Hybrid Multi-Stage Cooker EWB Challenge 2012

EWB Challenge 2012
Hybrid Multi-Stage Cooker
School of Electrical, Computer and Telecommunications Engineering
The University of Wollongong
Wollongong, Australia
Prepared by:
Scott Tillman
James Firman
Rajeev Prasad
Nikola Bojkovic
Alexander Moller
Peng Chen
Executive Summary
This report proposes a low cost hybrid multi-stage cooker as a low cost energy efficient cooking
method for Mekong Delta community. Four alternative methods were analysed based on the
criteria of cost, efficiency, reliability, durability, safety, portability, and sanitary. The four
solutions were electric hotplates, biomass, hybrid cooker and solar cells. After analysing the
alternative solutions based on the review criteria it was deduced that the hybrid multi-stage
cooker as the most suitable option. The purpose of this multi-stage cooking process is to create a
safe, clean and energy efficient method of cooking. The first stage of this process is a solar oven,
it utilises UV rays from the sun to slowly heat the food inside an oven chamber. The solar oven
relies on solar energy which is a renewable energy resource, resulting in an extremely energy
efficient and environmentally friendly cooking process. A solar oven will easily provide enough
power to cook a meal for a family of 4-5. The second stage of the cooking process consists of a
Rocket Stove. This is simply a controlled fire fuelled with biomass; however it differs from an
open fire by providing the system with heavy insulation as well as preheated air. This process
uses less fire wood in comparison to an open fire; it is also smokeless which enables a wide
distribution without harming the environment. Finally, the last stage of this process is heat
retention, simply an insulating basket (i.e. hay basket) which enables users to store food for up
to 4-6 hours. This report also explores financial benefits, as well as benefits to the environment
in terms of utilising a cleaner source of energy. It is expected that this solution will provide
Mekong Delta Region community with a variety of other benefits, such as economic boost in the
community.
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Team Reflection
The EWB (Engineers without Borders) challenge has given us an opportunity to be exposed to a
real world problem. It has allowed us to develop variety of skills important required for a
professional engineer, such as research, creative thinking, social and economic analysis and
management. This project has enabled us to work together as a team, it has broadened our
understanding of the importance of effective communication, working as an effective team
member, performing as a team, putting out ideas, and providing leadership.
During the first few weeks of the EWB challenge our group had issues with regard to
communication. Ideas were also not put forward and certain elements of the project were
unclear, however, as the time progressed the objectives became clear. The group meetings and
social networking provided us with the opportunity to gather resources and analyse their
suitability to the proposed design. Working as a team helped us to find a solution and thoroughly
design the solution from many ideas provided by each group member. The report was compiled
based on the strengths and weaknesses of each group member; this has enabled us to develop a
more comprehensive solution to the problem.
The most enjoyable experience of the EWB challenge was to get to know other people, able to
collaborate and test our creative thinking. It has also shown us the significance of an engineer in
the society. In particular, how engineer can help to improve the quality of life of the people all
around the world.
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Contents:
Executive Summary ................................................................................................................................. i
Team Reflection ....................................................................................................................................... ii
Contents .................................................................................................................................................. iii
1. Introduction
................................................................................................................................... 1
1.1 Problem Definition……… .................................................................................................................... 1
1.2 Problem Scope .................................................................................................................................. 1
1.3 Technical Review ............................................................................................................................... 2
1.4 Design Requirements ........................................................................................................................ 3
1.4.1 Temperature .................................................................................................................... 3
1.4.2 Efficiency ........................................................................................................................ 3
1.4.3 Reliability .......................................................................................................................... 3
1.4.4 Durability .......................................................................................................................... 3
1.4.5 Portability ......................................................................................................................... 3
1.4.6 Safety................................................................................................................................ 3
1.4.7 Sanitary ............................................................................................................................ 3
2. Design Options..................................................................................................................................... 4
2.1 First Design (Hybrid cooker) ................................................................................................ 4
2.2 Second Design (Solar Cells) ................................................................................................. 5
2.3 Third Design (Biomass) ........................................................................................................ 5
2.4 Fourth Design (Hotplates) .................................................................................................. 4
2.5 Option Selection .................................................................................................................. 5
3. Summary of Design/Detailed Description ........................................................................................... 8
3.1.1 Solar cooker ...................................................................................................................... 8
3.1.2 Rocker stove ...................................................................................................................... 9
3.1.3 Hay basket ......................................................................................................................... 10
3.2 Detailed Description .......................................................................................................................... 12
3.2.1 Function block diagram .................................................................................................... 12
3.2.2 Functional Description ..................................................................................................... 12
3.2.3 Manufacturing Procedure ................................................................................................ 13
4. Implementation plan ........................................................................................................................... 16
4. 1 Implementation overview .................................................................................................. 16
4.2 Usage instructions ............................................................................................................... 16
4.3 Additional Uses ................................................................................................................... 17
4.4 Next Steps ........................................................................................................................... 17
5. Evaluation Plan and Results ................................................................................................................. 18
5.1 Temperature Testing ........................................................................................................... 18
5.2 Efficiency Testing................................................................................................................. 19
5.3 Reliability Testing ................................................................................................................ 20
5.4 Durability Testing ................................................................................................................ 21
5.5 Portability Testing ............................................................................................................... 22
5.6 Safety Testing ...................................................................................................................... 23
5.7 Sanitary Testing ................................................................................................................... 24
6. Forecasted Impact ............................................................................................................................... 25
6.1 Economic Impact ................................................................................................................. 25
6.2 Environmental Impact ......................................................................................................... 25
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6.3 Social and Cultural Impact .................................................................................................. 25
6. Conclusions .......................................................................................................................................... 26
References ............................................................................................................................................... 27
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EWB - Introduction
1.
