Renewable_Energy_in_the_home (PDF 1422KB)

Renewable_Energy_in_the_home (PDF 1422KB)
YOUR GUIDE TO
RENEWABLE ENERGY IN THE HOME
Who is Sustainable Energy Ireland?
Sustainable Energy Ireland (SEI) was set up by the government in 2002 as Ireland’s
national energy agency with a mission to promote and assist the development of
sustainable energy. SEI’s activities can be divided into two main areas:
•
Energy Use - Energy is vital to how we live our daily lives but most of us don’t use
energy as efficiently as we could. By assisting those who use energy (mainly
industry, businesses and householders), to be more energy efficient, SEI can help
to reduce the amount of energy we use overall.
•
Renewable Energy - Energy that is generated from renewable sources such as
wind and solar power is clean and doesn’t produce harmful greenhouse gases.
By promoting the development and wider use of renewable energy in Ireland
SEI can help to further benefit the environment, in particular reducing the threat
of climate change.
SEI is also involved in other activities such as stimulating research and development,
advising on energy policy and publishing energy statistics.
Sustainable Energy Ireland is funded by the National Development Plan 2000-2006
with programmes part financed by the European Union.
Did you know…
•
Energy use is responsible for two-thirds of Ireland’s greenhouse gas emissions.
•
Irish homes use around a quarter of all energy used in the country– that’s even
more than industry.
•
The average home consumes almost 40% more electricity than it did in 1990.
•
Renewable energy currently accounts for approximately 2% of Ireland’s energy
supply.
Introduction
Energy is essential to the comfort of our homes, providing space and water heating
and electricity. However, there are many ways in the design, construction and
operation of our homes of reducing energy needs and meeting those needs with
renewable sources, without compromising warmth and comfort.
Currently, we rely heavily on fossil fuels such as coal, oil, and gas to provide our
energy needs. Fossil fuels are non-renewable, that is, they draw on finite resources
that will eventually run out. In contrast, renewable energy resources, provided from
the sun, wind and water are constantly replenished and will never run out.
Fossil fuels are also damaging to the environment. They contribute significantly to
many of the environmental problems we face today such as greenhouse gases, air
pollution, and water and soil contamination - while renewable energy technologies
enjoy lower running costs and are clean sources of energy that have a much lower
environmental impact.
Energy is available from a variety of renewable sources appropriate to our homes,
including solar, geothermal, biomass, hydro and wind.
1
Solar Energy
A horizontal surface of 1m2 receives an average of between 1,000 and 1,100 kWh of
solar energy per year, similar to that of central Europe. This energy is provided by
both direct sunlight (40%) and indirect sunlight (60%) and can be harnessed in
many ways to heat your home, provide hot water and generate electricity.
Passive Solar Design
Passive solar design is a design approach that maximises the collection of solar heat,
minimises heat loss from the building and provides natural ventilation and daylight.
Unlike active solar heating systems,it doesn't involve the use of mechanical and electrical
devices,such as pumps,fans or electrical controls to collect or store the solar heat.Instead
energy costs are reduced and the comfort of your house increased by:
• selecting a sheltered location to build on
• constructing a compact building form with high levels of insulation
• positioning the house at an orientation that maximises passive solar heating and
daylight
Direct gain is the simplest passive solar design technique. It necessitates glazing to be
concentrated to the south façade and minimised to the north façade.Sunlight enters the
house through south-facing windows and is absorbed and stored in the masonry walls
and floors. At night, as the room cools, the heat stored in the thermal mass convects and
radiates into the room.This maintains a comfortable, even temperature in the home.
SOUTH
NORTH
South facing
sunroom
to
maximise
solar gain
north
Small
windows
facing
Deciduous
trees
let
radiation
solar
through
their
bare crown
during
the
winter and
shading
provide
during
the summer
circulates
Warm air
distribute
heat
freely to
within the building
Walls
and
floors
absorb
heat
the
during
day
2
A well designed sunspace or conservatory on the south façade can also reduce the
heating needs of a house by acting as a solar collector in late spring, summer and
early autumn, and by acting as a buffer against heat loss at other times. It is
important to choose a high performance glazing, at least double-glazing with a lowemmisivity coating, to limit heat loss through glazed areas. However, there are many
examples of sunspaces which are poorly designed from an energy point of view and
increase heating requirements. Fully glazed conservatories should not be heated
and should be separated from the heated space by closeable doors.They should not
be regarded as being habitable all year round, as the energy losses from heated
conservatories can negate the energy saved by passive solar collection.
