Experimental analysis of an evacuated tube solar collector using different phase change materials

In today's world, research is being focused on the use of renewable sources of energy which include solar energy, wind energy, and geothermal energy. Among all these renewable sources of energy, solar energy is the most promising, but one of the major issues with utilising solar energy is its discrepancy in demand and supply. Therefore, the current work aims at harnessing solar energy to heat water by using a tube-type evacuated solar collector integrated with a thermal energy storage unit. This will ensure the heating of water without the use of electricity. Erythritol and paraffin wax, which have a higher melting point, are utilised as phase change materials (PCMs) in the present research work. The experimental readings show that, due to the presence of PCMs, the temperature of water is much higher than that of the ambient temperature, even after sunset. Further paraffin wax was found to be more effective than erythritol because, during discharging, more energy is released in the case of paraffin wax as it completely melts, whereas erythritol does not completely melt. The highest temperature of hot water without PCMs was 56.2 degrees C; in the case of erythritol, it was 78.4 degrees C; and in the case of paraffin wax, it was 75.1 degrees C. Also, the backup obtained in the case of paraffin wax is more than 2.5 h, and in the case of erythritol, it was 1.5 h. So, the present system can be used for generators of vapour absorption refrigeration systems, as well as air conditioners and cold storage chillers.