of the concrete product, as such
cranes and machines might be used if necessary.
Storing
After the de-moulding process, the concrete products are placed in the stockyard or the storage
room to achieve delivery strength. Forklifts or trucks are used to transport the concrete product
from the de-moulding area to the stockyard.
Transporting
The precast concrete product is transported to the construction site.
2.2.3 Energy Use
The energy demand in the precast concrete process is determined by various factors related to the
production system used, product range manufactured, production capacity, and location. The
range of energy consumption in a precast plant is around 350 – 1113.2 MJ (97.2 – 309 kWh) per
cubic metre of concrete product (Elhag et al., 2005). As mentioned before, this wide gap of
energy use in a precast plant may have too many dependent variables to be more specific.
In the precast concrete process, electricity is used to supply machines in different processes and
building services. In the mixing process, electricity is used to transport all the concrete mixtures
to the mixer via a conveyor belt or pipe using a motor. It is also used in mixing and batching
where a machine is used to combine all the mixtures together, thus creating the concrete.
Prefabricating reinforcement steel and the mould making process also needs electricity which is
supplied to the equipment used for cutting, trimming, bending, seaming and welding the
materials (steel, wood or fibreglass). Moreover, electricity is used to operate cranes and hoppers
to cast the concrete into the mould, and is used to supply the concrete vibrator in the casting
process. Electricity may be used in the curing process if the electrical resistance curing is being
used.
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Besides space heating, thermal energy is usually used for the concrete to achieve its potential
strength and durability in the curing process. Vollenweider (2004) stated that there is a
relationship between the rate of compressive strength and curing temperature in concrete.
Increasing the curing temperature will increase the strength of the concrete. There are various
methods to increase the curing temperature in this process including simple convection by hot
water or oil through a mould, framework or pipe, electric resistance heating by reinforcement
steel, and pressure steam. The convection and pressure steam method requires boilers to produce
heat. The source of thermal energy can be generated from electricity, biomass, gas or fuel oil.
Apart from electricity and thermal energy, transportation (to the construction site) has a
significant impact on the overall energy used in the precast process (Elhag et al., 2005).
Depending on the weight and size of the precast concrete product and the length of the delivery,
the fuel used in transportation can be the largest portion of energy usage. Transportation includes
the delivery of the cement, aggregates, and admixtures to the site, as well as the process of
delivering the waste from the precast concrete process.
Precast concrete plants need energy in the form of electricity to supply the production plant, and
thermal energy for the curing process and space heating. The electricity can be imported from the
grid or generated by natural gas, biomass, or from the plant itself while the thermal process can
be generated from the electricity, natural gas, biomass or fuel oil. Meanwhile, these two forms of
energy, electrical and thermal, make it possible to develop a combined heat and power system.
However, the concurrency and the capacity of these two energy demands have to be considered;
this depends on the particular precast concrete plant.
2.2.4 Environmental Impact in Precast Concrete Production
Environmental impact in precast concrete production is mainly associated with the cement
content and the transportation (Bijen, 2002 cited in Elhag et al, 2005, p.4). Cement
manufacturing and transportation has a significant impact on the environment because of the
CO2 emissions of the cement production and the delivery of the heavy and big precast concrete
products to the construction site. The average amount of CO2 emitted by the production of
cement is about 880 kg/tonne (Gilbert, 2005 cited in Elhag et al, 2005, p.5). The use of
12
conventional fuels in transportation of the precast concrete product also plays a big part in CO2
emissions. This problem is not easily to tackle and improve, if the location of the precast
concrete plant is far from all the construction sites. However, good logistical transport operations
can help solve this problem.
However, there are other aspects that can easily reduce the environmental impact from the
precast concrete production: which are waste and energy consumption in the precast concrete
plant.
Recycling and reusing the by-products of precast concrete plants assures the reduction of waste
from the precast plant itself and also from other manufacturers. The reusing of slag (from steel
manufacturing) can be mixed with cement, water, aggregate, and admixture to strengthen the
concrete over a long period (American Concrete Pavement Association, 2003). Slag mixing with
cement also reduces the amount of cement, which in turn reduces the CO2 emissions (ASCENT,
2007). Furthermore, precast concrete panels, forms and moulds can be reused again many times
depending on the type of materials. The reuse or recycle of waste not only reduces the
environmental impact, but also saves on cost or even increases profit. Instead of delivering waste
from the precast plant to the landfill, reusing and recycling waste can be a better choice. The
Landfill tax penalises poor use of waste materials meaning that companies that have more waste
will have to pay more, and also the cost of transportation of the waste to the landfill site.
Additionally, the landfill tax tends to increase as time goes on (Deloitte, n.d.). The worn and
obsolete wood can be used as biomass fuels to create energy, which in turn reduces the amount
of conventional fuels used and electricity imported from the grid. Even concrete can be recycled
as fill or road base (ASCENT, 2007).
All the materials used in precast concrete production are local to the United Kingdom. This
makes the UK self-sufficient in concrete production (The Concrete Centre, 2009). However, the
increase in economic growth might stop the UK from being self-sufficient in the future.
Therefore the level of mineral extraction needs to be considered as well. A reduction of
environmental impact and cost of producing precast concrete can support the UK economy as
well as UK environment.
13
2.3 Biomass
2.3.1 What is Biomass
Biomass is a biological material from organic substances or living organisms that can be
converted to an energy form. These materials usually come from virgin wood, energy crops,
agricultural residues, food waste and industrial waste. Energy obtained from these sources can
replace or reduce the use of conventional fuels such as oil, natural gas, coal and electricity
(which is generated by these conventional fuels). Increasing the use of biomass is not only able
to decrease CO2 emissions, but also decrease the amount of money for buying or importing the
conventional fuels for private sectors or a country as a whole. The table below shows the CO2
emitted by full combustion of some conventional and biomass fuels, per unit of energy.
Table 1 : Carbon emissions of different fuels per unit of energy (Biomass Energy Centre, 2003)
Approx. life cycle CO2 emissions
Fuel
kg / GJ
kg / MWh
Hard coal
134
484
Oil
97
350
Natural gas
75
270
LPG
90
323
Electricity (UK grid)
150
530
Electricity ( large scale wood chip combustion)
16
58
Electricity ( large scale wood chip gasification)
7
25
Wood chips (25% MC)
2
7
Wood chips (25% MC) Including boiler
7
25
Wood pellets (10% MC) starting from dry wood waste
4
15
Wood pellets (10% MC) Including boiler
9
33
Grasses/straw (15% MC)
1.5 to 4
5.4 to 15
Fuel only
From table 1, biomass fuels CO2 emissions are far less than conventional fuels. Moreover, the
next table shows the typical prices of fuel per unit of energy.
14
Table 2 : Fuel prices per kWh (Biomass Energy Centre, 2011)
Fuel
Price per unit
kWh per unit
Pence per kWh
Wood chips (30% MC)
£ 90 per tonne
3,500 kWh / tonne
2.6p / kWh
£ 185 per tonne 4,800 kWh / tonne
3.9p / kwh
Wood pellets
Natural gas
4.1p / kWh
1
4.1p / kwh
Heating oil
56p per litre
10 kWh / litre
5.6p / kwh
LPG (bulk)
54p per litre
6.6 kWh / litre
8.2p / kwh
Electricity
13.0p / kWh
1
13.0p / kwh
The cost of biomass fuel is not cheaper when compared to the cost of conventional fuels. This is
because biomass fuels need to be purchased. If waste, wood and agricultural residues were
obtained from industries by-products, these costs would be lower.
There are a number of energy production technologies for many different types of biomass fuel.
Biomass fuel can be converted by thermo and/or chemical and bio-chemical conversion
technologies to produce energy. Biomass is considered an inexhaustible fuel source as it can be
grown over and over again. Furthermore, it can be grown all over the world. However, biomass
releases a certain amount of CO2 emissions into the atmosphere when it is burned, not as much
as fossil fuels, but in order to balance the amount of CO2 emissions, biomass sources need to be
grown in the same amount to absorb the CO2 emissions from the atmosphere. Biomass usually
comes from grain, sugar and oil crops, all of which are foods. Despite the increasing energy
consumption demand, the increasing demand for food still exists, hence the balance of crop for
energy, crop for food must be put into place. Aside from that, waste, wood and agricultural
residues can be utilised to produce energy instead of eliminating them or throwing them away
where they will end up in landfill sites.
Nonetheless, biomass energy production technologies have considerable investments due to their
immature technologies compared with conventional fuel energy production technologies. Capital
costs of biomass energy production technologies are also higher than those of gas and oil fired
due to the nature of the fuel sources (Kellet, 1999). Therefore, it is extremely important to
understand and be able to choose suitable types of biomass technology in order to make energy
efficient and financially benefit from it.
15
2.3.2 Wood Waste as a Biomass Fuel
Biomass is any organic material that can be converted into energy. Biomass energy comes from
wood, waste wood, agricultural waste materials, animal waste, agricultural processing plant
wastes and wastes from the community.
Waste wood can be obtained from various types of sources such as municipal waste,
construction, demolition, commercial and industrial waste.
According to The Waste &
Resources Action Programme (2005), it was estimated that the total waste wood arising in the
UK is about 10,586,000 tonnes per annum. This figure indicates the large amounts of energy that
could be produced from wood waste. The table below shows the total wood waste separated by
sectors.
Table 3: Estimate of total wood waste arisings in the UK (The Waste & Resources Action Programme, 2005)
Waste Stream
In the UK (Thousand Tonnes per
Annum)
Municipal Waste
1,065
Commercial and Industrial
4,481
Construction and Demolition (an average of the
5,040
maximum and minimum estimates)
Total Wood Waste
10,586
There are various options to deal with wood waste. It can be reused, recycled, energy recovered
or disposed. The way in which wood waste can be dealt with depends on the quantity and the
quality of the wood. Waste wood has been conventionally seen as an inconvenient material that
has to be disposed of. Landfill disposal is the easiest way to deal with waste wood. It is also
suitable for all types of waste wood in terms of quality and quantity. However, it is not the most
desirable option as the number of landfill areas is growing each year, therefore this scarcity of
landfill areas might increase the landfill fee in the future. The cost per tonne of sending waste
wood or other waste to landfill has also been increasing over the past decade (Department for
Environment, Food and Rural Affairs, 2008). Moreover, landfill taxes have been increasing over
the years. The landfill tax was £ 24 per tonne in 2007 and 2008, and it has been increasing at a
16
rate of £ 8 per tonne from 2008 to 2011 (Department for Environment, Food and Rural Affairs,
2008).
Another option would be using waste wood as a biomass fuel. This option is strongly influenced
by the quantity and quality of the waste wood. Producing energy from waste wood can help
reduce the electricity imported from the grid as well as heat from conventional fuel. Therefore,
producing energy from wood waste would result in a long term cost reduction (wood fuels price
can be cheaper than conventional fuels (£ per kWh)) and CO2 emissions would be reduced. On
the other hand, the capital costs of technologies for producing biomass are more expensive than
that of conventional fuel.
Waste wood usually has one advantage over virgin wood; waste wood has a lower moisture
content from the process than that of virgin wood (Department for Environment, Food and Rural
Affairs, 2008). Wood chip made from waste wood can be used in normal wood chip boilers with
suitable moisture and ash content. The characteristics of wood waste such as moisture content,
heating value, ash content, size, and contaminant have to be well considered before choosing the
suitable biomass conversion technology.
Moisture Content
Moisture content of biomass fuels is an important consideration for energy generation. If the
moisture content of biomass is very high, such as in pulp, starch or yeast (where the moisture
content of about 80-90%) (Penn State College of Agricultural Sciences, 2010), it is not
appropriate for incineration. However it can be put through a process of compression
(dewatering) to reduce the moisture content prior to incineration, or an anaerobic treatment
process to produce biogas. In the case of fresh green wood, moisture content is about 50% (Penn
State College of Agricultural Sciences, 2010). However, it also depends on the species, age,
growth area and the part of the tree. One option to reduce moisture content is to store biomass
fuel in a controlled environment to decrease the moisture content. Another option is to store and
dry it by heat radiation. As for waste wood, the moisture content is usually less than that in fresh
wood, and the value is likely to be less than 20% (National Association of Forest Industries,
2006). The moisture content of waste wood from industrial, residential, municipal, institutional,
17
or commercial backgrounds depends significantly on which process they went through, and
whether the wood fuel has been drying throughout that process.
Heating Value (Calorific Value)
Each type of biomass gives different amounts of energy depending on the chemical elements and
percentage of moisture it contains. The heating value or calorific value of biomass indicates the
total amount of heat released per unit weight of biomass being burned (kJ/kg). These can be
expressed in two terms: higher heating value and lower heating value. The high heating value
(gross calorific value) is the total amount of heat energy derived from burning biomass fuels
including the latent heat of vaporisation of water in biomass fuel. The low heating value (net
calorific value) is the total amount of heat energy derived from burning biomass fuel excluding
the energy required to evaporate the water that accumulates in the biomass fuel (Kauriinoja,
2010).
As mentioned before, the heating value of a biomass fuel type can vary significantly depending
on the species of wood and moisture content. Even the heating value of some species of biomass
fuel can vary depending on the different climatic and geographical conditions when grown
(Biomass Energy Centre, 200-). The table below gives an example of lower heating values of
different types of wood at specific range of moisture content.
Table 4: Wood Fuel Lower Heating Value (ELECTROWATT-EKONO (UK) LTD, 2003; Biomass Energy Centre)
Wood Fuel
Lower Heating Value (Net Calorific Value)
(kWh/kg)
Wood chips (30% MC)
3.5
Wood chips (20% MC)
4.22
Forest wood chip dry (40% MC)
2.89
Forest wood chip fresh (55% MC)
2
Log wood (stacked - air dry: 20% MC)
4.1
Wood (solid - oven dry)
5.3
Wood pellets
4.8
Wood waste (18-25% MC)
≈4
Poplar wood (5-15% MC)
4.72 - 5.27
Willow wood (12% MC)
4.72 - 5.27
18
4.16 – 4.72
Plywood residue (5-15% MC)
Logging residue chips (50-60% MC)
1.67 - 2.5
Whole tree chips (45-55% MC)
1.67 - 2.5
Log chips (40-55% MC)
1.67 - 2.78
Stump chips (30-50% MC)
1.67 – 3.05
Soft wood bark (50-65% MC)
1.67 - 2.5
Birch bark (45-55% MC)
1.94 – 3.05
Wood Residue chips (10-50% MC)
1.67 – 4.16
Uncoated Wood (15-30% MC)
3.33 – 4.16
In wood fuel, the heating value has a linear relationship with moisture content. Increasing the
moisture content decreases the heating value because the part of heat energy released is used to
vaporise the water within the wood fuel. The figure below shows the lower heating value (net
calorific value) compared with moisture content.
Figure 2: The effect of moisture content on the lower heating value of wood (kWh/kg) (ELECTROWATT-EKONO (UK) LTD , 2003)
The high moisture content will decrease the lower heating value of the biomass fuel and in turn
affect the fuel efficiency, as well as the size of the boiler. Therefore a more expensive boiler has
to be installed, if the moisture content is high.
19
Ash Content
Inorganic materials of biomass fuels or waste wood that cannot be burned will turn into ash,
which is called ash content. Ash will remain in the process after burning. Each type of biomass
has different proportions of ash content. These inorganic materials can exist as part of the
organic structure of the biomass fuel, or it can be added to the biomass fuel via processing,
harvesting, or handling (Livingston, 2007). Most wood waste contains considerable inorganic
materials depending on the process that they have undergone, this can affects the efficiency in
the wood waste conversion system. A few examples of the main ash-related problems of a
biomass conversion system in furnace and boilers are (Livingston, 2007):

Larger particle of ashes that fall through the bottom during the combustion process are
called bottom ash, these ashes need to be handled and dispose of from the furnace.
Bottom ashes can be recycled as fertilizer, road construction or landscape materials.

Smaller particles that are carried with the flue gas are called fly ash. High amounts of fly
ash impacts the performance of the flue gas cleaning equipment such as the filter or
cyclone and it can stick on the furnace and the heat exchanger surface, which, in turn,
reduces the efficiency of the plant.

The formation of some chemical compounds in the ash can produce slag that will
decrease boiler components and other components‟ life spans.
The exact amount of ash content and its effect largely depends on the type of waste wood, which
process they went through, and the biomass conversion technology involved. The following table
gives some examples of the amount of ash content in wood.
Table 5: Ash content from wood fuel (Eleotrowatt-ekono (UK) ltd, 2003)
Wood Fuel
Ash content in dry matter in percentage of
total weight
Plywood residue
0.4-0.8
Logging residue chips
1-3
Whole tree chips
1-2
Log chips
0.5-2
Stump chips
1-3
Wood Residue chips
0.4-1
Uncoated Wood
1-5
20
Size
Waste wood has to be cut or chipped into an appropriate size before being uses in a biomass
boiler or CHP. This not only helps improve the efficiency of the boiler, but it also eases the
handling, transporting, and storing of waste wood. Smaller sized wood waste has a larger surface
area than bigger sized wood waste of the same weight, therefore it can release moisture more
quickly than the bigger sized wood waste (Penn State College of Agricultural Sciences, 2010).
As a result, it has a better burning efficiency. The smaller sized of waste wood need less space
for handling, transporting, and storing compared to the bigger sized of waste wood, which in turn
reduce the cost of these factors. However, the cost of size reduction has to be considered too. The
size of the wood fuel should comply with the technological requirements of the biomass boiler or
CHP.
If the wood waste needs to be chipped, there are three main design technologies to produce wood
chip: disk chippers, drum chipper, and screw chipper (Biomass Energy Centre, n.d.). A disk
chipper is suitable for solid pieces of wood waste and provides a better quality of chip size than
drum chipper. While a drum chipper is more suitable for small pieces of wood waste, but it
might provide some oversized wood chips. A screw chipper or cone chipper is also suitable for
solid pieces of wood waste, and produces high quality and uniformed sized chips (Spinelli &
Hartsough, 2000) however it typically more expensive than disk chippers (BioRegional
Development Group, 2006).
Wood Fuel Storage
Wood fuel storage purpose is to keep or improve the wood fuel characteristics before feeding
them into energy conversion technologies. If the moisture content of the wood fuel (solid pieces
of wood or wood chips) reaches the requirements of the particular biomass boiler or CHP, it is
important to keep it in a dry controlled environment. If the moisture content of the wood fuel is
still too high, it needs a further drying process in storage. Storing the wood fuel in a dry
environment with well design natural ventilated air would be enough, if the wood fuel does not
need to be dried in a short period of time. Mechanical ventilation and heating can be used to dry
21
the wood fuel more rapidly, but it also increases the overall energy consumption and capital cost
(Macmillan, 2001).
Besides the methods of drying the wood fuel, the size of the storage is also essential. The storage
size must be big enough to be able to store and deliver the wood fuel all year round. It is obvious
that the bigger s storage facility is the better in terms of the amount of wood fuel it can store.
Moreover, bigger storage can reduce wood fuel delivery frequency to the site, which reduces the
transportation cost of wood fuel. However, bigger storage will increase more capital cost.
Therefore, the optimum size of the storage needs to be evaluated with the rate of wood waste
being produced from the process, rate of wood fuel consumption, wood fuel transportation cost,
and the storage cost (Biomass Energy Centre, n.d.).
The position of the storage should be designed to make it convenient for delivery vehicles to
access it. The height level of the storage system is also important especially for wood chips.
Above ground storage must be coupled with the hoppers or tools to elevate the wood fuel from
the vehicle to the storage, if the height of the storage is above the transportation vehicle.
Underground storage eases the delivery of wood chips from the vehicle, removes the building
structure, and provides more space above the ground. However, the cost of underground storage
is likely to be more than above ground. The ventilation and heating system is also more
complicated to install if it is needed (Millar, 2006).
Contaminant
Contaminant in waste wood is an important issue to be overcome in order to have safe and
successful use of waste wood as a biomass fuel. Wood waste by manufacturing, processing,
construction and demolition or other industries may have received some kind of treatment,
contaminant or heavy metal. The wood waste that is contaminated with chemical matter has
limitations of use as biomass. Wood waste can be viewed in different ways, mainly separated
into hazardous wood waste and non-hazardous wood waste.
Waste wood has stricter regulations when being used in energy production than virgin wood
(Biomass Energy Centre, 200-). These regulations are for contaminated wood waste from
22
treatments, manufacturing processes, or accidental spills of chemicals. These place wood waste
under control of the Waste Incineration Directive (WID) and Pollution Prevention and Control
(PPC). These restrictions are set to prevent poisonous emissions from burning contaminated
wood. The wood waste is considered hazardous wood waste if it has been treated with the
following (TRADA Technology & Enviros Consulting Ltd, 2005):
-
Chromated Copper Arsenate (CCA)
-
Copper Organics
-
Creosote
-
Light Organic Solvent Preservatives
-
Micro-emulsion
-
Paint/strain
-
Varnish
The use of contaminated wood waste as mentioned above can be used as a biomass fuel if and
only if the appropriate filtering and ash handling process and level of emissions control are
applied (TRADA Technology & Enviros Consulting Ltd, 2005).
Heavy metals such as copper, chromium and lead in waste wood can be removed by magnetic
force during the wood chipping process. If heavy metals are not removed before energy
production process, it will exist in bottom ash and fly ash that needs to be taken care of. The
bottom ash can reduce the efficiency of the boiler in the combustion process and it is needed for
suitable handling and disposal of ash. The fly ash can contaminate the emissions from energy
production, therefore an appropriate filter or cyclone has to be installed to prevent unacceptable
emissions.
