Batteries do not maintain the same performance under all temperature conditions. Whether it is the low temperature in winter or the high temperature in summer, temperature directly affects the electrochemical reactions inside the battery. For energy storage systems, if the cell temperature is too low, continuously high, or there is a large internal temperature difference, it may affect the available capacity, power output, and lifespan of the system, and increase maintenance costs.

Low Temperature: Limiting Available Capacity and Charging/Discharging Performance

In a low-temperature environment, the electrochemical reaction rate inside the battery slows down, and the internal resistance increases. For an energy storage system, this may result in a decrease in available capacity, limited power output, and a reduction in charging acceptance capability.

The performance degradation caused by low temperature may limit the system's ability to execute charging and discharging plans. After the temperature rises, some performance usually can be restored, but improper low-temperature charging may cause irreversible damage. During operation, preheating and current limiting should be performed according to the charging conditions allowed by the battery cells to avoid large-power charging before the cell temperature reaches the required level.

Taking TN-B5MWh-S as an example, its lower working temperature limit is -30℃. Under low-temperature conditions, the system first preheats the battery cells through an intelligent liquid cooling circuit, and then the battery management system limits the charging power according to the real-time state of the battery cells to avoid large-power charging beyond the allowable conditions of the battery cells, thereby reducing irreversible damage and ensuring the available capacity and scheduling capability in winter.

High temperature: Accelerates aging and increases system risks

Although higher temperatures can accelerate the speed of short-term electrochemical reactions, if batteries are kept in a high-temperature environment for a long time, the electrolyte and active materials may age more rapidly, resulting in an increase in the rate of capacity degradation and a shorter overall lifespan, and increasing the safety risks during system operation.

For energy storage projects, this means that the battery cycle life may be shortened, the long-term available capacity may decrease, and the demand for maintenance, battery replacement or capacity replenishment will increase, which will also raise the cost. Excessively high temperatures may also increase the pressure on system safety management.

The TN-B5MWh-S is equipped with an intelligent liquid cooling system, which is used to remove the heat generated during charging and discharging and control the cell temperature. Its 314 Ah semi-solid battery cell has a cycle life of more than 8,000 times and a capacity retention rate of 70%. In addition, in combination with the IP55 protection level and intelligent aerosol and immersion fire protection design, it not only inhibits the rate of capacity degradation in high-temperature conditions but also reduces the safety management pressure of the system.

Temperature consistency is equally important

In addition to controlling the temperature range, the energy storage system also needs to reduce the temperature difference between battery cells. The system is composed of a large number of battery cells, and the heat dissipation conditions and operating temperatures at different positions may vary.

If the battery cells remain at different temperatures for a long time, the aging speed may gradually widen the gap. Some battery cells may deteriorate prematurely, which will widen the performance difference between battery cells and thereby limit the available capacity of the battery pack and the entire system, and affect the operational stability.

The thermal management of the energy storage system should not only prevent local overheating but also reduce the temperature difference between battery cells. A well-designed liquid cooling system can help improve temperature uniformity, reduce aging differences caused by temperature differences, thereby slowing down the decline in system available capacity and improving long-term operational stability.

Thermal management affects the long-term performance and operating costs of energy storage systems.

When evaluating an energy storage system, in addition to the initial capacity, attention should also be paid to the available capacity after many years of operation, system availability rate, and maintenance requirements. The thermal management plan should be combined with the local climate, charging and discharging frequency, and power requirements, and completed in collaboration with the BMS for temperature monitoring, preheating, cooling, and necessary power control.

Reasonable temperature control helps to slow down capacity degradation and reduce operational restrictions caused by temperature exceeding limits. When selecting, attention should also be paid to the energy consumption of the temperature control equipment, maintenance requirements, and performance changes under different environmental temperatures to assess the actual impact of thermal management on system efficiency and operating costs.