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| | + | [[File:GIZ HERA Cooking Energy Compendium small.png|left|831px|GIZ HERA Cooking Energy Compendium|alt=GIZ HERA Cooking Energy Compendium small.png|link=GIZ HERA Cooking Energy Compendium]]<br/><br/><!-- |
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| − | [[File:GIZ HERA Cooking Energy Compendium small.png|left|831px|GIZ HERA Cooking Energy Compendium|alt=GIZ HERA Cooking Energy Compendium small.png|link=GIZ HERA Cooking Energy Compendium]]<br/>[[GIZ HERA Cooking Energy Compendium#Basics about Cooking Energy|Basics]] | [[GIZ HERA Cooking Energy Compendium#Policy Advice on Cooking Energy|Policy Advice]] | [[GIZ HERA Cooking Energy Compendium#Planning Improved Cook Stove .28ICS.29 Interventions|Planning]] | [[GIZ HERA Cooking Energy Compendium#Designing and Implementing Improved Cookstoves .28ICS.29 Supply Interventions|Designing and Implementing (ICS Supply)]]| '''[[GIZ HERA Cooking Energy Compendium#Cooking Energy Technologies and Practices|Technologies and Practices]]''' | [[GIZ HERA Cooking Energy Compendium#Designing and Implementing Woodfuel Supply Interventions|Designing and Implementing (Woodfuel Supply)]]| [[GIZ HERA Cooking Energy Compendium#Climate Change Related Issues|Climate Change]] | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | Cooking Energy System |'''[[GIZ HERA Cooking Energy Compendium#Cooking Energy Technologies and Practices|Cooking Energy System]]''' {{!}} | [[GIZ HERA Cooking Energy Compendium#Cooking Energy Technologies and Practices|Cooking Energy System]] {{!}} | }} <!-- |
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| | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | Basics |'''[[GIZ HERA Cooking Energy Compendium#Basics about Cooking Energy|Basics]]''' {{!}} | [[GIZ HERA Cooking Energy Compendium#Basics about Cooking Energy|Basics]] {{!}} | }} <!-- |
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| | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | Policy Advice |'''[[GIZ HERA Cooking Energy Compendium#Policy Advice on Cooking Energy|Policy Advice]]''' {{!}} | [[GIZ HERA Cooking Energy Compendium#Policy Advice on Cooking Energy|Policy Advice]] {{!}} | }} <!-- |
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| | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | Planning |'''[[GIZ HERA Cooking Energy Compendium#Planning Cooking Energy Interventions|Planning]]''' {{!}} | [[GIZ HERA Cooking Energy Compendium#Planning Cooking Energy Interventions|Planning]] {{!}} | }} <!-- |
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| | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | ICS Supply |'''[[GIZ HERA Cooking Energy Compendium#Designing and Implementing Improved Cookstoves .28ICS.29 Supply Interventions|Designing and Implementing ICS Supply]]''' {{!}} | [[GIZ HERA Cooking Energy Compendium#Designing and Implementing Improved Cookstoves .28ICS.29 Supply Interventions|Designing and Implementing ICS Supply]] {{!}} | }} <!-- |
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| | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | Woodfuel Supply |'''[[GIZ HERA Cooking Energy Compendium#Designing and Implementing Woodfuel Supply Interventions|Designing and Implementing Woodfuel Supply]]''' {{!}} | [[GIZ HERA Cooking Energy Compendium#Designing and Implementing Woodfuel Supply Interventions|Designing and Implementing Woodfuel Supply]] {{!}} | }} <!-- |
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| | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | Climate Change |'''[[GIZ HERA Cooking Energy Compendium#Climate Change Related Issues|Climate Change]]''' | [[GIZ HERA Cooking Energy Compendium#Climate Change Related Issues|Climate Change]] {{!}} | }} <!-- |
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| | + | -->{{#ifeq: {{#show: {{PAGENAME}} |?Hera category}} | Extra |'''[[GIZ HERA Cooking Energy Compendium#Climate Change Related Issues|Extra]]''' | [[GIZ HERA Cooking Energy Compendium#Climate Change Related Issues|Extra]] }} |
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| | The reactor is emitting heat, but also light, gasses and particles. While the emission of heat is wanted, the emission of gasses, particles and light are rather unintended. Good stove designs can reduce the quantity of unwanted emissions in favor of additional heat generation. The heat does not enter automatically into a cooking pot. The design of the heat transfer unit has a big effect on the percentage of the heat transferred into the food to be cooked. | | The reactor is emitting heat, but also light, gasses and particles. While the emission of heat is wanted, the emission of gasses, particles and light are rather unintended. Good stove designs can reduce the quantity of unwanted emissions in favor of additional heat generation. The heat does not enter automatically into a cooking pot. The design of the heat transfer unit has a big effect on the percentage of the heat transferred into the food to be cooked. |