Other contaminants such as halogens and halides could be released in the flue gas emissions
therefore, a scrubber or trap has to be installed to reduce or eliminate them. Wood waste that is
comprised of more than 1% halogenated organic compounds would be categorised as hazardous
waste (Department of the Environment Planning and Environmental Policy Group, 2007). It is
essential to counter these issues to prevent harmful emissions and to increase the efficiency of
the energy generation technology, but it is also seen as a great barrier to utilise waste wood as
biomass fuel.
23
2.4 Small Scale Wood fuel Conversion Technology
Biomass conversion technology is the first stage of converting biomass fuel into various forms of
energy such as heat, flue gas, product gas, biogas, bioethanol, etc. There are a number of
technologies to convert biomass to those forms of energy depending on the type and quantity of
biomass feedstock, as well as the desired form of energy. Environmental standard and economic
issues also have to be considered when choosing suitable biomass conversion technologies.
Not all conversion technologies will be addressed in this chapter. Only the combustion and
gasification conversion technology will be focused on because only these two technologies are
suitable for small scale wood waste biomass boilers and combined heat and power (CHP), which
are well established (Kauriinoja, 2010). The overview principle of conversion technologies will
be discussed in terms of technical and availability, small-scale wood waste biomass boilers and
CHP. The figure below shows the intermediate energy carriers and final energy products of each
conversion technology.
Figure 3: Main Biomass Energy Conversion Routes (Turkenburg, 2000)
24
2.4.1 Combustion
Combustion is the most direct conversion process from biomass into usable energy. This direct
combustion of biomass fuel creates a chemical reaction between biomass fuel and oxygen,
resulting in heat output. Biomass fuel is burned completely when there are three main criteria:
sufficient air, a good mixture of fuel and air, and a high combustion temperature. Because this
technology is straightforward and easy to implement, it is the oldest and most well established
technology compared to the others biomass conversion technologies. Biomass direct combustion
systems are commercially available from a few kW up to more than 100 MW (Nussbaumer,
2003). The overall efficiency is significantly high for generating heat. The power production
would be efficient, if combined heat and power technology is implemented. Biomass fuels that
are usually used in direct combustion is paper, wood, straw, miscanthus, switch grass, etc.
Principles
The combustion process can be divided into two sections which are the furnace (the place where
the fuel is burned) and the heat exchanger (the place where the heat from the flue gas in
transferred to other energy carriers, such as water, steam, or air) (Knoef et al., 1999).
Figure 4 : Basic Process Flow for Biomass Combustion (Knoef et al., 1999)
The flue gas coming out of the furnace can be used for space heating, water heating or steam
raising(generate electricity) via different types of heat exchangers. Thus, combustion furnace and
heat exchangers are available in different designs, depending on their end-use energy
requirement, biomass properties and characteristics. In general, combustion process of biomass
25
occurs in the furnace releasing hot flue gas. This hot flue gas is the heat output product from the
furnace. The type of furnace can be differentiated by the flow conditions of the bed in the
furnace. Two main types of furnaces are the fixed bed combustion and fluidized bed combustion.
Fixed bed Combustion Systems
Fixed bed systems are the most widely spread technology for biomass combustion technology
(Knoef et al., 1999). Fixed bed systems are distinguished by the types of grates and the way the
biomass is supplied to the furnace. It includes the grate-fired system and the underfeed stoker
system. This section will give an overview of the most frequently used furnace type for smallscale biomass technology.
-
Grate-Fired System
Biomass will be fed into the combustion chamber, where it is most likely to lay on the grate and
be burnt to ashes. There are various ways to feed biomass into the combustion chamber,
manually or automatically, where biomass is supplied above or under the grate. These
technologies are appropriate for biomass fuels with a high moisture content, of different sizes,
and high ash content (Vos, 2005).
o Fixed-Grate System
This system is suitable for small scale (Obernberger, 1998). The grate is fixed in place (often
sloped) in the combustion chamber. Biomass may enter by gravity from the top of the grate.
Primary air is supplied under the grate for the combustion of the material that remains after being
burnt (char) and biomass. Secondary air is supplied above the grate for the combustion of the
volatile gases (fuel gas from burning biomass). The newly added biomass fuel will be repeatedly
burnt by heat from the char combustion. Ash can be manually removed or automatically
removed below the grate (Knoef et al., 1999).
26
o Moving Grate Furnaces
In this system, the grate is in a horizontal or inclined position and will be moved by the drive
gears (usually by hydraulic cylinder) (Van Loo & Koppejan, 2003). Flow directions of the fuel
and the flue gas can be counter-current flow, co-current flow, and cross-flow.
In counter-current flow, the flame is in the opposite direction of the feeding fuel, is suitable for
wet bark, wood chips, or saw dust. In co-current combustion, the flame is in the same direction
as the feeding fuel, is suitable for waste wood or straw. In the cross-flow, the flame is removed
in the middle of the furnace, is suitable for wet and dry biomass (Van Loo & Koppejan, 2003).
Biomass fuels enter by the screw feeders on the grate at one end. Biomass on the grate will be
transported along to the other side and burned as well. Biomass fuels will be burned into ashes,
when the grate is at the other end. Ash will fall towards the bottom and be removed (U. S.
Environmental Protection Agency Combined Heat and Power Partnership, 2007).
In moving grate furnaces, mixture of wood fuels can be burned, but not wood fuels, straw,
cereals and grass together due to the different combustion behaviour of each biomass fuel.
Moreover, high ash and moisture content biomass can also be used in this technology
(Nussbaumer, 2003).
o Travelling Grate Furnaces
Travelling grate furnace is made of grate bars moving in circle in the combustion chamber (Van
Loo & Koppejan, 2003). Biomass fuels enter into the grate by screw feeders or spreader stokers.
Spreader stokers feed biomass into the furnace above the reaction zone. Heavier biomass
particles will fall further than the lighter biomass particles from the spreader stokers. Very light
and small biomass particles will be burnt above the reaction zone on the grate. The grate will
move in the opposite direction of the feeding biomass. This method will let heavy and large
biomass stay longer on the grate to be burnt (U. S. Environmental Protection Agency Combined
Heat and Power Partnership, 2007). This system can burn wood chips and wood pellets in
constant combustion conditions (Vos, 2005).
27
-
Underfeed Stokers
Underfeed stokers are usually suitable for small-scale systems and mostly used for wood chips
and small biomass particles (Van Loo & Koppejan, 2003). This technology is a relatively cheap
and safe option for biomass combustion (Nussbaumer, 2003). Biomass fuels are fed into the
combustion chamber and the grate by a screw conveyor from below. The pressure from the
feeding system pushes the biomass fuels upward. This will lead to a volatile substance being
contained in the fuel vapour and into the upper part to make it easier to ignite and burn up
completely (U. S. Environmental Protection Agency Combined Heat and Power Partnership,
2007). Ash from biomass fuel combustion will be pushed to the ash removal by air and small
particles flowing with the flue gas and will be extracted by the cyclone. However, it is not
feasible to burn high ash content biomass as this can affect the airflow and lower the quality of
combustion (Van Loo & Koppejan, 2003).
This technology has an advantage of being easier to control in partial-load behaviour than other
technologies, since load changes can be achieved quickly and easily by fuel feed supply (Van
Loo & Koppejan, 2003).
28
-
Fluidized bed Combustion Systems
In fluidised bed combustion systems, air will flow throughout a layer of a non-combustible
material bed. The system includes a combustion chamber with the non-combustible bed inside
(heat transfer medium). This non-combustible bed is fluidised by blowing air beneath the
chamber. This method increases the efficiency of the biomass combustion because of the
intensive mixing between biomass fuel, bed, and air, resulting in high specific heat transfer (Van
Loo & Koppejan, 2003).
There are two types of fluidised bed combustion systems, which is the bubbling fluidised bed
and circulating fluidised bed. The difference between these two technologies is the air velocity
blowing beneath the chamber. In the bubbling fluidised bed, the air with a velocity of 1-2.5 m/s
will only move the bed (usually sand). While in the circulating fluidised bed, the air velocity (510 m/s) is higher than that in the bubbling fluidized bed, resulting in all the small and light
particles in the chamber flowing up along with the heat flue gas (Obernberger, 1998). The
cyclone is used to extract such particles from the heat flue gas and send it back to the chamber.
This way the large and heavy particles will be burnt until they become small and light, thus the
complete combustion is rather easily done and it gives the flexibility of fuel properties, sizes and
shapes. Moisture content and ash content usually accept up to 60 and 50 percent respectively
(Obernberger, 1998). Bubbling fluidised bed and circulating fluidised bed boilers are usually
used in large-scale applications (Nussbaumer, 2003).
29
2.4.2 Gasification
Biomass gasification is the process that turns solid fuel into fuel gas, producer gas or syngas, by
heat process (thermal conversion). Producer gas is a gas that can be used as fuel consisting of
carbon monoxide (CO), hydrogen (H2), and methane (CH4) (Sanderson & Feltrin, n.d.). The
combustion of the producer gas provides heat that can be used in heating, water heating, and
electricity generation (U. S. Environmental Protection Agency Combined Heat and Power
Partnership, 2007). Moreover, producer gas can also be used as a fuel in gas combustion engines
or even modified diesel engines. The biomass gasification process can be divided into four
processes.
1. Drying process: The moisture content in biomass fuel will be reduced by heat from
the combustion zone of a reactor.
2. Pyrolysis process: This is the first step of burning biomass fuel by the heat from the
combustion zone. Organic compounds in biomass fuels will erupt in a solid, liquid
and gas.
3. Combustion process: The process of biomass fuel is burned in the reactor; air is
blown into the reactors where it then reacts with solid fuel which is derived from the
pyrolysis process.
4. Reduction process: Many reactions occur in which carbon monoxide (CO) and
hydrogen (H2) are produced as producer gases. This is the second step so that the
combustion air is controlled.
Biomass gasification systems are mainly used in the present and can be divided into three
systems. The difference of the various gasifiers is the way in which the fuel is transported into
the gasification stage. These are: updraft, downdraft, and fluidised-bed gasifiers technologies are
commercially available (Sinjab, 2009).
-
Updraft or Countercurrent Gasifiers
An updraft gasifier is the simplest type of gasifier and it has been used for a long period
of time. Biomass fuel is fed into the top of the stove and the air is passed through from
30
the bottom of the reactor. When the air goes into the combustion area, a reaction occurs
producing carbon dioxide and water. The gas from the combustion zone reaches a high
temperature as it goes into the reduction zone. In this area, carbon dioxide and water will
react with carbon to make the carbon monoxide and hydrogen as the main component of
the producer gas. The producer gas will flow into the area where the temperature is lower
than in the reduction zone. Then the high temperature producer gas will flow into the
layer of moist biomass in order to evaporate the water contained in the biomass. As a
result, the producer gas temperature from the furnace is low (Knoef et al., 1999).
Producer gas contains tar as the contaminant, which is due to the efficiency of the
gasification process. A more efficient process would contain less tar in the producer gas.
However, tar has to be removed before using producer gas in a boiler or gas combustion
engine. (Food and Agriculture Organization of the United Nations, 1986)
-
Downdraft or Cocurrent Gasifiers
Downdraft gasifiers have been used since World War 2 and are still widely used today
(Overend, 2004). This technology is particularly designed to eliminate tar in producer
gases. Biomass fuel is fed from the top of the reactor and air is drawn through from the
top or the sides, by a group of nozzles (tuyers) whereas producer gas comes out from the
bottom. The zones are similar to the updraft gasifier, but the order of the process is
different. On the way down to the bottom, the component in the biomass fuel must pass
through a glowing bed and turn into hydrogen, carbon dioxide, carbon monoxide and
methane (Knoef et al., 1999).
Composition of the tar in the producer gas from the downdraft gasifiers is less than 10%
tar from the updraft gasifier. However, there are high amounts of ash and dust particles in
the producer gas. Thus this technology is not suitable for high ash content or moisture
content biomass. It might make the combustion process slower and lose pressure inside
the furnace (U. S. Environmental Protection Agency Combined Heat and Power
Partnership, 2007).
31
-
Fluidized-Bed Gasifiers
With three of the gasifiers mentioned above, the operation depends solely on the
chemical properties and size of the biomass fuel. Fluidised-bed gasifiers were originally
developed to solve such problems (Knoef et al., 1999). In this technology, air flows
throughout the chamber with hot sand bed and biomass fuel. Biomass fuel is fed into the
bubbling fluidised bed or circulating fluidised bed depending on the airflow velocity from
the bottom of the chamber. Biomass fuel will be burnt and mixed quickly with the bed
material, resulting in continuous pyrolysis. Fluidised-bed gasifiers have the advantage of
flexibility in biomass characteristics and sizes due to high combustion efficiency.
However, this technology is more complex than others mentioned and more expensive
(U. S. Environmental Protection Agency Combined Heat and Power Partnership, 2007),
therefore this technology is mostly suitable for large scale operation power plants (Knoef
et al., 1999).
32
2.5 Small Scale Wood Fuel Power Generation Technology
Combined heat and power technologies (CHP) can produce heat and electricity from the same
source. The CHP efficiency can easily reach 80-90%, because thermal energy normally lost in
the process of producing electricity is utilised in many forms such as process steam, hot water, or
hot air (Alakangas & Flyktman, 2001). CHP systems (if well designed) are capable of
dramatically reducing carbon footprints and fuel bills. The installation of the CHP should be
based on thermal energy demand not electrical energy demand due to the fact that it is easier to
export the electrical energy surplus to the grid rather than dissipate or utilise thermal energy
surplus (Biomass Energy Centre, 2009).
Figure 5: The typical efficiency of the CHP compared to traditional heat and power generation (Self Energy UK,
2009)
Small scale biomass CHP technologies are not as mature as larger scale biomass CHP (Biomass
Energy Centre, 2009). Commercially available small scale biomass CHP is very limited, due to
economic and technical issue (Dong et al., 2009). Therefore the cost of small scale biomass
might be expensive, and the efficiency might not be as high as larger biomass CHP.
Many technologies have been researched and developed for small scale biomass CHP. This
includes the conversion technology that converts biomass to hot water, hot air, steam, or gas
mentioned earlier in this chapter. Another conversion technology that has to be considered is the
transforming of those products from the first conversion to heat and power.
33
Dong, Liu, & Riffat (2009) and Alakangas & Flyktman (2001) stated that direct combustion and
gasification processes combined with small sized steam turbines are normally for large scale
biomass CHP. In large scale, this technology is commercially available and traditional. The heat
to power ratio dramatically increases when the system size decrease because of the inefficiency
of small steam cycles and losses. The gasification process can be used with gas turbines and
micro-turbines, but it is also suitable for large scale biomass CHP (Biomass Energy Centre,
2009). Many of the current small scale biomass technologies are still under research and
development, and are immature however, some are already established
2.5.1 Internal Combustion Engine
Internal combustion engines use gas products from the gasification process to produce heat and
power. The down-draft gasification process is the majority process for used with internal
combustion engines. It has several advantages such as a short start-up and shut down time, and
good load-following, but it is noisy (U. S. Environmental Protection Agency Combined Heat and
Power Partnership, 2007). This technology requires good, clean gas in order to operate the
internal combustion engine to its potential. The filer, cyclone or tar remover must be put in place
before letting the gas product into the engine. The commercial biomass CHP system using
internal combustion engine capacity ranges from 10 kWe to 100 kWe, and it can give low heat to
power ratio as 2:1 or 1:1 (Biomass Energy Centre, 2009).
2.5.2 Stirling Engine
Unlike the internal combustion engine, the Stirling engine is an external combustion engine. The
heat from the combustion process or the combustion of product gas from the gasification process
is transferred to the engine to create work and then drive the turbine. The gasification process
would be a better option due to the purity of the gas in order to avoid erosion and corrosion of
the engine. In this engine, the combustion process takes place outside the engine (U. S.
Environmental Protection Agency Combined Heat and Power Partnership, 2007). The heat is
transferred to the engine by a heat exchanger. This process gives some advantages such as more
complete combustion of the wood fuel, which in turn emits lower emission. Stirling engines are
34
commercially available from 1 kWe to 75 kWe with a heat to power ratio around 4:1 (Biomass
Energy Centre, 2009).
2.5.3 Organic Rankine Cycle (ORC) engine
Organic Rankine cycle operation is similar to steam turbines, but the water working fluid is
replaced by a low boiling point working fluid such as silicone oil, freon, or an organic solvent.
The system can work in much lower temperatures than the steam turbine. For this reason, an
ORC engine is more suitable for small scale biomass CHP and gives higher efficiency than using
water (Dong et al., 2009). The lower operating temperature also lowers the cost of the material
and insulation. ORC engines are commercially available from about 350 kWe to 3,500 kWe and
they are successfully demonstrated with heat to power ratio of around 5:1 (Biomass Energy
Centre, 2009).
2.5.4 Micro-turbine
Gas turbines are commercially available in large scale biomass CHP, and the efficiency of these
turbines reduces with size. Therefore in recent years, many studies have focused on downsizing
such turbines whilst maintaining electrical efficiency and also instantaneously improving
economic viability. The micro-turbine can be driven with flue gas or air. Therefore micro
turbines can be combined with direct combustion technology. This technology has to comply
with a compressor to raise the gas or air pressure to the required value before being transferred to
the turbine. ORC engines are commercially available from about 30 kWe to 250 kWe with a heat
to power ratio of around 3:1 (Biomass Energy Centre, 2009; U. S. Environmental Protection
Agency Combined Heat and Power Partnership, 2007).
35
2.6 Financial Incentives
2.6.1 Renewable Heat Incentive (RHI)
Renewable heat incentive has been set up to promote the use of renewable technologies to create
heat. The purpose of the renewable heat incentives is to increase the proportion of non-domestic
sectors heat generated from renewable technologies (Department of Energy and Climate Change,
2010). Due to the high capital costs of renewable technologies, this scheme will compensate by
paying money to non-domestic sectors for every kWh of heat generated by renewable
technology.
Renewable heat incentives will support biomass, biomethane, biogas used on site, solar thermal,
heat pumps etc., but not fossil fuel CHP, co-firing CHP, or solar transpired panels. Some of the
technologies will be eligible for certain output capacities. More details of the renewable heat
incentive eligibility of renewable technologies can be found in the department of energy and
climate change website. The heat that will be taken into account in this scheme has to be useful
heat used for water, process, or space heating.
Table 6: Table of tariffs support for biomass in renewable heat incentive
Tariff
Eligible
Tariff name
technology
Eligible sizes
rate
(pence/
kWh)
Small
biomass
Solid biomass;
Medium
Municipal Solid
biomass
Waste (incl.
CHP)
Tariff
duration
Support calculation
(Years)
Tier 1:
Metering
Less than 200
7.6
Tier 1 applies annually
kWth
Tier 2:
up to the Tier Break, Tier
1.9
2 above the Tier Break.
Tier 1:
The Tier Break is:
4.7
installed capacity x 1,314
200 kWth and
above; less than
1,000 kWth
Tier 2:
20
peak load hours, i.e.:
1.9
kWth x 1,314
2.6
Metering
Large
biomass
1,000 kWth and
above
36
For biomass, the small size and medium size mentioned in the above table will fall under a
„tiered‟ tariff structure. Tier 1 tariff allows installations to receive support until they reach the 15
% of annual heat load, which is the 1,314 x installation capacity. Subsequently tier 2 tariff will
support the remaining thermal energy generated.
2.6.2 Feed-In Tariffs (FITs)
Feed-in Tariffs have been created to promote the use of renewable technologies for electricity
generation. The purpose of the feed-in tariffs is to increase the proportion of all sectors‟
electricity being generated from renewable technologies. This scheme will give three financial
benefits, which are the payment for electricity generated, exported, and saving from using
electricity produced.
The generation tariffs will pay for every kWh of electricity generated. The export tariff will pay
for every kWh of electricity exported to the grid and any renewable technologies can obtain
support by the generation tariffs and export tariff as long as the production capacity is less than 5
MW. However some renewable technologies such as biomass, liquid biofuels, biogas, tidal and
wave power, and geothermal energy are excluded from this scheme (Feed-In Tariffs Ltd, 2011).
The Energy Act defines that the mentioned excluded renewable technologies could be eligible
for this scheme, but the government has not included them yet (Feed-In Tariffs Ltd, 2011).
2.6.3 Renewable Obligation Certificates (ROCs)
Renewable obligation certificates have been created to increase the percentage electricity created
by renewable technologies for each licensed electricity supplier. Renewable obligation
certificates are issued by Ofgem for each MWh of electricity generated by renewable
technologies. Theses certificates can be traded to the licensed electricity supplier. The licensed
electricity suppliers have to pay a selling price (£/ROC) for each certificate from the electricity
generators, if they cannot reach the percentage of electricity supplied from renewable
technologies set by the renewables obligation. If the licensed electricity suppliers do not have
enough ROCs, they have to pay the buy-out price (£/MWh) to the buy-out fund.
37
This scheme helps renewable technologies generators to increase their incomes by selling their
ROCs to licensed electricity suppliers. This scheme runs for one year but it could be reissued
with ROCs for twenty years as long as it is before 31 March 2037 (Office of Gas and Electricity
Markets, 2011).
There are many definitions and factors to define eligibility under this scheme for each renewable
technology. The details of renewable technologies eligible for this scheme can be found in
department of energy and climate change website.
The table below shows the amount of ROCs given per MWh of electricity generated by biomass.