Introduction
1.1 Problem definition
Engineers Without Borders (EWB) is an Australian based non-government organization that
aims to assist communities in developing countries around the world. This is achieved by
engineering innovative solutions towards solving the problems faced by a given
community. The EWB hosts yearly challenge projects, in which first year engineering
students develop solutions to the problems of a real developing community. The best
solutions are then selected by the EWB for further development and later implementation
within the community. This year, the EWB has selected the South Vietnamese An Minh
province as the subject of the 2012 challenge.
The An Minh district is within the Kieng Giang province located in the Mekong Delta region which
is situated in the south western part of Vietnam with the Mekong River flowing into the ocean,
lying west of Ho Chi Minh City. There is a total population of approximately 17.4 million people in
the Mekong Delta with approximately 112 000 of these living in the An Minh district. The main
export from the region is rice, Vietnam is actually second largest exporter of rice globally after
Thailand. Life in the Mekong Delta is largely connected to the river, with a number of people
using boats for their livelihood or living along the riverside for needed resources.
The Mekong Delta is known for its good electrical coverage with 80%-90% of households being
connected to the grid. Electricity is predominantly used for lighting in a typical household. The
main source of power is electricity from power stations. The power plant is powered by
petroleum, which is not a cheap source of energy with large carbon emissions and bad
environmental impacts. The electricity is turned off in summer (hot season from April to July) for
about one day a week during daylight hours, this is a scheduled outage and residents are
informed of the day in advance. Due to their lack of infrastructure and absence of sustainable
energy, they have lagged behind the rest of Vietnam and the world with their development.
Without sustainable management the future is uncertain. This leaves the Mekong Delta area
vulnerable to environmental issues, which leads to the need for an affordable and efficient
solution that uses an environmentally friendly source of energy, producing minimal carbon and
environmental emissions.
1.2 Problem Scope
The problem area focus in our project is energy; in particular we focus on energy efficient device
for cooking purposes. At present Mekong Delta community use variety of energy inefficient
cooking methods, therefore this project aims to develop a more fuel and energy efficient method
while keeping the operating cost (i.e. fuel) and initial cost affordable to the Mekong Delta
community.
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1.3 Technical Review
In the Mekong Delta the most commonly used cooking method is open fire and gas cookers. This
project expect to propose a safe and reliable method of cooking that is feasible for the Mekong
Delta community and which doesn’t impact the local environment and culture. Since Mekong
Delta community live closer to the delta canals, the energy resources required for modern
cooking methods is inaccessible. However, some communities have access to electricity, but due
to high electricity prices it is not being used by many people. Gas and other fuel sources are
available for most of the community as they are transported down the channels of the delta. The
fuel cost is increasing each year as the global need for fuel increases. i.e. petroleum and gas. The
poor and unreachable members of the Mekong Delta community use open fire places for their
cooking purposes. The fires are fuelled by charcoal, wood or the left over husks form the harvest,
usually rice.
There were many factors that must be considered when developing a cooking method. The
community requires a reliable and easy to use product that has little parts as possible that could
be lost or easily broken. The parts and utensils have to be readily available to the community if
the parts are lost or broken. The storage is another issue. The cooking platform must be able to
be stored easily inside a house, so it is out of the way and concealed so it can’t be stolen.
The cooker must be resilient with the climate and hazards associated with the Mekong Delta
region. The Delta region is situated close to the equator thus has a high moisture and temperate
climate with dry and monsoon seasons. The region regularly experiences flash flooding in the
monsoon season [1-2]. These factors add the boundaries to the project; hence the cooking
platform must be able to stand up to the high temperatures and humidity. This means any
electric component must be sealed and the cooker must be water resistant.
The cooker must be environmentally friendly. The cooking platform shouldn’t leach and generate
potently harmful chemicals and should not be heavy.
Culture of Vietnam is diverse, the cooking platform must not disrupted or disrespect the culture
of the Mekong delta community. The culture governs their eating habits and style.
“The Vietnamese eating habit tends towards vegetarianism; rice and vegetables are the main
course of the meal that may be diversified by aquatic products. Boiling is a special way of cooking
of the Vietnamese people. Vietnamese people like a synthetic food processing style that involves
many materials and ingredients. Today, although meat and fish are the main dishes of the meal”
[8]
The Mekong Delta is a rural rice farming area. The community has a low socio-economic status
compared to the neighbouring city, Ho chi Min. The cost of the cooker and its replacement parts
must be within an acceptable range for the community to afford the cooker platform otherwise
the project is impractical.
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1.4 Design requirements
1.4.1 Temperature:
Temperature is one of the most important design requirements for cooking device. The
maximum temperature of the cooker can withstand will determine the cooking time, safety and
hygiene. A desired temperature suitable for cooking is in the range of 100 – 250 °C. It is
important that the temperature is consistent, since varying temperature may lead to
undercooked or overcooked food which ultimately makes the design unreliable.
1.4.2 Efficiency:
The efficiency of each design must be at a standard higher than the current cooking method such
as gas or open fire. The efficiency is purely based on the amount of heat energy absorbed by the
cooker from the amount of energy input to the cooker. Energy losses can be resulted due to poor
structural design (position, wires, insulation and poor choice of materials) which reduces the
overall efficiency of a design.