Passive solar homes can look like any other home, and need not cost any more to
build, but they are more comfortable to live in and cost less to run.
Active Solar for Space and Water Heating
Introduction
Active solar energy systems generally
incorporate a roof mounted solar collector, which
receives direct and indirect sunlight and changes
it into heat. This heat may be used to provide for
hot water, or in a combined system, for space and
hot water needs. At the end of 2003, approx. 12
million m2 of solar thermal collectors were
installed in the EU. There is great potential to
increase this further.
How it works
Solar collectors can provide 50% of the annual hot water demand of a typical home,
depending on the orientation, size, mounted angle and efficiency of the collector.
The most common application is for water heating, and 4m2 of solar collector can
provide about 80% of hot water needs in summer and 20% in winter (when there is
less solar heat available) for a typical family. The solar water system needs to be
backed up with a conventional heat source to provide the remainder of the hot
water needs such as an electric immersion in the storage cylinder.
Installation in the Home
Solar water heating systems for homes have two main parts: a solar collector and a
hot water storage cylinder.Typically, a flat-plate collector (a thin, flat, rectangular box
with a transparent cover) is mounted on the roof, facing the sun. The sun heats an
absorber plate (usually a black metal plate) in the collector, which, in turn, heats the
fluid running through pipes within the collector. To move the heated fluid between
the collector and the storage cylinder, a system either uses a pump or gravity, as
3
Solar
Panel
Backup
Heater
Storage
Cylinder
water has a tendency to naturally circulate as it is heated. Systems that use fluids
other than water in the collector's pipes usually heat the water by passing it through
a coil of tubing in the storage cylinder. Evacuated tube collectors can also be used
instead of the flat plate. These consist of an array of evacuated glass tubes each
containing an absorber tube, which collects solar energy and transfers it to a heat
transfer fluid. During the manufacturing process, air is evacuated from the space
between the two tubes, forming a vacuum. This vacuum greatly reduces heat loss
from the system because there is no air to conduct the heat away.
The heat absorbed by the collectors is then transferred to the hot water storage
cylinder through a number of heat exchangers. Evacuated tube systems tend to be
more efficient than flat plate systems. However, a similar output could be achieved
with a flat plate system simply by increasing the area of the collector.
Ideally, panels need to face directly south. However, a good output can still be
achieved between south east and south west. A typical installation will take 2-3 days.
Today, solar thermal systems are readily available, easy to install and are reliable in
operation. Flat plate systems are imported from Northern Europe and evacuated
tube systems are manufactured in Northern Ireland. Generally systems come with a
10 year warranty. A professional installer will advise on an optimised solution for
your specific needs.
4
Payback and Maintenance
The payback period of a solar water heating system will vary depending on the cost of the
fuel you are replacing and the amount of hot water you consume. A typical correctly
installed system has a payback period of between 7 and 15 years and little maintenance
is necessary.Most systems are run by an electricity-powered pump,which will cost a small
amount to run per year.Generally systems come with a 10 year warranty and their lifetime
is about 25 years. For a list of suppliers, contact us (see back of booklet for details).
Active Solar for Electricity
Introduction
Photovoltaics (PV), which also collect sunlight, are a very different technology to solar
water heating,as they use the light to generate electricity.Today,the industry’s production
of photovoltaic (PV) modules is growing at approximately 25% annually, and major
programs in the U.S.A., Japan and Europe are rapidly accelerating the implementation of
PV systems on buildings and connection to electricity grid networks.
How it works
Photovoltaic solar cells, which directly convert sunlight into electricity, are made of
semi-conducting materials, such as crystalline silicon. The power output of a PV cell
depends on its efficiency and surface area, and is proportional to the intensity of
sunlight striking the surface of the cell.
Groups of PV cells are electrically
configured into modules and
Cells
Modules
arrays, which can be used to charge
batteries, operate motors, and to
power electrical loads. With the
appropriate power conversion
equipment, PV systems can
produce alternating current (AC)
compatible with any conventional
appliances, and operate in parallel
CELL
MODULE
ARRAY
with and interconnected to the
electricity grid network.
PV has the great advantages of being silent in operation with a low visual impact
making them particularly suitable for urban areas.
There are two general types of PV systems, stand-alone and grid-connected systems:
Stand-Alone Systems
Stand-alone systems produce power independently of the electricity grid network.