Table 7: Banding provision (Office of Gas and Electricity Markets, 2011)
Level of support
Technologies
(ROCs/MW)
Co-firing of biomass
0.5
Co-firing of energy crops, Co-firing of biomass
with CHP, Standard gasification or pyrolysis
Co-firing of energy crops with CHP, Dedicated
biomass
1
1.5
Anaerobic digestion, Advanced gasification or
pyrolysis, Energy crops (with or without CHP),
2
Dedicated biomass with CHP, Microgeneration
The ROCs are only applied to the eligible electricity output of the renewable technologies
defined by RO Order. Usually eligible output is the gross output subtracted by input electricity.
Input electricity is all the electricity used in generation of electricity including operating of
generators, fuel handling and preparation, maintenance, etc.
38
2.6.4 Other Grants and Support Schemes
-
Energy Saving Scotland – Small Business Loans
Loans from £ 1,000 to £ 100,000 with 0% interest rate can be given to businesses to
install renewable energy technologies. This scheme is for businesses in Scotland that are
defined as small and medium-sized Enterprise, private sector, and non-profit
organisation.
-
The Enhanced Capital Allowance (ECA) scheme
This scheme allows businesses to claim 100% first year qualifying capital allowances
against the taxable profit in the investment year. This scheme only supports new and
unused equipment and this equipment has to meet the energy-saving criteria issued by the
Energy Technology Criteria List.
-
EU Emissions Trading System (EU ETS)
This scheme allows companies to trade the CO2 emissions allowance to other companies,
if their CO2 emissions do not exceed the level of emissions allowance. However, if their
emissions exceed the allowance, they have to buy more allowance from another company
or pay the buy-out price.
39
3. The Biomass Boiler and CHP Tool
3.1 Introduction
The previous chapters gave the background overviews of using wood waste as biomass fuel, the
conversion technologies of biomass boilers as well as the combined heat and power (CHP)
technologies. The significant environmental advantages of using biomass to produce heat or
electricity is that it does not increase the net amount of carbon dioxide (CO2) in the Earth's
atmosphere, only if we produce enough biomass to balance this usage. It will make the
absorption of CO2 in the production of new biomass equal to the amount of CO2 produced by
burning biomass. Besides, biomass has lower sulphur content than many fossil fuels. This means
that the use of biomass will reduce the greenhouse gases (Greenhouse effect) as opposed to the
use of conventional fossil fuels. However, biomass needs more storage space, because of the
lower calorific value of biomass compared to that of conventional fossil fuels, it requires larger
storage space than the fossil fuels to heat evenly. Providing and collecting biomass to be used
constantly all year round has to be well managed sufficiently to provide heat or electricity
needed. Therefore, developing ways to store and transport biomass is very important and
necessary.
This helps us to choose appropriate biomass boilers and CHP to use from existing wood waste.
Moreover, it also gives us ideas of the environmental impact of using and not using wood waste
as a biomass fuel. After examining many mentioned aspects of using wood waste as biomass
fuel, we can conclude that using waste wood as a biomass fuel has more criteria and regulation
that has to be fulfilled and approved in order to have the maximum economic and environmental
benefit. The commercially available technologies to convert wood waste to thermal energy are
more developed and widespread than that of CHP technologies in small-scale. Small-scale
biomass electricity generation has a relatively low efficiency. Therefore CHP technologies will
not be suitable, if the heat generated from CHP is not used profitably. Besides Renewable Heat
Incentives, the electricity generation for CHP can have other benefits such as Feed-in Tariffs or
Renewable Obligation Certificate as mentioned before.
40
Most of the industrial applications that require process heat can obviously have the benefit of
using their wood waste by-product to produce heat. As for wood waste CHP, the technologies
are more expensive than that of the boiler. The detailed energy demand and energy supply have
to be considered with the benefits from costs, fuel saving, and financial incentives to be able to
compare the economic and environmental performance between the wood waste boiler and the
wood waste CHP.
3.2 Aims and Objective
The aim of this tool is to analyse the economic and environmental performance between selected
wood waste boilers and CHPs at a particular site. This tool allows the user to quickly calculate
the economic and environmental performance using the thermal and electrical demand profile,
technology specification, the operation mode, the costs, financial incentives and other financial
factors. This tool is a preliminary decision support analysis tool that can be used for those who
are investigating and investing in wood waste boiler and CHP.
Specifically, within the background of higher education, the objectives of this tool are to:
1. Specify the important parameters regarding the biomass boiler and CHP performance
2. Generating thermal and electrical hourly demand profile
3. Provide a tool for the analysis of economic and environmental performance between
selected wood waste boilers and CHPs
4. Compare the economic and environmental performance between selected wood waste
boilers and CHPs
For the purpose of each of the above objectives, objective 1 focuses on identifying the important
parameters for biomass boilers and CHP to use for calculation in this tool. Objective 2 focuses
on generating thermal and electrical demand either from a constant or variable demand.
Objectives 3 and 4 will make the key comparisons of biomass energy technologies, especially in
wood waste boiler and wood waste CHP.
41
3.3 Limitation
1. This tool can be used for woody biomass either from forestry or waste. For the case of
wood waste, waste has to contain 100% wood because this tool assumes that all the
contaminant has already been taken out of the waste. However, the mixture of different
type wood can be used in this tool.
2. As for the boiler and CHP technical specification, they have to be suitable for producing
thermal and/or electrical energy from wood only. And the technologies should be made
for solid wood biomass not for biogas or bioliquid.
3. This tool does not consider holiday dates during the year.
4. The thermal and electrical energy demand profile set by the user will be the same for the
project lifetime.
5. The thermal storage in this tool is a sensible heat storage designed to help improve the
performance of biomass boilers and CHP. The user cannot change the system type to
latent heat storage or bond energy storage system. This tool provides the basic calculation
for this thermal storage system. Since the thermal storage calculation largely depends on
the heating circuit and control configuration, an exact calculation for one specific setting
and technology would be inaccurate.
6. Wood storage size calculation will be neglected in this tool due to the many parameters
involved. Wood waste by-product from the manufacturer is varying throughout the year.
Further investigation is needed to calculate the storage size. However, the tool will
provide the monthly fuel consumption of biomass fuel in the result section.
7. The tool has a number of specific inputs; therefore it is really important to fill in the
accurate data in order to have an acceptable range of results.
8. The final figure results of this tool should be looked as estimated figures. There are some
parameters that are estimated or not considered in this tool such as the fixed inflation rate
over a 30-year period and the energy demand that will be the same every year.
42
3.4 Cell Colour Coding
The user only types data into the yellow cell provided, and chooses the data from the dropdown
list in the dark blue cell. All other cells that do not require input are in the white cell and other
colours.
Figure 6: Input and Output Cells
User Input (Manually)
User Input (Dropdown List)
Model Output or Cell that Do
not Required Input
3.5 The Biomass Boiler and CHP Tool Structure
This tool can be divided into five main sections, which are energy demand, wood fuel, biomass
boiler and CHP specifications, comparing the biomass boiler and CHP results, and results
comparison.
3.5.1 Energy Demand
Figure 7: Choosing demand characteristic
Energy demand section allows the user to enter
hourly thermal and/or electrical energy demand for
further calculation in this tool. If the user already has
the hourly energy demand profile, the user can
manually enter the hourly thermal and/or electrical
energy demand by choosing “Variable” in the
demand characteristic dropdown list for each month.
43
Then user can manually enter the hourly demand data in the space provided below the
spreadsheet.
Figure 8: Manually enter the hourly demand data
Otherwise user can generate the hourly energy demand profile by choosing constant in the
demand characteristic dropdown list and choosing the maximum demand in a year in kW.
Figure 9: Generating hourly energy demand profile
1st Step
3rd Step
2nd Step
3rd Step
4th Step
44
There are four steps to generate energy demand profile. First step, user can adjust the constant
demand throughout the year in each month. For example in the graph below, in December
(winter) the heat demand is at maximum so it is set to 100%, while in July (summer) the heat
demand is at half of the maximum demand so it is set to 50%.
Figure 10: Result of the first step of generating hourly demand profile
As for the second step, the user can choose the day and time that demands occur and end in every
week for each month. For example in the graph below, in January the demand occurs at 7:00am
on Monday and ends at 18:00 on Friday.
Figure 11: Result of the second step of generating hourly demand profile
45
Thirdly, the user can choose the time that demands occur and end every day of every week in
each month. For example in a week in January, the demand occurs at 7:00am on Monday and
end at 18:00pm on Friday. Then the demands occur at 8:00am to 19:00pm from Tuesday to
Thursday.
Figure 12: Result of the third step of generating hourly demand profile
M
T
W
T
F
S
S
o
u
e
h
r
a
u
n
e
d
u
i
t
n
d
s
n
r
d
u
d
a
d
e
s
a
r
a
y
a
s
d
y
d
y
y
d
a
a
a
y
y
y
And this is the example of hourly thermal demand result for January.
Figure 13: Example of hourly demand profile result in January
46
The user has to repeat these steps for every month in one year to get the hourly demand profile
for one year. Finally in the fourth step, user can enter the average heat loss in percentage for each
month. This will increase the hourly heat demand according to the input for each month.
This demand generation method is to help user that does not have the hourly energy demand
data, but has some ideas about how the energy is being used throughout the year. This energy
demand data can represent the approximate hourly energy usage or approximate hourly energy
that needs to be supplied by the biomass boiler or CHP.
After this, user has to fill the existing thermal and electrical energy supply information at the site
in the designated area. The list of required information is:
1. Type of heating Supply Fuel
2. Lower heating value of the supply fuel (kWh/Litre)
3. Fuel price (£/Litre)
4. Boiler efficiency existing at the site in percentage
5. CO2 emission factor for fuel (kgCO2/Litre)
6. Electricity supply source
7. Electricity price rate (£/kWh)
8. CO2 emission factor for electricity imported (kgCO2/kWh)
Figure 14: Input area for existing energy information
47
3.5.2 Wood Fuel
This section allows the user to enter wood fuel to use in the biomass boiler and CHP. It is mainly
divided into two parts. The first part is wood waste. The user can enter one type of wood or a
mixture of wood in this tool. This sector is really important because the rate at which the wood
will be consumed and the price are based on the wood fuel characteristics. The user can define
four different wood waste fuel cases. In each case, mixed or single type of wood waste can be
chosen.
First of all, user enters the name, chooses the type of wood in the dropdown list, and specifies
the total amount of waste wood available at site per annum. Then the user enters the type of
wood, mass percentage (weight proportion of mixed wood), moisture content, ash content (dry
basis), fuel density (dry basis), lower heating value (dry basis), and CO2 emission factor as input.
Finally, the tool will calculate the ash content (as received), fuel density (as received), and lower
heating value (as received).
Figure 15: Input area for wood waste information
1st Wood Fuel Case
Name
Type
Available at Site
Type of Wood
Pine
Plywood
Precast Concrete Site
Mixed Type of Wood
150,000.00
Percentage Mositure Content
(%)
(%)
50
50
kg / year
Ash Content (%)
Fuel Density (kg/m3)
Dry Basis As Received Dry Basis
20
20
100
0.6
80
0.48
0
0
0
0
0
0
0
100
20
As Received
125
25
0
0
0
0
0
0
0
Lower Heating Value (kWh/kg)
Dry Basis
5.138888889
5.277777778
As Received
CO2 Emission
Factor (kg·CO2/kg)
3.622511111
3.733622222
0
0
0
0
0
0
0
The tool will summarise the waste wood fuel characteristics in the bottom table, after the user
completes the information.
48
Figure 16: Wood waste summary table
Wood Waste Summary
Name
Mositure Content
Ash Content (%)
(%)
(%)
Precast Concrete Site
b
c
d
20
15
15
15
40.24
35.3
35.3
35.3
Fuel Density (kg/m3)
Lower Heating Value (kWh/kg)
75
81.42857143
81.42857143
81.42857143
3.678066667
6.10855
6.10855
6.10855
CO2 Emission
Available at
Site (kg)
Factor (kg·CO2/kg)
0
0
0
0
Price per kg (£)
150,000.00
150,000.00
150,000.00
150,000.00
0
0
0
0
The second part is the extra biomass that needs to be purchased for each waste wood case. This
part was created in the case that energy from waste wood is not enough to supply the thermal
energy demand throughout the year. Therefore, the user needs to purchase extra wood fuel to
support the shortfall of waste wood fuel. The inputs are similar to those in waste wood fuel
except for the price per kg delivered that has to be entered.
Figure 17: Input area for extra wood needed to purchase information
Extra Biomass Needed to Purchase
For Wood Waste
a
b
c
d
Mositure
Content (%)
30
Ash Content (%)
Fuel Density (kg/m3) Lower Heating Value (kWh/kg) CO2 Emission
Dry Basis
As Received Dry Basis As Received Dry Basis
As Received Factor (kg·CO2/kg)
100
70
100 142.85714
7
4.1671
0.6
0.6
20
20
0
0
0
0
0
0
0
Price per kg
Delivered (£)
1
1
1
1
The meaning of each parameter and the calculations involved will be described later in the
appendix 3.
49
3.5.3 Biomass boiler and CHP Specification
After specifying the wood fuel characteristics of a particular site, the next step is to choose the
suitable biomass boiler and CHP to supply the energy demand. Then 10 or less suitable biomass
boiler and/or CHP information can be inserted in the bottom table of this section. The
information required is:
Figure 18: Input area for biomass boiler and CHP information
1. Boiler or CHP
2. Manufacturer name
3. Manufacturer model name
4. Electricity consumption for the technology in
kW
5. Biomass conversion technology
6. Power generation technology
7. Rated thermal output in kWth
8. Efficiency at 75-100% Load
9. Efficiency at 50-75% Load
10. Efficiency at 25-50% Load
11. Efficiency at 0-25% Load
12. Maximum power output in kWe
13. Heat to power ratio at 75-100% load
14. Heat to power ratio at 50-75% load
15. Heat to power ratio at 25-50% load
16. Heat to power ratio at 0-25% load
17. Thermal storage size (m3)
18. Thermal storage min temp (°C)
19. Thermal storage max temp (°C)
20. Thermal storage fluid type
21. Thermal storage fluid specific heat capacity (kWh / kg·C)
22. Density of fluid in thermal storage (kg/m3)
23. Thermal storage average temp drop (°C / hour)
24. Thermal storage initial temperature (°C)
25. Initial cost (£)
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26. Operation and maintenance cost (£)
It is important that user finds a suitable wood waste biomass boiler and CHP to fill in this section
based on the understanding mentioned in the literature review chapter. The detailed calculation
of each parameter will be described later in the appendix 3.
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3.5.4 Comparing Biomass Boiler and CHP
This section of the tool is considered the main section. Type of wood waste, and biomass boiler
and CHP specified in the previous section are chosen to compare the economic and
environmental performance in this section. The total number of comparison is seven; therefore it
has seven cases to be compared. It can compare the same biomass boiler and CHP with different
type of wood waste, or the same type of wood waste with different biomass boiler and CHP. This
section has eight subsections which are:
1. Annual energy demand
This subsection indicates the total amount of electrical and thermal energy demand per year
in kWh based on the energy demand section.
2. Choose wood fuel
In this subsection, user is able to choose the type of wood waste specified before. Wood fuel
type can be selected from the dropdown list based on the wood waste fuel section. After
choosing the wood fuel type, the tool will show the important parameters for that particular
wood fuel such as moisture content, ash content, calorific value, fuel cost, and wood fuel
available at site.
Figure 19: Wood fuel choosing area
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3. Choose biomass boiler and CHP
In this subsection, user is able to choose biomass boiler and CHP specified before. The
biomass boiler and CHP can be selected from the dropdown list based on the biomass boiler
and CHP specification section. The tool will show the biomass conversion technology, power
generation technology, and maximum thermal and electrical output after the boiler or CHP is
chosen.
Figure 20: Biomass boiler and CHP choosing area
Then the user has to choose the operation mode for the boiler or CHP chosen. There are
three operation modes to choose from, which are constant load, follow thermal load, and
follow monthly thermal base load.
Figure 21: Choosing operation mode area
-
Constant load operation mode will let the boiler or CHP operate at constant thermal
output, if the boiler or CHP is turned on. Users can choose to operate the boiler or CHP at
one particular constant output throughout the year or choose to operate at different
constant outputs for each month.
53
-
Follow thermal load operation mode will let the boiler or CHP modulate its thermal
output following the thermal demand, if the boiler or CHP is turned on.
-
Follow monthly thermal base load operation mode will let the boiler or CHP operate at
different constant thermal output each month following the thermal base load of each
month, if the boiler or CHP is turned on.
After this, users can choose the time to operate the boiler or CHP. It can be operated all year
round or by a weekly basis. If the user chooses to operate the boiler or CHP all year, it will run
24 hours for 365 days at a particular set running capacity. If user chooses to operate the boiler or
CHP by a weekly basis, it can be set to operate at one particular running capacity for each month.
And it also can be turned on and off at a set time every day or every week of each month. There
are four steps to operate boiler or CHP by a weekly basis. These steps are similar to those in
generating energy demand mentioned before in energy demand section.
Figure 22: Choosing operation mode and operation time area
54
After choosing the biomass boiler and CHP, operation mode, and operation time, this tool will
provide information on biomass fuel used, thermal and electrical energy supply-demand
matching results for all cases in this subsection based on all the input. The figure below shows
the result in this subsection. The detailed calculation of biomass fuel used and energy supplydemand matching will be mentioned later in the appendix 3.
Figure 23: Results in choosing biomass boiler and CHP subsection
4. CO2 emissions
In this subsection, the tool will calculate the annual amount of CO2 emissions from biomass
for each case, which is usually considered as carbon neutral. However, it can be calculated, if
the user enters the CO2 emissions factor in the wood fuel section. Then the tool will give the
annual CO2 emissions reduction based on fossil fuel usage for the same amount of electrical
and thermal energy produced to load for each case. The detailed calculation of CO2
emissions reduction will be mentioned later in the appendix 3.
55
5. Costs
The Initial cost represents the costs which is the sum of the design, purchase, construction,
installation and grid connection costs of all the elements of the new biomass boiler or CHP
system.
The operating and maintenance (O&M) costs are the sum of the annual costs to operate and
maintain the new biomass boiler or CHP system.
The initial and O&M costs will be transferred to the result section for further financial
calculation.
6. Savings, Grants, Renewable Heat Incentives (RHI), Renewable Obligation Certificate
(ROC) and Feed in Tariff (FIT)
This subsection involves the financial benefit or loss for installing the biomass boiler and
CHP. It can be separated into three main parts.
Firstly, this subsection calculates the fuel and electricity saving by replacing the existing
technology with the biomass boiler or CHP for each case.
Secondly, users can enter the grant or subsidy that is paid for the initial cost of the biomass
boiler or CHP. As for the grant that reduces loan interest rate, the user has to manually
subtract it from the rate of interest on loan in the next subsection.
Finally, renewable Heat Incentives (RHI), Renewable Obligation Certificate (ROC) and Feed
in Tariff (FIT) can be applied and analysed in this tool. Users have to enter all the required
information in the designated cell. The detailed calculation of these financial incentives will
be mentioned later in the appendix 3.
The savings, grants and financial incentives will be transferred to the result section for
further financial calculation.
56
7. Loan
The model calculates the annual repayment, which is the portion of the total capital cost
required to implement the project and that is financed by a loan. The annual repayment is
calculated from the rate of interest on loan and number of years to complete the repayment.
The detailed calculation of the loan will be mentioned later in the appendix 3.
8. Financial parameters
Users can enter a discount rate (%), which is the rate used to discount future cash flows in
order to obtain their present value, as well as the inflation rate (%). The inflation rates that
can be entered are biomass fuel price, electricity price, conventional fuel, operation and
management cost, RHI, and FIT inflation rate. These parameters will be used to determine
the economic performance for each case.
3.5.5 Results
There are seven results for seven cases in seven spreadsheets. This subsection contains the
results of the calculations from all the input parameters entered in previous subsections. Supplydemand thermal and electrical energy matching graph is shown at the top of this section for each
case. Below that, the net income and cumulative profit is calculated and shown every year for 30
years from the year zero (investment year) to the year thirty mainly based on these parameters:
1. Initial costs,
2. O&M costs,
3. Fuel saving,
4. Renewable heat incentive tariff,
5. Electrical saving,
6. Electricity Incomes from feed in tariff, and
7. Renewable obligation certificate incomes.
8. Grants
57
All the inflation rates are also applied to calculate more realistic and acceptable results in this
section. Moreover, this also gives the amount of biomass available at site, biomass fuel used and
CO2 emissions reduction for each year. All the detail calculations will be described later in the
appendix 3. This subsection helps users analyse the detailed economic performance of the
biomass boiler or CHP each year.
Below the table, the tool provides the table of monthly fuel consumption of wood fuel in the
result section to help design the biomass storage size.
3.5.6 Results comparison
This section gathers and summarises the economic, energy, and environmental performance
between seven cases. Users will be able to compare these performances in this section. The
economic factors that will be calculated and presented in this section are
-
Payback period
The tool calculates the payback period (years), which represents the length of time that it
takes for installing the biomass boiler or CHP to repay the sum of its own investment.
The basic analysis of the payback period is that the shorter periods are more desirable
than longer periods of payback. This is not the parameter that measures the profits of the
case compared to another. Instead, it measures the time required to recover the
investment compared to another.
-
Cumulative cash flow
This tool calculates the total profits or losses over 30 years. This is the parameter that
measures the profits of the case compared to each other. This is based on the cash flow
analysis in the results section.
