A novel strategy of thermal management system for battery energy storage system based on supercritical CO₂

Supercritical CO₂ (sCO₂) is examined as a working fluid for the first time in a unique thermal management strategy that aims to control undesirable thermal behavior in battery cooling applications. In the pseudocritical region, sCO₂ has a high volumetric thermal capacity with low critical pressure and temperature, which not only reduces system complexity and costs but also eliminates the possibility of two-phase critical heat flux and flow instabilities. A pack of 20×5 Li-ion batteries for battery energy storage system (BESS) applications was designed and employed in a structurally optimized thermal management system. Further, the effects of different dielectric fluid media on the number of flow inlets, flow rates, and discharge rates were numerically investigated. Compared with conventional coolants, sCO₂ exhibited superior temperature suppression and temperature differences. The rise in both mass flow rate and the number of flow inlets significantly suppressed the maximum temperature and temperature difference. Besides, the pressure drop was slightly increased with the increased mass flow rate. Moreover, sCO₂ controls the thermal behavior of a large battery pack at high discharge rates within an optimal range. The finding offers various attributes for cooling large battery packs, particularly for high-power grid stations and BESS. In the future, the practicality of high working pressures and power requirements for the pump should be carefully studied.