Optical Storage House | Comparison of Technical Solutions for User-Side Energy Storage
2023-07-10
User-side Energy Storage mainly includes industrial and commercial energy storage and household energy storage. At present, the cost of household energy storage is more than 0.6 yuan / kWh, the domestic residential electricity price is low and the peak-valley price difference is also low, and the main customers and markets are in Europe, North America, Australia and other overseas regions with high residential electricity prices. Industrial and commercial energy storage systems are above 0.7 yuan / kWh, mainly used in places where electricity prices are higher and peak-valley price differences are also high, the market is widely used, and the schemes are also diverse, which can be selected according to application scenarios. 
From the structural point of view, energy storage products include containers or prefabricated cabins, outdoor cabinets or indoor cabinets; According to the cooling mode, there are two types: air cooling and liquid cooling; According to the classification of electrical structure, there are two types: centralized and string; According to the classification of energy storage systems, there are two types: equipment and battery split and equipment and battery integrated, according to voltage level, there are two types: 1000V system and 1500V system; There are two types of energy collection points: DC coupling and AC coupling. Large/medium-sized energy storage products, currently based on the structure of containers or prefabricated cabins, are generally used on the power supply side and the power grid side, a small number of applications are on the user side, the cooling mode gradually transitions from air cooling to liquid cooling, the electrical structure is mainly centralized, string energy storage is also gradually added, the voltage is gradually based on 1500V, and the AC coupling method is the mainstay. The income model of energy storage on the industrial and commercial user side is peak-valley arbitrage, full of release; The more charge and discharge volume, the greater the benefit; The higher the energy conversion efficiency, the smaller the loss and the greater the benefit. Therefore, the user-side energy storage system equipment with string cluster-controlled energy storage integrated system has a higher yield than the centralized energy storage integrated system. The effective utilization rate of each cluster of clustered energy storage system is high, and there is no barrel short board effect; There is no parallel connection between clusters, no circulation, and high energy conversion efficiency. Due to the decentralized layout, distributed small energy storage cabinets consider the high after-sales cost of maintenance; The demand purchase volume is small, so the unit price of related components and the overall system is higher. At present, the market price of small energy storage outdoor cabinets is estimated to be about 1.8 yuan / Wh. The price of centralized energy storage system is 1.3‒1.5 yuan/Wh (tens of MWh purchase). DC coupling
As shown in the figure below, the direct current generated by the photovoltaic modules is stored in the battery pack through the controller, and the grid can also charge the battery through the bidirectional DC-AC converter. The energy pooling point is at the DC battery end. 
The working principle of DC coupling: when the photovoltaic system is running, the battery is charged through the MPPT controller; When the electrical load is demanded, the battery will release the power, and the size of the current is determined by the load. The energy storage system is connected to the grid, and if the load is small and the battery is full, the photovoltaic system can supply power to the grid. When the load power is greater than the photovoltaic power generation, the grid and the photovoltaic can supply power to the load at the same time. Because photovoltaic power generation and load power consumption are not stable, it depends on the battery to balance the system energy. AC coupling
The direct current generated by the photovoltaic modules is changed into alternating current through the inverter, directly to the load or sent to the grid, and the power grid can also charge the battery through the bidirectional DC-AC bidirectional converter. The gathering point of energy is at the AC end. 
The working principle of AC coupling: including photovoltaic power supply system and battery power supply system. The photovoltaic system consists of a photovoltaic array and a grid-connected inverter; The battery system consists of a battery pack and a bidirectional inverter. The two systems can operate independently without interfering with each other, or they can be separated from the large grid to form a microgrid system. From the currently installed cases, user-side energy storage using modular, string, AC-side coupling scheme has become a trend, occupying more than 80% of the market share, this scheme has low cost, flexible configuration, high safety, suitable for industrial and commercial and off-grid energy storage power stations, and DC-side coupling centralized scheme, simple wiring, stable system, suitable for small and medium-sized independent power stations. www.ufobattery.com