1.4.3 Reliability:
The reliability of a design is a very important factor to consider. Constant faults and maintenance
required for a design will increase the overall cost in the long run; it also inconvenient to the
consumers as they are left without a cooking source for the down time. Complex designs may
suffer a reduction in reliability as there are more components which have the probability of
failing. Delicate/fragile designs will also have a reduction in reliability as they usually require
higher maintenance and checking for physical damage. In addition, by constantly replacing the
components in delicate designs may significantly increase the maintenance cost of the design.
1.4.4 Durability:
The durability of a design is basically the amount of wear and tear the design can withstand over
its life spam. The durability may also increase the reliability as it will require less maintenance
over its life span. The durability is usually related to the designs structural integrity as well as the
choice of materials used.
1.4.5 Portability:
The portability of a design is not a primary requirement, however it may be convenient for the
user. A portable solution may result in a lesser amount of space taken up within a household also
the ability to have a cooking method regardless of the consumers’ residential location.
1.4.6 Safety:
Safety is a major factor of the design specifications. It can be related to the structural design also
the maximum temperature it can handle. It is imperative that a safe solution is provided to
families with children because the possibility of an accident is much higher. Safe designs may
include contained heat while unsafe designs will expose an open flame.
1.4.7 Sanitary:
Sanity is a considerable part of the design requirements. Sanitary is the hygiene and the ability to
maintain hygiene in a design. This is a very important factor especially for the Mekong Delta
Region as a third world country they lack common hygiene, poor sanitary may lead to the
spreading of infectious bacteria, viruses and diseases.
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EWB - Design options
2. Design Options
2.1 First Design Option: Hybrid three-phase cooker
The hybrid three-phase cooker is comprised of a solar cooker, rocket stove and a heat retention
hay basket. The purpose of this set-up is to maximise efficiency and flexibility in accordance to
the Mekong Delta weather conditions and patterns, during sunny days, the solar cooker can be
used and food can be kept warm in the hay basket, during cloudy days, the rocket stove can be
used by efficiently burning wood to prepare food and then stored ready for later consumption in
the hay basket, this setup is also aimed to provide the best cost to efficiency ratio available as
funding is limited.
The solar cooker price ranges from $70 - $500+ [13] depending on quality of product, and can
reach temperatures of up to 200 degrees, they are generally built out of an aluminium frame to
help retain heat within the oven, this also makes the solar oven very light and portable, as
Aluminium does not absorb heat it makes it safe to touch after use, this also make it very
durable, since Aluminium does not react so readily and is sturdy by nature. Aluminium is
generally aesthetically pleasing compared to its alternatives such as steel which rusts, the food is
suspended within the solar oven which avoids contact from other materials, hence it is sanitary,
it can also store food and keep it warm within it for up to 6 hours, which is crucial in humid areas
such as the Mekong Delta which provides superb unhygienic conditions such as mud
accumulation. Additionally, the solar oven is easy to operate and user friendly. Also it solely
relies on the UV radiation from the sun to heat the oven, it does not rely on electricity, which is
very vital as the Mekong Delta’s economic situation is not of the greatest, this will save plenty of
energy and aid in their economical standings.
The Rocket cooker and Hay basket combination is also a very economically viable arrangement.
This setup is also perfect for any weather condition and can be used indoors as it is very
contained, unlike the solar oven. The hay basket/rocket stove is also a very effective way of
cooking and storing food for later use, as opposed to what is currently used, natural gas, wood
can be burn in thick insulated chambers, only use energy where it is needed, as opposed to open
fires, the rocket stove is 80% more efficient, the hay basket is made of thick insulated material
and can hold food warm for up to 6 hours, showing to be very efficient, the rocket stove is made
of a steel body and a cast iron stove top, making it very durable and reliable, the overall
dimension of the two are very compact and portable, it is very easy to use, caution must be
taken, however as the outer metal of the rocket stove can reach very high temperatures.
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2.2 Second Design Option: Solar cells
Using solar cells to provide energy to stovetops and ovens can be economically viable to the
population of the Mekong District, however, due to their weather patterns of heavy constant
rain, the solar cells would prove to be extremely inefficient and depending on the conditions,
hence can be very susceptible to wear and tear and prove not to be very durable. Solar
generators are also generally fairly expensive starting at $1200 AUD per unit [13], and have to be
maintained and changed every several years on top of the initial fee; this proves to be very
inconvenient to the population and places a heavy financial burden upon them. However, solar
power is very reliable, in a sense that once the energy is collected, it can then be stored and used
to power any appliance, in this sense being flexible as well, the only problem that remains from
this alternative solution is the lack of sun to produce energy due to the weather patterns of the
Mekong Delta.
Given the budget for the project and
weighing the disadvantages to
advantages, if the budget was more
flexible, then the solar generator
would be considered as an alternative
as the energy it generates can also be
used for other household appliances.
Such as powering the lights and in turn
will aid the Mekong Delta population in
their economic stance.
Figure 1: Solar Generator [16]
2.3 Third Design Option: Biomass
The burning biomass in open fire to cook food is common in many areas of Vietnam as an
alternative option to Natural gas, due to the abundant biomass resources in the Mekong delta.
The flames produced can produce endless amount of heat as long as fuel (i.e. biomass)
constantly feed into the fire. However it is not very efficient, since the majority of the heat is
released into the atmosphere. In addition, the burning of biomass produces a large amount of
carbon dioxide, which when inhaled is damaging to the lungs and can cause eye irritation.
