Wood Stove

Desiderata

• Protection from wind
• Fuel supply
  • Continuous supply mechanism is better.
• Air supply
  • Bottom, top, sides in case of gasification.
• Chimney effect support
• Portability
• Pot support
• Life
  • Small gauge Iron wires degrade with use
• Repairability

Gasification

• Aka wood gas.
• Gasifiers can separate gas generation from gas combustion in space and time. In a reactor (gas generator) that is optimized for heat-dependent drying and pyrolysis, solid biomass is first converted into gases and vapors. These are guided into a combustion zone (gas burner) where they are burnt with a surplus of oxygen from a secondary air inlet.
• In a conventional fire the heat is controlled by regulating the fuel supply: the more fuel we add, the more heat we generate, provided sufficient air is available for the combustion. Gasifiers control and optimize both fuel and air supply.
• Gasifier stoves are currently the cleanest burning option to burn solid biomass in a cook stove. The “gas burner” provides the convenience and efficiency similar to cooking on fossil gas with very little soot and other emissions.
• Heat output is not easy to regulate.

Design patterns

• Provide holes below

Material

Cubes with top side open

• If the combustion area is large enough and not cramped, equivalent to burning wood out in the open. Or in principle equivalent to a “Cube with 2 sides open” type stove with pot on top.
• Example: traditional homa-kUNDa-s (Idealized).

Characteristics

• Consumes quite a bit of wood.
• Lot of smoke when the fire is low, and in the initial and terminal stages.
• Ash accumulation + charcoal creation observed.

Improvement with grill and sieve

This seems to achieve characteristics similar to “Cube with 2 sides open + holes for ventilation at the bottom and sides” type described below.

Improvement with holes, fan fitted at bottom

• IISc PEPL Biostove - amz

supernova model

• “this kund generates lowest % of carbon-monoxide and needs less quantity of yagna herbal material as the material is vaporized and gasified 100% without waste because the temperature attained by the kunda is always above 300°C along with the purified flames upto 1300°C, the Kund is designed from copper pot to get the uniform temperature along with the impact of copper oxygenation which play vital role in purification of atmosphere. "

  

• “The fallen ash collects in a bottom plate, above the fan, which can be disposed easily. You can adjust the speed of the fan, or use it for initial jwalanam, then switch off. I think this will be more useful where charu, apoopa etc are offered as havis.”

Cube with top + 1 sides open

Characteristics

• Relatively inefficient burning - tends to produce charcoal besides ash, quite a bit of smoke.
• Indian cooking smoke (indoor) said to equal 20 cigarettes a day (source: prakti promotional video).
• Temperature at top: max 580°C (IG18)

Realizations

• mud stoves cost 250 Rs in 2018 and lasted 6 months.

Modifications

• Collapsible
  • Disadvantage - need to wait to cool down before disassembly. A hazzle.

Ventilation at the bottom and sides

Realizations

• Prakti woodstove.

Characteristics

• Relatively efficient burning. 70 to 90% less smoke compared to basic “Cube with 2 sides open”. (Numbers from prakti woodstove videos 2018.) Is this still equal to 2 cigarettes a day (going by prakti promotional videos)?

Rocket stove

• Good YT explanation here.
• Types: L and J shapes.

Characteristics

• Temperature at top: 715°C (IG18). With good insulation, can even reach 1100°C (IG18)
• Burns about 1 kg of fuel per hour (himalayan video).

Operation

• Must clean up ash buildup at the bottom so as to not block air.
• One needs to keep pushing the wood in - with hand or with gravity to keep the stove burning.

Key principles

• Air intake: One leaves generous space to suck in air from under the mesh which holds the wood fuel sticks - or one provides a separate air intake pipe at the bottom.
• Chimney effect - described seperately.
  • Needs a minimum height.
• Even the smoke/ soot burns in good models.
• Limited fuel consumption:
  • Only a small part of the wood ever burns - very efficiently at that, at high temperature.
• Insulation: Combustion, air-sucking and cooking efficiency keeps increasing with temperature increase. So, the stove body is ideally well insulated.

Construction videos

• Clay moulds - HS19
• With just bricks - basic - HS19

Chimneys

See chimney page.

• It’ll make the smoke exit point higher, at least - which will make standing around comfortable.

Elevation

• कुण्डानाम् उच्चतया धूमप्रभावेणायुर्हरणं न स्यात् तावत्।