Monday, September 3, 2012

Improved cookstove design

Because so much time is spent in the cook-house, stove designs are a leverage point we can focus on improving to create multiple benefits:

  • Better air quality means better health
  • Faster cook times
  • Less fuel required
  • More time to spend on other activities

By controlling only two factors - airflow and thermal mass - we can improve stove design to optimize heat efficiency and transfer. 


How a Rocket Stove works:

A rocket stove achieves efficient combustion of the fuel at a high temperature by ensuring a good air draft into the fire, controlled use of fuel, complete combustion of volatiles, and efficient use of the resultant heat.

As the fuel burns within the combustion chamber, convection draws new air into the combustion chamber from below, ensuring that any smoke from smoldering wood near the fire is also drawn into the fire and up the chimney. The chimney can be insulated to maximize the temperature and improve combustion; according to studies this will increase efficiency by up to two percent more.

For cooking purposes, the design keeps the cooking vessel in contact with the fire over the largest possible surface area. A pot skirt can be used to create a narrow channel that forces hot air and gas to flow along the bottom and sides of the cooking vessel.

Optional baffles guide hot air and flame up the sides of the pot. For space heating purposes, the heat is transferred to a heat store which can, in some cases, be part of the structure of the house itself. The exhaust gasses then pass out of the building via the chimney.

The design of the rocket stove allows it to operate on about half as much fuel as a traditional open fire and can use smaller diameter wood. If the stove is insulated and raised from the floor, the danger of children burning themselves is reduced. Some more recently designed rocket stoves are self-feeding, using gravity to add fuel to the fire as required.

 - Wikipedia, 09/04/12 -


Existing stoves observed in all 3 communities look like this:


Photos: Typical cookstove in Vanuatu, built on the ground with little or no insulation or airflow control, resulting in a smokey fire (indicating an incomplete & inefficient burn); Soot on the ceiling of cookhouse indicates how much particulate matter is released into the air with an inefficient burn

Our favorite Village Crazyman had already come up with improvements to his stove design:


Photo: Sawi's improved stove design.

A class brainstorm was conducted to explore ways we could improve Sawi's design:


Photo: Class brainstorm on improved stove design.

Not surprisingly, Sawi had created another improved stove design:

Photo:  Although this design focused primarily on improving the thermal mass, it still halved the typical cooking time for a suckling pig to just an hour; it was left to the class to further improve the design by harnessing airflow.

Here are some other variations on rocket stove from our friends at

A_whole_lot_of_rocket_cook_stoves_(wood_burning_stoves_forum_at_permies).pdf Download this file

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