An experimental study of hybrid solar and geothermal energy with applying heat pipe to enhance the performance of the cacao beans drying process

In the conventional cacao beans drying process with solar energy, the commodity of cocoa will reabsorb water content from the air at night, which makes the drying process not optimum. This research aims to conduct an experiment of the hybrid of solar thermal energy and geothermal energy with Heat Pipe Heat Exchanger (HPHE) so that the cocoa drying process can run 24 hours a day regardless of the weather. The indirect solar dryer convection system made from the polyurethane sheet with 20 mm thickness and its length x width x height is 160 x 76 x 10 cm. The zinc galvalume sheet with 0.3 mm thickness coated by the black doff colour was installed throughout the inner of the container wall and covered by a transparent plastic lid above it. The source of geothermal energy was simulated by 60⁰C water that was heated by a 9-kW heater and flowed by a pump. This experiment used 42 copper heat pipes in a staggered arrangement with 181 fins added on it. Its wick is sintered copper with water as the working fluid and 50% of filling ratio. The heat pipe had 700 mm in length and 10 mm outer diameter. The fins were made from aluminium with a thickness of 0.105 mm and a size area of 76 mm × 345 mm. The use of a hybrid system has shown the best performance in terms of the time needed for the cocoa drying process. Hybrid of solar collector and geothermal energy make the drying process faster and eliminate the intermittent effect as a result of 24 hours drying heating by the solar collector during daytime and utilizing geothermal energy by HPHE during night-time.