Multi-mode solid–gas thermochemical resorption heat transformer using NiCl2-SrCl2/NH3

Abstract

Thermal energy storage is considered as an attractive technology for waste heat recovery and solar energy utilization. A multi-mode solid–gas thermochemical resorption heat transformer for thermal energy storage has been developed. The working principle of three different operating modes, including the direct thermal energy storage and release mode, thermal energy upgrade mode and combined cooling and heating effect mode, is addressed. Performance analysis and comparisons of thermochemical resorption heat transformer are carried out by employing NiCl2-SrCl2/NH3 under the different operating modes. Thermodynamic analysis showed that the lowest and highest heat storage efficiency occur in the thermal energy upgrade mode and the direct thermal energy storage and release mode, respectively. The highest heat storage efficiency obtained is 0.978. Among three operating modes, the thermal energy upgrade mode has the lowest thermal energy storage density, while the combined cooling and heating effect mode has the highest thermal energy storage density. The smallest and largest thermal energy storage density are 1320.66 kJ/kg and 2646.92 kJ/kg, respectively. The developed thermochemical sorption energy storage provides a compact high energy density heat storage approach and therefore can boost the application of thermal energy storage in large-scale industrial processes and renewable energy utilization.