Experimental investigation on an innovative resorption system for energy storage and upgrade

Highlights: • A resorption thermal energy storage system is established and investigated for energy upgrade. • The highest heat release temperature is 155 °C. • The maximum thermal storage density is about 662 kJ/kg. • The energy efficiency and exergy efficiency range from 27.5% to 40.6% and from 32.5% to 47%. • ENG-TSA as the additive improves the heat and mass performance of composite adsorbent. - Abstract: Progress of efficient thermal energy storage (TES) has become a key technology for the development of energy conversion system. Among TES technologies, sorption thermal energy storage (STES) has drawn burgeoning attentions due to its advantages of high energy density, little heat loss and flexible working modes. Based on STES, this paper presents an innovative resorption sorption energy storage (RTES), and the experimental system is established and investigated for energy storage and upgrade. 4.8 kg and 3.9 kg MnCl₂ and CaCl₂ composite sorbents are separately filled in the sorption reactor, and expanded natural graphite treated with sulfuric acid (ENG-TSA) is integrated as the matrix for heat transfer intensification. It is indicated that the highest energy storage density are 662 kJ/kg and 596 kJ/kg when heat input temperature is 125 °C and heat release temperature are 130 °C and 135 °C, respectively. For different heat input and release temperature, the energy efficiency and exergy efficiency range from 27.5% to 40.6% and from 32.5% to 47%, respectively. The novel RTES system verifies the feasibility for energy storage and upgrade, which shows the great potential for low grade heat utilization especially for industrial process.