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In 1976, teams from Aprovecho assisted indigenous stove builders in the highlands of Guatemala to create the Lorena stove. Since then thousands of these stoves have been built, not only in Central America, but all over the world. The Lorena, made from sand and clay, removes smoke from the kitchen, is low cost and makes a stable platform assisting kitchen activities.
By 1983, however, Aprovecho consultants realized that while the Lorena high mass stove had beneficial attributes, it was not very fuel-efficient. The dense materials around the fire diverted heat from the intended purpose: to cook food. The earthen walls around the fire also cooled the combustion chamber, creating smoke.
An Improved Generation of Stove Designs
Dr. Larry Winiarski, Mechanical Engineer, has directed the research and development at Aprovecho of a next generation of improved cooking stoves. Larry has refined a set of design principles that can be used to help any type of stove to burn cleanly and effectively. The improved combustion chamber is made from natural sources of insulation, not dense earth. A short internal chimney above the insulated fire (the Rocket elbow)creates beneficial draft resulting in the clean burning of wood and other biomass. Isolating the heat flow from the stove body dramatically increases heat transfer efficiency to the pot(s).
Insulative, Refractory Materials
The Winiarski stove principles encourage high temperatures in the combustion chamber. High temperatures degrade most materials. Even stainless steel will be damaged in a relatively short time. Ceramic parts can be made, however, that will last for years in stoves. Many different recipes, using locally available materials, have been developed by Aprovecho that create insulative ceramic Combustion chambers that stand up to the higher temperatures. Certain kinds of indigenous pottery also do well in Rocket stoves. A floor tile called a baldosa is used in many of the 5,000 Aprovecho designed stoves built in Central America since 1997.
Flexible Designs
There is always a need for variation in stove design. One village may insist that pots stay clean. A village fifty miles away may need greater fuel efficiency. Aprovecho designed stoves can change to meet the cook’s expectations but the essential combustion and heat transfer principles remain the same. Working with local people, it is important to be flexible in creating stoves that meet local needs. Not changing the outward appearance of the traditional stove can be helpful in gaining acceptance of the new technology inside the stove.
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Sustainable
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