Another by product is soot, carbon which sticks on to materials such as cooking pots and can
contaminated with food and give a very unpleasant charcoal-like taste. Burning biomass also
depends on weather conditions, since it is difficult to cook a meal during rainy conditions. So it
does not prove to be a very reliable source of energy.
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2.4 Fourth Design Option: Hotplates
Hotplates are also known as electrical cook tops which are fairly cheap to install, starting from
$40 [13] apiece, however they operate using electricity which can end up as costly alternative in
the long term. An advantage over the other alternatives is it is readily available at all times, and
most reliable of all the alternatives. Hot plates are efficient in terms of the heat provided.
However, the energy used to create the electricity (burning of fossil fuels) which is not efficient,
and is harmful to the environment, since fossil fuels are burnt to generate electricity in Vietnam.
Hotplates aren’t portable as solar ovens as an electrical source must be present close to the
hotplate to power it. They can also be very dangerous, as they remain at high temperatures well
after it has been turned off. Hotplates are an excellent alternative if there are no other reliable
means of cooking as it will always be available; however the pollution involved and cost related
may not be ideal for the population of the Mekong Delta.
2.5 Option Selection
The hybrid cooker was chosen as the best alternative over the solar cells, biomass and hotplates,
as it tailored to the population of the Mekong Delta more suitably, in comparison to the solar
cells, it was more reliable and durable. In contrast to biomass, hybrid cooker was clearly more
efficient, safe, since users are not exposed to open flames, more sanitary, and avoid the charcoal
like flavour from the carbon by product from combustion. Finally, when comparison to the
electrical hotplates, the hybrid cooker has a large initial fee; however, over long run cost of
electrical hotplates will surpass hybrid cooker due to the electricity cost and maintenance cost. In
overall the hybrid cooker prove to be the easiest to set up, user-friendly and require least
amount of maintenance, which is vital as in an area such as Mekong Delta where professional
electrical assistance would be difficult to locate.
Table 1 illustrates the performance criteria weight for each of the alternatives solution, which
gives an insight on the thought process in determining the best alternative solution and will
benefit in justification in which is the most viable solution.
Total
Sanitary
Safety
Portability
Durability
Reliability
Efficiency
Temperature
Cost
Table 1: Evaluation of Alternative Solutions
Solar
cells
1
5
5
2
3
1
5
4
26
Biomass
4
3
3
4
4
5
2
3
28
Hybrid
3
4
5
5
4
4
3
5
33
Hotplates
5
3
2
4
4
5
3
3
29
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Each criterion is given a score out of 5, 1 being the least. Clearly indicates that the highest rated
and most suitable would be the Hybrid Solar cooker, Rocket stove and Hay basket. In conclusion,
considering the budget, weather patterns and economic status, and the performance criteria
which consists of reliability, durability, efficiency, portability, safety, temperature and sanitary,
the Hybrid 3 phase cooker can be determined as the most viable solution.
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EWB - Design Description
3. Design Description
3.1.1 Solar cooker
The solar cooker works on the principles of energy conversion and retention. It requires UV
radiation provided from the sun to effectively be transferred into infrared. Solar cookers are
effective regardless of the ambient temperature as they are not powered specifically by the heat
of the sun. As long a constant UV source is provided the solar cooker is capable of trapping
enough energy to cook a meal for a family of 4 or 5 people.
The “Sun Oven” is a solar box cooker, which is a variation of a solar panel cooker. It utilises the
absorption and retention of infrared radiation to slowly and efficiently cook food. It differs from
a solar parabolic cooker through not generating as much heat and being a slower form of
cooking.
Reflective Mirrors
Temperature gauge
Oven chamber
Figure 2: Solar Cooker [17]
Black Polish Oven Pot
Transparent seal
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The Sun Oven consists of four reflective panels placed on each side of the oven; these panels
concentrate the UV rays into the oven chamber. The oven chamber consists of a large interior
space coated with a black polish. This allows the UV rays to be absorbed more effectively
producing more heat. The solar oven acts much like an inside of a car parked in the heat on a hot
day. The suns energy is absorbed by the body of the car and converted to a radiant energy which
cannot escape thus building up extreme temperatures over long periods of time. The solar oven
is tightly sealed by a transparent cover which allows UV rays to pass through and keep infrared
radiation trapped in the oven chamber.
3.1.2 Rocket Stove
A rocket stove is an extremely efficient cooker which works on the basis of combusting biomass.
The StoveTec wood fire rocket stove will allow civilians to cook a family sized meal using 20% less
fire wood in comparison to an open fire regardless of the weather.
Figure 3: Rocker Stove [18]
The StoveTec rocket stove consists of one main combustion chamber and a large opening which
allows small blocks of wood to be inserted. The reason the rocket stove is so much more efficient
than an open fire is the airflow and heat retention within the combustion cylinder.
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Figure 4: Operation of Rocket Stove [19]
An open fire is only exposed to the air which is at the ambient temperature. The rocket stove
preheats the ambient air by allowing it to pass under the shelf of fire wood; this increases the
overall efficiency of the combustion. The chimney is orientated vertically which provides an
updraft to keep the fire going. The chimney is heavily insulated which effectively contains the
heat within the combustion cylinder considerably increasing the overall efficiency. The height at
which the food is placed is optimised so that the smoke produced is burned and transferred to
heat as it reaches the top. The StoveTec rocket stove is an extremely energy efficient method of
cooking on rainy days when the sun box oven is not in use.
