Theoretical and experimental assessment of a double exposure solar cooker

Abstract

A novel design of solar cooker is introduced in which the absorber is exposed to solar radiation from the top and the bottom sides. A set of plane diffuse reflectors is used to direct the radiation onto the lower side of the absorber plate. The performance of the new cooker and the conventional box type solar cooker is extensively investigated. The general energy balance of the cooker is derived and is used to predict the temperature variation of each part of the cooker under both steady and transient conditions. The predicted values are compared with measurements made under actual weather conditions. Results under the same operating conditions show that the absorbers of the box type cooker and the double exposure cooker attain 140 and 165 °C, respectively. The temperatures of the air inside the two cookers are 132 and 155 °C, respectively. The predicted temperatures agree with measurements under transient conditions within ±1.2 °C for the absorber plate, ±1.8 °C for the oven air and within ±2.5 °C for the glass cover. The time taken for cooking of several foods and for boiling the same amount of water is obtained for the two cookers under the same conditions and at the same location. The double exposure cooker reduces the cooking time by about 30–60 min. The taste and appearance of the food is quite good.