Performance and economic analysis of a heat pump water heater assisted regenerative solar still using latent heat storage

In this paper, the performance and economic analysis of a heat pump water heater assisted regenerative solar still using latent heat storage was experimentally studied. The heat released during condensation of water vapour inside the solar still was regenerated using a heat pump to pre-heat the saline water before entering the basin and producing hot water for domestic use. The experimental observations have been made under the influence of solar irradiation, ambient temperature and ambient wind speed. The results showed that the heat pump water heater assisted regenerative solar still has attained cumulative productivity between 14.0 and 16.0 kg/day during 12 h of operation. Moreover, the system delivers more than 100 L of hot water at 46.8-52.8 degrees C for domestic use. The monthly average coefficient of performance of the heat pump was estimated in the range between 2.21 and 2.55. The cost per litre of distillate obtained from the system is estimated as 0.05471 USD. The payback period was estimated as 21.46 months for 275 days of operation in a year at 12% interest and distillate selling price of 0.08 USD/litre. The water samples obtained from the experiments are suitable for drinking and met the Bureau of Indian Standard requirements.