Enhancing solar still productivity in tropical climate with conductive particle-assisted phase change material

Abstract

Solar desalination may become the sustainable solution to mitigate freshwater scarcity with growing demand. However, conventional solar stills for desalination are limited to low production efficiency caused by low/unavailable solar irradiation. Current research in thermal energy storage (TES) for solar desalination utilizes phase change materials (PCM) to store solar heat, ensuring uninterrupted energy for distillate production. Some PCMs have high melting point which would not melt entirely during low solar radiation periods; hence, this study investigates on the addition of conductive particles in PCMs. This study reports the results from experiments combining various types of PCMs and conductive particles in a solar distiller. Petroleum jelly (PJ) and paraffin wax (PW), along with aluminium scrap and aluminium oxide (Al₂O₃) nanopowder as conductive particles, were tested in single-slope solar stills to evaluate their performance under varying solar irradiation in a tropical climate country. It can be concluded that the addition of PW as PCM has increased the efficiency of the solar still significantly, and the addition of conductive particles has shown further notable improvements. Interestingly, the relatively expensive Aluminium oxide (Al₂O₃) nanoparticles and the cost-effective Aluminium scrap chip exhibited similar performance levels. Among the different sets of experiments, solar still with PW and Aluminium scrap was 17.98 % efficient with a yield of 0.457 kg/m² per day, and its production was 2.8 times higher than the conventional solar still. The solar still with Al₂O₃ nanoparticle embedded PW showed an increase in productivity by 27 % compared to the still with aluminium scrap mixed PW; where the water yield is 0.342 kg/m² per day, 0.038 kg/m² more than the solar still with aluminium scrap mixed PW. The cost of water produced per litre was up to 0.011 US$/litre. This study opens a pathway for further investigation on the efficiency and productivity associated with different categories of conductive particles usually associated with PCM in solar still research in the tropics.