Performance analysis of high-capacity thermal energy storage using solid-gas thermochemical sorption Principle

Energy storage is an effective technology for improving the energy utilization efficiency, and it can be used to adjust the instability and time-discrepancy between energy supply and energy demand. The conventional sensible and latent heat storage technologies have energy densities ranging from 100 kJ/kg to 200 kJ/kg. The low storage capacity usually hinders their application in large-scale situation. A potential solid-gas thermochemical sorption method is proposed in the paper for achieving the high-capacity thermal energy storage with little heat losses. Thermal energy is stored in form of chemical bonds resulting from thermochemical sorption process of solid-gas working pair. The operating principle and working performance is described and analyzed using four typical sorption working pairs with different working temperatures, and the candidates of possible working pairs are presented for thermal energy storage with a temperature range between 50~280℃. Thermodynamic analysis showed that the advanced thermochemical sorption energy storage method has a distinct advantage of high energy density when compared with conventional sensible and latent heat storage methods. An energy density higher than 2000 kJ/kg of salt was obtained by employing the proposed thermochemical sorption energy storage technology, and it was about 10~20 times the energy density obtained with sensible and latent heat storage. The presented thermochemical sorption energy storage is a potential high-capacity heat storage method, and thus it can promote the application of thermal energy storage in large-scale industrial processes and the utilization of renewable energy.