3.1.3 Heat retention (Hay Basket)
Heat retention is a vital part of multistage cooking. It can be utilised in combination with solar
cooking. As rainfall is predicted, heat retention provides civilians with the ability to use the sun
oven to cook their food earlier in the day and keep it hot for 4-6 hours. A simple hay basket
consists of pot sized basket filled with readily available insulating material such as straw, feather,
rags, sawdust, wool and hay etc. While making the hay basket air tight it can decrease the heat
loss to surrounding air. The typical configuration of the hay basket is shown in Figure 5.
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Figure 5: Hay Basket for Heat Retention [20]
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3.2 Detailed Description
3.2.1 Function block diagram
Figure 6: Functional block diagram of the hybrid multi-stage cooker
3.2.2 Functional Description
Solar Cooker – The solar cooker is one of the first steps in the multi stage cooking process. This
device allows the sunlight to be passed through the glass or any other plastic materials to the
food item placed inside the container. At first the food item must be placed inside the container,
then glass or plastic window must be closed (see Figure 2). The reflection plates allow for extra
heat to be transmitted into the box container storing the food, this will heat up the box much
faster due to extra radiation of sunlight are projected into the box to warm up the food. The box
container made up of aluminium which has a base colour of black, which allows it to absorb the
sunlight to heat the food inside container. This enables solar cooker to become more energy
efficient device. The solar cooker can be made out of any kind of material, as long as heat is
transferred into the container. Any reflective surfaced objects could be used for the reflection
panels.
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Rocket Stove – The rocket stove can be used instead of the solar cooker for the first step of the
multi stage cooker. This is used when the solar cooker is unable to use under certain weather
conditions, such as if there is no sunlight during the day, or when it is raining. The rocket stove is
like a regular stove but uses biomass instead of gas or electricity to power the stove. This would
be more convenient and cheap method of cooking for Mekong Delta community due to the
electricity shortage and the abundant biomass recourse in the Mekong Delta.
At first the food to be boiled or fried is placed on top of the rocket stove, and then the biomass
(preferably timber) is put into the base of the rocket stove. The stove is then lit via the biomass
by using any kind of device which uses to create fire such as a match stick. When biomass burns
it creates flames which reach the pan or pot and ultimately provide sufficient heat to cook the
sustenance in the pot or pan. The rocket stove is an environmentally friendly stove which is
beneficial for the people in the Mekong Delta and better than a regular stove.
The next step of the multi stage cooker is the hay basket. The hay basket is used mainly to keep
the warmth of the food prepared from previous stages. The hay basket enables to preserve the
food for a longer period. The hay is an excellent insulation material which can store heat
extremely well; the basket is woven to allow heat to be trapped inside it. The basket is mainly
used to contain the food while the hay and the blanket wrapped around the food in order to
maintain the heat without becoming it cold. The hay basket can store heat of the cooked food
for up to 4 – 6 hours. This means that food may be cooked at lunch time and it still be warm (if it
is kept in a hay basket) until dinner time, or from breakfast to lunch.
3.2.3 Manufacturing Procedure
To manufacturing procedure is a simple process. Each individual system can be made out of parts
freely available in the environment. The basket can be woven from home or bought at a low cost.
The reflective panels are possible the most expensive or hardest to find due to the necessity of
having a reflective surface.
Figure 7: Reflective Panels [1]
The solar cooker is made from an aluminium base and use dark material for the enclosure in
order to retain the heat within it. The box container is made through a process of cast moulding
where there is a specific mould which is compressed with heat and force to produce a specific
shape, in this case a box type of a container. The swing is made of stainless steel which can be
resistant to any spills from the food. It is made from the process of dye casting where the metal
is at its molten level and is poured into a mould where it is shaped and created for whatever
purpose it is required for.
13
The metal sheets which are used for the reflection of the sunlight into the main box container
are made of steel and then glazes with a specific glaze which can reflect extra radiation into the
box. All components will be fixed using hinges. In particular, the window of the container and
reflective plates are fixed to the main container.
Figure 8: Box Container for Solar Cooker [2]
The rocket stove is made out of tin which is mainly casted into a cylindrical shape to allow for the
flame to reach the pan/pot above to cook the food. The rack which holds the biomass is made of
any metal which can withstand for a high amount of heat. The rocket stove is manufactured by
hardening and tempering the tin for the main part to create the shape of it, and the either
welding or simply placing the rack into the bottom of the stove. Most of these metallic
components can be freely found from junkyards, in particular from unused barrels.
Figure 9: Rocket stove [3]
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The hay basket is the simplest component of the hybrid three stage cookers. It is made from a
regular basket which could be woven with any material such as pine, hay, etc. The hay basket is
then put together after the creation of the basket. This is done by placing hay around the walls of
the basket and then putting a blanket or cloth around the hay, then food will be placed and kept
warm after the blanket has enclosed the top of the basket. The Mekong Delta community can
easily make hay basket while sourcing the required material from their environment.
Figure 10: Hay Basket [5]
As mentioned, manufacturing procedure for solar-cooker and rocket stove may be complex;
however most of the required materials can be sourced from environment. Our team proposes
to develop a small team comprised of volunteers from Vietnamese community to manufacture
the proposed hybrid three-stage cooker. Therefore, initially the volunteers will be provided with
the technical training to develop these cookers. In addition, equipments to build will also provide
to them through soft loans agreed from local banks.
