Rocket stove

The rocket stove is a variety of wood-burning cooking stove. It is easy to construct, and it uses low-cost materials. The rocket stove's main components are:

* Chimney: a metal box (such as a 5-gallon tin can) or pipe standing vertically and supporting the cooking vessel
* Fuel magazine: a short length of steel or ceramic pipe fitted horizontally into the base of a chimney
* Fuel shelf: a flat plate to hold the fuel clear of the bottom of the magazine to allow air to flow underneath
* Heat exchanger: a tubular metal shield that forces hot gases from the chimney to pass over the sides of the cooking vessel

The chimney and magazine are joined at a right angle, forming the 'rocket elbow', and it is at this junction that primary combustion occurs.

Overview

Compared with open fire cooking methods still used in many areas of the world (sometimes known as 'three stone fire' - a small fire contained by three or more rocks such that a pot or pan can rest on the flames), this stove operates on about half as much fuel, and produces substantially less smoke. Furthermore, the design of the stove requires small diameter lengths of wood, which can generally be satisfied with small branches. As such, sufficient fuel for cooking tasks can be gathered in less time, without the benefit of tools, and ideally without the destruction of forested areas.

Because these qualities improve local air quality, and discourage deforestation, the rocket stove has attracted the attention of a number of Appropriate Technology concerns, which have deployed it in numerous third-world locales (notably, the Rwandan refugee camps). This attention has resulted in a number of adaptations intended to improve convenience and safety, and thus the size of the target audience. The Justa Stove [ [http://www.ashdenawards.org/winners/trees Justa stove wins award] ] , for example, is a cousin of the rocket stove adapted for indoor use and family cooking needs. While it contains a 'rocket elbow' (the working core of a Rocket Stove), it differs in that it contains a flat griddle surface and a simple smokestack.

Traditional cooking method

A rocket stove addresses the environmental problems of using an open pit fire for cooking and home heating, the most important concern being indoor air quality. Biomass fuels release large amounts of air pollutants when burned on traditional open pit fire, and these pollutants become concentrated in inadequately ventilated homes and dwellings.

Another concern with traditional wood fires is the inefficiency of fuel consumption. Traditional open pit wood fires are very efficient at turning wood into energy, but inefficient at transferring the released energy into the cooking vessel. Most of the released energy in the wood is wasted heating the surrounding air rather than heating the cooking vessel. The inefficient transfer of energy requires the use of more wood, which has to be harvested from the surrounding environment, causing environmental stress.

The third drawback of traditional wood fires is the danger to children. Because open fires are located on the floor of the dwelling, children can easily fall into the fire.

Benefits

The main justifications for rocket stoves are economical, social, and environmental. Stove programs can produce economic benefits, saving time and money for the users. In urban areas where people purchase biomass fuel, the payback time for the cost of a rocket stove is short, thus saving on the cost of fuel.

Rocket stoves can help reduce the over-harvesting of trees. Improved indoor air quality and fuel efficiency have social and health benefits, especially for women and children. In order to reduce indoor air pollution, rocket stoves must improve combustion of the wood fuel, which means reducing the amount of smoke and harmful emissions produced during the burning process. The key to efficient combustion is to burn wood at a high temperature, and there are several ways to achieve this: -

* A good air draft into the fire
* Insulation around the fire
* Metering the fuel
* Complete combustion of volatiles

The most important factor, metering the fuel, requires only the burning portion of the wood to be heated. Convection draws new air in below and through the fuel, and any smoke from smoldering wood near the end of the magazine is pulled directly into the flame. Fully burned biomass fuel produces less smoke and emissions.

The main way to improve the fuel efficiency of rocket stoves is to improve the heat transfer from the fire to the cooking vessel. Most importantly, the hot air and gas released from the fire must contact the cooking vessel over the largest possible surface area. This is accomplished through the use of a pot skirt that creates a narrow channel forcing hot air and gas to flow along the bottom and sides of the cooking vessel. Heat transfer can also be increased by using wide pots. Increasing the speed of the hot gases that flow around the pot can also improve heat transfer.

Rocket stoves are insulated and lifted off of the floor. This reduces the danger of children burning themselves, which is an important improvement over traditional open pit fires.

See also

* Rocket (disambiguation)
* Franklin stove
* Ashden Awards (several winners using Rocket-style stoves)

External links

* [http://video.google.com/videoplay?docid=797446823830833401 instructional video on how to make your own rocket stove]
* [http://www.aprovecho.org/web-content/publications/publications.html Detailed design instructions from Aprovecho Research Center]
* [http://www.pyroenergen.com/articles08/eco-rocket-stove.htm Building Environmentally Friendly Rocket Stove] - History of eco-rocket stove and detailed specifications in building one.
* [http://www.appropedia.org/CCAT_rocket_stove Demonstration rocket stove for The Campus Center for Appropriate Technology at Humboldt State University]
* [http://www.crest.org/discussiongroups/resources/stoves/Wilmes/Buildjusta.html crest.org]

References