Development of ammoniated salts. Thermochemical energy storage systems: Phase IB. Final report, February--September 1977

Thermal energy is usually stored in energy storage systems as sensible heat at temperatures well above the ambient temperature. Most energy storage systems of this type suffer from two drawbacks: (1) the thermal losses to the surroundings are large, and (2) the energy is only available for recovery at the bulk temperature of the storage material; therefore, the stored energy can only be partially recovered. If the energy could be stored at near ambient temperature and recovered at the desired use temperature, thermal losses can be minimized and a high degree of efficiency can be maintained. The purpose of the program is to develop an energy storage system that accepts thermal energy at high temperatures, stores that energy at ambient temperature, and recovers the energy at the original high temperature. The energy is stored as chemical energy. The concept consists of storage and subsequent extraction of the heat of reaction from a pair of ammoniated salts near equilibrium conditions. By shifting the equilibrium in the forward or reverse direction, the heat of reaction can be stored or recovered. The system can be used for many different applications (i.e., different temperature levels) by selecting the appropriate salt pair for the high and low temperature reactions. In this phase of the program, the technical feasibility of the concept was demonstrated using several ammoniated salt pairs.