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 20x5 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.

Automated summary

For the first time, supercritical CO2 (sCO2) is examined as a working fluid in a unique thermal management strategy for battery cooling. The characteristics of high volumetric thermal capacity, low critical pressure and temperature in the pseudocritical region make sCO2 advantageous by reducing system complexity and costs, as well as eliminating critical heat flux and flow instabilities. Experimental results show that sCO2 exhibits superior temperature suppression and temperature differences compared to conventional coolants. This finding offers potential benefits for cooling large battery packs in high-power grid stations and energy storage systems.