Performance mapping of an open absorption thermal battery with crystallization and sorbent circulation

• Published in: Energy conversion and management Vol. 308; p. 118385
• Main Authors: Gao, J.T., Wang, R.Z., Xu, Z.Y.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15-05-2024
• Subjects: CaCl2-H2O; Crystallization; Discharge rate; Open system; Sorption thermal battery; Sorption thermal battery; Open system; Discharge rate; CaCl2-H2O; Crystallization
• ISSN: 0196-8904; 1879-2227
• DOI: 10.1016/j.enconman.2024.118385

•Three-phase sorption cycle is conducted with sorbent circulation.•Performance mapping from liquid absorption to complete crystallization is presented.•The energy storage density is in the range of 470–525 kWh/m3.•Synergy promotion in storage density and discharge stability is realized.
Sorption thermal battery is promising for long-term heat storage of renewable energy. Recent advances in three-phase sorption thermal battery using fixed sorbent pursue remarkable improvement in energy storage density. However, the synergistic change in storage capacity and discharge rate has posed a challenge for capacity regulation and large-scale application. To address this issue, a three-phase sorption thermal battery accompanied with sorbent circulation is proposed, which completes crystallization while performing falling film heat transfer. Ambient humidity is utilized as working fluid to simplify the operation. A comprehensive analysis is conducted for LiBr-H2O and CaCl2-H2O working pairs in terms of energy density, coefficient of performance, temperature lift, and charge/discharge rates. Simulation results reveal that both the two working pairs exhibit high energy storage density (470.8 kWh/m3 and 525.6 kWh/m3) in the fully crystallized cycle, which is around 2.9–5 times compared to the conventional two-phase cycle. Stable and controllable discharge rate could be achieved via solution circulating and re-concentrating. The stable discharge of CaCl2-H2O could be much longer, owing to larger sorption capacity difference between hydrate and saturated solution (2.2 times of LiBr-H2O). With collaborative promotion in storage density and discharge stability, the proposed system shows great potential for real applications.