As the main force of new energy storage, electrochemical energy storage has begun to move from the megawatt level of demonstration applications to the gigawatt level of the scale of the market, the choice of the cooling system has become an important issue in the design of the current power plant. So, what is the difference between air cooling and liquid cooling, the mainstream cooling systems for energy storage power plants? Which cooling system is more suitable for electrochemical energy storage power plants? This tweet, I will analyze these two cooling programs in detail!

First, the cooling program in detail

Liquid cooling system:

The liquid cooling system of the electrochemical energy storage power station covers the refrigerant system and antifreeze system. Among them, the refrigerant system includes condenser, evaporator, compressor, liquid storage tank and axial fan; while the antifreeze system is mainly composed of water pumps. A honeycomb-shaped liquid cooling plate is installed at the bottom of the battery pack, which absorbs the heat released during battery operation through the circulating flow of antifreeze. This antifreeze is usually an aqueous solution of ethylene glycol, whose specific heat capacity is higher than that of air, thus providing excellent heat-carrying capacity, low flow resistance and high heat transfer efficiency.

Air cooling system:

The air-cooling system of an electrochemical energy storage power plant consists mainly of air conditioners, air ducts and module fans. The fan is installed right in front of the module and is responsible for bringing the heat generated by the electric cores in the module to the air ducts in the prefabricated compartment, after which the air conditioning system in the prefabricated compartment dissipates the heat by thermal convection.

Comparison of advantages

1. Floor space

Through intensive design and the application of large-capacity batteries, the footprint of liquid-cooled energy storage products can save more than 50% compared with container solutions of the same capacity. For future large-scale energy storage power stations of more than 100MW class, the cost saving of footprint is even more obvious.

2. Cost Consideration

Although the current equipment material price and process complexity of the liquid cooling system result in a relatively high cost, the extra cost of the liquid cooling system over the air-cooled system can be reduced in other projects, taking into account factors such as the small footprint of the liquid cooling solution, the small amount of cables, and the reduction of on-site installation work. In addition, the cooling system does not account for a high proportion of the total cost of the energy storage power plant, so from the overall investment point of view, the investment of the energy storage power plant under the liquid-cooled heat dissipation method will not be much higher than the air-cooled scheme.

3. Battery life

Most of the current electrochemical energy storage power stations use lithium-ion batteries, battery performance and life cycle is largely affected by the operating temperature. The ideal temperature range for lithium battery operation is 25~35℃. In energy storage power stations with high battery energy density, fast charging and discharging speeds and large variations in ambient temperature, the high degree of integration of the liquid cooling system with the battery pack can realize the smooth regulation of the internal temperature of the battery and ensure that the temperature of the battery pack is controlled within a reasonable range. Through the circulation of antifreeze in the liquid cooling system, the temperature difference between the batteries can be made smaller, ensuring balanced temperature control and improving the temperature control efficiency of the cooling system.

In contrast, the temperature control effect of the air-cooling system is affected by the operating conditions of the module fan, which may result in uneven temperatures between the cells and relatively low temperature control efficiency. In addition, some of the cells operate outside the ideal operating temperature range of the battery, thus shortening battery life. Therefore, the liquid cooling system is more conducive to maintaining the performance and life cycle of the battery, and by increasing the operating hours and extending the life of the battery, the liquid cooling solution has an economic advantage in the consideration of the whole life cycle of the energy storage power plant.

Compared with air-cooled systems, liquid cooling systems for electrochemical storage power plants have the following advantages: small footprint, high operating efficiency, low cooling system loss, easy selection of station variables, and more friendly to battery performance and life cycle. From the perspective of the whole life cycle, the liquid cooling program has more economic advantages.