Ultra low cost solar cookers: design details and field trials in Tanzania

A family-sized ultra low cost solar cooker has been developed. The hot box style cooker is designed to be built on site by the users with minimal tools, skills or special materials. It consists of a shallow 1 m² square hole in the ground, insulated with straw and lined with adobe (mud and straw), a glass or plastic roof, and a 1 m² aluminised plastic reflector with guy ropes for adjustment. An insulated fabric door allows access to the oven; pots are slid in, onto a metal base plate. The cost is about £8. The cooker has been shown to provide cooked food for 10–12 people on clear days with meals around midday and dusk (assuming 0.4 kg dry weight of food per person daily). A four litre load of water can be brought up to cooking temperature (80°C) in 60–70 min. The adobe linear provides some thermal mass to even out temperature swings in cloudy weather.The cooker was developed at the Sunseed Trust's Spanish Project, Sunseed Desert Technology. It is being field tested by Sunseed in Tanzania. The paper reports on technical results and observations on how the cooker technology can best be integrated into this particular African context.