Lithium Bromide and Water Thermal Storage System

Abstract

An analysis of a thermal storage system using a lithium bromide and water solution both as a refrigerant and as a storage material is considered. The proposed thermal storage system can be used to shift electric demand from periods of high demand to periods of low demand. The system is considered for both the summer cooling and winter heating season. The system’s evaporator and absorber are similar to that of a conventional heat-operated absorption refrigeration system; however, the generator heat is supplied by a self-contained electrically-driven vapor compression heat pump. The heat pump is operated during the off-peak period to recover the thermal storage by reprocessing the stored solution to a higher lithium bromide concentration. The water vapor liberated from solution in the generator is compressed and then condensed in the generator. The storage volumetric efficiency is determined and compared to storage systems based on water ice for the cooling season only and on a liquid water storage system for both cooling and heating. The storage volumetric efficiency of the proposed system is greater than or comparable to that of a thermal storage system based upon water ice and far exceeds the value for a thermal storage system based upon liquid water. The system can be constructed from standard HVAC components and appears to be a competitive alternative to a water ice storage system for summer cooling only, and it could be a competitive alternative to a liquid water system for combined summer and winter operations.