-
Internal rate of return (IRR)
The internal rate of return is the interest rate provided by the investment over the project
lifetime. Alternatively, IRR is the value that makes the net present value (NPV) of net
cash flow from the investment equal to zero. This parameter measures the desirability of
58
investments. The basic analysis of IRR is that a higher IRR is more desirable than a lower
IRR to undertake the project.
-
Net Present Value (NPV)
NPV is the present money value of the total net cash flow over the project lifetime. If the
NPV is positive, it indicates that the project should be invested. Projects that provide the
highest NPV are more desirable to undertake the project. However, the NPV alone may
have limitations in decision-making; in case the projects with different investments have
equal NPV. Therefore other parameters alongside NPV should be taken into
consideration to support the decision-making.
-
Profitability index (PI)
Profitability index is the ratio of present value of the total net cash inflow to the initial
investment (does not include the investment) over the project lifetime. This parameter
measures the desirability of investments. The basic analysis of profitability index is that a
higher positive PI is more desirable than a lower positive PI to undertake the project. If
the PI is less than zero, it is not desirable to undertake the project.
The total thermal and electrical energy generated, delivered to load, surplus, and deficit are
calculated and shown here over the project lifetime for each case. The environmental
performance results are also shown in terms of equivalent CO2 emission reduction for each case.
59
3.6 Detail Calculation and Analysis of the Tool
The following are the detailed calculations and analysis which describes the calculations and
how the parameters are connected with each other in energy demand, wood fuel, biomass boiler
and CHP specification, comparing the biomass boiler and CHP, results, and results comparison
section in this tool. The methodology of this tool can be illustrated in the figure below.
Figure 24: Tool Methodology
This figure illustrates the main methodology this tool considers in order to assess the feasibility
of using waste wood as biomass fuel for the boiler and CHP.
The first step is to enter or generate thermal and electrical energy demand at the site. Then the
user identifies the type of wood fuel to use as a biomass fuel. It was also identified that the
different types of wood fuel have a big influence in the energy production.
Then, based on these two key facts with chosen biomass boiler or CHP with or without thermal
storage, the tool calculates the energy demand supply matching and all the initial cost involved.
After that, CO2 emissions reduction and cost savings were calculated from the energy demandsupply matching in terms of CO2 emissions reduction based on fossil fuel usage reduction, and
electricity imported reduction.
Finally, the tool will analyse the financial benefit or loss based on the cost and cost savings of
selected biomass boiler or CHP and wood fuel.
60
The calculation of this tool will be based on the methodology of the above figure. And the
description will be separated into 6 sectors according to this tool structure.
3.6.1 Energy demand
After the user enters or generates the hourly thermal and electrical energy demand profile (the
steps to generate are already described in 4.5.1), these parameters are entered by the user or
calculated by the tool.
Heating supply fuel
The user enters the fuel type that supplies heating for existing technology before the biomass
boiler and CHP were proposed.
Lower heating value
The low heating value (net calorific value) is the total amount of heat energy from burning fuel
excluding the energy required to evaporate the water that accumulates in the fuel. The user enters
the lower heating value and selects the suitable unit for the heating supply fuel.
This tool calculates energy based on kWh unit. When there is information of lower heating value
in Joules unit, the user can convert to kWh by these formulas.
Fuel price
The user enters the fuel price rate according to the unit given by the tool.
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Electricity price rate
The user enters the price of electricity imported from the grid per kWh.
Boiler efficiency
The user enters the efficiency of the boiler for heating of existing technology before proposed
biomass boiler and CHP.
Annual fuel consumption
The tool calculates annual fuel consumption from this equation
The unit of the fuel consumption depends on the selected unit in the lower heating value cell by
user.
Annual fuel cost
Annual fuel cost is the product of annual fuel consumption and fuel price. This is the estimation
of the money spent for supplying fuel from the existing technology. The reason that this figure is
just an estimated cost is because the fuel price usually varies throughout the year. But only one
particular fuel price is calculated in this tool.
CO2 emission factor
The user enters CO2 emission factor for the thermal supply fuel. This figure represents the
greenhouse gas emissions converted into kilograms of carbon dioxide equivalent (kg CO2) per
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unit of fuel or kWh. Users can find more information on this in the Guidelines to Defra /
DECC‟s GHG Conversion Factors for Company Reporting (2011).
Annual CO2 emission
The tool calculates the total of equivalent CO2 emission per year by multiplying CO2 emission
factor with the annual fuel consumption.
3.6.2 Wood fuel
After the hourly thermal and electrical energy demands are generated or entered, the user enters
the wood waste fuel characteristics. The following parameters are entered and calculated by the
user and the tool respectively.
Name
The user enters the name of the waste wood fuel in each case for reference purposes only.
Type
The user chooses the type of wood waste from the dropdown list. Single Type of Wood means
that there is only one type of wood characteristic in this wood waste case. Mixed Type of Wood
means that there is more than one type of wood characteristic in this wood waste case. Users can
enter up to ten wood characteristics when Mixed Type of Wood is chosen.
Available at site
User enters the amount of wood waste available at site per year in kg.
Type of wood
The user enters the type of waste wood fuel in in the table for reference purposes only.
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Mass Percentage (%)
The user enters the weight proportion in percentage of each type of wood in the table.
Moisture content (%)
The user enters the moisture content of each type of wood in the table. This value depends on the
type of wood and the process it went through.
Dry basis ash content (%)
The user enters the dry basis ash content of each type of wood in the table. Dry basis ash content
is the ash content in the wood when it is completely dried (0% moisture content).
Ash content as received (%)
This value is calculated from moisture content and dry basis ash content of the wood with this
equation.
Dry basis fuel density (kg/m3)
The user enters the dry basis fuel density of each type of wood in the table. Dry basis fuel density
is the fuel density of the wood when it is completely dried (0% moisture content).
Fuel density as received (kg/m3)
This value is calculated from the moisture content and dry basis fuel density of the wood with
this equation.
64
Dry basis lower heating value (kWh/kg)
The user enters the dry basis lower heating value of each type of wood in the table. Dry basis
lower heating value is the lower heating value of the wood when it is completely dried (0%
moisture content).
When the dry basis lower heating value is in MJ/kg unit rather than kWh/kg, the user has to
convert the unit by these formulas.
Lower heating value as received (kWh/kg)
This value is calculated from the moisture content and the dry basis lower heating value of the
wood with this equation (British Standards Institution, 2010).
[
Where
]
is the correction factor of the enthalpy of vaporisation at constant pressure for
water at 25°C in kWh/kg.
CO2 emission factor (kgCO2/kg)
The user enters the CO2 emission factor of each wood type in the table. Normally, this value is
zero due to the neutral carbon cycle characteristic of biomass. However, users can enter this
figure, if the CO2 emission from biomass combustion is needed.
65
Price per kg (£)
The user enters price per kg of the type of wood. This price shows the money spent and chipping
wood waste before using it in the biomass boiler or CHP. This price does not include the price of
the wood itself, because wood waste is the waste or by-product from manufacture.
Wood waste summary
The tool calculates average characteristic value of all the wood waste types for each case by
using mass percentage of each wood waste. For each case,
∑
Price per kg delivered (kg)
The user enters the price per kg delivered of the wood fuel, which transportation cost is already
taken into account.
3.6.3 Biomass boiler and CHP specification
After entering the wood fuels for biomass boiler and CHP, the user has to enter the suitable
boiler and CHP specification in this sector.
Boiler or CHP
User has to specify the type of energy supply from Boiler, Boiler + Thermal Storage, CHP, and
CHP + Thermal Storage from the dropdown list.
Manufacturer
The user enters the manufacturer name for reference purposes only.
66
Manufacturer model name
The user enters the manufacturer model name for reference purposes only.
Electricity consumption
The user enters the electricity consumption of the boiler or CHP while operating in kW
according to the manufacturer specification. This figure will be added to an hourly electrical
energy demand load profile for later calculation.
Conversion technology
The user enters the biomass conversion technology of boiler or CHP for reference purposes only.
This information helps make the decision on eligibility and tariff level of renewable heat
incentives.
Power generation technology
The user enters the power generation of CHP for reference purposes only.
Rated thermal output (kWth)
The user enters rated thermal output of boiler or CHP in kWth according to the manufacturer
specifications. This figure will be used to calculate the thermal energy supply by the boiler or
CHP, and biomass fuel used at different operating capacities, and the renewable heat incentive
tariff incomes.
Efficiency at 75-100%, 50-75%, 25-50%, and 0-25% Load
67
The user enters the thermal efficiency in percentage at range of the operating capacity of boiler
or CHP. These figures will be used to calculate the thermal energy supply by the boiler or CHP,
and the biomass fuel used at different operating capacities. Normally, the efficiency would be
lower when the operating capacity is turned down.
Rated power output in kWe
The user enters rated power output of CHP in kWe according to manufacturer specification. This
figure will be used to calculate the electrical energy supply by CHP, and help make the decision
on eligibility and tariff level of feed in tariff, as well as eligibility and banding of renewable
obligation certificate.
Heat to power ratio at 75-100%, 50-75%, 25-50%, and 0-25% load
The user enters heat to power ratio at range of operating capacity of CHP. These figures will be
used to calculate the electrical energy supply by CHP at different operating capacity. Normally,
the heat to power ration would be higher when the operating capacity is turned down.
Thermal storage size (m3)
The user enters the size of the thermal storage in cubic metre (m3) to help increase the
performance of the boiler or CHP. This figure will be used to calculate the amount of heat
absorbed from the boiler or CHP, and release it to the load. When the size of the thermal storage
is in other units rather than cubic metre, the user has to convert the unit by these formulas.
68
Thermal storage min temp (°C)
The user enters the minimum temperature in Celsius that the thermal storage can handle and
operate. This temperature represents the limitation of temperature when the thermal storage
supplies heat to the load and losses its temperature. This figure is entered to help with the
calculation as said before in the limitation of this tool, this tool provides basic calculation for the
thermal storage system. Therefore it does not represent the thermal storage in real practice, but
the simple one.
When the temperature is in other units rather than Celsius, the user has to convert the unit by
these formulas.
Convert from Fahrenheit
Convert from Kelvin
Thermal storage max temp (°C)
The user enters the maximum temperature in Celsius that thermal storage can handle and
operate. This temperature represents the limitation of temperature when the thermal storage
absorbs heat from the boiler or CHP and increases its temperature. In practice, the maximum
temperature largely depends on the insulation of the thermal storage.
When the temperature is in other units rather than Celsius, the user has to convert the unit by
above formulas.
Fluid type
The user enters the type of fluid in the thermal storage for reference purposes only.
69
Specific heat capacity (kWh / kg·C)
The user enters the specific heat capacity at constant pressure of the fluid in the thermal storage.
The specific heat capacity of fluid is the heat required to increase or decrease the fluid
temperature by one degree of temperature. This figure will be used to calculate the amount of
heat absorb from the boiler or CHP, and releases it to the load.
This tool calculates energy based on kWh unit. When there is information on specific heat
capacity in the Joules unit, the user can convert it to kWh by formulas mentioned before in the
energy demand section in this chapter.
Density of fluid (kg/m3)
The user enters the density of fluid in the thermal storage. This figure will be used to calculate
the amount of heat absorbed from the boiler or CHP, and releases it to the load.
Average temp drop (°C / hour)
The user enters the average temperature drop in the thermal storage in Celsius per hour
throughout the year. This figure represents the heat loss in the thermal storage per hour.
Initial temperature (°C)
The user enters the initial temperature of the fluid in the thermal storage in Celsius. This figure
represents the temperature at the start of the calculation. In other words, it shows the temperature
of the fluid in the thermal storage right before the 00:00am on the 1st of January since the
calculation will always start at 00:00am on the 1st of January in this tool.
70
Initial cost (£)
The user enters the initial cost, which is the sum of the design, purchase, construction,
installation and grid connection costs of all the elements of the new biomass boiler or CHP
system.
Operation and maintenance cost (£)
The user enters the operating and maintenance (O&M) costs, which are the sum of the annual
costs to operate and maintain the new biomass boiler or CHP system.
3.6.4 Comparing Biomass Boiler and CHP
After choosing the wood fuel and biomass boiler or CHP (the method of choosing biomass boiler
and CHP, and their operation mode is described in the previous chapter), the tool will calculate
the technical and economic outcomes based on the entered parameter. The technical outcomes
are biomass fuel used, thermal and electrical energy supply-demand matching, and CO2
emissions.
Biomass fuel used
-
Annual biomass fuel consumption
Annual biomass fuel consumption is the sum of hourly biomass fuel consumption for one year.
Biomass fuel used per hour is calculated from the lower calorific value of wood fuel, the thermal
output, and the efficiency of that of the thermal output of biomass boiler or CHP.
The equation used for calculate biomass fuel consumption every hour is
Thermal energy output depends on the specification and operation mode at that hour of biomass
boiler or CHP.
71
Efficiency depends on the thermal energy output at that hour compared to the rated thermal
output. For example, the boiler rated thermal output is 100 kW, and the boiler thermal output is
70 kW at one particular hour. Therefore its operating capacity is 70% of rated thermal output at
that hour. If the user enters the thermal efficiency of the biomass boiler and CHP specification
like the following table, the tool will take the thermal efficiency of this boiler at 50-75% load
from this table, which is 77%.
Figure 25: Thermal efficiency at range of operating capacity
-
Efficiency at 75-100% Load (%)
94
Efficiency at 50-75% Load (%)
77
Efficiency at 25-50% Load (%)
64
Efficiency at 0-25% Load (%)
40
Surplus and deficit biomass fuel
The tool to calculate the annual surplus and deficit biomass fuel is by comparing the annual
biomass fuel consumption with the biomass fuel available at the site. If there is surplus biomass
fuel, the tool will add it to the following year. If there is deficit biomass fuel, the tool will
calculate the cost of purchasing this shortfall of wood waste fuel based on the price per kg
delivered input in the wood fuel section.
Thermal energy supply-demand matching
-
Annual thermal energy generated
Annual thermal energy generated is the sum of hourly thermal output of the biomass boiler or
CHP for one year. The hourly thermal output based on specification and operation mode of the
biomass boiler or CHP.
72
-
Thermal Storage
Before the description of the annual thermal energy delivered to the load of biomass boiler or
CHP operate with thermal storage, it is essential to explain how the thermal storage works in this
tool and all the calculations involved.
Thermal energy storage would help increase the efficiency of the biomass boiler and CHP by
storing excess thermal energy when thermal energy supply exceeds the thermal energy demand,
as well as releasing thermal energy when the thermal energy supply is less than the thermal
energy demand. Thermal storage allows the biomass boiler or CHP to be operated at maximum
efficiency and output, resulting in clean combustion, which extends lifetime of the boiler.
The thermal storage system simulated in this tool is sensible for heat storage systems. In this
system, the thermal energy is stored or released by heating or cooling a liquid or a solid. This
liquid or solid will not change its phase during the process in this system.
The thermal storage system capacity is given by
Where V is volume,
is density, c is specific heat capacity, and
is temperature difference
between maximum temperature and minimum temperature of the medium.
If the user chooses to couple the biomass boiler or CHP with thermal storage, the user has to
enter the volume of the thermal storage (V) in m3, the specific heat capacity (c) in kWh/ kg·C
and density ( ) in kg / m3 of the liquid medium. Then from the above equation
Where
is the temperature at time considered, and
It can be derived to
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is the temperature at 1 hour before.
At every hour the tool will calculate using this equation and below algorithm.
When the thermal energy supply from biomass boiler or CHP > thermal energy demand, the
thermal storage will store energy so Q is > 0. Then the temperature at next hour is
| |
This temperature can be increased until it reaches the maximum temperature set by the user. The
thermal energy supply from biomass boiler or CHP will be deducted by this Q.
When the thermal energy supply from biomass boiler or CHP < thermal energy demand, the
thermal storage will release energy so Q is < 0. Then the temperature at next hour is
| |
This temperature can be decreased until it reaches the minimum temperature set by the user.
Then thermal energy supply from biomass boiler or CHP will be added by this Q.
Moreover, the thermal storage can be set to loss its temperature due to heat loss. The user can set
temperature loss of thermal storage per hour.
-
Annual thermal energy delivered to load
Annual thermal energy delivered to the load is the sum of the hourly thermal energy delivered to
the load of the biomass boiler or CHP with or without thermal storage for one year. The
explanation of how the thermal storage works and all the calculation involved in this tool is
described before. Hourly, thermal energy delivered to the load is calculated by the following
algorithm and equations.
If thermal energy supply by the system is more than or equal to thermal energy demand at that
particular hour, then
74
But if thermal energy supply by the system is less than thermal energy demand at that particular
hour, then
-
Annual thermal energy surplus and deficit
Annual thermal energy surplus and deficit is the sum of hourly thermal energy surplus and
deficit of the biomass boiler or CHP with or without thermal storage for one year. Hourly
thermal energy surplus and deficit is calculated by the following algorithm and equations.
If thermal energy supply by the system is more than thermal energy demand at that particular
hour, then
But if thermal energy supply by the system is less than thermal energy demand at that particular
hour, then
Electrical energy supply-demand matching
-
Annual electrical energy generated
Annual electrical energy generated is the sum of hourly electrical energy generated for one year.
Electrical energy generated per hour is calculated from the thermal output, and the heat to power
ratio at that thermal output of biomass CHP.
75
The equation used for calculate electrical energy generated every hour is
Thermal energy output depends on the specification and operation mode at that hour of biomass
CHP.
Heat to power ratio depends on the thermal energy output at that hour compared to the rated
thermal output. For example, the CHP rated thermal output is 100 kW, and the boiler thermal
output is 80 kW at one particular hour. Therefore its operating capacity is 80% of the rated
thermal output at that hour. If the user enters the heat to power ratio in the biomass CHP
specification like the following table, the tool will take the heat to power ratio of this boiler at
75-100%load from this table, which is 3.2.
Figure 26: Heat to power ratio at range of operating capacity
-
Heat to Power Ratio at 75-100% Load
3.2
Heat to Power Ratio at 50-75% Load
10
Heat to Power Ratio at 25-50% Load
20
Heat to Power Ratio at 0-25% Load
30
Annual electricity delivered to real load
Real load is the electrical demand at the site excluding electrical energy consumed by CHP.
Annual electricity delivered to real load is the sum of hourly electricity delivered to real load in
one year. Hourly, electricity delivered to the real load and is calculated by following algorithm
and equations.
If electrical energy supply by the CHP is more than or equal to the electrical energy demand at
that particular hour, then
76
Therefore
But if the electrical energy supplied by the CHP is less than the electrical energy demand at that
particular hour, then
Therefore,
-
Annual electricity energy surplus and deficit
Annual electrical energy surplus and deficit is the sum of hourly electrical energy surplus and
deficit of the biomass CHP for one year. Hourly electrical energy surplus and deficit is calculated
by the following algorithm and equations.
If electrical energy supplied by the system is more than the electrical energy demand at that
particular hour, then
77
But if electrical energy supplied by the system is less than electrical energy demand at that
particular hour, then
CO2 Emissions
-
Annual CO2 emission from biomass
The tool calculates amount of equivalent CO2 emission from biomass for one year by this
equation.
[
]
[
]
CO2 emission factor is entered in wood fuel section.
-
Annual CO2 emission reduction
The tool calculates the amount of equivalent CO2 emission reduction for one year by this
equation.
when,
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[
]
Annual CO2 emission reduction from imported electricity can be positive or negative value,
because the electricity consumption by boiler or CHP is also considered.
,and
(
)
Costs
The tool will take and show the initial and O&M cost from the biomass boiler specification
sector according to the manufacturers model selected for each case.
Savings, Grants, Renewable Heat Incentives (RHI), Renewable Obligation Certificate (ROC)
and Feed in Tariff (FIT)
-
Thermal supply fuel saving
This is the amount of money saving from installing new biomass boiler or CHP regarding to
thermal supply fuel.
When,
79
(
)
Thermal supply fuel cost indicates the amount of money spent on thermal supply fuel to be able
to deliver the same amount of thermal energy as to biomass fuel.
, and
[
]
[
-
]
Imported electricity saving
[
]
Annual imported electricity saving can be a positive or a negative value because the electricity
consumption by the boiler or CHP is also considered. The positive value means the user saves
some money from installing new biomass CHP system. The negative value means that the user
has to spend more money on electricity.
-
Grant
The user enters the grant or subsidy that is paid for the initial cost of the biomass boiler or CHP.
These total grants will deduct the initial cost of installing the new biomass boiler or CHP system.
80
-
Renewable Heat Incentive
The explanation of renewable heat incentives is provided in the literature review chapter. Firstly,
the user chooses the tiered tariff structure between the single and the double tiered tariff
structure. Then the user enters the tariff rate for tier 1, tier 2 (if the double tiered tariff structure is
chosen) and the tariff duration in years, if the renewable heat incentive is eligible for the new
biomass boiler or CHP system.
Secondly, the tool will calculate the annual tariff income for the tier 1 using the following
algorithm and equation.
If single tiered tariff is chosen, then
But if double tiered tariff is chosen, and
Then,
Or double tiered tariff is chosen, and
Then,
81
Thirdly, the tool will calculate the annual tariff income for tier 2 using the following algorithm
and equation.
If double tiered tariff is chosen, and
Then,
Or double tiered tariff is chosen, and
Then,
{
[
]}
Finally, the tool will calculate the total tariff incomes by the sum of Annual tariff income in Tier
1 and Tier 2.
-
Renewable Obligation Certificate
The explanation of renewable obligation certificate is provided in the literature review chapter.
