Experimental and numerical investigation of multistage sorption energy storage system

• Published in: Applied thermal engineering Vol. 218; p. 119313
• Main Authors: ElBahloul, Asmaa A., Zeidan, El-Shafei B., El-Sharkawy, Ibrahim I., Hamed, Ahmed M., Radwan, Ali
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.01.2023
• Subjects: Multistage Energy Storage; Sorption Composites; Sorption Thermal Energy Storage; Sorption Composites; Multistage Energy Storage; Sorption Thermal Energy Storage
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2022.119313

•Experimental prototype of multistage closed sorption system is built and verified.•Composite sorbents MnCl₂, CaCl₂, and Nh₄Cl are used with Nh3 as sorbates.•Total ESD of 3474.28 kJ/kgsalt is achieved at a charging temperature of 155 °C.•highest ESD is achieved at optimum oil mass flow rate of 0.04 kg/s. In this paper, thermal energy storage is utilized to store heat from solar energy and also use waste heat to counterbalance the demand and supply of energy. A laboratory multistage closed sorption thermal energy storage (STES) unit is designed and tested to study the performance of a cascade sorption system. The experimental unit consists of three sorbent reactors, an ammonia cycle, and an oil cycle. Composite sorbents namely, MnCl₂, CaCl₂, and Nh₄Cl are used with ammonia as sorbate. Expanded natural graphite (ENG) is mixed with sorbents to increase the thermal conductivity and improve the mass transfer performance of sorbents. Further, a computational fluid dynamic model using COMSOL Multiphysics is built to study the performance of triple, double, and single closed STES systems. For the triple experimental STES system, a charging temperature up to 155 °C is used. At Nh3 pressure of 7.5 bar, the discharging temperatures are found to be 132.9 °C, 99.1 °C, and 60.3 °C for MnCl₂-ENG , CaCl₂-ENG , and Nh₄Cl-ENG composite sorbents, respectively, while a total energy storage density (ESD) of 3474.28 kJ/kgsalt has been achieved. For a double experimental STES system, a charging temperature up to 105 °C is used. Discharging temperatures are found to be 95.3 °C and 60.1 °C for CaCl₂-ENG , and Nh₄Cl-ENG  composite sorbents, respectively, and a total ESD of 2471.94 kJ/kgsalt is achieved at Nh3 pressure of 7 bar. A parametric study is carried out to study the effect of different parameters on the performance of STES system at different arrangements. Increasing the inlet oil temperature during discharge results in a reduction of total ESD. For the specified design condition, the optimum oil mass flow rate is found to be 0.04 kg/s to achieve the highest ESD.