Cooking with the sun

In many energy-poor areas of the world, solar energy provides a potential boon.

by Alice Martinez
hose of us fortunate enough to live in the industrialized world don't spend much time thinking about cooking. Flip a switch, turn a valve - presto - instant heat, clean, fast and always available.
The picture in poor nations is radically different. Heat for cooking is generally only available by gathering and burning some local fuel: wood, charcoal, dung, leaves, etc. The direct and indirect consequence of this simple daily necessity are dramatic:

Here comes the sun

Fortunately - almost unbelievably - there is a simple solution that could have a profound impact on these problems: the solar box cooker (SBC).
At noon on a clear, sunny day, each square yard of the earth's surface receives about 1100 watts of solar energy. Of course, there are may factors that reduce the amount of available energy, including latitude, time of year, time of day and atmospheric conditions. Nevertheless, even on an overcast day, the amount of energy reaching the ground is substantial.
The SBC traps this energy as heat and makes it available for cooking. The structure of the SBC is simplicity itself: an insulated box with a transparent lid (to let sunlight in) that is black on the inside (to absorb the solar energy). Reflectors outside the box direct sunlight onto the lid and into the box. You just point the box at the sun, and the inside gets hot. If you've ever gotten into a car parked in the sun that has had its windows rolled up, the principle should be familiar.
An SBC can be constructed from a wide variety of materials, often using what is on hand or easily available. The box can be constructed from any material with decent insulating properties; wood works well, but a demonstration unit can be built with cardboard. A sheet of glass is preferred as a lid, but plastic sheeting can be used. Non-toxic black paint can be used to make the inside absorb heat, but so can soot from a smoky fire or fire-darkened clay. Workable reflectors, to reflect sunlight onto the lid, can be made from aluminum foil wrapped over any rigid, flat material.
An SBC with excellent cooking characteristics can be constructed for about $20 in materials. In many parts of the world, this is less than a family will spend for fuel in two weeks.

The payoff

The SBC can improve health in the third world in numerous ways. It can be used to pasteurize water, thereby reducing the incidence of diarrheal illnesses. Since the SBC is smokeless, its use will reduce the incidence of respiratory and eye ailments. It could even be used to disinfect medical instruments. Several pots of food can be cooked simultaneously, permitting separate preparation of weaning foods for babies. Breadstuffs can be baked in an SBC, yielding foods which have some degree of stability.
Use of the SBC will reduce dependence on fuel wood and charcoal. Reduced rates of deforestation will yield reduced rates of soil erosion. In many villages there is a complete lack of fuel wood and the people have resorted to burning dried animal dung or crop residues. These practices deprive the soil of much of its potential fertility. Use of the SBC minimizes the burning of dung and crop residues, thereby permitting those materials to be used as natural fertilizers.
Lastly, the SBC is a significant labor-saving device since less time would need to be spent in accumulating and transporting fuel wood or dung.

The advocates

Two key organizations advocating the SBC are Solar Cookers International (SCI) and Solar Box Cookers Northwest (SBCN). These are primarily volunteer-based organizations - the spread of solar cooking is basically people-to-people. They provide a number of ways that you can participate, including: giving demonstrations at public or private events, advocacy with leaders and policy makers, membership, and fund-raising. In addition, they need help translating educational materials from English to other languages. If you are fluent in another language, they would appreciate your help. Please see the sidebar below for contact information.
The SBC is no panacea - it isn't going to eliminate poverty, hunger or disease. But it could provide a solution to some traditional problems that will make these conditions a little more tractable.

Call to action - What You Can Do

f you are interested in volunteering to help spread the word about solar cookers, please contact SCI or SBCN at the addresses below. If you have access to the World Wide Web, the Solar Cooking Archive can be found on the internet at: This is an excellent source of information about all aspects of solar cookers.
Solar Cookers International (SCI) has published a directory of 500+ solar cooking experts and advocates in 63 countries. Along with contact information, other pertinent info is provided, such as activities, funding, and number of cookers in the local area. The directory is available for $9.20 (includes postage) from SCI, 1724 11th St., Sacramento, CA 95814 USA.
Solar Box Cookers Northwest (SBCN) is now offering a compact, light-weight kit that brings together hard-to-find materials needed in international projects. They ask a donation of $60 or more to pay their costs. Everything is neatly packed inside a mailing tube ready for easy transport. The kit includes: A 24" x 36' roll of 3M UV-resistant 4-mil plastic film
100' of 1" high-temp aluminum tape
9 oven cooking bags for use with the solar panel cooker
4 utility knives
2 packages of extra utility blades
2 Acu-rite aluminum oven thermometers (cut down to save space and weight)
5 SCI reusable water pasteurization indicators
8 ounces (235 dl) of non-toxic black paint

Recipes for making wheatpaste
To order a kit, write to: Solar Box Cookers Northwest/ 7036 18th Ave. NE/ Seattle, WA 98115.
Sol Food is a 56-page cookbook of healthy solar cooker recipes such as Solar Stew, Sun Lasagne, Pasta Solar Salad, Zucchini Sun Feast, Elegant Cherry Pie, and Oatmeal Raisun Cookies. Author Harriet Kofalk also gives brief illustrated directions for building a solar cooker. Available from Peace Place, 175 East 31, Eugene, OR 97405 USA ($7.95 includes postage).