Field investigation on the performance of a novel hybrid cooling system for containerized energy storage batteries under mismatched conditions

Traditional liquid cooling systems of containerized battery energy storage power stations cannot effectively utilize natural cold sources and have poor temperature uniformity. To address these problems, a novel hybrid liquid cooling system with three operating modes and a two-phase cold plate is developed. In order to investigate its applicability and performance, the intentioned mismatched conditions are set up and the annual field tests are carried out. The energy-saving effects and thermal management performance are analyzed by investigating the key performance indicators, including the cooling system characteristics and fluctuations in battery temperature (i.e. equipment energy consumption, equipment start-stop state, supply liquid temperature, pipe pressure, and battery temperature uniformity). The results showed that the hybrid cooling system exhibits excellent adaptability to varying outdoor temperatures. At the outdoor temperature of 10 °C, the maximum Energy Efficiency Ratio (EER) reaches 11.7 with a supply liquid temperature of 25∼28 °C. Compared to mechanical cooling, natural cooling is more readily effective in maintaining battery temperature uniformity. When the outdoor temperature becomes 20 °C, the system can still use the free cooling with a supply liquid temperature of 22∼25 °C. The cooling system can maintain a maximum temperature difference of 4 °C during continuous charging and discharging processes throughout different outdoor temperatures. In short, this novel system can effectively make full use of the natural cold source and employ a two-phase liquid cooling system to maintain battery cell temperature uniformity even under mismatched conditions.