The user has to enter the number of ROC per MWh, qualifying percentage and average ROC
price, if the renewable obligation certificate is eligible for the new biomass CHP system. Then
the tool will calculate the annual ROC income by
82
-
Feed-in tariff
The explanation of feed-in tariff is provided in the literature review chapter. The user has to enter
the tariff rate for generation, the tariff rate for exporting and the tariff duration for generation, if
feed-in tariff is eligible for the new biomass CHP system. Then the tool will calculate the annual
tariff income by
(
)
(
-
)
Loan
The loan can be applied to this tool, if the user wants to pay the initial cost in regular instalments,
or partial repayments. Rate of interest on loan and number of years to complete the repayment
has to be entered. Then the tool will calculate the annual repayment for that period by
where C is the values of initial cost subtracted by any grants
n is the number of years to complete the repayment
r is the rate of interest on loan
83
-
Financial parameters
The user enters the inflation rates of biomass fuel price, electricity price, conventional fuel,
operation and management cost, RHI, and FIT that will increase their value in percentage every
year for the project period.
Then user can enter discount rate (%), this value will be calculated in the results comparison
section.
3.6.5 Results
Most of the figures in this chapter are taken from the previous sections and are applied with
inflation rates involving every year throughout the project lifetime. The annual pre-tax cash flow
is calculated by
Then the tool calculates the cumulative cash flow from annual pre-tax cash flow. These two
parameters, cumulative cash flow and pre-tax cash flow, will be used to analyse economic
performance of each case in the results comparison section.
The bottom table in this sector contains the monthly biomass fuel used in weight and volume.
The monthly biomass fuel used in weight is taken from the sum of hourly biomass fuel used for
each month. Then it is divided by fuel density of the wood waste fuel to get the hourly biomass
fuel used in volume.
84
3.6.6 Results comparison
This section calculates and shows the economic, energy, and environmental performance
between seven cases. The following parameters are calculated to evaluate the mentioned
performance for each case.
-
Payback period
The tool calculates the payback period based on the cumulative cash flow. It will count the
number of years until the cumulative cash flow in the results section turns positive, and returns
the value.
-
Cumulative cash flow
The tool takes the cumulative cash flow at the 30th year in the results section.
-
Internal rate of return (IRR)
The tool calculates the internal rate of return from the pre-tax cash flow over the project lifetime
starting from the investment year (year zero). This tool uses a function in Microsoft Excel to
determine the internal rate of return. The calculation of IRR can be shown by this equation
∑
Alternatively, IRR is the rate that turns NPV to zero.
-
Net present value (NPV)
NPV is also calculated by using a function in Microsoft Excel using the discount rate, pre-tax
cash flow, and the initial cost at year zero. Since the investment year is at year zero and the
income starts to come at year one, the initial cost at year zero is added to the NPV result. The
calculation of NPV can be shown by this equation
85
∑
-
Profitability index (PI)
PI is calculated by using NPV divided by the initial cost at year zero.
-
Energy and environmental performance
Since this tool assumes the similar thermal and electrical demand profile for every year for 30
years, the total thermal and electrical energy generated, delivered to load, surplus, deficit, and
equivalent CO2 emission reduction over 30 years are calculated by an annual value of mentioned
parameters multiplied by 30.
86
4. The Case Study
4.1 Introduction: Background of Solway Precast
Solway Precast is one of the divisions of Barr Limited, and was established in 1945. This site is
located in Barrhill village, South Ayrshire, Scotland. Solway Precast site has an area of around
20 acres, including 10,000 square metres of factory area. Their product range includes
terracing/seating units for stadiums, pre-stressed flooring, box culverts, drainage channels, stair
flights and landings, bridge parapets, beams, railway products, as well as marine and sea
defence.
Figure 27: Solway Precast (Barr Ltd, n.d.)
The site has an on-site batching plant and mould making workshops to produce precast concrete.
The cement, wood, steel and aggregates have to be purchased to produce precast concrete at the
site.
Figure 28: Moulding Workshop (Barr Ltd, n.d.)
Figure 29: On-site Batching Plant (Barr Ltd, n.d.)
87
Solway Precast was chosen as a case study because the site has a large amount of wood waste as
their by-product. Moreover, the manufacturing of concrete produces large amounts of CO2
throughout the process. Replacement of biomass fuel can enhance the financial and
environmental performance at the site. Barr Limited is committed to improving and reducing
energy use by improving efficient use of all energy sources, investing in low carbon and
sustainable energy efficient technologies, and reducing their environmental impact on the
environment.
The site usually operates from Monday to Friday except for some periods that have high demand
for products. Electrical energy is imported from the grid, and thermal energy is supplied by
purchased kerosene and gas oil. Diesel is also purchased for the site for transportation purposes.
This study included a site visit to the Solway Precast site to collect data such as energy usage,
existing technology specification, specific fuel types and fuel usage figures.
4.2 Energy Demand
The energy demand at the Solway Precast site was conducted by gathering the measured data
and analysing the energy usage in the precast concrete process.
4.2.1 Electrical Energy Demand
Electricity is used in the office and the factory at the Solway Precast site. It rises and falls
throughout the day according to the process in the factory and the number of occupancts in the
office.
Following the order of the processes, the electricity is used to drive the motor which will in turn
run the conveyor belt for delivering the aggregate, slag, and admixture to the mixing and
batching machine. It is also used at the cement silo to expel the stored cement, as well as at the
water tank to pump the water into the mixing and batching machine. After that the mixing and
batching machine, using the electricity, mixes and batches the cement, aggregates, water and
admixture until the concrete is ready. The overall process mentioned so far is controlled by
computer.
88
Figure 31: Conveyor Belt
Figure 30: Cement Silo
After the concrete is ready, electricity is used in motors to move the overhead cranes and hoppers
to pour the concrete into moulds. At the moulding area, a vibrator is used to consolidate the
concrete and to make the concrete compact. Electricity is also used in mould making process to
cut, trim, weld, bend, and seam the material like timber and steel.
Figure 32: Vibrating Process
In the office, electricity is used in office appliances. The space heating in the office and the hot
water process in the factory use kerosene heaters which also consume electricity.
The electricity demand at the Solway Precast site is monitored every half an hour throughout the
year. Since the electricity consumption is measured for the whole site, these figures will be used
as an electrical energy demand profile to analyse in demand-supply matching with biomass CHP.
The table below shows the monthly electricity consumption in 2010.
89
Table 8: Monthly electricity consumption in kWh
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
40,409
41,582
48,450
42,344
34,909
37,306
39,469
43,050
44,059
50,305
55,666
45,849
4.2.2 Thermal Energy Demand
Thermal energy for space heating and hot water heating at the Solway Precast site use kerosene
and gas oil (propane). The amount of the mentioned fuel consumption has never been monitored
and measured except for the fuel quantity ordered per month.
Table 9: Monthly quantity of kerosene ordered in litres
Jan
Feb
Mar
Apr
May
Jun
Jul
11,000
15,000
8,000
7,000
6,000
6,000
6,000
Aug
0
Sep
Oct
Nov
Dec
3,000
9,000
9,000
14,000
Table 10: Monthly quantity of gas oil ordered in litres
Jan
5,000
Feb
0
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
5,000
5,000
3,000
4,500
3,000
4,500
1,000
4,000
10,000
1,000
Therefore, in order to predict the thermal energy demand profile, these fuels have to be analysed
in terms of time, duration, and frequency of use in a year.
Two kerosene heaters are used for heating hot water in two pre-stressed beds in the factory
during the casting process to increase the strength of the concrete. A kerosene heater also uses
for space heating in the office. Two kerosene heaters in the factory have a 36.6 kW thermal
output each. The kerosene heater in the office has a 26.4 kW thermal output.
Two kerosene heaters in the factory are turned on for 24 hours 5 days per week except during
sub-zero temperatures (such as winter), when they will be turned on at full potential 24 hours 7
days per week to prevent the water in the system from becoming too cold. These heaters are
operated at a temperature that ensures concrete achieves the minimum strength in an adequate
time. One of the heaters is most likely to operate at half potential during the summer as this will
90
provide sufficient heat whilst not curing the concrete too rapidly. The other operates at full
potential during the summer because the water pipe line is much longer, therefore losing more
heat.
Figure 34: Kerosene heaters in the factory
Figure 33: Kerosene tank
The kerosene heater in the office is controlled by thermostat and, the thermostat setting changes
throughout the year depending on the ambient temperature. At times during summer, the
kerosene heater in the office is turned off completely.
Figure 35: Kerosene heater in the office
Gas heaters are used occasionally when double casting. (2 units simultaneously cast, twice per
day) and are also used during winter. There are two gas heaters with a thermal output of 82.43
kW and 102.3 kW. However, the amount of fuel used varies depending on the number of precast
units required and the ambient temperature.
91
4.2.3 Fuel consumption and CO2 Emissions
The annual electricity imported from the grid at the Solway Precast site was 523,398 kWh in
2010. Assuming the average electricity import price is 10 pence per kWh (A National Statistic
Publication, 2011), then the annual electricity cost would be around £ 52,339.8. The CO2
emission from electricity consumption can be calculated by multiplying the total amount of
electricity consumption with the CO2 emission factor.
(
)
Where the CO2 emission factor is greenhouse gas emissions converted into kilograms of carbon
dioxide equivalent (kg CO2) per kWh. 0.59368 is based on Guidelines to Defra / DECC‟s GHG
Conversion Factors for Company Reporting (2011).
The kerosene and gasoil at the Solway Precast site were 94,000 and 46,000 litres respectively in
2010. Assuming the average kerosene and gas oil price is 48.83 and 53.63 pence per litre (A
National Statistic Publication, 2011), then the annual kerosene and gas oil cost would be around
£ 45,900 and £ 24,699 respectively.
This CO2 emission factor is 3.0122 kgCO2 per litre for kerosene, and 3.5865 kgCO2 per litre for
gas oil. Therefore, CO2 emissions from kerosene and gas oil in 2010 were 283,146.8 kgCO2 and
164,979 kgCO2 respectively.
So the total kgCO2 emission from electrical and thermal energy consumption is 758,855.92
kgCO2, and the total electrical and thermal energy consumption cost is £ 122,938 in 2010.
92
4.3 Wood Waste at Site
Woods are purchased for the site for the purpose of constructing moulds. Wood moulds can be
reused for a certain amount of time before disposal. In regards to the wood, there are three
suppliers: Rowan Timbers (located at Ayr) provides joiners timber which tends to be red and
yellow pine as well as plywood. Garnaburn (located at Colmonell) provides stacking timber for
the yard which is Douglas fir softwood or other soft pine. Lastly there is Penkiln Sawmill
(located outside Wigtown) which provides larger cuts of wood for different purposes. All the
sawmills are approved by Forest Stewardship Council (FSC) which means that the trees cut
down are from legally designated forest areas.
Figure 36: Wood waste at Solway Precast site
Wood wastage is in the form of solid pieces of wood removed from the mould or the process of
making the mould. However, there are some metal materials in the wood such as nails or metal
plates which must be taken out before using the wood in the biomass boiler or CHP. Wood waste
can be chipped by the chipper to make them suitable for some biomass boilers or CHPs that use
wood chips as fuel.
The average total amount of wood waste at the Solway Precast site is 150 tonnes per year. The
wood waste is a mixture of red pine, white pine, plywood, Douglas fir, and other soft pine. The
exact amount of each type of wood in wood waste is unknown because it has never been
monitored or recorded. It also depends on the shape of the mould, which depends on the precast
concrete product.
93
4.4 Biomass in Solway Precast
Since Solway Precast produces wood residues and wood waste, it has a very large potential to
replace conventional fuel boilers with biomass boilers and CHP. The following section will point
out all the parameters involved at the site that need to be used in the biomass boiler and CHP
tool. The thermal energy demand profile has to be generated from the tool based on the
knowledge of the heat usage at the site. Electrical demand profile will use the site‟s data
monitored over one year. Subsequently the biomass boilers and CHPs specification will be
entered in the tool to observe their economic and environmental performance.
4.4.1 Thermal Demand Profile
The thermal energy consumption at the site is supplied by three sources. Firstly, the two
kerosene heaters heat two pre-stressed beds in the factory. Secondly, two gas heaters are used to
cure the double casting process, and for space heating during winter in the factory. Thirdly, a
kerosene heater is used for space heating to provide a comfortable temperature in the office.
From these three sources of thermal supply, two kerosene heaters used to heat pre-stressed beds
consume the biggest proportion of thermal energy consumption. Due to the fact that they operate
all day, 5 days a week during summer, and all day, 7 days a week during winter. Two gas heaters
only operate occasionally depending on the type of precast product demand, and they also turn
on manually when the temperature becomes too low for the employees to work. The kerosene
heater in the office is also turned on and off manually during summer and it operates in
accordance with the thermostat during winter.
In this analysis, only two kerosene heaters in the factory will be focused on, this is because they
are the main thermal energy consumption at the site. Furthermore, these kerosene heaters‟
operations have a certain operation method hence thermal energy consumption can be more
accurately predicted. As for the gas heaters in the factory and the kerosene heater in the office,
they largely depend on the precast concrete product type ordered by the customer, and the human
factor. The prediction of these heaters might lead to a significantly inaccurate thermal energy
demand profile to use in the tool.
94
Input
As mentioned before, the two kerosene heaters will operate from Monday to Friday during
summer, and Monday to Sunday during winter when the temperature decreases to below zero.
Both heaters operate at full potential during winter but during summer, only one of them operates
at full potential while the other will operate at half potential. This method of operation was put to
the kerosene heaters‟ operator on site. The setting of the full potential operation and half
potential operation were found out by the operator experience to get enough strength for the
precast concrete product. Based on the specification of the two kerosene heaters in the factory,
the maximum thermal energy demand would be 73.2 kW during winter and 54.9 kW during
summer. In other words, two kerosene heaters operate at 75% potential in summer compared to
their potential during winter.
Data from the met office indicates that the minimum temperature in January, February, and
December was below zero in 2010 at the paisley climate station (the nearest climate station to
Barrhill) (Met Office, 2011). Therefore, the kerosene heaters operate 7 days a week for these
three months. In the summer season between June and September assumption was made due to
the higher maximum and minimum temperatures in this period.
According to the above kerosene heaters usage characteristic can be summarised as:
1. In January, February, and December, two kerosene heaters operate at full potential seven
days a week.
2. From June to September, only one operates at full potential, and the other operates at half
potential for five days a week.
3. Two kerosene heaters operate at full potential for five days a week for the rest of the year.
This table shows the settings in thermal demand section of the tool.
95
Figure 37: Thermal demand settings of the tool for Solway Preacast
Monthly Thermal Demand Information
Month
January
Demand Characteristic
Maximum Demand
Operating Capacity (%)
Weekly Start Date
Weekly Start Time
Daily Interval Start Time
Daily Interval End Time
Weekly End Date
WEekly End Time
February
Constant
March
April
May
June
July
August
September
October
November
December
Constant
Constant
Constant
Constant
Constant
Constant
Constant
Constant
Constant
Constant
Constant
100%
Monday
0:00
0:00
23:59
Sunday
23:59
100%
Monday
7:00
0:00
23:59
Friday
18:00
100%
Monday
7:00
0:00
23:59
Friday
18:00
100%
Monday
7:00
0:00
23:59
Friday
18:00
75%
Monday
7:00
0:00
23:59
Friday
18:00
75%
Monday
7:00
0:00
23:59
Friday
18:00
75%
Monday
7:00
0:00
23:59
Friday
18:00
75%
Monday
7:00
0:00
23:59
Friday
18:00
100%
Monday
7:00
0:00
23:59
Friday
18:00
100%
Monday
7:00
0:00
23:59
Friday
18:00
100%
Monday
0:00
0:00
23:59
Sunday
23:59
73.2 kWth
100%
Monday
0:00
0:00
23:59
Sunday
23:59
The hourly thermal demand profile is generated by the tool. The table below shows the graph
result of the hourly thermal demand.
Figure 38: Hourly thermal demand profile of pre-stressed beds in Solway Precast for one year
The annual thermal energy demand for two pre-stressed beds is 431,971.50 kWh with a
maximum and minimum thermal load of 73.2 kWth and 54.9 kWth respectively. The number of
demand hours is 6,374 hours per year.
The amount of kerosene used is calculated by the tool with the assumption of 70% efficiency of
the kerosene heaters. The lower heating value of the kerosene is 10 kWh per litre (Biomass
Energy Centre, 200-). The kerosene price is £ 0.48 per litre, and the CO2 emission factor is 3.01
kgCO2 per litre (AEA Technology, 2011). Therefore the total amount of kerosene used for two
96
pre-stressed beds is 61,710.21 litres with the cost of £ 29,620 per year. The total amount of
equivalent CO2 emission is 185,883.51 kgCO2 per year.
It is assumed that the gas heaters in the factory and the kerosene heater in the office at the site
have 70% efficiency, using 6.6 kWh per litre as the lower heating value of the propane (Biomass
Energy Centre). The pie graphs below shows the proportion of thermal energy usage by type of
demand and by type of fuel.
Figure 39: Thermal Energy Usage by Type of Demand (kWh)
26%
Pre-stressed beds
50%
Double Casting
24%
Space heating in the
office
Figure 40: Thermal Energy Usage by Type of Fuel (kWh)
24%
Kerosene
76%
97
Gas oil (Propane)
4.4.2 Electrical Demand Profile
The electrical energy consumption at the site is supplied by the grid. The half hourly energy
consumption was monitored in 2010. Therefore, the monitored data has been converted to hourly
energy consumption and entered into the tool.
This table shows the setting in electrical demand section in the tool.
Figure 41: Electrical demand settings of the tool for Solway Preacast
Monthly Electrical Demand Information
Month
January
Demand Characteristic
Maximum Demand
Operating Capacity (%)
Weekly Start Date
Weekly Start Time
Daily Interval Start Time
Daily Interval End Time
Weekly End Date
WEekly End Time
February
March
April
May
June
July
August
September
October
November
December
Variable
Variable
Variable
Variable
Variable
Variable
Variable
Variable
Variable
Variable
Variable
Variable
Fill manually Fill manually Fill manually Fill manually Fill manually Fill manually Fill manually Fill manually Fill manually Fill manually Fill manually Fill manually
0 kWe
100%
Monday
0:00
0:00
23:59
Sunday
23:59
100%
Monday
0:00
0:00
23:59
Sunday
23:59
100%
Monday
0:00
0:00
0:00
Sunday
0:00
100%
Monday
7:00
0:00
23:59
Friday
0:00
100%
Monday
7:00
0:00
0:00
Friday
0:00
75%
Monday
7:00
0:00
0:00
Friday
0:00
75%
Monday
7:00
0:00
0:00
Friday
0:00
75%
Monday
7:00
0:00
0:00
Friday
0:00
75%
Monday
7:00
0:00
0:00
Friday
0:00
100%
Monday
7:00
0:00
0:00
Friday
0:00
100%
Monday
0:00
0:00
0:00
Sunday
0:00
The hourly electrical demand profile is entered by the user. The table below shows the graph
result of the hourly electrical demand.
Figure 42: Hourly electrical demand at Solway Precast site for one year
98
100%
Monday
0:00
0:00
0:00
Sunday
0:00
The annual electrical energy demand for the site is 523,398.00 kWh with a maximum and
minimum electrical load of 186 kWe and 6 kWe respectively. The number of demand hours is
8,760 hours per year.
The imported electricity price is assumed to be £ 0.10 per kWh, and the CO2 emission factor is
0.59 kgCO2 per kWh (AEA Technology, 2011). Therefore the total cost for electricity at the site
is £ 52,339.80 per year. The total amount of equivalent CO2 emission is 310,730.92 kgCO2 per
year.
4.4.3 Wood Fuel
The wood waste characteristics are taken from the PHYLLIS database (Energy research Centre
of the Netherlands (ECN), n.d.). The table below shows the characteristics of plywood, white
pine, yellow pine, Douglas fir, and average mixed waste wood taken mainly from the PHYLLIS
database and also other sources.
Table 11: Wood fuel characteristics
Ash Content
Fuel Density (Dry
LHV (Dry Basis)
(Dry Basis) (%)
Basis) (kg/m3)
(kWh/kg)
Plywood
2.1
700-800*
4.91
White pine
0.1
450**
5.38
Yellow pine
1.3
450**
5.77
Douglas fir
0.54***
479
5.39***
1.4
432*****
4.44
Type of Wood
Mixed waste
wood****
*
**
***
****
*****
general plywood density taken from CES 2010 Edupack software
average value of plywood density taken from biomass energy centre website
average value of all Douglas firs listed in PHYLLIS database
typical mixed wood waste in PHYLLIS database
average soft wood density taken from biomass energy centre website
99
Mixed wood waste in the last row of the table represents the unknown types of wood waste at the
site. This data is entered into the wood fuel section in the tool. Wood fuel will be separated into
two cases.
The 1st case is a mixture of all the wood mentioned in the above table. They will be cut into
appropriate sizes and since the exact proportions of each type of wood is unknown, each will
have the same amount in weight. The table below shows the wood fuel setting in the tool for the
1st case.
