The panel style Cookit, which is made of cardboard and aluminum foil is the simplest type of solar cooker.
Advantages: It's very cheap, it can be manufactured anywhere by anyone; it works well with the lightweight aluminum pots that most refugees and others in the developing world already have; once the food is in, the cook can go off and do other things. The Cookit only needs to be turned once or twice during the cooking process to keep it facing the sun.
Issues: In order to best absorb infrared light, the cooking pot and lid must be painted black with non-toxic "blackboard paint" which is readily available in the developing world (in the U.S. we would use barbecue paint or just buy a black enameled pot); the pot must be placed inside an oven-proof plastic bag (like the one we use to cook turkeys at Thanksgiving) to concentrate the heat. The plastic bags wear out--each bag lasts for about a month. Temperatures range from 225-275 F. It takes two to three hours to cook a pot of beans or a chicken stew. The Cookit can last one to two years as long as it is kept dry and the goats don't get to it.
A more durable version of the pot and plastic bag system used with the Cookit. It is manufactured in Mexico, but the DC-based organization that developed it (Solar Household Energy) may be willing to share the design.
Advantages: It is very durable and if cared for can last for years. It is made of heavy duty glass with a steel bowl that fits inside. Instead of the plastic bag, the glass bowl and lid keep the heat in. Also the lid can be lifted to add ingredients or taste the food while it is cooking. The Hot Pot works with the Cookit, but it can also be ordered with a very durable polished aluminum reflector that folds up like a Japanese fan. These two products will last for years. The Hot Pot also cooks like a crock pot.
Issues: The glass bowl is heavy and much bulkier to ship and it can break. The bowl is more expensive than the cheap aluminum pots used by refugees and the poorest of the poor. It is made in a factory.
This is a box cooker. The two models above are panel cookers. It is manufactured in Illinois and is used by campers and even ice fishermen. I even know of some little old ladies in desert retirement communities who do their roasting and stewing in a Sun Oven during the summer months so they don't have to turn on the oven in their air conditioned houses.
Advantages: This box cooker provides more insulation and is less affected by the ambient temperature or the wind that are the panel cookers described above. (note that solar cookers work in cold weather--all they need is bright sun). The box cooker can (depending on its size) hold more than one pot. You can see the food cooking. The box cooker reaches temperatures between 325-375 f. in bright sun.
Issues: The Sun Oven is relatively expensive, but similar designs (which can be made of cardboard, wood, or other locally available materials) are available in the public domain on the solar cooking archive.
This is the mother of all solar cookers. It can bake up to 300 loaves of bread a day.
Advantages: The Villager is for large operations and is completely reliable, because it has a propane back-up. It is portable (it is on a trailer), durable and when used as a bakery, can save 150 tons of wood a year. I think the Army should be using these in Iraq to save fuel.
Issues: Villagers are made to order in Illinois by Sun Ovens International and are quite expensive. The donation of Villagers to community-based micro-enterprises in Afghanistan, South Africa and elsewhere have been funded primarily by Rotary Clubs.
This is another type of box cooker. It is made of recycled soda bottles. Coca Cola donated the money to the Solar Oven Society to buy a mold to press out the black boxes and the clear lids. This one can hold two pots or a sheet of cookies.
Advantages: Relatively inexpensive, lightweight, easy to use. I use one frequently in my back yard here in Arlington.
Issues: I am told that after a few years of extensive use, the plastic eventually begins to warp in the sun and the clear plastic cover begins to get cloudy, however I got mine in Afghanistan from a non-profit in Kabul in 2005 and it is still working just fine.
This box cooker (which has electric back-up) is made in India and marketed in the U.S. with a few modifications.
Advantages: Reliable because a thermostat can be set at a desired temperature and if the sun goes behind a cloud and the temp drops, the electric power kicks in to keep the temp steady.
Issues: Expensive. The box is designed to hold several small pots (for Indian cooking). Large U.S. pots won't fit.
This is a parabolic solar cooker that focus all light on a small area at the bottom of the pot.
Advantages: It can be used for boiling and frying. It cooks as fast as an open fire. Versions of this model can be manufactured locally. Millions of parabolic cookers are used in China, Tibet and India. China and Tibet also use modified parabolic cooker called a Papillon, which has also been successfully introduced in Somalia by a California non-profit called Sun Fire Cooking.
Issues: Parabolic cookers require continuous adjusting (about every ten minutes) as the sun moves across the sky. They cannot be left unattended (but then neither can an open fire). People need more training in how to use these because of the possible risk from sun glare.