A fundamental challenge involves climate and weather. Sometimes people who live in places where the sun feels very strong and the air is hot expect solar cooking will work well for them. However, the strong sun may be an infrequent sun, one that is often obscured by clouds, or the sunny hours might be very different from the hours when people are used to cooking and eating their major meals.
Perhaps the most fundamental challenges are economic. The most obvious economic benefit to solar cooking is reduction in costs for cooking fuel. In many developing countries, especially in urban areas, poorer families may spend 20 percent or more of their total income on fuel for cooking. Increasingly, as scarcity drives up prices, they pay more for the cooking fuel than for the food being cooked. Because cooking fuel makes up such a high percentage of the cost of living for the poorest sectors of the world's population, solar cookers offer the greatest relative advantage to these sectors. The problem is that these sectors are the least able to invest in a new technology--and the least likely to want to risk cooking their one meal per day on a device that is new and unknown. In addition, large numbers of poor people live in what are thought of as "poor" countries--where the infrastructure for producing cookers, distributing cookers, educating the public about solar cooking, etc., is least developed. Something as basic as typing up a report or doing the accounting for expenses in a solar cooking dissemination project is made much harder by the fact that in many leading cities in developing countries, the electricity flickers on for only a few hours per day.
Solar cookers are not used more frequently primarily because they are not well known. In the few areas where promoters have made solar cookers well known, adoption of solar cooking does take place. These places are scattered. The village of Villa Seca, Chile, was the site of a promotion program sponsored by the University of Chile, and now almost every household has a solar cooker, and the cookers are used often. CEDESOL (an acronym meaning roughly "Center for Development of Solar Energy") in Paraguay reports that there are several "solar villages" in that country. The Sun Fire Cooking organization in Somalia reports that a strong majority of the people in the village of Bander Beyla cook with solar energy. In the Nyakach district in Western Kenya, at least fifteen percent of the families have solar cookers in a project that is far from being fully mature.
I am not saying that all that is required to spread solar cooking is to simply let people know that it exists. Usually, people need to see a solar cooker in action and taste the food. Often, it helps for a person to have a chance to try a solar cooker for themselves. When people start solar cooking, they usually benefit from a short formal training in using the cooker and also from follow up visits and coaching by an experienced solar cook. All of those activities cost something, and in most of the world, the solar cooking promotion that is going on is performed by well-meaning individuals and small organizations who have trouble finding the funding to expand their programs to reach large numbers of people.
Some solar cookers are so inexpensive that the cost of the awareness-building and teaching activities is far higher than the cost of the cookers needed to supply a community. But even in these cases, the cost of the cookers--or the supplies to make them--is a factor that challenges low-income organizations even as it challenges low-income individuals.
Many of the less expensive cooker types can be made at home or by semi-skilled craftspeople. But in many remote villages--and in many not-so-remote provincial capitals--key supplies such as aluminum foil or glass may be unavailable or prohibitively expensive.
In short, solar cooking promotion programs face many logistical problems that help drain their meagre resources. And these logistical problems are intensified by the fact that the most important groups of potential beneficiaries for these programs often live in areas without roads, electricity. or even literacy.
In addition to problems related to climate, economics, logistics, and the fact that solar cooking is not well known, most solar cooking promoters are able to cite other specific problems they have encountered. As stated before, most of the lower-cost solar cookers do not fry foods, so where frying is the major cooking activity, these cookers are received less enthusiastically. Promoters have also reported that disbelief in the possibility of solar cooking is a serious obstacle. Sometimes when people with no background in physics and engineering see food cooking with no fire, they are forced by their belief system to conclude that some sort of evil spirits are involved. At the request of an interested member of the general public, I wrote a list of examples of various types of cultural barriers and inhibitions to the swift, smooth uptake of solar cooking. While many, many factors affect the spread of solar cooking, the really important ones are lack of awareness, lack of funding for dissemination programs, and lack of buying power among those who would most benefit from solar cooking.
However, a factor that has to be mentioned is that solar cooking promoters often make mistakes. Solar cooking promotion has been a very grassroots phenomenon in most parts of the world where it has taken place. I think that in many cases, the promoter may believe that he or she is the first person in the world to come up with the idea of spreading solar cooking to fuel-short communities in the developing world. In their honorable enthusiasm, they may rush to action without careful research and planning first and without entering into a full give-and-take dialogue with their intended beneficiaries. Solar cooking promotion projects have been launched with neither the foresight nor the budget to allow for sufficient teaching and follow-up. When a project is begun, it will not be sustained if there is no permanent way for the new solar cooking community to access replacement parts and supplies. Lack of planning for this fact undermines the spread of solar cooking.
[Let me digress at this point and say that Solar Cookers International, while investing substantial percentages of its inadequate budget on general promotion and on field projects in developing countries, does also spend a substantial portion of its funds on helping the solar cooking promoters of the world to learn about each other, to share information and ideas, and, where feasible, to collaborate with each other. We also try to share the lessons we have learned about planning and implementing field projects.]