In some off-the-grid locations, stand-alone photovoltaic systems can be more cost5
effective than extending existing power lines. Direct-coupled systems need no
electrical storage because they operate only during daylight hours, but most
systems rely on battery storage so that energy produced during the day can be used
at night. Some systems, called hybrid systems, combine solar power with additional
power sources such as wind or diesel generators. As well as domestic applications,
stand-alone systems can be used to power traffic warnings, parking meters,
emergency telephones and buildings in remote locations.
Grid-Connected Systems
Grid-connected photovoltaic systems, supply surplus power back onto the grid and
electricity is drawn from the grid at periods when demand in the home exceeds the
PV output. Grid-connected systems are generally integrated into the structure of
buildings, but can also be ground mounted. These systems remove the need for
battery storage. In some cases, utility companies allow additional metering*, which
allows the owner to sell excess power back to the utility company.
Installation in the Home
A PV array produces power when exposed to sunlight. They can be installed on an
existing roof, be an integral part of the roof covering as panels or tiles installed within
roof glazing systems or installed on a nearby structure. It is important that nothing
casts a shadow over the area where the PV panels will be mounted. PV panels
generate more electricity on bright days but do not require direct sunlight, so normal
daylight is sufficient to produce electricity.The ideal orientation for PV panels is south
facing, although they still produce around 80% of the optimum output when facing
east or west.
Daylight hits the
PV and is converted
to clean electricity
The electricity is DC
(Direct Current), so the
converter makes it AC
(Alternating Current) in sync
with mains electricity so it
can be used normally
The solar system is
connected to the
mains via your fuse box
The PV roof generates
electricity all fay
6
* At time of print no utility company offered this option for domestic scale generation in ROI
A number of other components are required to properly conduct, control, convert,
distribute, and store the energy produced by the array. Depending on the
functional and operational requirements of the system, the specific components
required, may include major components such as a DC-AC power inverter, battery
bank, system and battery controller, auxiliary energy sources and sometimes the
specified electrical load.
Payback and Maintenance
PV is expensive, but with new materials and ongoing product development, it is
expected that the price of PV cells will become more competitive in the future. In
fact, the price has reduced by one third in the last ten years. Stand-alone systems
often provide the most effective solution when grid electricity is not available. For
installations in larger buildings, cost savings are possible when PV panels are
integrated in the building design, where they can substitute for other construction
materials providing the external skin of a building.
Today’s photovoltaic modules are extremely safe and reliable products, with
minimal failure rates. Most major manufacturers guarantee the high efficiency
operation of their PV modules for 20 or more years, with projected service lifetimes
in excess of this. PV panels have no moving parts and require minimum
maintenance.
7
Ground Source Heat Pumps
Introduction
Ground source heat pumps, also known as geothermal heat pumps, are used for
space heating and cooling, as well as water heating. They operate on the fact that
the earth beneath the surface remains at a constant temperature throughout the
year, and that the ground acts as a heat source in winter and a heat sink in summer.
They can be used in both residential and commercial or institutional buildings.
How it works
The earth’s surface acts as a huge solar collector, absorbing radiation from the sun.
In this country the ground maintains a constant temperature between 11oC and
13oC, several metres below the surface. Ground source heat pumps take advantage
of this by transferring the heat stored in the earth or in ground water to buildings in
winter and the opposite in summer for cooling. Through compression, heat pumps
can ‘pump up’ heat at low temperature and release it at a higher temperature so that
it may be used again. A heat pump looks similar and can perform the same functions
as a conventional gas or oil boiler, i.e. space heating and sanitary hot water
production. For every unit of electricity used to operate the heat pump, up to four
units of heat are generated. Therefore for every unit of electricity used to pump the
heat, 3-4 units of heat are produced.
Installation in the Home
The system has three main components: a series of pipes in the ground, a heat pump
and a heat distribution system. Lengths of plastic pipes are buried in the ground,
either in a borehole or a horizontal trench near the building to be heated or cooled.
Fluid, normally water with anti-freeze, absorbs or emits heat to the soil, depending
8
on whether the ambient air is colder or warmer than the soil. In winter, the heat
pump removes the heat from the fluid, upgrades it to a higher temperature for use
in the building, typically in under-floor heating.
A distribution system is needed to transfer the heat extracted from the ground by
the heat pump. The heat is often in the form of hot water and is distributed around
the dwelling by radiators or a low temperature underfloor heating system.
