Numerical and experimental Analysis of Solar Injera Baking with a PCM Heat Storage
Today, many developing countries are using biomass as their primary energy supply. However, this energy affects the environment, health and safety of women and children. In addition, utilization of this energy using traditional cooking stoves is causing indoor air pollution and in turn health problems to millions of people. To overcome such problems, efforts are being made by researchers globally and are suggesting alternative safe energy sources. This paper demonstrates solar cooker with an integrated PCM thermal storage and heat transportation loop system suitable for high temperature applications. The system has designed to address Injera baking application. Injera, a fermented flat bread type, is the most common food type served three to four times a day in Ethiopia. Other countries like Eritrea, Somalia, Sudan and Yemen also use this food. The storage system has storing capacity of heat up to 2500C and it can retain this heat for about two days. The storage has coupled to a polar mounted concentrator, fixed receiver and used steam heat transfer fluid. The steam circulates naturally between the evaporator and condenser in a closed loop. The paper focuses on indirect charging, simultaneous charging-discharging and discharging of the stored heat for the purpose of Injera baking. The frying pan is a custom-made aluminum plate casted by embedding a 10mm coiled stainless steel steam pipe as heating element. The pan is 500mm in diameter and 30mm thick; and the fins are 20mm in diameter and 140mm long. The fins have immersed into a 20kg PCM, which is coupled to a 1.8m diameter parabolic dish collector. The solar fryer demonstrates Injera baking for average family size. Baking is tested from the stored heat, while storage is charging. A fully charged storage has supplied enough heat to baked average household Injera demands about 19Injeras and additional breads with the remaining heat.
Keywords: Solar Injera baking; PCM charging; PCM storage; Solar Injera stove design; Solar cooking; Ethiopia.