Solar Water Heater: Efficient, Once-Through Heating Above 90 °C

Abstract

A novel multi-utility, medium temperature, seasonally tracked, concentrated solar technology-based collector with absorber integrated heat storage is developed and tested in Heat Pump Laboratory at IIT Bombay. This solar collector can be used for different applications such as water heating, steam generation, cooking and liquid desiccant regeneration. Theoretical and experimental performance of the novel solar thermal collector as a one through water heater is presented in this paper. Theoretical analysis of the evacuated glass-based solar collector shows the optical efficiency to be 62%. The five solar collector panels, 1.42 m2 each, were connected in series and were used for once-through water heating. Water was heated from 30 °C to above 95.4 °C. Weighted average efficiency of 55 ± 1.7% was recorded over 6 h periods, for average global insolation of 800 W/m2 and ambient temperature of about 30 °C. Absorber integrated heat storage enabled generation of hot water even after sunset. The solar thermal collectors have already been deployed for solar cooking and will be used for regeneration of liquid desiccant in a solar air-conditioning system in the near future.