Abstract

The performance of different thermal energy storing systems to provide over-night air-conditioning for a limited space in an institutional building in south Spain are compared with conventional air-conditioning (both for refrigeration and heating). In summer, the storage tanks are charged with a solar-assisted absorption chiller during day-time, and used to cover the over-night demand, whereas in winter a heat exchanger is used during the day to charge the tanks. Thermal energy has been stored in two chilled water tanks (with total capacity of 5000 L) or in two tanks (total volume 4000 L) containing two phase change materials (PCM): a PCM with melting point of 10 degrees C for refrigeration, and a PCM with melting temperature of 46 degrees C for heating. Our results show that the storing in PCM is more convenient, providing air-conditioning service for approximately 4 h 30 min in refrigeration, with a significant reduction of the electricity consumption with respect to the conventional system. The chilled water tanks can cover the demand for 4 h (scaled down to 3 h 12 min if the capacity is 4000 L), with even lower electric consumption. In winter, on the other hand, the tanks can cover fully the demand of overnight heating. Our results prove the viability of thermal storing, in particular using PCM, to extend the application solar cooling and heating to night-time, which is economically feasible, in a fully operational building.