Rocket stove

Rocket stove with oven

A rocket stove/Rocket mass heater is a type of stove combining the air-intake with the fuel-feed slot in an opening terminated by the combustion chamber, further leading to a chimney and heat exchanger. A rocket stove is signified by ease of construction and simplicity of building materials while accepting small-diameter fuel such as twigs or small branches, yielding high combustion efficiency and directing the resultant heat onto a small area.

Übersicht

A small manufactured Rocket cooking stove

A rocket stove achieves efficient combustion of the fuel at a high temperature by ensuring that there is a good air draft into the fire, controlled use of fuel, complete combustion of volatiles, and efficient use of the resultant heat. It has been used for cooking purposes in many third-world locales (notably Rwandan refugee camps) as well as for space and water heating.

A rocket stove's main components are:

• Fuel magazine: Into which the unburned fuel is placed and from where it feeds into the combustion chamber
• Combustion chamber: At the end of the fuel magazine where the wood is burned
• Chimney: A vertical chimney above the combustion chamber to provide the updraft needed to maintain the fire
• Heat exchanger: To transfer the heat to where it is needed, ie the cooking pot.

The fuel magazine can be horizontal where additional fuel will be added manually or vertically for automatic feeding of fuel. 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 to the fire is also drawn into the fire and up the chimney. The chimney should be insulated to maximize the temperature and improve combustion. From the chimney the heat passed into a suitable heat exchanger to ensure the efficient use of the generated heat.

For cooking purposes the design keeps the cooking vessel in contact with the fire over the largest possible surface area by use of a pot skirt to create a narrow channel which forces hot air and gas to flow along the bottom and sides of the cooking vessel. Optionally 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 stove means that it can operate on about half as much fuel as a traditional open fire and can use smaller diameter wood. They are insulated and raised from the floor which reduces the danger of children burning themselves. Some more recent designs use are self feeding using gravity to add fuel to the fire as required.

History

Dr. Larry Winiarski, now Technical Director of Aprovecho, began developing the Rocket Stove in 1980 and invented the principles of the Rocket stove in 1982. TWP and AHDESA were winners at the Ashden Awards for Sustainable Energy in 2005 in the 'Health and Welfare' category for their work in Honduras with the 'Justa Stove' which is based on principles of the rocket stove. Aprovecho were winners of the Special Africa Award at the Ashden Awards in 2006 for their work with rocket stoves for institutional cooking in Lesotho, Malawi, Uganda, Mozambique, Tanzania and Zambia.

Types of stove

attached to a heat exchanger to heat water

Cooking stove

The rocket stove was originally developed for cooking purposes where a relatively small amount of heat is required on a continuous basis which is applied to the bottom and sometimes also the sides of the cooking pot. Stoves can be constructed from brick, old tin cans, steel or be purchased.

Rocket Stoves are found more commonly in the third world countries where wood fuel sources are more scarce but it has been introduced in the United States in the recent years. Some of them are small for portability with insulation inside a double-walled design with a chamber for partial biomass gasification and additional mixing to increase BTUs and provide a cleaner, more complete burn. The advantage of these rocket stoves is very little fuel they need, such as wood and dry weeds, to be able to cook a whole meal with it, keeping the air more clean with less hydrocarbons.

Space heater

For space heating the aim is normally to use the rocket stove to heat a mass of material which will hold the heat and slowly release it. The chimney is sometimes developed as a horizontal heat exchanger to distribute heat around a building before the exhaust gasses are released outside.

Water heater

Rocket stoves can be used to heat water via a heat exchanger which transfers heat to a body of water in a nearby container.

See also

• Air-tight stove
• Beverage-can stove
• Franklin stove
• Hobo stove
• Portable stove
• Kelly Kettle

Further reading

• Bilger, Burkhard. “Hearth Surgery - The quest for a stove that can save the world”. The New Yorker, 21st and 28th December 2009. Pages 84 to 97.

External links

• Step by step plans for constructing rocket stoves
• Poster on how to make your own rocket stove
• Instructional video on how to make your own rocket stove
• Detailed design instructions from Aprovecho Research Center
• Building Environmentally Friendly Rocket Stove - History of eco-rocket stove and detailed specifications in building one.
• Demonstration rocket stove for The Campus Center for Appropriate Technology at Humboldt State University
• Build a Rocket Mass Heater
• Rocket Stove Mass Heater Tour and How-To includes video samples of 12 heaters and a 10 minute how-to.