DEVELOPMENT AND EVALUATION OF AN IMPROVED HEMISPHERICAL SOLAR COOKER
An estimated 5 million children in the developing countries die each year from respiratory diseases caused mainly by smoke from biomass fuel. Solar cookers are alternatives to biomass cookers. However, the available solar cookers have an average efficiency of only 14% with 16%, 30% and 35% optical, geometrical and thermal heat losses respectively. The rest of the losses are classified as edge losses. Amongst the solar cookers, only the solar concentrator cookers can attain the frying temperature. However, its design doesn’t suit the solar cooking well in terms of the portability, ergonomics, cooking flexibility and concentration ratio. An improved hemispherical solar concentrator cooker was therefore designed with proper ergonomics, portability and high concentration ration to address the identified limitations of the existing cookers. The designed cooker with a sun tracking mechanism and anchored on mobile tripod was covered with a double glass to attenuate the greenhouse effect. The cooking pot was covered with a clear lid to further enhance heat concentration within the pot. A comparison was then made between the performance of the improved cooker and the control case. The results showed that when the cooker was covered with double glass and the pot covered with a transparent lid, the water attained its boiling temperature (95.5oC-96oC), and heat was retained even with highly fluctuating solar radiation. Without the transparent lid on the pot but with double glass, water temperature could not rise above 80oC and without both the transparent lid and double glass the water temperature could not rise above 72oC. The improved hemispherical solar concentration cooker therefore offers a partial solution to many cooking problems faced by people associated with low incomes in addition to the mitigation of global warming as the technology does not involve emissions of gases such as CO2 into the atmosphere.