Figure 43: Data entered in the wood fuel section for the 1st case
1st Wood Fuel Case
Name
Type
Available at Site
Type of Wood
PLywood
White Pine
Yellow Pine
Douglas Fir
Mixed Wood Waste
Wood waste pieces
Mixed Type of Wood
150,000.00
kg / year
Mass
Fuel Density (kg/m3)
Mositure Content
Ash Content (%)
Percentage
(%)
Dry Basis As Received Dry Basis As Received
(%)
20
25
2.1
1.58
750.00
1000.00
20
25
0.1
0.08
450.00
600.00
20
25
1.3
0.98
450.00
600.00
20
25
0.54
0.41
479.00
638.67
20
25
1.4
1.05
432.00
576.00
0
0
0
0
0
0
0
0
Lower Heating Value (kWh/kg)
Dry Basis
4.91
5.38
5.77
5.39
4.44
As Received
CO2 Emission
Factor (kg·CO2/kg)
3.51
3.87
4.16
3.87
3.16
0
0
0
0
0.07738
0.07738
0.07738
0.07738
0.07738
Price per kg (£)
0
0
0
0
0
The 2nd case is a mixture of all the wood mentioned in the above table. They will be chipped into
small wood chips and since the exact proportions of each type of wood is unknown, each will
have the same amount in weight. The assumption of softwood fuel density of 195 kg/m3 will be
used in this case (Food and Agricutural Organization of the United Nations, 2004) . The table
below shows the wood fuel setting in the tool for the 2nd case. Price per kg is £ 0.0085 per kg,
this price indicates the amount of money needed to chip wood fuels (E4tech, 2010).
100
Figure 44: Data entered in the wood fuel section for the 2nd case
2nd Wood Waste Case
Name
Type
Available at Site
Type of Wood
PLywood
White Pine
Yellow Pine
Douglas Fir
Mixed Wood Waste
Wood waste chips
Mixed Type of Wood
150,000.00
kg
Mass
Fuel Density (kg/m3)
Mositure Content
Ash Content (%)
Percentage
(%)
Dry Basis As Received Dry Basis As Received
(%)
20
25
2.1
1.58
195.00
260.00
20
25
0.1
0.08
195.00
260.00
20
25
1.3
0.98
195.00
260.00
20
25
0.54
0.41
195.00
260.00
20
25
1.4
1.05
195.00
260.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Lower Heating Value (kWh/kg)
Dry Basis
As Received
4.91
5.38
5.77
5.39
4.44
CO2 Emission
Factor (kg·CO2/kg)
3.51
3.87
4.16
3.87
3.16
0.00
0.00
0.00
0.00
Price per kg (£)
0.06141
0.06141
0.06141
0.06141
0.06141
0.0085
0.0085
0.0085
0.0085
0.0085
The CO2 emission factors of wood waste are 0.07738 and 0.06141 kgCO2 per kg for the 1st and
2nd case respectively (AEA Technology, 2011). Even though biomass or wood are considered as
neutral carbon emissions, emissions involved in the production, distribution, storage and
transport of biomass or wood must be considered. The prices are 0 and £ 0.0085 per kg for the 1st
and 2nd case respectively. There is no need to purchase this wood waste since it is the waste from
the precast concrete process. However, the cost of making wood chip has to be considered
(E4tech, 2010).
Subsequently, the tool calculates average characteristic value of two cases by using mass
percentage of each wood waste. The results are shown in the table below.
Figure 45: Wood waste summary for both cases
Name
Wood waste pieces
Wood waste chips
-
Mositure Content
Ash Content (%)
(%)
(%)
25.00
25.00
0
0
0.82
0.82
0
0
Fuel Density (kg/m3)
Lower Heating Value (kWh/kg)
682.93
260.00
0
0
3.71
3.71
0
0
CO2 Emission
Factor (kg·CO2/kg)
0.08
0.06
0
0
Available at
Site (kg)
150,000.00
150,000.00
0.00
0.00
Price per kg (£)
0.00
0.01
0
0
The only difference between these two cases is the fuel density, since both cases have the same
type and amount of wood.
The reason to have two cases is so that the performance of the boiler that is suitable for solid
pieces of wood and wood chips can be compared. Moreover, waste wood usually has a moisture
content of around 18-25%, and fresh wood usually has a moisture content of around 40%
(Department for Environment, Food and Rural Affairs, 2008). Therefore the 25% moisture
content will be used to see the range of biomass boiler and CHP performance. The moisture
content is used with the assumption that the user has to store the wood long enough in order for it
101
to reach the defined moisture content. The other moisture content value will not be used in this
analysis. However, the user can make use of this tool to implement different values of moisture
content.
The wood fuel characteristics of extra wood waste and wood chips that need to be purchased in
case of a shortfall in wood waste are assumed to be the same as wood waste, since the author did
not receive detailed information from the nearby wood suppliers. The price of wood chips is £
0.09 per kg delivered respectively (E4tech, 2010). As for the extra wood wastes that need to
purchase, the price is £ 0.0825 per kg delivered derived from the price of wood chips per kg
delivered subtracted from the price of chipping (£ 0.0075 per kg) (E4tech, 2010).
102
4.4.4 Biomass Boiler and CHP Specification
After specifying the wood fuel characteristics, many enquiries were sent to suitable biomass
boiler and CHP suppliers in the UK to obtain prices and specifications. Four suppliers sent their
prices and specifications, three of them supply biomass boilers, only one, however, supplied
supply biomass CHP suitable with Solway Precast energy demand. However, only one boiler
supplier provided enough boilers information to be used in this tool. There is also only one
biomass CHP supplier that their wood fired CHP is not too big for Solway Precast thermal
demand. Therefore, three biomass boilers and one biomass CHP will be used in the tool in this
analysis.
Biomass boiler and CHP specifications
1. Supplier:
FARM 2000 / TEISEN PRODUCTS LTD
Manufacturer boiler model: REFO 80
Conversion technology:
Combustion technology
Wood fuel type:
Woodchip, wood pellets, grain, rape mash, shredded
timber, and sawdust
Thermal efficiency:
85-94% (claimed by the manufacturer)
Maximum thermal output:
75 kWth (20%MC woodchip)
70 kWth (26%MC woodchip)
40 kWth (35-40%MC woodchip)
Woodchip size:
Wide range (can burn shredded pallets)
Suitable moisture content:
0-35%
Initial cost:
£ 22,350 (boiler, including auger and sluice valve)
+ £ 6,670 (10 m3 silo/feeder system)
+ ≈ 7,500 (installation cost)
+ ≈ 325 (delivery cost)
+ ≈ 700 (chimney cost)
O&M cost:
≈ 750 per year
All values mentioned above are approximate values from the REFO 80 boiler
specification and discussions with the supplier therefore they should be treated as
103
guidelines. The values may be amended due to specific site characteristics, fuel types,
user requirements and more detailed analysis of the particular projects.
REFO 80 boiler is an auto stoker boiler that has to be operated 24 hours per day, because
it is designed to operate continuously in order to reach high efficiency and reliability. It
cannot be turned on and off as often as oil and gas boilers. This model can modulate the
thermal output from 10-100% of maximum output. Therefore it is not necessary to couple
this boiler with thermal storage. However, it is better to operate at high thermal output
due to the production of smoke and tar at low temperature combustion.
Figure 46: REFO 80 (Teisen Products Ltd, n.d.)
Figure 47: REFO 80 composition (Teisen Products Ltd, n.d.)
104
2. Supplier:
FARM 2000 / TEISEN PRODUCTS LTD
Manufacturer boiler model: HT 45
Conversion technology:
Combustion technology
Wood fuel type:
Solid pieces of wood and straw
Thermal efficiency:
70% (claimed by the manufacturer)
Maximum thermal output:
54 kWth (20%MC woodchip)
Initial cost:
£ 4,650 (boiler)
+ ≈ 7,500 (installation cost)
+ ≈ 300 (delivery cost)
+ ≈ 700 (chimney cost)
O&M cost:
3. Supplier:
Can be neglected
FARM 2000 / TEISEN PRODUCTS LTD
Manufacturer boiler model: HT 50
Conversion technology:
Combustion technology
Wood fuel type:
Solid pieces of wood and straw
Thermal efficiency:
70% (claimed by the manufacturer)
Maximum thermal output:
85 kWth (20%MC woodchip)
Initial cost:
£ 5,435 (boiler)
+ £ 6,670 (accumulator tank)
+ ≈ 7,500 (installation cost)
+ ≈ 300 (delivery cost)
+ ≈ 700 (chimney cost)
O&M cost:
4. Supplier:
Can be neglected
FARM 2000 / TEISEN PRODUCTS LTD
Manufacturer boiler model: HT 80
Conversion technology:
Combustion technology
Wood fuel type:
Solid pieces of wood and straw
Thermal efficiency:
70% (claimed by the manufacturer)
Maximum thermal output:
195 kWth (20%MC woodchip)
105
Initial cost:
£ 8,950 (boiler)
+ £ 6,670 (accumulator tank)
+ ≈ 7,500 (installation cost)
+ ≈ 300 (delivery cost)
+ ≈ 700 (chimney cost)
O&M cost:
Can be neglected
All values mentioned above are approximate values from the HT 45, 50, and 80 boiler
specifications and discussions with the supplier therefore they should be treated as
guidelines. The values may be amended due to specific site characteristics, fuel types,
user requirements and more detailed analysis of the particular projects.
HT 45, 50, and 80 boilers are boilers that wood fuel has to be manually fed. These boilers
are able to be turned on and off in a day. Manufacturer suggests installing the boiler that
has a higher maximum thermal output than maximum thermal demand, so the
accumulator tank will have enough thermal energy to supply the load when the boiler is
turned off. Therefore the boilers usually operate at full potential and are coupled with the
accumulator tank in the water circuit to supply the thermal energy demand. This way the
boiler can operate at full potential resulting in complete combustion (less production of
smoke and tar).
The reason for choosing HT 45, 50, and 80 boilers is the difference in combustion
chamber size, and maximum thermal output. Combustion chamber size indicates the
amount of wood fuel that can be fed into the boiler at one time which affects the stoking
frequency of the boiler. Boilers that have a greater maximum thermal output can store
more energy in the accumulator tank which also affects the stoking frequency of the
boiler. This is the crucial parameter because there is thermal energy thermal demand
during the night during weekdays all year, and at the weekend during the winter. Since
wood fuels have to be manually fed to these boilers, a sufficient thermal energy supply at
night and during the weekend is crucial as there will be no one available to feed the wood
fuel into the boiler.
106
Figure 48: HT boiler with accumulator tank (Teisen Products Ltd, n.d.)
Figure 49: HT boiler composition (Teisen Products Ltd, n.d.)
5. Supplier:
Talbott‟s Biomass Generators Ltd.
Manufacturer CHP model:
BG 25
Conversion technology:
Combustion technology
Power generation Technology:
Heat engine
Wood fuel type:
Woodchip, wood pellets, and crops
Thermal efficiency:
62% (claimed by the manufacturer)
Maximum thermal output:
80 kWth (25%MC woodchip)
Maximum electrical output:
25 kWe (25%MC woodchip)
Heat to power ratio (100% load)
3.2
107
Initial cost:
£ 165,000 (boiler)
+ ≈ 10,000 (plumbing cost)
+ ≈ 3,000 (grid connection)
≈ £ 7,500 (delivery, installation, and
commissioning cost)
O&M cost:
≈ £ 6,010
All values mentioned above are approximate values from the BG 25 CHP specifications
and discussions with the supplier and therefore should be treated as guidelines. The
values may be amended due to specific site characteristics, fuel types, user requirements
and more detailed analysis of the particular projects.
The principle of the BG 25 CHP operation is that the wood fuel is burnt and the hot
gasses enter the air-to-air heat exchanger tubes on the shell side. The compressed air is
heated and passed into a turbo-compound heat engine which drives the generator. This
CHP is designed to operate at constant full power for 24 hours a day, 7 days per week.
Modulation of thermal and power output can be done but it is not an economical use of
the system since the loss of electrical output is much higher as the top temperature
declines. Shutting down the CHP over the weekend or at night is also not recommended
by the manufacturer due to thermal stresses induced in the CHP and the length of time
required to build up temperature and electrical power.
Figure 50: BG 25 CHP (Talbott’s Biomass Generators Ltd, n.d.)
108
Input
The previously mentioned biomass boiler and CHP specifications are entered in the biomass
boiler and CHP specification section in the tool. Some of the following assumptions have to be
made to be able to analyse and calculate the performance of each boiler and CHP.
-
REFO 80
The efficiency at different operation capacity will be 90% taken from the average of
efficiency range given by the supplier. Since the thermal output of this boiler can be
modulated, the boiler will operate following the thermal demand of two pre-stressed beds
at the site.
-
HT 45
HT 45 will operate at full potential without thermal storage because the maximum
thermal output is less than nominal thermal demand of two pre-stressed beds. HT 45 will
be turned on during office times (Monday to Friday from 7:00am to 18:00pm). The
thermal energy deficit will be supplied by the kerosene heaters. This method will be
compared with HT 50 and HT 80 with an accumulator tank.
-
HT 50, HT 80 + Accumulator Tank (Thermal Storage)
As HT 50 and 80 boilers are the boilers that wood fuel has to be manually fed. They can
only be operated when there are occupants at the site (until 18:00 pm). Two operation
methods of these boilers will be analysed.
109
1st operation method
HT 50 and HT 80 boilers will be operated at full potential during office time (Monday to
Friday from 7:00am to 18:00pm) and coupled with the accumulator tank. It is assumed
that the kerosene heaters can be automatically turned on during unoccupied periods on
site when the thermal supply from the boiler and accumulator tank is not enough. The
kerosene heaters will supply the thermal demand when needed. The graph below shows
the example of the 1st operation method for HT 50 and HT 80 boilers with an
accumulator tank in one day.
Figure 51: Example day of 1st operation method for HT 50 and HT 80 boilers with accumulator tank
The kerosene heaters need to supply the thermal energy in the blue section of the above
graph.
2nd operation method
HT 50 and HT 80 boilers will be operated at full potential for a few hours during the day
from Monday to Friday and coupled with the accumulator tank. The number of hours of
110
operation will only be enough to supply the thermal energy demand until around
18:00pm with the support of an accumulator tank. It is assumed that the kerosene heaters
cannot be automatically turned on during unoccupied period on site when the thermal
supply from the boiler and accumulator tank is not enough. Therefore, the kerosene
heaters will supply the thermal demand during unoccupied periods of time starting from
18:00pm to 7:00am of the next day. The graph below shows the example of the 2nd
operation method for HT 50 and HT 80 boilers with accumulator tanks in one day.
Figure 52: Example day of 2nd operation method for HT 50 and HT 80 boilers with accumulator tank
The kerosene heaters need to supply the thermal energy in the blue section of the above
graph. This method needs to use more kerosene than the first method, but it uses less
wood fuel with less stoking frequency, and provides less energy surplus.
The size of the accumulator tank is 15,000 litres which is the maximum size supplied by
TEISEN PRODUCTS LTD. The maximum accumulator size is chosen to be able to
minimise the stoking frequency, and have longer periods of supply without using the
boiler.
111
Water is used as the working fluid in the thermal storage with a specific heat capacity of
0.0012 kWh per kg °C. The assumptions of minimum and maximum temperature of the
thermal storage are 8.6 and 90°C. 8.6°C was the mean temperature at paisley climate
station in 2010. 90°C is the set temperature of the boiler control thermostat. Also the
temperature drop is assumed to be 0.1 °C per hour for 15,000 litres of thermal storage.
-
BG 25
BG 25 will operate 24 hours per day, every day in the year since it is designed to operate
at constant full power. It will operate without thermal storage in this case study because
the thermal output of the CHP will always exceed the thermal demand of two pre-stressed
beds at the site. However, the accumulator tank should be installed in practice to balance
other peak thermal demands at the site.
112
4.4.5 Financial Incentives and Parameters
Renewable Heat Incentives
Biomass boilers and CHP are eligible for the renewable heat incentive with the assumption that
the wood fuels, biomass boiler and CHP comply with waste incineration and environmental
permitting legislation. Since all the boilers and CHP installation capacities considered in this
analysis are between 45kWth and 1 MWth, they will receive 100 % of the biomass renewable heat
incentive tariff.
The installation capacity for all the biomass boilers and CHP considered is less than 200 kWth,
therefore they fall under the double tiered tariff structure with the following parameters
(Department of Energy and Climate Change, 2010).
Tier 1 tariff rate:
7.6
pence/kWh
Tier 1 tariff rate:
1.9
pence/kWh
Tariff duration:
20
years
Renewable Obligation Certificate
Biomass CHP is considered eligible for the support of renewable obligation certificate with the
claim that the biomass CHP is accredited under the Combined Heat and Power Quality
Assurance (CHPQA) programme by the supplier. Since the biomass CHP considered only
consumes wood fuel, it is assumed that it will be cleaned and the metal materials will be
removed from the wood waste.
Microgeneration stations (declared net capacity below 50 kWe) and dedicated biomass CHPs will
receive 2 ROCs/MWh. The length that ROCs can be issued for is twenty years, but not beyond
2037 (Office of Gas and Electricity Markets, 2011). Since the CHP only uses wood fuel, the
qualifying percentage is 100 %. The average ROC sale price of £ 46.87 per ROC will be used in
113
this analysis taken from the price on 28 July 2011 (Non-Fossil Purchasing Agency Limited,
2011).
Feed-in Tariff
Electricity generated from biomass is not eligible for the generation tariff and export tariff.
However, it might be eligible for the feed-in tariffs in the future.
Grants and Loan
Grants and loans will be neglected in this analysis. Nevertheless, users can make use of this
function provided by the tool.
Financial Parameters
Assume that all the long term inflation rates and long term discount rate are 4 %.
114
4.4.6 Results and Analysis
First of all, each case in the tool stated here will represent each boiler, CHP and their operation
mode.
1st Case: HT 45 boiler operates at full potential during office times (Monday to Friday from
7:00am to 18:00pm) all year without the thermal storage.
2nd Case: HT 50 boiler operates at full potential during office times (Monday to Friday from
7:00am to 18:00pm) and coupled with the thermal storage (accumulator tank) all year.
3rd Case: HT 80 boiler operates at full potential during office times (Monday to Friday from
7:00am to 18:00pm) and coupled with the thermal storage (accumulator tank) all year.
4th Case: REFO 80 operates following the thermal demand of two pre-stressed beds at the site
without thermal storage all year.
5th Case: BG 25 CHP operates at constant full potential without thermal storage all year.
6th Case: HT 50 boiler operates at full potential for a few hours during the day from Monday to
Friday all year with thermal storage supplying thermal energy demands until around 18:00pm.
7th Case: HT 80 boiler operates at full potential for a few hours during the day from Monday to
Friday all year with thermal storage supplying the thermal energy demands until around
18:00pm.
115
Thermal Energy Results and Analysis
After entering the required information into the tool, it calculates the thermal energy
performance per year of each biomass boiler and CHP. The calculations are performed for the
same hourly thermal energy demand profile for all cases. The table below shows the thermal
energy supply demand matching results and their wood fuel consumption for one year.
Table 12: Thermal energy demand-supply matching results
Thermal Energy
Generated (kWh)
1st Case
2nd Case
3rd Case
4th Case
5th Case
6th Case
7th Case
155,034
244,035
559,845
431,972
700,800
206,890
220,155
155,034
226,579
391,415
431,972
431,972
196,203
207,078
Surplus (kWh)
0
0
138,890
0
268,828
0
0
Deficit (kWh)
276,938
205,393
40,556
0
0
235,769
224,894
59,636
93,871
215,350
129,238
251,599
79,582
84,685
Delivered to Load
(kWh)
Wood Fuel
Consumption (kg)
The 1st case, which is HT 45 boiler, generates the lowest thermal energy per year (155,034 kWh)
out of seven cases. As a result, it has the highest thermal energy deficit without any energy
surplus. This is because HT 45 boiler can only operate during office hours, and it is not able to
supply the total demand during its operation. The maximum thermal output (54 kWth) of this
boiler is even less than the minimum thermal demand of the two pre-stressed beds during
summer (54.9 kWth). In the winter, it can only supply about 75% of the thermal energy demand
during its operation. Moreover, HT 45 boiler cannot operate out of office hours and during the
weekend, because it needs to be manually fed wood fuel. Kerosene heaters still need to be used
in this case to supplement the thermal energy supply to the two pre-stressed beds thermal
demand. Besides, the boiler needs to be fed wood fuel many times in one day because it operates
all day. This might cause an inconvenience in the usage of the boiler.
The 2nd case, which is HT 50 boiler with an accumulator tank, generates 155,034 kWh of thermal
energy per year. It supplies half of the thermal energy demand to the load in one year due to the
116
thermal energy stored in the accumulator tank being sufficient to supply during out of office
hours or the weekends. It can only supply thermal energy for about 1 hour after the boiler is
turned off in the winter, and 5 hours after the boiler is turned off in the summer. However, it can
supply all the thermal demand needed during its operation. Kerosene heaters also need to be used
in this case to supplement the thermal energy supply to the two pre-stressed beds thermal
demand. This case also has a high stoking frequency of wood fuel.
The 3rd case, which is HT 80 boiler with an accumulator tank, generates the second highest
thermal energy per year (559,845 kWh) out of seven cases, this is because it operates at its
maximum output (195 kWth) during office hours. However, it still has thermal energy deficit of
138,890 kWh per year. The energy stored in the accumulator tank is able to supply thermal
energy all night after the boiler is turned off in the summer and the winter. However, it can only
supply thermal energy for 17 hours during weekends after the boiler is turned off. Therefore the
kerosene heaters are also needed in this case to supply thermal energy during the weekend. This
case also has high stoking frequency of wood fuel. Extra wood fuel needs to be purchased,
because the amount of wood fuel available at site is not sufficient for this case.
The 4th case, which is REFO 80 boiler, provides no thermal energy deficit and surplus. This
boiler provides the best thermal energy performance out of seven cases. With the automatic
wood fuel fed system, it can operate all year round. Moreover, this boiler can modulate its
thermal output following thermal demand of two pre-stressed beds. Kerosene heaters are not
needed in this case, because the boiler can supply all the thermal energy needed from two prestressed beds. Furthermore, it has very low stoking frequency. Because wood chips only need to
be stored in the designated storage area once in a while, it depends on the size of the storage and
it will be automatically fed into the boiler.
