Electrical and thermal performance analysis of photovoltaic module having evaporating surface for cooling

Abstract

This paper presents a method of water evaporative cooling for a photovoltaic module, particularly the floating type, to reduce the module temperature, thereby enhancing its electrical energy performance. An experimental test was performed by attaching a hydrophilic pad made of polypropylene mixed with synthetic fiber at the rear surface of a 320 Wp mono-crystalline module with an aperture area of 1.94 m2. A small pump supplied feed water through the pad at various flow rates and inlet water temperatures. The module faced south with an 18° inclination and was installed at Chiang Mai, Thailand. A set of heat and mass transfer models was developed to investigate the module temperature and the electrical power generated from the module. The simulated results conformed with the experimental data, and over 90 % of the data were within ± 10% deviation. Using the cooling technique, the maximum photovoltaic module temperature on a clear sky day could be reduced from 73.2 °C in the case of a normal unit to approximately 46 °C, and a 10% increase in total generated electrical power could be obtained. Moreover, a higher feed water flow rate and lower feed water temperature resulted in a higher photovoltaic module performance. The models were also used to investigate the monthly net electrical energy generated by the photovoltaic module, both with and without evaporative cooling. Evidently, the concept of evaporative cooling yielded high benefits during the summer period. An approximately 6.5%–11.1% increase in net electrical energy could be obtained compared to the electrical energy generated from the unit without an evaporating surface when the inlet feed water temperature was between 20–30 °C.