Microstructural, optical and thermal characterization of synthetic clay as a passive cooling medium

This work reports on assessing the suitability of synthetic clay as a porous medium that promotes evaporative cooling for various applications, especially temperature control of photovoltaic modules. When applied to the back of these modules and supplied with a fine mist spray of water, clay reduces the operational temperatures of photovoltaic modules by 30–40 °C, depending on weather conditions. The characterization of the microstructure (crystallinity, pore size and distribution) and composition of the clay is essential in understanding the enhancements that the clay provides for evaporation. A cooling element made from the clay was tested to quantify the evaporative portion of heat transfer, while spectroscopic profiles of two photovoltaic modules under typical operational conditions were tested for thermal footprint differences. The results indicate a good match between obtained SEMs and porosity tests in estimating average pore sizes responsible for enhancing the evaporative cooling and thus lowering thermal emittance from photovoltaic modules, improving their efficiency for given ambient conditions.