The 5th case, which is BG 25 CHP, generates the highest thermal energy per year (700,800 kWh)
and consumes the highest amount of wood fuel out of seven cases. This is because BG 25 CHP
117
operates at constant full potential all year round. As a result, it also has the highest thermal
energy surplus. This thermal energy surplus needs to be dealt with by the heat dissipater or an
alternative way of utilising this heat. Kerosene heaters are not needed in this case, because the
boiler can supply all the thermal energy needed from two pre-stressed beds. Furthermore, it has a
very low stoking frequency. Because wood chips only need to be stored in the 25 m 3 fuel bunker
,it will be automatically fed into the boiler. However, extra wood fuel needs to be purchased,
because the amount of wood fuel available on site is not enough for this case.
The 6th case, which is the HT 50 boiler with an accumulator tank, generates 206,890 kWh of
thermal energy per year. This boiler has to operate from 7:00am to 17:00pm to be able to have
thermal energy stored in the accumulator tank in order to supply until 18:00pm during the winter.
This case seems to be quite similar to the 2nd case due to the fact that the thermal energy stored in
the accumulator tank can only supply thermal energy for about 1 hour after the boiler is turned
off in the winter. However, it only needs to operate until 15:00pm during summer. Hence, this
operation mode lowers the wood fuel consumption and stoking frequency compared to the 2nd
case. However, it does increase the amount of kerosene needed to be used compared to the 2nd
case during out of office hours and weekends.
The 7th case, which is the HT 80 boiler with an accumulator tank, generates 220,155 kWh of
thermal energy per year. This boiler only needs to operate from 7:00am to 12:00pm in order to
have thermal energy stored in the accumulator tank to supply until 18:00pm during the winter.
Also it only needs to operate until around 10:00am during summer. This case consumes much
less wood fuel than the 3rd case, because it operates for a few hours per day. Hence, this
operation mode lowers the wood fuel consumption and stoking frequency compared to the 3rd
case. However, it increases the amount of kerosene needed to be used compared to the 3rd case
during out of office hours and weekends.
118
Electrical Energy Results and Analysis
After entering the required information to the tool, it calculates the electrical energy performance
per year of each biomass boiler and CHP. The calculations are performed for the same hourly
electrical energy demand profile for all cases. The table below shows the electrical energy supply
demand matching results for one year.
Table 13: Electrical energy demand-supply matching results
Electrical Energy
1st Case
Generated (kWh)
2nd Case
3rd Case
4th Case
5th Case
6th Case
7th Case
0
0
0
0
219,000
0
0
0
0
0
0
143,761
0
0
Surplus (kWh)
0
0
0
0
13,919
0
0
Deficit (kWh)
523,398
523,398
523,398
552,973
379,637
523,398
523,398
Delivered to Real
Load (kWh)
There is only one CHP in this analysis. The 5th case, which is BG 25 CHP, is the only case that
can generate electricity giving the lowest electrical energy deficit out of seven cases. This CHP
generates 219,000 kWh of electrical energy per year. Since its electrical output is relatively low
(25 kWe) and the CHP consumes about 7 kWe when it operates, the CHP can only supply about
27% of the electrical energy demand at the site. The electrical energy surplus is assumed to be
exported to the grid. The 1st, 2nd, 3rd, 6th and 7th case consume the same amount of electrical
energy as before, because the low electricity consumption of boilers can be neglected. The 4 th
case, which is REFO 80, consumes about 4.64 kWe when it operates.
Energy Result Summary
In terms of matching thermal energy supply and demand, the 4th case, REFO 80 boiler, would be
the most suitable boiler for this analysis because it can supply thermal energy with no thermal
surplus and deficit. Therefore, there is no need to use kerosene heaters or to dissipate the extra
heat. All other boilers except for BG 25 CHP have to be manually fed the wood fuel.
Consequently REFO 80 and BG 25 are more convenient to be fed the wood fuel rather than other
119
boilers. As for the BG 25 CHP, it can supply thermal energy to the load without any thermal
energy deficit, but it produces a considerable amount of thermal energy surplus. Heat dissipaters
or the methodology to utilise this extra heat will have to be considered.
In terms of matching electrical energy supply and demand, the 5th case, BG 25 CHP, is obviously
the most suitable option. However, it is the only CHP in this analysis, and its capital cost is the
highest cost compared to other boilers. For that reason, a financial analysis has to be put in place
to determine the best option between biomass boilers and CHP.
Financial Results and Analysis
Economic performance is considerably important when choosing renewable technologies along
with energy performance. The tool calculates financial results over 30 years. The following table
shows the important financial parameters for seven cases.
Table 14: Financial results
Financial Parameters
1st Case
2nd Case
3rd Case
4th Case
5th Case
6th Case
7th Case
Initial Cost (£)
13,150
20,605
24,120
37,545
185,500
20,605
24,120
1
1
1
1
4
1
1
804,386
1,168,548
1,844,347
1,765,870
1,957,343
1,034,541
1,324,337
138%
131%
185%
107%
32%
118%
140%
427,936
632,790
1,023,183
944,130
1,030,086
561,607
742,015
33.54
31.71
43.42
26.15
6.55
28.26
31.76
Payback Time (Years)
Cumulative Cash Flow (£)
IRR
NPV (£)
Profitability Index
As for economic factors, every case can provide positive cumulative profit over 30 years, and the
period of payback times are within 4 years. The 3rd case has the highest profit with £ 1,957,343
with 4 years payback time. This is because it can provide the highest amount of thermal and
electrical energy delivered to load, but it has the highest initial cost and operation and
maintenance costs compared with the other boilers.
120
The other boilers have only 1 year payback time, but they give a smaller amount of profit over
30 years. The 3rd case and the 4th case, HT 80 with accumulator tank and REFO 80 respectively,
give the second and third highest profit. This indicates that the technology that can deliver more
energy to the load will have more economic benefits. However, one interesting point is
noticeable between the 3rd case and the 4th case: the 4th case delivers more thermal energy to the
load, but the 3rd case gives more profit over 30 years. This is mainly because the 3rd case has
more RHI incomes per year due to the bigger installation capacity of the boiler. The double
tiered tariff structure is more beneficial to the bigger size installed capacity of the boiler.
Nevertheless the capital costs of seven cases are different. So the profitability index (the amount
of profit created per unit of capital cost) has to be taken into account. From the above table, it
can be clearly seen that 3rd case has the highest profitability index. In other words, if the amount
of investment money from the 5th case is taken and invested in the 3rd case, it will make more
profit. In conclusion, the 5th case is the best option in terms of highest profit and NPV, but only if
there is unlimited investment fund and it only has to be chosen from these seven cases. However,
if there is limited investment funds, the 3rd case would be the best option in terms of profit per
investment fund.
Environmental Impact Results and Analysis
The environmental impact of using biomass boilers and CHP in this analysis is the reduction of
greenhouse gases. Greenhouse gases are released into the atmosphere by burning conventional
fossil fuels, one of the main issues in climate change. The use of biomass will reduce the amount
of greenhouse gases released into the atmosphere, since biomass is considered carbon neutral.
However, it is not completely carbon neutral because biomass consumes some amount of energy
to grow, store and transport biomass. This tool calculates the amount of equivalent CO2
emissions produced by biomass, and the amount of equivalent CO2 emissions produced by the
kerosene or imported electricity for the same amount of energy produced by biomass. The
amount of equivalent CO2 emissions produced by increasing electrical demand is also
considered. Finally, it calculates the amount of equivalent CO2 emissions reduced by using
biomass for seven cases. The table below shows the amount of CO2 emissions produced by
121
installing biomass boilers and CHP, and the amount of equivalent CO2 emissions reduction for
seven cases per year.
Table 15: Equivalent CO2 emission results for one year
Annual CO2 emission from
Biomass (kg CO2)
Annual CO2 emission
reduction (kg CO2)
1st Case
2nd Case
3rd Case
4th Case
5th Case
6th Case
7th Case
4,614
7,263
16,962
7,936
20,425
6,158
6,552
62,098
90,236
151,468
160,388
250,806
78,270
82,555
The 5th case, BG 25 CHP, can reduce more CO2 emissions (250,806 kgCO2) than other cases, but
it also produces large amounts of CO2 emissions from biomass. This is because it has the highest
biomass consumption out of the seven cases. In the meantime, it delivers not only more thermal
energy than other boilers to the pre-stressed beds, but also electrical energy to the site. Therefore
the large amount of energy produced from kerosene and imported electricity are replaced by
wood fuel. The 3rd case and the 4th case, HT 80 with accumulator tank and REFO 80
respectively, give the second and third highest CO2 emissions reduction because they also deliver
large amounts of thermal energy to the load.
From the above table, it is indicated that the technologies that generate more energy will emit
more equivalent CO2 emissions. However, the technologies that deliver more energy to the load
will reduce more equivalent CO2 emissions. Because the more fossil fuel energy production is
replaced by biomass, the less equivalent CO2 emissions will be released. The table below shows
the equivalent CO2 reduction over 30 year period.
Table 16: Table 15: Equivalent CO2 emission reduction results for 30 years
1st Case
2nd Case
3rd Case
4th Case
5th Case
6th Case
7th Case
1,862,962
2,707,090
4,544,069
4,811,611
7,524,186
2,348,121
2,476,665
Annual CO2
emission
reduction (kg
CO2)
122
4.5 Overall Results and Analysis
When considering energy, economic and environmental performance of biomass boilers and
CHP, it can be concluded that the 3rd, 4th and 5th cases are more suitable for this case study than
others. The 4th case, which is REFO 80 boiler, operates following the thermal load giving the
best energy performance without thermal energy surplus and deficit, while the 3rd and 5th case,
which are HT 80 boiler with the accumulator tank and BG 25 CHP, generate large amounts of
thermal energy surplus that has to be dealt with. This thermal energy surplus can be used in other
processes in the factory and space heating in the office, but the more accurate usage of gas
heaters in the factory and space heating in the office have to be measured and investigated
further. The BG 25 CHP in the 5th case can also generate electricity which will give the benefit
from using and exporting its generated electricity. The energy deficit in the 3rd case can be
supplemented by kerosene heaters, however, the HT 80 in the 3rd case needs to be manually fed
the wood fuel which could be an inconvenience of using this boiler at the site.
The financial and environmental analysis also indicates that the 3rd, 4th and 5th cases are more
suitable for this case study than the others. The BG 25 CHP in the 5th case gives the largest
amount of profit and equivalent CO2 reduction over 30 years, but the longest period of payback
time. The 3rd and the 4th case gives lower profit and equivalent CO2 reduction than the 5th case,
but their payback periods are only one year.
The best boiler or CHP suitable for this case study is difficult to define. The 3rd, 4th and 5th cases
have their advantages and disadvantages. The 3rd and 4th case, which is HT 80 boiler with
accumulator tank and REFO 80 boiler respectively, would be the best suitable technologies for
this case study, if the firm does not have the financial capacity to invest or want to wait for their
investment to be paid off. However, the large amount of energy surplus and stoking problem has
to be considered in the 3rd case. The 5th case, which is BG 25 CHP, would be the best suitable
technology for this case study, if the firm has the financial capacity to invest and really want to
commit to CO2 emissions reduction. The installation of BG 25 CHP will give the highest profit
over 30 years, but issue of the large amounts of energy surplus also has to be considered.
123
5. Conclusion
5.1 Conclusion
In line with the objectives mentioned this thesis has identified the precast concrete process and
its energy usage, investigated the feasibility of biomass energy production technologies,
evaluated the financial benefits and CO2 emissions reduction of biomass energy production
technologies, and created a scalable tool that can be adapted for other manufacturing processes.
The precast concrete process consumes both thermal and electrical energy. The amount of energy
used in the precast concrete varies depending on the type of product, product ordered, and the
technologies used. The majority of the thermal energy demand in this case study is from the
curing process in pre-stressed beds. In practice, there are other methodologies of curing the
concrete such as adding mineral admixture or chemical admixture. From the site visit, a rough
hourly thermal energy demand profile has been made based on the two kerosene heaters usage
for the two pre-stressed beds. Other thermal energy demand information has never been recorded
nor has certain patterns of usage. Hence only the thermal energy demand from two pre-stressed
beds was used in calculation of finding suitable a biomass boiler and CHP.
Wood waste at the Solway Precast site comes from the mould used in the process. There are
around 150 tonnes of wood waste at the site and they are all different sizes and types of wood.
Therefore the wood waste has to be cut or chipped into an appropriate size before using them in
the some of the biomass boiler or CHP. It is also essential to make sure that the wood wastage is
clean and does not contain any metal materials before being used in the biomass boiler or CHP.
The biomass boilers and CHP analysed in this tool are based on the manufacturer‟s specifications
and discussions. This is done by sending an enquiry of suitable biomass boilers and CHPs to the
suppliers. Then suppliers will send their quotation and specifications back. The boilers which are
used in this case study can be manually fed or automatically fed the wood fuel. As for the CHP,
the author could not find any supplier that could supply a suitable size of CHP for this thermal
demand except for one. Therefore only biomass boilers and CHP specifications received from
the supplier are analysed and calculated in the tool. The tool was created for the purpose of
124
analysing the economic and environmental performance between selected wood waste boilers
and CHPs at a particular site. It can be used in other manufacturing processes and different size
of boilers or CHPs.
For this case study, proper biomass boilers or CHP and their operation methods can demonstrate
economic and environmental benefits. One of the automatically fed wood fuel biomass boilers
analysed in this thesis can easily supply the thermal energy demand from the two pre-stressed
beds without thermal energy surplus or deficit. The manually fed wood fuel boiler can be used
with the supplementary kerosene heaters. However, it still gives a certain amount of thermal
energy surplus and deficit. The payback time for the boilers analysed in this tool is around 1
year. However, the boilers are not the best options in terms of long term profit.
Biomass CHP can give more long term profit than boilers in this analysis. Yet, it has a longer
payback time, around 4 years. The quantity of CO2 emission reduction from biomass CHP is also
more than boilers in this analysis. However, the initial cost of the biomass CHP is much more
expensive than boilers of the same size.
The best boiler or CHP suitable for this case study is not simple to define. It depends on the
financial capacity of the firm. Investing in biomass CHP obviously has more risks than boilers
due to the higher initial cost of the CHP. It also depends on the amount of commitment firms
have to achieving a reduction in CO2 emissions.
This analysis is based on the thermal and electrical energy demands at the Solway Precast site.
The energy efficiency and reduction at the site is not implemented in this analysis. If it were to
be implemented at the site, it could reduce the size of the thermal and electrical demand, which
in turn affects the size of the biomass boiler and CHP.
125
5.2 Further Investigation
Due to time constraints and limited information at the Solway Precast site, the results of this
study should be treated as a guideline. The tool provided would gain more specific results if
certain parameters had been clearly defined. Further investigation can be done on the Solway
Precast site includes:
-
Monitoring the use of kerosene and gas oil (propane) at the site to have a more accurate
thermal demand profile
-
Monitoring and recording the types of wood and the amount of wood wastage in more
detail at the site in order to have a more accurate wood fuel characteristic
-
Discussing in more detail specification and performance of the biomass boiler and CHP
with the supplier, a site visit by the supplier could help them to be more accurate on
specification and cost of their product
-
Evaluating the wood storage methods and their costs
-
Evaluating the price of wood chip and wood waste delivered to the site from nearby
sawmills from whom, since the author did not received any replies
-
Evaluating the utilisation of the thermal energy surplus on site, some of it could be used
to dry the wood fuel
-
Applying the energy efficiency scheme on site to decrease energy demand
-
Assessment of all the inflation and discount rates in order to have more acceptable
financial analysis
126
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Appendix 1: Financial Results
1st Case: HT 45 boiler operates at full potential during office times (Monday to Friday from 7:00am to 18:00pm) all year without the
thermal storage.
Table 17: 1st case financial result
Year
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Initial
costs
O&M
Costs
£
£
13,150
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass Fuel
Price (£ / kg)
At
Site
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Purchase
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.11
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.16
0.16
0.17
0.18
0.18
0.19
0.20
0.21
0.21
0.22
0.23
0.24
0.25
Biomass
Available
at Site
(kg)
150,000
240,364
330,729
421,093
511,458
601,822
692,187
782,551
872,916
963,280
1,053,645
1,144,009
1,234,374
1,324,738
1,415,103
1,505,467
1,595,832
1,686,196
1,776,561
1,866,925
1,957,290
2,047,654
2,138,019
2,228,383
2,318,748
2,409,112
2,499,477
2,589,841
2,680,206
2,770,570
Biomass Fuel
Consumption(kg)
At Site
Purchase
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
59,636
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass
Fuel
Cost
Conventional
Fuel Cost
Fuel
Saving
CO2
Reduction
£
£
£
kg CO2
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
10,631
11,056
11,498
11,958
12,437
12,934
13,451
13,990
14,549
15,131
15,736
16,366
17,020
17,701
18,409
19,146
19,911
20,708
21,536
22,398
23,294
24,225
25,194
26,202
27,250
28,340
29,474
30,653
31,879
33,154
133
10,631
11,056
11,498
11,958
12,437
12,934
13,451
13,990
14,549
15,131
15,736
16,366
17,020
17,701
18,409
19,146
19,911
20,708
21,536
22,398
23,294
24,225
25,194
26,202
27,250
28,340
29,474
30,653
31,879
33,154
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
62,099
RHI ( £ / kWh)
Tier 1
Tier2
0.0760
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0190
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Useful
Heat
Produced
RHI
Tariff
Electricity
Price
Rate
Electricity
Reduction
(+) or
Extra(-)
Electrical
Saving or
Cost
kWh
£
£ / kWh
kWh
£
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
155,034
6,990
7,270
7,561
7,863
8,177
8,505
8,845
9,199
9,566
9,949
10,347
10,761
11,191
11,639
12,105
12,589
13,092
13,616
14,161
14,727
0
0
0
0
0
0
0
0
0
0
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1st Case (continue)
FIT for generate
£ / kWh
Fit for export
£ / kWh
Electricity Generated
kWh
Electricity Exported
kWh
Feed-In Tariff Incomes
£
ROC Incomes
£
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
134
Pre-Tax Cash Flow
£
-13,150
17,621
18,326
19,059
19,821
20,614
21,439
22,296
23,188
24,116
25,080
26,083
27,127
28,212
29,340
30,514
31,734
33,004
34,324
35,697
37,125
23,294
24,225
25,194
26,202
27,250
28,340
29,474
30,653
31,879
33,154
Cumulative Cash Flow
£
-13,150
17,621
35,947
55,006
74,827
95,441
116,880
139,176
162,364
186,480
211,560
237,644
264,770
292,982
322,323
352,836
384,571
417,575
451,899
487,596
524,721
548,014
572,240
597,434
623,636
650,886
679,227
708,701
739,353
771,232
804,386
2nd Case: HT 50 boiler operates at full potential during office times (Monday to Friday from 7:00am to 18:00pm) and coupled with
the thermal storage (accumulator tank) all year.
Table 18: 2nd case financial result
Year
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Initial
costs
O&M
Costs
£
£
20,605
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass Fuel
Price (£ / kg)
At
Site
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Purchase
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.11
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.16
0.16
0.17
0.18
0.18
0.19
0.20
0.21
0.21
0.22
0.23
0.24
0.25
Biomass
Available
at Site
(kg)
150,000
206,129
262,259
318,388
374,517
430,647
486,776
542,905
599,034
655,164
711,293
767,422
823,552
879,681
935,810
991,940
1,048,069
1,104,198
1,160,327
1,216,457
1,272,586
1,328,715
1,384,845
1,440,974
1,497,103
1,553,233
1,609,362
1,665,491
1,721,620
1,777,750
Biomass Fuel
Consumption(kg)
At Site
Purchase
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
93,871
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass
Fuel
Cost
Conventional
Fuel Cost
Fuel
Saving
CO2
Reduction
£
£
£
kg CO2
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
15,537
16,158
16,805
17,477
18,176
18,903
19,659
20,445
21,263
22,114
22,998
23,918
24,875
25,870
26,905
27,981
29,100
30,264
31,475
32,734
34,043
35,405
36,821
38,294
39,826
41,419
43,075
44,798
46,590
48,454
135
15,537
16,158
16,805
17,477
18,176
18,903
19,659
20,445
21,263
22,114
22,998
23,918
24,875
25,870
26,905
27,981
29,100
30,264
31,475
32,734
34,043
35,405
36,821
38,294
39,826
41,419
43,075
44,798
46,590
48,454
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
90,236
RHI ( £ / kWh)
Tier 1
Tier2
0.0760
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0190
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Useful
Heat
Produced
RHI
Tariff
Electricity
Price
Rate
Electricity
Reduction
(+) or
Extra(-)
Electrical
Saving or
Cost
kWh
£
£ / kWh
kWh
£
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
226,579
10,671
11,098
11,542
12,004
12,484
12,983
13,503
14,043
14,604
15,189
15,796
16,428
17,085
17,769
18,479
19,218
19,987
20,787
21,618
22,483
0
0
0
0
0
0
0
0
0
0
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2nd Case (continue)
FIT for generate
£ / kWh
Fit for export
£ / kWh
Electricity Generated
kWh
Electricity Exported
kWh
Feed-In Tariff Incomes
£
ROC Incomes
£
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
136
Pre-Tax Cash Flow
£
-20,605
26,208
27,256
28,347
29,481
30,660
31,886
33,162
34,488
35,868
37,302
38,794
40,346
41,960
43,638
45,384
47,199
49,087
51,051
53,093
55,217
34,043
35,405
36,821
38,294
39,826
41,419
43,075
44,798
46,590
48,454
Cumulative Cash Flow
£
-20,605
5,603
32,860
61,206
90,687
121,347
153,233
186,395
220,883
256,750
294,053
332,847
373,194
415,154
458,792
504,176
551,376
600,463
651,514
704,607
759,823
793,866
829,271
866,092
904,386
944,212
985,630
1,028,706
1,073,504
1,120,094
1,168,548
3rd Case: HT 80 boiler operates at full potential during office times (Monday to Friday from 7:00am to 18:00pm) and coupled with the
thermal storage (accumulator tank) all year.
