Temperature Reduction of Solar Panel by Composite Phase Change Material – Calcium Chloride Hexahydrate / Expanded Graphite

Abstract

This research developed a device to reduce the temperature of solar panels to enhance electricity generation efficiency. The selected material was calcium chloride hexahydrate (CaCl₂·6H₂O), which was fabricated into a composite with expanded graphite. The resulting composite, in the form of a fine solid powder, helps retain the molten calcium chloride hexahydrate’s shape and improves the thermal conductivity of the material. The composite was prepared using a mixture of 80% by weight calcium chloride hexahydrate and 20% by weight expanded graphite powder. The mixture was compressed into rectangular blocks measuring approximately 20 x 20 x 80 mm and weighing about 45 grams each. These blocks were sealed in plastic bags using a vacuum heat sealer and then placed inside aluminum rectangular pipes measuring 25 mm in width and 1 meter in length, with approximately 360 grams of composite per pipe. The aluminum pipes served to dissipate heat into the atmosphere beneath the photovoltaic panels, where the temperature was lower. A total of 20 pipes were installed on the back of solar panels. The results showed that this setup reduced the panel temperature by approximately 10 ^oC, leading to about a 5% improvement in electricity generation efficiency. The stability of the composite phase change material was tested by simulating temperature cycles in an oven ranging from 25 to 65 ^oC for 5,000 cycles. Each cycle represents a daily temperature increase and decrease, equivalent to approximately 13.5 years of usage. The tests demonstrated that the composite phase change material maintained its performance and did not undergo any significant changes in properties throughout the testing period.