Investigating the Suitability of Different Heat Storage Media in Double Exposure Box Type Solar Cookers

Abstract

A comparative evaluation of the performance of three phase change materials (PCM) used as heat storage media in double exposure box type solar cookers was carried out. Stearic acid, benzoic acid and palm olein oil were placed in each with another similar design solar  cooker without PCM was used as control. These cookers were set up and the temperatures of charging and discharging of the PCM inside the cookers were monitored. The ambient temperature, solar inten sity and wind speed of the location were equally monitored  correspondingly. The maximum temperatures attained during charging by the heat storage materials were 89.2, 79.3 and 84.4 o C for  benzoic acid, stearic acid and palm olein oil respectively. During h eat discharge, the temperatures of the pots of the cookers after 3 hours were 52.4, 40.9, 61.7 and 53.4 o C for benzoic, control, stearic and palm olein oil cookers respectively. The temperatures of 1 kg of water after over 4 hours of discharging were 46.4, 40.6, 50.5 and 50.3 o C respectively. Cooking of 70 g of noodles was only achievable in the cooker with benzoic acid in 34 minutes. During charging, the cooker with benzoic acid performed best followed by the cooker with palm olein oil while the cooker with stearic acid performed least. On the other hand, the cooker with stearic acid was observed to perform best during discharging followed by palm olein oil and benzoic acid performed least.