In the field of energy storage, user-side energy storage technology solutions include industrial and commercial energy storage and household energy storage. Currently, the cost of household energy storage is higher and is widely used in high electricity price areas such as Europe, North America, and Australia. On the other hand, industrial and commercial energy storage systems are mainly used in areas with high electricity prices and large price fluctuations, with various solutions and wide market applications.
Diversity of energy storage solutions
From a structural perspective, energy storage products come in various forms, including containers, prefabricated cabins, outdoor cabinet-style, and indoor cabinet-style. Depending on the cooling method, they can be divided into air-cooled and liquid-cooled. Electrically, they can be divided into centralized and string systems. Depending on the energy storage system, they can be divided into separate equipment and battery systems, as well as integrated equipment and battery systems. In addition, there are two systems based on voltage levels, 1000V and 1500V. In terms of energy aggregation, there are two categories: DC coupling and AC coupling.
Large/medium-scale energy storage products: Towards efficient integration
In large/medium-scale energy storage products, container or prefabricated cabin structures have become mainstream. These products are usually applied on the power supply side and the grid side, and in some cases on the user side. The cooling method has transitioned from air-cooled to liquid-cooled, and the electrical structure is mainly centralized, but string energy storage is gradually being introduced. The 1500V voltage is gradually dominating, and AC coupling has become a common method.
Industrial and commercial user-side energy storage: Benefits of peak shaving
The profit model of industrial and commercial user-side energy storage mainly lies in peak shaving and optimization of charge and discharge volume. The more discharge volume, the greater the profit, the higher the energy conversion efficiency, and the smaller the loss. Therefore, the cluster-controlled energy storage integrated system has a higher rate of return compared to the centralized system. The cluster-controlled system has a high utilization rate of each cluster of energy, without parallel circulation between clusters, resulting in high energy conversion efficiency.
Comparison between small storage cabinets and centralized systems
Distributed small storage cabinets have higher maintenance and after-sales costs due to their dispersed layout, resulting in a higher unit price. The market price of small outdoor storage cabinets is approximately 1.6 yuan/Wh, while the price of centralized energy storage systems is around 1.1-1.2 yuan/Wh (for a purchase quantity of several tens of MWh).
Integrated energy storage container: Efficient energy conversion
The All in One AC/DC integrated energy storage container system uses one cluster of batteries connected to one PCS, with cluster-controlled management. The battery has a high utilization rate, without parallel circulation between clusters. The price difference between these two integration methods is constantly narrowing. However, the return on investment of the string energy storage system is much higher than that of the centralized system. The effective capacity utilization rate (DOD) of the centralized energy storage system is 7.5% lower than that of the string system.
DC coupling vs. AC coupling: A comparison of two solutions
DC coupling and AC coupling are two common solutions in energy storage systems. In DC coupling, solar power is stored in the battery pack through a controller, and the grid can also charge the battery through a bidirectional DC-AC inverter. In AC coupling, solar power is converted into AC power through an inverter and can be directly used or injected into the grid. AC coupling is suitable for both solar power systems and battery power systems.
Overall, the current market is dominated by modular, string, and AC-coupled user-side energy storage solutions, accounting for more than 80% of the market share. This solution not only has low cost and flexible configuration, but also has high safety and is suitable for industrial and commercial off-grid power stations. On the other hand, DC-coupled centralized solutions are suitable for small and medium-sized independent power plants, with high system stability and simple wiring.