China's evolution of electrochemical energy storage technologies and integration method




Since 2010, the development of electrochemical energy storage in China has enjoyed a good reputation for a long time, but it is still in a quiet period of market downturn. Until 2018, with the outbreak of grid-side energy storage and user-side in Hunan, Henan, Jiangsu and other provinces, the energy storage market increased by more than 150% year-on-year. And in the following years, due to the role of energy storage in building a new power system, the energy storage market has gradually entered a golden age of multiplication growth, especially the rapid development of energy storage represented by lithium iron batteries

With the rapid development of the energy storage market, the energy storage technology and the integration method of energy storage units using lithium iron phosphate batteries have also undergone profound changes. From small-capacity cells to large-capacity cells, from 1000V DC energy storage systems to 1500V DC energy storage systems, from air-cooled to liquid-cooled, from walk-in to non-walk-in. While improving the performance and safety of the energy storage system throughout the life cycle, it also greatly reduces the price of energy storage equipment, saves floor space, and promotes the commercialization and large-scale application of energy storage.

1.Large-capacity cells effectively reduce the cost of energy storage cells and integration

Large-capacity cells effectively reduce the cost of energy storage cells and integration


Before 2018, whether the lithium iron phosphate battery are the "CHOSEN ONE" in the next few years is still controversial. Due to its low price advantage, the lead battery is on an equal footing with the lithium iron phosphate battery in the energy storage market(such as home energy storage). In the energy storage market at that time, the capacity of lithium iron phosphate battery cells was generally below 100Ah, the price of battery cells was about 1.2 RMB/Wh, the price of energy storage converters was about 0.4 RMB/kW, and the price of lithium iron phosphate battery energy storage equipment higher. Taking the mainstream energy storage unit integration method in the market as an example, a single 40-foot battery cabin is used as an example.

The cabin generally adopts a walk-in cabin, the energy of a single cabin cell is about 2.5MWh, the DC side is connected to a 500kW or 630kW PCS, and the maximum voltage of the PCS DC side does not exceed 1000V. CATL launched the 271Ah large-capacity cell to open the era of large-capacity cells, which also brought profound changes to the integration method of energy storage units. Subsequently, the product was also iteratively upgraded, and the cell capacity was determined to be 280Ah. Because large-capacity cells effectively reduce the cost of energy storage cells and integration costs, mainstream battery stores in the industry have followed suit. Many stores have launched 280Ah cells or even larger-capacity cells, and large-capacity cells have gradually become the industry's first choice.

2.1500V DC system greatly increases power density and energy density

1500V DC system greatly increases power density and energy density


Since 2020, the 1500V DC system has gradually been applied in China's energy storage power stations. Compared with the previous 1000V DC energy storage system, the 1500V DC energy storage system greatly improves the power density of the PCS and the energy density of the battery compartment. Taking the equipment parameters of a battery store as an example, the rated power of a single PCS is increased from 630kW to 1725kW, the energy of a single walk-in 40-foot battery compartment (air-cooled) is increased from 2.5MWh to about 3.8MWh, and the energy density is increased by about 50%.

If the non-walk-in structure is adopted, the energy density can be further improved, and the energy density of the cells in the 40-foot battery compartment (air-cooled) can be increased to about 5MWh. At the same time, due to the improvement of power and energy density, the price of PCS has dropped significantly, and the same scale of energy storage power station can reduce the cost of battery management system, cabin, auxiliary facilities and so on. Energy storage unit equipment can be reduced by about 0.1 RMB/Wh, effectively saving floor space and reducing civil construction and installation costs.

3.Liquid cooling technology improves consistency of energy storage battery systems

Since 2021, major battery stores in the energy storage industry are scrambling to deploy liquid-cooled products, including CATL, BYD, SUNGROW, KEHUA, ENVISION and many other manufacturers have launched energy storage battery complete sets of liquid-cooled integrated technology. Compared with the previous air-cooled energy storage units, the liquid-cooled system generally uses ethylene glycol aqueous solution as the cooling liquid to form a closed-loop system. Especially in combination with various technologies or integration methods such as large-capacity cells, CTP technology, 1500V DC energy storage system, and non-walk-in cabins.

Liquid cooling technology improves consistency of energy storage battery systems


The whole life cycle performance and price advantage are obvious, and it has the characteristics of high energy density, low auxiliary power load, convenient installation and small footprint. In addition, the liquid cooling technology can control the temperature difference between the cells to be around 3-5℃. Compared with the temperature difference of about 10°C in the air-cooled system, the consistency level of the battery system can be greatly improved, and the life cycle performance and safety level of the energy storage system can be improved.

Liquid cooling technology is expected to become the main technology route model in the future.Under the background that the price of battery raw materials such as lithium carbonate is still hovering at a high level, due to the significant development opportunities of energy storage under the advocacy of dual carbon, many stores have jumped into the field of energy storage, and the industry competition is fierce. Energy storage unit integration is not just a simple stacking of battery modules, but a system that integrates multiple disciplines such as power electronics, electrical, materials, structures, HVAC, and fire protection.

The industry's leading battery store, including top 10 energy storage battery cell companies in China, accelerate technology research and development, reduces the equipment cost of storage systems through technology upgrades and integration optimization, improves full-life cycle performance, enhances market competitiveness, and promotes the healthy development of the industry and the commercialization of energy storage.

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