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| | Overall there are two major dimensions for efficiency gains for firewood stoves: | | Overall there are two major dimensions for efficiency gains for firewood stoves: |
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| − | *Achieve complete combustion (=‘create more heat per unit of fuel used’)
| + | #Achieve complete combustion (=‘create more heat per unit of fuel used’) |
| − | *Improve heat transfer (=‘get more heat actually into the pot’)
| + | #Improve heat transfer (=‘get more heat actually into the pot’) |
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| | = Three-stone Fires or Open Fires = | | = Three-stone Fires or Open Fires = |
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| − | Worldwide, millions of people cook on so-called 3-stone fires or open fires as this is the simplest and cheapest “stove” to create. Only three suitable stones of the same height are needed to balance a pot over a fire. However, the daily use of these 3-stone fires has the following disadvantages: | + | [[File:GIZ-Feldmann-Malawi-3-stone-fire.jpg|thumb|right|300px|3-stone fire in Malawi]]Worldwide, millions of people cook on so-called 3-stone fires or open fires as this is the simplest and cheapest “stove” to create. Only three suitable stones of the same height are needed to balance a pot over a fire. However, the daily use of these 3-stone fires has the following disadvantages: |
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| | High fuel consumption:<br/>The open fire consumes a lot of fuel as | | High fuel consumption:<br/>The open fire consumes a lot of fuel as |
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| | *Health risks:<br/>As the flames are not directed or shielded, the cook can easily catch fire when approaching the cooking pot. Sparks pose an additional risk when approaching the fire. Burns are a common effect of open fires. The smoke might also cause eye infections. | | *Health risks:<br/>As the flames are not directed or shielded, the cook can easily catch fire when approaching the cooking pot. Sparks pose an additional risk when approaching the fire. Burns are a common effect of open fires. The smoke might also cause eye infections. |
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| − | [[File:GIZ-Feldmann-Malawi-3-stone-fire.jpg|thumb|left|300px|three-stone fire in Malawi]]<br/>
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| | On the other hand, users welcome some of these inefficiencies due to their positive side effects: | | On the other hand, users welcome some of these inefficiencies due to their positive side effects: |
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| | *Open flames emit light, which is welcome before sunrise or after sunset; | | *Open flames emit light, which is welcome before sunrise or after sunset; |
| | *Open fires emit heat, which is favorable in cold areas. | | *Open fires emit heat, which is favorable in cold areas. |
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| | |} | | |} |
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| | = <br/>The Rocket Stove Principle<br/> = | | = <br/>The Rocket Stove Principle<br/> = |
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| | One of the most successful concepts in stove design is the rocket stove principle, invented by Dr. Larry Winiarsky. Rocket stoves’ characteristics are:<ref name="http://www.ashden.org/files/Aprovecho2006.pdf">http://www.ashden.org/files/Aprovecho2006.pdf</ref> | | One of the most successful concepts in stove design is the rocket stove principle, invented by Dr. Larry Winiarsky. Rocket stoves’ characteristics are:<ref name="http://www.ashden.org/files/Aprovecho2006.pdf">http://www.ashden.org/files/Aprovecho2006.pdf</ref> |
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| | *An elbow-shaped combustion chamber (1:1.5) with a shelf for the fuel wood, which supports the pre-drying of the firewood and allows a controlled, and sufficient, flow of primary air to be warmed as it passes under the wood to the burning wood tips. | | *An elbow-shaped combustion chamber (1:1.5) with a shelf for the fuel wood, which supports the pre-drying of the firewood and allows a controlled, and sufficient, flow of primary air to be warmed as it passes under the wood to the burning wood tips. |
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| | *These hot flue gases pass through a well-defined gap between a ‘skirt’, and the pot, resulting in a large percentage of the heat being forced against the sides of the pot, and being transferred to the pot. Where various sizes of pot are used on the same stove, the skirt can be funnel-shaped to accommodate different pots, although some efficiency will be lost. | | *These hot flue gases pass through a well-defined gap between a ‘skirt’, and the pot, resulting in a large percentage of the heat being forced against the sides of the pot, and being transferred to the pot. Where various sizes of pot are used on the same stove, the skirt can be funnel-shaped to accommodate different pots, although some efficiency will be lost. |
