Abstract:
Ethiopia is the country which use fossil fuel as main source of energy. About 83% people of the country live in countryside area and use fossil fuel as a source energy for any baking and cooking purpose. Among this 70% of the energy is used for baking injera which needs a high temperature in range of 180-220℃ in a control environment. Thus, substituting it by renewable energy is an admirable solution of the season. The work of this thesis proves it is possible and propose new type of baking system with renewable energy source in indoor baking mechanism using solar thermal energy source of power. The possibility for baking injera is investigated using thermal energy transfer to thermal storage and baking pan by means of circulating heat transfer fluid (HTF) heated by parabolic dish solar collector. The existing three stone baking pan and electric pan causes environmental pollution, healthy affection, much amount of energy lose and in accessible in rural area.
The thermal energy is collected using 2𝑚2 area parabolic dish collector to the heat transfer fluid through spiral coil copper absorber and the hot HTF flow and placed to a hot oil container volume of 16litters which is covered by solar salt (60%𝑁𝑎𝑁𝑂3/40%𝐾𝑁𝑂3) properly insulated by wood ash. The fluid stored in hot oil storage flow baking pan with 0.5m diameter and 5mm thickness when baking is required and allow flow to cold oil storage after a pan absorbs heat from the HTF and circulate bake to spiral copper coil receiver to heat up again. There is metal plate between the clay pan and the fluid to avoid cracking of pan by hot HTF. The experimental setup is manufactured from locally available material. Leakage of fluid was difficult to control during experimental test. Instruments like thermo couple, infrared thermometer and Pyranometer are used in the experimental test. Thus, HTF is heated by parabolic dish collector at the absorber plate and attain up to a temperature of 253℃ and the average day thermal efficiency was around 51.44 %. Using the fluid temperature as an input data and manipulating using MATLAB software the upper surface temperature of the baking pan raised up to 210℃ which is absolutely enough to bake injera and the first heat up time was around 10minutes and the retaining time after one lap was 3minutes. Finally, the correlation of the parameter was developing by sigma plot.