15
EWB – Implementation Plans
4. Implementation plan
4.1 Implementation overview
To implement our proposed design in Mekong Delta, we require a detailed plan on how to
construct and assemble this cooker. The most effective way is to use detailed diagrams and basic
written instructions. From the diagrams it is easy to understand the written instructions. These
instructions should be given to each household in Mekong Delta. However, instructions may not
be enough for them to assemble the cooker, and therefore a demonstration and tutorial is
required to further enlighten the people to assemble and operate this cooker. From the
instructions and tutorial they will able to construct, use and maintain the cookers by themselves.
A demonstration of the cooking process may be required this can be done by using volunteers
from Vietnamese community.
Instructions to use the hay basket are also required. Therefore, detailed diagrams and written
text to support the images will be prepared. This will assist them to correctly use the basket so
that heat can be retained for a long time period. The woven basket is a basic design, hence does
not require much instructions compared to solar oven and rocket stove. Thermal storage basket
allows the Vietnamese people to keep the food prepared in the sunlight hours for the dinner;
hence it will assist to save the biomass resources. Therefore, the hay basket further helps to save
natural resources in this region. To introduce the hybrid cooker to Vietnamese community it
requires:
1. Published instructions – These instructions will be prepared by the project team for the
implementation process.
2. Projector, projector screen and computer –For demonstrations
The above items are required for the presentation and tutorials in order to enlighten the
community on operation and maintenance of this cooker.
4.2 Usage Instructions for Hybrid Cooker
Solar cooker
Instructions for Assembling and Cooking
1. Open the package and check whether all components are included in it, assemble the
cooker according to the diagrams. Open the reflector panels to direct the sunlight into
the centre of the cooker, where the food is placed.
2. Place meal inside the cooker and check that it is secured firmly, check that the meal is in
the tilt free position, tilt the solar oven (the food should stay level with the ground level)
so that the transparent section of the cooker is facing the sun (making sure nothing will
obstruct the cooker from direct sunlight).
3. Wait sufficient time for the food to be properly cooked (refer the table to find the time
required to cook various items).
4. If the cooker is still hot, touch it with caution; store the food in the hay basket.
16
5. Clean the cooker if required and fold the reflector panels up so they are pressing up
against the transparent section of the cooker.
6. Store the cooker in a safe location (away from children).
Rocket cooker:
Process Procedure:
1. Open the package and check whether all the components are present, assemble the
rocket cooker according to the diagrams.
2. Place biomass on shelf ready to be burnt, light the fire in the bottom with an accelerant
(be careful of open flame).
3. Push biomass in as required and monitor the flame location.
4. Remove unburnt biomass and check that the fire has been eliminated and wait for it too
cool before store in a safe location.
4.3 Additional Uses
The solar cooker can be used for other purposes other than cooking. It can be used as a storage
container; since its oven chamber has a considerable amount of space and it can be used to dry
out materials which contain moisture like firewood and clothes. The cooker can also be used as
an alternative food preserver; the temperatures inside the oven can reach temperatures hot
enough to kill bacteria and cool enough not to burn food.
4.4 Next Steps
The next step is to enlighten the Mekong delta community on repair and maintenance of the
cooker. In addition, it is essential to establish connections with metal and plastic suppliers, so in
case a cooker has been broken, it can easily be repaired for a low cost. The cookers Aluminium
reflector sheets must be kept clean so a proper storage location and method should be shown to
the locals so they can take care of their own product.
17
EWB - Evaluation
5. Evaluation Plan and Results
5.1 Temperature Testing
Points are allocated to designs which produce a maintainable temperature between 100 –
250 °C, also the rate of heating and the ability to control the temperature is also taken into
account in evaluation.




Hybrid (solar, stove) – Solar Ovens of similar builds such as the “The GLOBAL SUN OVEN®
will reach temperatures of 360 to 400 degrees Fahrenheit” [8].
Research in rocket stoves show that maximum temperatures range from 1400 to 1800
degrees Fahrenheit depending on the amount of fuel provided [9]. The hybrid solar
solution is allocated a score of 4/5 due to the sufficient ability to heat food however; it
loses marks on its limited controllability of the solar cooker and the excessive max
temperature of the rocket stove.
Biomass - “Temperatures of fires that have not developed to post-flashover stage will not
exceed 1000°F.” [10]. since biomass reaches temperatures well exceeding the
temperature range, also have a limited amount of controllability it is allocated 3 points.
Solar Cells – Solar cells are not directly used as a cooking method instead it creates the
energy which is utilised by an electronic heating device. Solar cells provide well above the
required power to run a cooking apparatus, it provides an extreme amount of
controllability; temperatures can be easily limited within the desired cooking
temperature range. Due to its controllability the solar cells are allocated a score of 5.
Electric Hot plates – Budget electric hot plates generally reach a maximum temperature
of up to 260 °C. The disadvantage of a budget hot plate is that it cannot constantly
maintain maximum temperature. Electric hot plates are allocated 3 points for a relatively
moderate maintainable temperature and controllability.
Table 4.1: Temperature Performance
Max Temperature(°C)
Allocated Points(out of
5)
Hybrid (solar, stove)
Solar: 204, Stove: 982
4
Biomass
538
3
Solar Cells
Hot Plates
100-250+
260
5
3
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5.2 Efficiency Testing
Points are allocated for the level of energy outputted from the energy inputted.