Table 19: 3rd case financial result
Year
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Initial
costs
O&M
Costs
£
£
24,120
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass Fuel
Price (£ / kg)
At
Site
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Purchase
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.11
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.16
0.16
0.17
0.18
0.18
0.19
0.20
0.21
0.21
0.22
0.23
0.24
0.25
Biomass
Available
at Site
(kg)
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
Biomass Fuel
Consumption(kg)
At Site
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
Purchase
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
65,350
Biomass
Fuel Cost
Conventional
Fuel Cost
Fuel
Saving
CO2
Reduction
£
£
£
kg CO2
Tier 1
Tier2
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
151,469
0.0760
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0190
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
5,228.03
5,437.16
5,654.64
5,880.83
6,116.06
6,360.70
6,615.13
6,879.74
7,154.93
7,441.12
7,738.77
8,048.32
8,370.25
8,705.06
9,053.26
9,415.39
9,792.01
10,183.69
10,591.04
11,014.68
11,455.27
11,913.48
12,390.02
12,885.62
13,401.04
13,937.08
14,494.57
15,074.35
15,677.32
16,304.42
26,840
27,913
29,030
30,191
31,399
32,655
33,961
35,319
36,732
38,202
39,730
41,319
42,972
44,690
46,478
48,337
50,271
52,281
54,373
56,548
58,810
61,162
63,608
66,153
68,799
71,551
74,413
77,389
80,485
83,704
137
21,612
22,476
23,375
24,310
25,283
26,294
27,346
28,440
29,577
30,760
31,991
33,270
34,601
35,985
37,425
38,922
40,479
42,098
43,782
45,533
47,354
49,248
51,218
53,267
55,398
57,614
59,918
62,315
64,808
67,400
RHI ( £ / kWh)
Useful
Heat
Produced
RHI
Tariff
Electricity
Price
Rate
Electricity
Reduction
(+) or
Extra(-)
Electrical
Saving or
Cost
kWh
£
£ / kWh
kWh
£
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
391,415
22,042
22,924
23,841
24,794
25,786
26,817
27,890
29,006
30,166
31,373
32,628
33,933
35,290
36,702
38,170
39,696
41,284
42,936
44,653
46,439
0
0
0
0
0
0
0
0
0
0
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3rd Case (continue)
FIT for generate
£ / kWh
Fit for export
£ / kWh
Electricity Generated
kWh
Electricity Exported
kWh
Feed-In Tariff Incomes
£
ROC Incomes
£
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
138
Pre-Tax Cash Flow
£
-24,120
43,654
45,400
47,216
49,105
51,069
53,112
55,236
57,445
59,743
62,133
64,618
67,203
69,891
72,687
75,594
78,618
81,763
85,033
88,435
91,972
47,354
49,248
51,218
53,267
55,398
57,614
59,918
62,315
64,808
67,400
Cumulative Cash Flow
£
-24,120
19,534
64,934
112,150
161,255
212,323
265,435
320,671
378,116
437,860
499,993
564,611
631,814
701,706
774,392
849,987
928,605
1,010,368
1,095,401
1,183,836
1,275,808
1,323,162
1,372,410
1,423,629
1,476,896
1,532,294
1,589,907
1,649,826
1,712,140
1,776,948
1,844,348
4th Case: REFO 80 operates following the thermal demand of two pre-stressed beds at the site without thermal storage all year.
Table 20: 4th case financial result
Year
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Initial
costs
£
37,545
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
O&M
Costs
Biomass Fuel Price
(£ / kg)
£
At Site
Purchase
750
780
811
844
877
912
949
987
1,026
1,067
1,110
1,155
1,201
1,249
1,299
1,351
1,405
1,461
1,519
1,580
1,643
1,709
1,777
1,849
1,922
1,999
2,079
2,163
2,249
2,339
0.0085
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.09
0.09
0.10
0.10
0.11
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.16
0.16
0.17
0.18
0.18
0.19
0.20
0.21
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
Biomass
Available
at Site
(kg)
150,000
170,762
191,525
212,287
233,050
253,812
274,575
295,337
316,100
336,862
357,625
378,387
399,150
419,912
440,675
461,437
482,200
502,962
523,725
544,487
565,250
586,012
606,775
627,537
648,300
669,062
689,825
710,587
731,350
752,112
Biomass Fuel
Consumption(kg)
At Site
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
129,238
Purchase
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass
Fuel Cost
Conventional
Fuel Cost
Fuel
Saving
CO2
Reduction
£
£
£
kg CO2
Tier 1
Tier2
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
160,389
0.0760
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0190
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1,098.52
1,142.46
1,188.16
1,235.68
1,285.11
1,336.52
1,389.98
1,445.58
1,503.40
1,563.53
1,626.08
1,691.12
1,758.76
1,829.11
1,902.28
1,978.37
2,057.51
2,139.81
2,225.40
2,314.41
2,406.99
2,503.27
2,603.40
2,707.54
2,815.84
2,928.47
3,045.61
3,167.43
3,294.13
3,425.90
29,621
30,806
32,038
33,319
34,652
36,038
37,480
38,979
40,538
42,160
43,846
45,600
47,424
49,321
51,294
53,346
55,479
57,699
60,007
62,407
64,903
67,499
70,199
73,007
75,927
78,964
82,123
85,408
88,824
92,377
139
28,522
29,663
30,850
32,084
33,367
34,702
36,090
37,534
39,035
40,596
42,220
43,909
45,665
47,492
49,392
51,367
53,422
55,559
57,781
60,092
62,496
64,996
67,596
70,300
73,112
76,036
79,077
82,241
85,530
88,951
RHI ( £ / kWh)
Useful
Heat
Produced
RHI
Tariff
Electricity
Price
Rate
kWh
£
£ / kWh
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
13,825
14,378
14,953
15,551
16,173
16,820
17,493
18,193
18,920
19,677
20,464
21,283
22,134
23,019
23,940
24,898
25,894
26,929
28,007
29,127
0
0
0
0
0
0
0
0
0
0
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
Electricity
Reduction
(+) or
Extra(-)
kWh
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
-29,575
Electrical
Saving or
Cost
£
-2,958
-3,076
-3,199
-3,327
-3,460
-3,598
-3,742
-3,892
-4,048
-4,209
-4,378
-4,553
-4,735
-4,925
-5,121
-5,326
-5,539
-5,761
-5,991
-6,231
-6,480
-6,740
-7,009
-7,289
-7,581
-7,884
-8,200
-8,528
-8,869
-9,224
4th Case (continue)
FIT for generate
£ / kWh
Fit for export
£ / kWh
Electricity Generated
kWh
Electricity Exported
kWh
Feed-In Tariff Incomes
£
ROC Incomes
£
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
140
Pre-Tax Cash Flow
£
-37,545
38,640
40,185
41,793
43,464
45,203
47,011
48,891
50,847
52,881
54,996
57,196
59,484
61,863
64,338
66,911
69,588
72,371
75,266
78,277
81,408
54,372
56,547
58,809
61,162
63,608
66,152
68,798
71,550
74,412
77,389
Cumulative Cash Flow
£
-37,545
1,095
41,280
83,073
126,537
171,740
218,751
267,642
318,490
371,371
426,367
483,563
543,047
604,910
669,248
736,160
805,747
878,119
953,385
1,031,662
1,113,070
1,167,442
1,223,989
1,282,799
1,343,960
1,407,568
1,473,720
1,542,519
1,614,069
1,688,482
1,765,870
5th Case: BG 25 CHP operates at constant full potential without thermal storage all year.
Table 21: 5th case financial result
Year
Initial
costs
O&M
Costs
Biomass Fuel Price
(£ / kg)
£
185,500
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
£
At Site
Purchase
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
6,010
6,250
6,500
6,760
7,031
7,312
7,605
7,909
8,225
8,554
8,896
9,252
9,622
10,007
10,407
10,824
11,257
11,707
12,175
12,662
13,169
13,695
14,243
14,813
15,405
16,022
16,663
17,329
18,022
18,743
0.0085
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.09
0.09
0.10
0.10
0.11
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.16
0.16
0.17
0.18
0.18
0.19
0.20
0.21
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
Biomass
Available
at Site
(kg)
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
Biomass Fuel
Consumption(kg)
Biomass
Fuel Cost
Conventional
Fuel Cost
Fuel
Saving
CO2
Reduction
£
£
kg CO2
Tier 1
Tier2
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
250,806
0.0760
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0190
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
At Site
Purchase
£
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
150,000
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
154,354
15,166.82
15,773.49
16,404.43
17,060.61
17,743.03
18,452.75
19,190.86
19,958.50
20,756.84
21,587.11
22,450.60
23,348.62
24,282.57
25,253.87
26,264.02
27,314.58
28,407.17
29,543.45
30,725.19
31,954.20
33,232.37
34,561.66
35,944.13
37,381.90
38,877.17
40,432.26
42,049.55
43,731.53
45,480.79
47,300.02
29,621
30,806
32,038
33,319
34,652
36,038
37,480
38,979
40,538
42,160
43,846
45,600
47,424
49,321
51,294
53,346
55,479
57,699
60,007
62,407
64,903
67,499
70,199
73,007
75,927
78,964
82,123
85,408
88,824
92,377
141
14,454
15,032
15,634
16,259
16,909
17,586
18,289
19,021
19,781
20,573
21,396
22,251
23,141
24,067
25,030
26,031
27,072
28,155
29,281
30,453
31,671
32,938
34,255
35,625
37,050
38,532
40,074
41,676
43,344
45,077
RHI ( £ / kWh)
Useful
Heat
Produced
RHI
Tariff
Electricity
Price
Rate
kWh
£
£ / kWh
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
431,972
14,199
14,767
15,358
15,972
16,611
17,276
17,967
18,685
19,433
20,210
21,018
21,859
22,734
23,643
24,589
25,572
26,595
27,659
28,765
29,916
0
0
0
0
0
0
0
0
0
0
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
Electricity
Reduction
(+) or
Extra(-)
kWh
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
143,761
Electrical
Saving or
Cost
£
14,376
14,951
15,549
16,171
16,818
17,491
18,190
18,918
19,675
20,462
21,280
22,131
23,017
23,937
24,895
25,891
26,926
28,003
29,123
30,288
31,500
32,760
34,070
35,433
36,850
38,324
39,857
41,452
43,110
44,834
5th Case (continue)
FIT for generate
£ / kWh
Fit for export
£ / kWh
Electricity Generated
kWh
Electricity Exported
kWh
Feed-In Tariff Incomes
£
ROC Incomes
£
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
219,000
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
13,919
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
14,781
15,372
15,987
16,627
17,292
17,983
18,703
19,451
20,229
21,038
21,879
22,755
23,665
24,611
25,596
26,620
27,684
28,792
29,943
31,141
0
0
0
0
0
0
0
0
0
0
142
Pre-Tax Cash Flow
£
-185,500
51,800
53,872
56,027
58,268
60,599
63,023
65,544
68,166
70,892
73,728
76,677
79,744
82,934
86,251
89,702
93,290
97,021
100,902
104,938
109,136
50,002
52,002
54,082
56,245
58,495
60,835
63,268
65,799
68,431
71,168
Cumulative Cash Flow
£
-185,500
-133,700
-79,827
-23,800
34,469
95,068
158,091
223,635
291,801
362,693
436,421
513,098
592,843
675,777
762,028
851,730
945,020
1,042,041
1,142,943
1,247,881
1,357,017
1,407,018
1,459,020
1,513,102
1,569,348
1,627,843
1,688,677
1,751,946
1,817,745
1,886,176
1,957,344
6th Case: HT 50 boiler operates at full potential for a few hours during the day from Monday to Friday all year with thermal storage
supplying thermal energy demands until around 18:00pm.
Table 22: 6th case financial result
Year
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Initial
costs
£
20,605
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
O&M
Costs
£
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass Fuel Price
(£ / kg)
At Site
Purchase
0
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.11
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.16
0.16
0.17
0.18
0.18
0.19
0.20
0.21
0.21
0.22
0.23
0.24
0.25
Biomass
Available
at Site
(kg)
150,000
220,418
290,835
361,253
431,670
502,088
572,505
642,923
713,340
783,758
854,175
924,593
995,010
1,065,428
1,135,845
1,206,263
1,276,680
1,347,098
1,417,516
1,487,933
1,558,351
1,628,768
1,699,186
1,769,603
1,840,021
1,910,438
1,980,856
2,051,273
2,121,691
2,192,108
Biomass Fuel
Consumption(kg)
At Site
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
79,582
Purchase
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass
Fuel Cost
Conventional
Fuel Cost
Fuel
Saving
CO2
Reduction
£
£
£
kg CO2
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
13,454
13,992
14,552
15,134
15,739
16,369
17,023
17,704
18,413
19,149
19,915
20,712
21,540
22,402
23,298
24,230
25,199
26,207
27,255
28,345
29,479
30,658
31,885
33,160
34,486
35,866
37,301
38,793
40,344
41,958
143
13,454
13,992
14,552
15,134
15,739
16,369
17,023
17,704
18,413
19,149
19,915
20,712
21,540
22,402
23,298
24,230
25,199
26,207
27,255
28,345
29,479
30,658
31,885
33,160
34,486
35,866
37,301
38,793
40,344
41,958
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
78,271
RHI ( £ / kWh)
Tier 1
Tier2
0.0760
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0190
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Useful
Heat
Produced
RHI
Tariff
Electricity
Price
Rate
kWh
£
£ / kWh
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
196,203
10,094
10,498
10,918
11,355
11,809
12,281
12,772
13,283
13,815
14,367
14,942
15,540
16,161
16,808
17,480
18,179
18,906
19,662
20,449
21,267
0
0
0
0
0
0
0
0
0
0
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
Electricity
Reduction
(+) or
Extra(-)
kWh
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Electrical
Saving or
Cost
£
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
6th Case (continue)
FIT for generate
£ / kWh
Fit for export
£ / kWh
Electricity Generated
kWh
Electricity Exported
kWh
Feed-In Tariff Incomes
£
ROC Incomes
£
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
144
Pre-Tax Cash Flow
£
-20,605
23,548
24,490
25,470
26,488
27,548
28,650
29,796
30,988
32,227
33,516
34,857
36,251
37,701
39,209
40,778
42,409
44,105
45,869
47,704
49,612
29,479
30,658
31,885
33,160
34,486
35,866
37,301
38,793
40,344
41,958
Cumulative Cash Flow
£
-20,605
2,943
27,433
52,903
79,391
106,939
135,589
165,385
196,372
228,600
262,116
296,973
333,224
370,925
410,134
450,912
493,321
537,426
583,295
630,999
680,612
710,091
740,749
772,634
805,794
840,280
876,146
913,447
952,239
992,583
1,034,541
7th Case: HT 80 boiler operates at full potential for a few hours during the day from Monday to Friday all year with thermal storage
supplying the thermal energy demands until around 18:00pm.
Table 23: 7th case financial result
Year
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Initial
costs
£
24,120
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
O&M
Costs
£
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass Fuel Price
(£ / kg)
At Site
Purchase
0
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.11
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.16
0.16
0.17
0.18
0.18
0.19
0.20
0.21
0.21
0.22
0.23
0.24
0.25
Biomass
Available
at Site
(kg)
150,000
215,315
280,630
345,945
411,260
476,575
541,890
607,205
672,520
737,835
803,150
868,465
933,780
999,095
1,064,410
1,129,725
1,195,040
1,260,355
1,325,670
1,390,985
1,456,300
1,521,615
1,586,930
1,652,245
1,717,560
1,782,875
1,848,190
1,913,505
1,978,820
2,044,135
Biomass Fuel
Consumption(kg)
At Site
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
84,685
Purchase
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Biomass
Fuel Cost
Conventional
Fuel Cost
Fuel
Saving
CO2
Reduction
£
£
£
kg CO2
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
14,200
14,768
15,358
15,973
16,612
17,276
17,967
18,686
19,433
20,210
21,019
21,860
22,734
23,643
24,589
25,573
26,596
27,659
28,766
29,916
31,113
32,358
33,652
34,998
36,398
37,854
39,368
40,943
42,580
44,284
145
14,200
14,768
15,358
15,973
16,612
17,276
17,967
18,686
19,433
20,210
21,019
21,860
22,734
23,643
24,589
25,573
26,596
27,659
28,766
29,916
31,113
32,358
33,652
34,998
36,398
37,854
39,368
40,943
42,580
44,284
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
82,556
RHI ( £ / kWh)
Tier 1
Tier2
0.0760
0.08
0.08
0.09
0.09
0.09
0.10
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.0190
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.04
0.04
0.04
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Useful
Heat
Produced
RHI
Tariff
Electricity
Price
Rate
kWh
£
£ / kWh
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
207,078
18,540
19,281
20,052
20,855
21,689
22,556
23,458
24,397
25,373
26,388
27,443
28,541
29,682
30,870
32,105
33,389
34,724
36,113
37,558
39,060
0
0
0
0
0
0
0
0
0
0
0.10
0.10
0.11
0.11
0.12
0.12
0.13
0.13
0.14
0.14
0.15
0.15
0.16
0.17
0.17
0.18
0.19
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
Electricity
Reduction
(+) or
Extra(-)
kWh
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Electrical
Saving or
Cost
£
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
7th Case (continue)
FIT for generate
£ / kWh
Fit for export
£ / kWh
Electricity Generated
kWh
Electricity Exported
kWh
Feed-In Tariff Incomes
£
ROC Incomes
£
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
146
Pre-Tax Cash Flow
£
-24,120
32,739
34,049
35,411
36,827
38,300
39,832
41,426
43,083
44,806
46,598
48,462
50,400
52,417
54,513
56,694
58,961
61,320
63,773
66,324
68,977
31,113
32,358
33,652
34,998
36,398
37,854
39,368
40,943
42,580
44,284
Cumulative Cash Flow
£
-24,120
8,619
42,668
78,079
114,906
153,206
193,038
234,464
277,546
322,352
368,950
417,412
467,813
520,229
574,742
631,436
690,398
751,717
815,490
881,814
950,790
981,903
1,014,261
1,047,913
1,082,911
1,119,309
1,157,163
1,196,531
1,237,473
1,280,054
1,324,337
Appendix 2: Monthly Biomass Consumption
Table 24: Monthly biomass consumption in kg
Month
Monthly Fuel Consumption (kg)
st
nd
rd
th
th
th
th
1 Case
2 Case
3 Case
4 Case
5 Case
6 Case
7 Case
January
4,798.26
7,552.81
17,327.05
16,293.62
25,849.21
6,866.20
7,875.93
February
4,569.77
7,193.16
16,501.95
14,716.81
23,347.67
6,539.23
7,500.89
March
5,255.24
8,272.13
18,977.24
10,796.71
25,849.21
7,520.12
8,626.02
April
5,026.75
7,912.47
18,152.14
10,293.01
25,015.36
7,193.16
8,250.97
May
4,798.26
7,552.81
17,327.05
9,745.51
25,849.21
6,866.20
7,875.93
June
5,026.75
7,912.47
18,152.14
7,818.31
25,015.36
5,754.53
4,950.58
July
5,026.75
7,912.47
18,152.14
7,719.76
21,849.21
5,754.53
4,950.58
August
5,026.75
7,912.47
18,152.14
7,703.33
21,849.21
5,754.53
4,950.58
September
5,026.75
7,912.47
18,152.14
7,818.31
25,015.36
5,754.53
4,950.58
October
4,798.26
7,552.81
17,327.05
9,767.41
25,849.21
6,866.20
7,875.93
November
5,026.75
7,912.47
18,152.14
10,271.11
25,015.36
7,193.16
8,250.97
December
5,255.24
8,272.13
18,977.24
16,293.62
25,849.21
7,520.12
8,626.02
Table 25: Monthly biomass consumption in m3
3
Month
Monthly Fuel Consumption (m )
st
1 Case
nd
rd
th
th
th
th
2 Case
3 Case
4 Case
5 Case
6 Case
7 Case
January
7.03
11.06
25.37
62.67
99.42
10.05
11.53
February
6.69
10.53
24.16
56.60
89.80
9.58
10.98
March
7.70
12.11
27.79
41.53
99.42
11.01
12.63
April
7.36
11.59
26.58
39.59
96.21
10.53
12.08
May
7.03
11.06
25.37
37.48
99.42
10.05
11.53
June
7.36
11.59
26.58
30.07
96.21
8.43
7.25
July
7.36
11.59
26.58
29.69
99.42
8.43
7.25
August
7.36
11.59
26.58
29.63
99.42
8.43
7.25
September
7.36
11.59
26.58
30.07
96.21
8.43
7.25
October
7.03
11.06
25.37
37.57
99.42
10.05
11.53
November
7.36
11.59
26.58
39.50
96.21
10.53
12.08
December
7.70
12.11
27.79
62.67
99.42
11.01
12.63
147
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