Study of ammoniated salts based thermochemical energy storage system with heat up-gradation: A thermodynamic approach

Abstract

Thermal energy storage (TES) system based on gas–solid interaction is an effective technology to store energy for long duration. TES systems based on ammoniated halide salts are extensively trusted due to availability of halide salts with wide range of thermodynamic properties and low cost. In this work, the thermodynamic analysis of TES system is presented for several working pairs of halide salts using their measured ammonia adsorption/desorption thermodynamic properties. The thermal energy available at wide temperature range of 100–210 °C is stored as ammonia desorption enthalpy of ammoniated salts (MnCl2, FeCl2, CaCl2 and SrCl2). The energy can be recovered from energy storage material at several temperatures corresponding to different regeneration (desorption) temperatures of regenerating material. The TES system using pair of MnCl2–CaCl2 can deliver the thermal energy with a maximum heat up-gradation of 40 °C at regeneration temperature of 120 °C. The maximum energy storage densities are observed to be 1165.61, 1139.51 and 1114.56 kJ kg−1 at 200 °C for the salt pairs of FeCl2–SrCl2, FeCl2–CaCl2 and FeCl2–NaBr, respectively. The coefficient of performance of TES system is observed to be maximum for SrCl2–NaBr pair due to high adsorption capacity of SrCl2 and low operating temperatures. © 2017 Elsevier Ltd