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| − | [[File:Rocket stove.JPG|thumb|left|200px|The rocket stove principle.|alt=Rocket stove.JPG]]<br/> | + | {| style="width:100%" |
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| | + | | [[File:Rocket stove.JPG|thumb|left|200px|The rocket stove principle.|alt=Rocket stove.JPG]]<br/> |
| | + | | [[File:Pic2.JPG|thumb|left|300px|A rocket-type stove in action, and showing insulation of the burning chamber, skirt around pot and support frame|alt=Pic2.JPG]]<br/> |
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| − | [[File:Pic2.JPG|thumb|left|200px|A rocket-type stove in action, and showing insulation of the burning chamber, skirt around pot and support frame|alt=Pic2.JPG]]<br/> | + | <br/>Today, most of the GIZ-promoted wood stoves follow this rocket stove principle (see fact sheets below for examples). Besides household stoves also stoves for institutional or productive purposes can incorporate the rocket stove principle. For example in Malawi, the considerable savings have made institutional rocket stoves very popular among school feeding programs (see also [http://www.ashden.org/media/films/192/watch Ashden Award video 2006]). |
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| | + | | [[File:Roth Malawi Institutional Rocket Stove 170-14 Comparison.jpg|thumb|left|350px|Institutional Stove Compared to an open Fire: 40 instead of 170 kg of firewood]] |
| | + | | [[File:GIZ Roth Malawi-probec-school feeding.jpg|thumb|left|350px|School feeding program Mary`s Meals Blantyre, Malawi]] |
| | + | |} |
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| | <br/> | | <br/> |
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| − | <br/>Today, most of the GIZ-promoted wood stoves follow this rocket stove principle (see fact sheets below for examples). Besides household stoves also stoves for institutional or productive purposes can incorporate the rocket stove principle. For example in Malawi, the considerable savings have made institutional rocket stoves very popular among school feeding programs (see also [http://www.ashden.org/media/films/192/watch Ashden Award video 2006]). | + | <br/> |
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| − | [[File:Roth Malawi Institutional Rocket Stove 170-14 Comparison.jpg|thumb|left|400px|Institutional Stove Compared to an open Fire: 40 instead of 170 kg of firewood]] [[File:GIZ Roth Malawi-probec-school feeding.jpg|thumb|left|400px|School feeding program Mary`s Meals Blantyre, Malawi]]
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| | = Wood Fuel Stoves with Forced Convection<br/> = | | = Wood Fuel Stoves with Forced Convection<br/> = |
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| | *[[:File:GIZ HERA 2011 Inkawasi-Port til Peru.pdf|Inkawasi portatil]], Peru (2011) | | *[[:File:GIZ HERA 2011 Inkawasi-Port til Peru.pdf|Inkawasi portatil]], Peru (2011) |
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| | = Further Information<br/> = | | = Further Information<br/> = |
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| | *<span style="color:#FF0000">Classification of Cookstoves</span> | | *<span style="color:#FF0000">Classification of Cookstoves</span> |
| − | *[[Cooking_with_Firewood|Cooking with Firewood]], article on energypedia | + | *[[Cooking with Firewood|Cooking with Firewood]], article on energypedia |
| | *[[Energy-Saving Cooking Equipment|Energy-Saving Cooking Equipment]]<br/> | | *[[Energy-Saving Cooking Equipment|Energy-Saving Cooking Equipment]]<br/> |
| | *[[Portal:Improved Cooking|Improved Cooking Portal]] on energypedia | | *[[Portal:Improved Cooking|Improved Cooking Portal]] on energypedia |
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| | = References<br/> = | | = References<br/> = |
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| − | [[Category:Cooking_Energy_Compendium_(GIZ_HERA)]]
| + | {{#set: Hera category=Cooking Energy System}} |
| − | [[Category:Rocket_Stove]]
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| − | [[Category:Improved_Cooking]]
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| − | [[Category:Cookstoves]]
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| − | [[Category:Wood_Energy]]
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| | [[Category:Cooking_Energy]] | | [[Category:Cooking_Energy]] |
| | + | [[Category:Wood_Energy]] |
| | + | [[Category:Cookstoves]] |
| | + | [[Category:Improved_Cooking]] |
| | + | [[Category:Rocket_Stove]] |
| | + | [[Category:Cooking_Energy_Compendium_(GIZ_HERA)]] |
Firewood is wood from logs, sticks or twigs. It has been used as a fuel since the beginning of mankind. In principle, it is renewable and relatively easy to produce, transport and store. However, the use of firewood for cooking is commonly associated with deforestation and health problems. This is not an inherent problem of the fuel, but is strongly influenced by the quality and quantity of its correct usage and can be overcome by improving the efficiency of the wood fuel usage.