Payback and Maintenance
The initial capital costs of installing a ground source heat pump system is usually
higher than other conventional central heating systems. A large proportion of the
outlay will be for the purchase and installation of the ground collector. However, the
system is among the most energy efficient and cost effective heating and cooling
systems available. Typically, four units of heat are generated for every unit of
electricity used by the heat pump to deliver it, and the payback is typically about 810 years. The life expectancy of the system is around 20 years. Once installed a heat
pump requires very little maintenance and anyone installing a heat pump should
speak with their installer regarding a maintenance agreement. For a list of suppliers,
contact us (see back of booklet for details).
9
Biomass / Wood
Introduction
The words biomass or bioenergy are used to describe energy resources derived
from organic matter, such as residues from forestry, agriculture and industry, or from
purpose grown crops. These resources can be used to provide heat, electricity and
transport fuels. It provides about 1% of Ireland’s energy needs in the form of
domestic and industrial wood heating. Using wood fuel instead of fossil fuels (oil,
coal, gas or peat) makes a positive contribution to the environment. Wood, is a
‘carbon neutral’ fuel. It absorbs as much CO2 when it grows as is released when it
burns – a natural cycle. Wood fuel takes just 5-20 years to grow, whereas fossil fuels
such as peat and coal were formed over hundreds of thousands of years.
The main types of wood fuel are chips and pellets. Wood chips are a bulk fuel and,
as such, are generally unsuitable for domestic properties. However, they are usually
a cheaper fuel than pellets and are appropriate for larger buildings such as offices,
public buildings or to heat clusters of domestic properties through a district heating
system.Wood pellets are compressed wood, usually sawdust or wood shavings.They
are typically 6-12 mm in diameter and 6-20 mm in length. Pellets have the
advantage of uniformity in shape and composition, are easy to ignite, are dry, create
little ash and will flow freely through feeding mechanisms such as hoppers and
augers. These properties make pellets ideal for automatic appliances.
Wood fuel can be used to create both electricity and heat and is a well established
renewable energy source in many countries, including the USA, Sweden, Austria and
Denmark. It has a great potential for use in the country, particularly for heating.
How it works
Pellets are highly suitable for houses and can be
burned in either a boiler or a stove. Pellet boilers
provide full central heating and hot water, with a
convenience normally associated with oil or gas.
Stoves provide heating for a single room. Stoves
are available in a range of styles, from
traditional-looking wood-burning stoves to
modern, minimalist designs. Good quality
appliances use modern controls to ensure an
efficient, clean burning fire. Because they use
thermostatic controls and fans to distribute
warm air around the room they are safer than
traditional stoves, which rely on radiated heat to
warm the room, making the room's temperature uneven and the body of the stove
dangerously hot.
10
Installation in the Home
The installation is similar to that of any central heating boiler or stove, and requires
a flue and a fresh air supply to be installed for safe and efficient combustion. Many
products are programmable to allow you to set the temperature that you require
and some can even be controlled by mobile phone remote control.
Stoves contain an integrated fuel hopper that must be filled manually. Once full, the
hopper automatically supplies fuel to the stove, allowing it to operate
independently for around 20-40 hours. For boilers or larger systems which require
a greater fuel input, you may decide to site your storage facility adjacent to the
boiler, and install a completely automatic fuel feed system, such as an auger, so that
you do not have to re-fill the hopper manually.
Fuel storage is an important consideration as pellets are a bulky fuel, requiring
about three times the storage space of oil. However this requirement could be met
with more frequent deliveries. The store must also be kept completely dry as pellets
disintegrate on contact with water.
Payback and Maintenance
Maintenance is similar to that of conventional stoves and boilers. The ash pans of
both stoves and boilers will require emptying, typically once per month for stoves
and once every three months for boilers.
Unlike many renewable energy technologies, with biomass you still need to buy
fuel. Wood chip boilers are usually cheaper to run than oil or mains gas. Pellet prices
vary, but are generally comparable with oil and mains gas. Pellets are usually
available in bags or are delivered loose in bulk.
Planning permission may be required if you need a flue or chimney to be installed
or if you live in a conservation area.
For a list of suppliers, please visit our website.
11
Hydro
Introduction
Hydropower has produced mechanical energy for hundreds of years but was first
used to produce electricity in the 1870’s. Most Irish installations are run of river
installations. As such, hydro installations in this country are generally dependent
upon precipitation and have little impact on their surrounding environment.
Hydro electricity has the greatest energy yield factor of the renewable technologies
meaning the energy it produces in its lifetime greatly exceeds the amount of energy
used in its manufacture, operation and eventual disposal. This is due to the
reliability and long lifespan of a hydro system. For example, a modest 20kW scheme
would save 70 tonnes of CO2 being released into the atmosphere each year from
fossil fuelled power stations.
