An Experimental Study of Hybrid Solar and Geothermal Energy with Applying Heat Pipe to Enhance The Performance of The Cacao Beans Drying Process

Abstract

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 60 0C 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 nighttime.