Photovoltaic module cooling with still seawater layer – Experimental study

Solar photovoltaic modules play a vital role in the global clean energy transition. However, their efficient performance is hindered by rising operating temperature especially under harsh environments. Conversion efficiency of modules drops by at least 0.4–0.5 % for each 1.0 °C increment in its operating temperature from the standard testing condition of 25.0 °C. Hence, thermal management is essential for a module's sustained efficient performance. Evaporative cooling with water is more effective than any other passive module thermal management technique. In spite of seawater's abundance and inexpensiveness, it has not yet been utilized for module evaporative cooling in any of the available literatures. Hence, in this work, a novel passive evaporative cooling system utilizing a still seawater layer over a horizontally oriented module is proposed and tested under the climatic conditions of Visakhapatnam, Andhra Pradesh, India. This approach reduced module temperature on an average by around 8.8 °C. A 5.0 mm thick seawater layer improved the module's instantaneous power output by 0.14–31.0 %. Despite providing a tremendous cooling effect, seawater layer thickness of 30.0 and 4.0-mm had negative impact on a module's daily energy output due to increased light attenuation at high thickness and salt deposition caused by fast evaporation under low thickness, respectively. Low relative humidity and high wind speed facilitated rapid seawater evaporation, resulting in salt buildup over the module, emphasizing the importance of constant makeup water supply while operating at low water thickness (less than 5.0 mm) to avoid dry out. The overall heat transfer co-efficient of evaporatively cooled module was about 69.38–92.89 W/m2K, which was at least twice the value observed with the reference module. The observed results justifies the proposed thermal management technique because it is efficient and competitive with fin and phase change material-based module thermal management strategies. This highlights the necessity for further research and development towards improvement of this proposed technique for large scale applications.