Evaporative cooling systems with underground cooling for photovoltaic panels in hot and arid climates

Solar energy can be mainly harnessed through heat, electricity, and photosynthesis. The utilization of solar energy is globally adopted because it is abundantly available and cost-effective compared to other renewable energy sources. Solar energy possesses light and heat, both of which can be directly converted into electricity. The main application of solar energy is electricity generation through photovoltaic (PV) systems, which include PV panels, a charge controller, batteries or other storage units, and inverters. PV panels consist of multiple solar cells that convert incident solar radiation into direct current electricity. Nonetheless, most of the solar radiation reaching solar cells is converted into heat energy rather than electricity, as solar cells cannot convert all irradiance spectral wavelength into electrical energy. This leads to an increase in the cell operation temperature. The elevated temperature worsens bandgap energy, thereby reducing open circuit voltage and fill factor. Consequently, higher temperatures diminish the conversion efficiency of the cells, and thus the overall efficiency of PV panels. For instance, for every 1 ºC rise in the temperature of a crystalline silicon solar cell, the cell voltage decreases by 2.2 mV, causing an estimate 0.5% drop in electrical power output. Furthermore, excessive heating can cause hotspot formation and material degradation, leading to a shortened lifetime of PV panels. Hence, it is essential to dissipate the surplus heat from solar cells by applying the optimal cooling technique to recover the efficiency of PV panels. Among the various cooling methods, evaporative cooling is a simple, sustainable, cost-effective, efficient, eco-friendly, and energy-saving technique. It is particularly effective in hot and arid climates. In this thesis study, evaporative cooling systems incorporating underground cooling were designed, and set up to prevent PV panels from experiencing a reduction in power output in hot and arid climates due to overheating. The evaporative cooling systems included three open-water-based systems: one utilizing a cellulose pad, another employing cotton wicks, and the third using hemp ropes as porous materials. The effects of these cooling systems and their configurations on PV panel temperature, electrical energy output, and efficiency were experimentally evaluated and compared with those of a reference panel without cooling. The findings indicated that the evaporative cooling approaches proved effective in arid and intensely hot climates. The cooling implementations continuously and uniformly lowered the PV panel surface temperature, thereby enhancing efficiency, energy output, and I-V characteristics. As a result, the evaporative cooling configuration with the cotton wicks, hemp ropes and cellulose pad achieved temperature reductions of up to 22.7 ºC, 22.1 ºC, and 10.3 ºC, respectively; efficiency improvements of 9.77%, 9.57%, and 5.38%; and cumulative energy enhancements of 10.4%, 9.56%, and 5.46%, respectively.