Hybrid (solar, stove) – The stove component of our hybrid solution runs purely on energy
from the sun. Since this is a natural source which requires no inputted electrical energy it
is awarded 5 points. The stove component simply utilises biomass as a fuel source,
however it is heavily insulated and does not allow ambient tempered air to reach the
exposed flame which results in a potential to double the maximum temperature of an
open flame. The stove component is also awarded 5 points.
Biomass – Biomass is simply an open fire which utilises plant matter as a fuel. Heat
energy in the system is usually lost to the environment; this is due to the lack of
insulation and it being exposed to ambient tempered air. An open fire can still maintain a
temperature of 1000 degrees Fahrenheit, however in comparison to the rocket stove use
20% more firewood. The Biomass alternative is allocated 3 points.
Solar Cells – Similar to the solar cooker, solar cells utilise solar energy as a primary energy
source. Solar panels are very effective at providing consumers with electricity due to its
ability to create large amounts of electrical energy from an otherwise unutilised energy
source such as the sun. Solar cells are allocated 5 points due to their outstanding
efficiency.
Electric hot plates – Electric hot plates are generally an effective method of cooking, it
involves the transfer of heat from a heating element to a metallic plate. The metallic plate
then comes into contact with the metallic base of a pot or pan. Since this process involves
numerous stages of transferring heat the system can easily lose energy to the
environment. This alternative is primarily focusing on budget cook tops so the chances of
resistance in wires due to impurities are much higher in comparison to a high quality
electric cook top. These attributes result in this alternative receiving 2 points.
Table 4.2: Efficiency of various options
Allocated Points(out of
5)
Hybrid (solar, stove)
5
Biomass
3
Solar Cells
5
Hot Plates
2
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5.3 Reliability Testing
Points are allocated for simplicity of design (less chance of malfunctions) and the rigidity/
structural integrity.




Hybrid (solar, stove) – The solar cooker is a relatively simple design; it only contains one
stage of energy conversion (UV  heat) there are no electrical components which results
in a very simple but effective design (5/5). The solar oven is structurally reliable, the body
of the oven is made from aluminium it is corrosion resistant and can withstand moderate
impact forces. It has the ability to fold up which protects the reflective mirrors for any
physical damage. (5/5)
Biomass – The idea of using biomass as a cooking method is relatively simple. (5/5)
However the main drawback is the requirement of dry firewood and a shelter for burning.
(4/5)
Solar Cells – A solar cell involves the photovoltaic process which is the conversion of
sunlight to electrical energy. This effect is quite complex when looking into the molecular
level however possibilities of malfunctions in the conversion of sunlight to electricity are
quite low.(3/5) Solar cells are very delicate, they must be protected from severe weather
such as strong wind and hail, any surface damage may result in decreased efficiency or
even complete product failure.(2/5)
Electric hot plates – The idea of using electricity to heat up a hot plate is quite a simple
process, there is only one simple energy conversion (electrical energy -> heat) however
this process does include involve electrical wiring which are a common item to
malfunction in electronic devices. (4/5) Electric hot plates are solid and rigid, they are
very reliable as they are made to withstand large amounts of heat and impact force.(5/5)
Table 4.3: Reliability Performance
Hybrid (solar, stove)
Biomass
Solar Cells
Hot Plates
Simplicity(/5)
Structure: (/5)
Simplicity:
Solar: 5 Stove: 5
Structure:
Solar: 5 Stove: 5
Simplicity: 5
Structure: 4
Simplicity: 3
Structure: 2
Simplicity: 4
Structure: 5
20
Allocated Points(out of 5)
5
4
2
4
5.4 Durability Testing
Points are allocated for the strength, hardness and corrosion resistance of the materials used
and the previously allocated mark for structural integrity.




Hybrid (solar, stove) – The material used to develop the body of the solar oven is
aluminium. Aluminium is a lightweight, relatively soft but durable material. This material
sacrifices its rigidity and strength for its lack in weight (to increase portability). It is also
corrosive resistant which is very important for long term use [12]. (3/5) – Structure (5/5).
The rocket stove is made of layers of stainless steel which is corrosion resistant, relatively
strong and hard. It can withstand large amounts of temperature variation and is not
affected by UV rays. (5/5)
Biomass – simply burning biomass cannot be analysed based on the properties of the
materials used or structural integrity. Instead it can be assessed based on its reliability,
since in this case a durable solution can lead to a reliable solution.
Solar Cells – Made out of crystalline silicone (semiconductor). It is coated in a low-iron
patterned glass with anti-reflective coating (refer to 5.1). Crystalline silicone is relatively
fragile; it does not provide any outstanding properties of strength or hardness. However
since it is a semi-metal it does not corrode. (3/5). –Structure (2/5).
Electric Hot plates – are usually composed of cast iron. Cast iron is an alloy of iron and
carbon, it has a very high compressive strength and resistance to deformation and it is
also highly resistant to oxidation [13]. (4/5). Structure – (5/5).
Table 4.4: Durability Test
Material
Allocated Points(out of 5)
Hybrid (solar, stove)
Solar: Aluminium
Stove: Stainless Steel
4
Biomass
Solar Cells
Hot Plates
Reliability: 4
crystalline silicone
Cast-iron
4
3
4
21
5.5 Portability Testing
Points are allocated for properties such as being light weight, compact and small in dimensions.




