10 Homebuilt Tech Tools for the Developing World


Solar Cooker

Illustration of a basic box cooker
Illustration of a basic box cooker

The people of many developing nations still use biomass -- wood, charcoal, dung or crop byproducts -- as fuel for cooking. In Mexico, for example, 95 percent of rural households cook with wood on open fires [source: Ashden]. Unfortunately, woodsmoke contains toxins that have been linked to a number of health problems, including pneumonia, lung cancer, chronic obstructive pulmonary disease and heart disease.

Well-designed stoves, such as rocket stoves, can improve the efficiency of wood burning. Rocket stoves use a vertical combustion chamber and a horizontal fuel and air inlet at the bottom. The design improves heat transfer and makes it possible to direct hot gases to the cooking pot or griddle. Families that cook with rocket stoves consume far less wood and expose themselves to less smoke.

But why not eliminate biomass altogether? That's the benefit of solar cookers, which concentrate the sun's energy to slow-cook food. Box cookers -- the most basic type -- can be built using simple, easy-to-find materials. One basic design requires just two cardboard boxes (one smaller than the other), a small piece of glass, black paint and newspaper. Cut the box sides at an angle of 30 to 40 degrees, making sure the front of the larger box has a lip. Then nest the smaller box inside the larger, fill the gap between the two boxes with newspaper or other insulating material, paint the inside black and set the glass on top so it rests against the lip. When you place this cooker in the sun, it will heat up to about 250 degrees Fahrenheit (121 degrees Celsius).

An improved design uses sturdier materials, such as wood instead of cardboard and foam instead of newspaper. It also adds four foil-coated panels to act as reflectors to concentrate the sun's energy. The result: a cooking temperature of 350 to 400 degrees Fahrenheit (177-204 degrees Celsius) -- hot enough to roast a whole chicken!