Two major factors determine if firewood burns clean and efficient: its moisture content and the oxygen supply of the fire. While it depends on the user to make sure that the fuel is dry, the air-flow depends on the stove design. In a natural draught stove, the supply of air is created by the chimney or stack height of the fuel. However, there must be a difference in temperature between the stove and the top of the chimney to generate draught. Natural draught is likely to cause incomplete combustion with higher emissions and energy losses through the chimney. Moreover, it is also difficult to regulate.
The main influencing agent for “a)” and “b)” is heat, whereas “c)” is regulated by the supply of oxygen.
As shown in the figure beside, in the wood-fuel cooking system, firewood is mixed with air in a reactor. After ignition, a chain reaction is triggered in which heat is generated. This heat is transferred through 3 processes:
Convection: Hot gasses are passing a surface transferring heat into surrounding materials;
Radiation: Red hot embers is radiating heat into surrounding materials;
Conduction: Heat is conducted through materials. Metal is a good heat conductor, whereas air is a poor heat conductor.
The reactor is emitting heat, but also light, gasses and particles. While the emission of heat is wanted, the emission of gasses, particles and light are rather unintended. Good stove designs can reduce the quantity of unwanted emissions in favor of additional heat generation. The heat does not enter automatically into a cooking pot. The design of the heat transfer unit has a big effect on the percentage of the heat transferred into the food to be cooked.
Overall there are two major dimensions for efficiency gains for firewood stoves:
Worldwide, millions of people cook on so-called 3-stone fires or open fires as this is the simplest and cheapest “stove” to create. Only three suitable stones of the same height are needed to balance a pot over a fire. However, the daily use of these 3-stone fires has the following disadvantages:
On the other hand, users welcome some of these inefficiencies due to their positive side effects:
The development of improved cookstoves is facing a dilemma: the same characteristics are at the same time responsible for both users’ complaints and appreciations of the 3-stone fire. There is no solution which can satisfy all expectations. Any new stove will be a trade-off between different user needs. This dilemma is summarized in the table below. Furthermore, users are used to a specific cooking system and any change in cooking habits needs time.
Households have to prioritize their needs in order to come up with the decision if an improved cook stove is suitable for them. In areas with fuel scarcity, the need for reduced fuel consumption might be ranked higher than the need for space heating or lighting after dark.
All improved firewood stoves apply at least some of the aspects listed below geared toward increasing efficiency and improving heat transfer.[1]
One of the most successful concepts in stove design is the rocket stove principle, invented by Dr. Larry Winiarsky. Rocket stoves’ characteristics are:[2]
Instead of naturally ‘pulling’ air through a stove by stack height, fans or blowers are useful to ‘push’ air into the combustion chamber. This enhances a good air-fuel mix and thus, more complete combustion. Electricity is the most convenient power source to create a forced air-flow. It can be provided by batteries or, if available, through the grid. Forced convection can reduce emissions of stoves by up to 90 %, thus alleviating Indoor Air Pollution (IAP) levels. See also the article onMicro-Gasifier Cookstoves. Recently, thermo-electric generators (TEG) have been developed to power fans in stoves. They use the temperature differences within the stove to generate electricity, thus eliminating the need for external power supply. TEGs also have great potential to provide power to other applications, such as LEDs or mobile phones. However, the unit makes a stove more expensive and can be destroyed easily, when getting too hot. Pico PV units could also easily provide that little electricity needed for mobile charging without burning firewood.
The stove factsheets are a series of technical information sheets on different stoves promoted by GIZ. Wherever available, additional information such as construction manuals and user guidelines for the respective stoves is also provided.