Hybrid (solar, stove) – The solar oven is a very portable device, a similar solar cooker
named the “Global Sun Oven” has the following characteristics:
“The size of the Sun Oven® is 19'' x 19'' with an average depth of 11''. The total weight is
only 21 pounds. “[1]. these dimensions and weight provide the users the ability to quite
easily move the solar cooker around to any desired position without too much hassle. The
design is also compact as the reflective panels can be folded flat onto the transparent lid
allowing easy storage and manoeuvrability.(4/5) The rocket stove is very light weight and
approximately 10 inches tall and 10 inches wide.(5/5)
Biomass – Fires can be started anywhere as long there is sufficient firewood and dry
conditions (5/5).
Solar Cells – Solar cells are always located in a fixed position, usually installed on a roof or
an upright pole. (1/5).
Hot plates – Light weight and compact they can generally be transported anywhere as
long as there is a power source available. (5/5)
Hybrid (solar, stove)
Biomass
Solar Cells
Hot Plates
Table 4.5: Portability Test
Weight(kg)
Dimensions(inches)
Weight:
Solar: 9.5
Stove: 1
Dimensions:
Solar: 19”x19”
Stove: 10”x10”
N/A
N/A
Weight: 1 to 2(approx.)
Dimensions:
9”x9” (approx.)
22
Allocated Points(out of 5)
4
5
3
5
5.6 Safety Testing
Points are allocated for designs that contain heat instead of exposing a flame. The temperatures
reached and the positioning of the design.




Hybrid (solar, stove) – The solar oven is a very safe design, it contains heat within the
oven chamber and the outer walls of the oven stay cool. It can also be placed to locations
unreachable to kids due to its portability. (4/5) The rocket stove on the other hand is very
unsafe and must be monitored at all times. It can reach very high temperatures and
exposes a flame, the outer walls of the stove can get extremely hot and must not be in
contact with during heating or minutes after heat.(1/5)
Biomass – Exposes an open flame, can reach high maximum temperatures and must be
positioned on the ground where children may be in reach. (2/5)
Solar Cells – Are very safe since it does not directly heat anything it simply creates energy
for cooking processes (5/5).
Hot Plates – provides direct heating from the cast-iron plate so it can be dangerous if in
contact with skin. Temperatures can reach up to a moderate level and can easily be
placed out of reach of children. (3/5)
Table 4.6: Safety Test
Allocated Points(out of 5)
Hybrid (solar, stove)
3
Biomass
2
Solar Cells
5
Hot Plates
3
23
5.7 Sanitary Testing
Points are awarded by observation.




Hybrid (solar, stove) – The solar oven provides a clean way to prepare food items. It is
kept off the ground and is contained within an airtight oven chamber which ensures that
no bacteria from the ground or air can enter into food (5/5). The rocket stove exposes
food to the air; however, it is kept off the ground and is a smokeless operation which kills
any pollutants created from burning biomass (4/5).
Biomass – Burning directly from an open fire will create temperatures sufficient to
destroy most of the bacteria present in the food items; however smoke is produced in the
process of combustion which may potentially contaminate food (3/5).
Solar Cells – Very clean way of producing electricity, does not create any pollutants (5/5)
Hot plates – Can be easily cleaned, does not create any pollution. Typically fossil fuels are
used to generate electricity in Vietnam (3/5). However, it indirectly causes pollution.
Table 4.7: Sanitary Test
Allocated Points(out of 5)
Hybrid (solar, stove)
4
Biomass
3
Solar Cells
5
Hot Plates
3
24
EWB – Forecasted Impacts
6.0 Forecasted Impacts
6.1 Economic Impact
The proposed project requires small manufacturing plants to be built within Mekong Delta
community to produce this hybrid three-stage cooker. This will enable Mekong Delta Community
to gain jobs, hence improve their income level. Ultimately, living standards of the Mekong Delta
will improve in long term. Furthermore, they can also experience financial savings in long term;
hence their financial position will improve in future.
6.2 Environmental impacts
The traditional cooking methods used in Mekong Delta are very energy inefficient and may pose threat to
the environment by emitting carbon dioxide to the environment.
However, the evaluations have
indicated that the proposed cooker is very energy efficient in comparison to the other devices they use
for the cooking purposes; hence it poses minimum threat to the environment. Further, since it can use
recycled materials this proposed design can reduce the waste damage to the environment.
6.3 Social and Cultural Impact
The Mekong Delta community is traditionally agriculture oriented community and their life style is very
simple. The proposed solution addresses one of the important issues related to their daily lives and the
proposed solution perfectly aligns with their life style since it is very simple design as it requires very little
knowledge to operate and maintain the cooker. Therefore, this design is socially and culturally very
suitable for the Mekong Delta community.
25
EWB –Conclusions
In this report our project team has proposed a three stage cooker for the Mekong Delta
community in Vietnam. The suitability of the proposed solution was extensively evaluated
against other cooking options available for Mekong Delta community. The proposed cooker is
cheap alternative cooking device since it requires renewable energy source (i.e. solar radiation)
and another freely available resource (i.e. Biomass) in Mekong Delta. Therefore, Mekong delta
community will be benefited from huge financial savings over long term. Furthermore, most of
the materials required to produce the hybrid cooker can be sourced from Vietnam without
sourcing them from material manufactures. In addition, this proposal enables to generate jobs
for Mekong Delta community, hence assist to improve their income level in long term. Therefore,
once it is implemented our proposed design will make a huge contribution towards improving
the quality of life in the Mekong Delta community.
26
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