• thermochemical sorption;
  • heat transformer;
  • energy storage;
  • energy upgrade;
  • low-grade thermal energy

An innovative target-oriented solid-gas thermochemical sorption heat transformer is developed for the integrated energy storage and energy upgrade of low-grade thermal energy. The operating principle of the proposed energy storage system is based on the reversible solid-gas chemical reaction whereby thermal energy is stored in form of chemical bonds with thermochemical sorption process. A novel thermochemical sorption cycle is proposed to upgrade the stored thermal energy by using a pressure-reducing desorption method during energy storage process and a temperature-lift adsorption technique during energy release process. Theoretical analysis showed that the proposed target-oriented thermochemical sorption heat transformer is effective for the integrated energy storage and energy upgrade, and the low-grade thermal energy can be upgraded from 87 to 171°C using a group of sorption working pair MnCl2-CaCl2-NH3. Moreover, it can give the flexibility of deciding the temperature magnitude of energy upgrade by choosing appropriate sorption working pairs. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1334–1347, 2013