Gearbox
Control Unit
AC Generator
Sluice Gate
Electricity
Distribution
to Network
Turbine
River Flow
12
How it works
The power generation from a hydro scheme is dependent upon two variables, the
height the water falls, (head) and the volume of water available, (flow). Water is
diverted from a given point on a river, ideally near a weir and piped through to a
turbine house downstream, where the water falls through a turbine and drives a
generator. The water passes through the turbine and returns to the river
unpolluted. Various measures are taken to ensure fish are not directed into the
channel, which feeds the turbine. These can include mesh screening and electric
currents in the water to deter fish from entering. If a hydro scheme is proposed on
a fish migratory route, a ‘fish pass’ is built which is designed to guide fish away from
the turbine house and up a series of basin-like steps.
Installation
The feasibility of a hydro scheme will depend very much upon the proposed site, as
much capital is often spent on civil engineering work such as the weir, water
channel and fish pass. A site such as a disused millrace may have an existing weir or
water channel and this will reduce the capital per kilowatt outlay.
Communication with downstream water users is essential to unite support. Fisheries
and anglers who use the river can be strong opponents and will seek assurances
that their livelihoods or leisure activities will not be harmed.
Your local planning authority should be consulted at an early stage and planning
permission must be sought for any hydro installation.
13
Wind
Introduction
Wind is an abundant source of energy,
especially in Ireland. Large-scale wind
turbines are now installed around the
country and off shore to provide for
Ireland’s electricity needs and supplying
‘green’ electricity to consumers from the
utility grid.
How it works
For residential sites that have connection to
the electricity grid, the cost effectiveness of
installing a wind turbine should be carefully
examined. In this situation, the annual
electricity demand, wind resource and daily
demand profile must be considered. If you
wish to purchase electricity from a wind
turbine, you may be able to sign up to a
‘green electricity’ supply tariff.
Small-scale wind turbines range in size from less than 1kW to 50kW. They can be
cost effective in off-grid applications and wind power can be more economic than
other renewable options. Energy storage in batteries is necessary in off-grid
applications. Large-scale turbines up to 3MW in size, usually installed on windfarms,
are generally connected to the grid.
Installation
Wind speed and direction will determine the most suitable position for a wind
turbine. Wind speed increases with height, so turbines will give a greater output if
placed at a higher level.
Further information on local wind speeds can be obtained from www.sei.ie/
renewableenergy for ROI or www.actionrenewables.org which has a postcodebased wind atlas for NI.
Payback and maintenance
Wind turbines have a number of moving parts so annual maintenance is required
and your installer can provide this. The payback period of a wind turbine is
dependent on utilisation of the electricity generated, which should be off set
against that taken from the grid. Payback is therefore highly variable, but could be
as short as 15 years.
14
Notes
15
Notes
16
Relevant Standards
Building Regulations, 2002
Part L: Conservation of Fuel and Energy
Part F: Ventilation/Part J: Heat Producing Appliances
ISEN 832 - Thermal performance of buildings - calculation of energy use for building
-residential buildings CEN 1998.
Useful Contacts for Further Information
For information on renewable energy in the home
SEI Renewable Energy Information Office, Shinagh House, Bandon, Co Cork
www.sei.ie
For information on energy efficiency measures
SEI, Glasnevin, Dublin 9
For information on sustainable living
ENFO Information on the Environment, 17 St. Andrew Street, Dublin 2
www.enfo.ie
For information on solar technologies
Energy Research Group, UCD School of Architecture, Richview, Clonskeagh, Dublin 14.
For information on insulation
Insulating Contractors Association, Construction Industry Federation,
Federation House, Canal Road, Dublin 6.
For information on building products standards
National Standards Authority of Ireland, Glasnevin, Dublin 9.
Irish Agrément Board, Glasnevin, Dublin 9.
Source Text
Energy Research Group UCD
This booklet is printed on environmentally friendly paper.
Read our other publications:
A Detailed Guide to Insulating Your Home
A Detailed Guide to Home Heating Systems
Your Guide to Renovating an Older Home
Your Guide to Building an Energy Efficient Home
A Consumer Guide to Sustainable Energy
How to Make Your Home More Energy Efficient
Sustainable Energy Ireland is funded by the
Irish government under the National Development
Plan 2000-2006 with programmes part financed by
the European Union.
SEI, Glasnevin, Dublin 9
tel: +353 1 836 9080
fax: +353 1 837 2848
www.sei.ie
[email protected]
SEI InfoLine
9 to 5, Mon to Fri, 1850-376 666
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