Comparison of ammonia sorption properties and thermodynamic performance of adsorption‐based thermal energy storage system for MnCl<sub>2</sub>, CaCl<sub>2</sub>, and their composites
Kedar Bharat Jivrakh, Sarath Babu Kaki, Rakesh Sharma, Siva Subrahmanyam Mendu, E. Anil Kumar
Abstract
Abstract In this work, composite adsorbent materials are prepared using metal halide salts and expanded natural graphite (ENG). Ammonia adsorption and desorption pressure concentration isotherms of composite adsorbents are experimentally measured. The van't Hoff plots are constructed to calculate the enthalpy of a reaction during adsorption and desorption. The average value of adsorption enthalpies (∆ H ad ) for MnCl 2 + ENG and CaCl 2 + ENG are 55.821 and 33.434 kJ mol −1 , respectively, and average values of desorption enthalpies (∆ H des ) are 73.817 and 73.016 kJ mol −1 , respectively. Comparison of ammonia sorption properties of composites and their corresponding plain salts is done. Thermodynamic analysis of adsorption thermal energy storage (ATES) system) showed that maximum gravimetric energy storage density for MnCl 2 + ENG based system is 1394.83 kJ kg −1 (158.85 kWh m −3 ) at energy storage and ambient temperatures of 172°C and 35°C, respectively. The same for CaCl 2 + ENG based system is 1350.86 kJ kg −1 (165.85 kWh m −3 ) at storage and ambient temperatures of 92°C and 35°C, respectively. Volumetric energy storage density is higher for CaCl 2 + ENG based ATES system since it has higher density. Thermodynamic performance of composite‐based systems is compared with plain salts (MnCl 2 ‐CaCl 2 ) based thermal energy storage system.