How to apply lithium-ion batteries in energy storage systems?

　　Lithium-ion batteries come in a variety of sizes and in two basic shapes: cylinders and rectangular prisms. Cylindrical cells are usually housed in steel cases, while prismatic cells may be housed in aluminum alloy casings or in airtight pouches made of multi-layer polymer sheets, forming so-called square cells.

　　The nominal voltage of a lithium-ion battery is determined by the specific combination of positive and negative materials, and the energy is determined by the positive and negative materials and sizes. A single lithium-ion battery can be directly used in electronic consumer products such as mobile phones. To provide the higher capacities and operating voltages required for larger-scale applications, multiple cells can be connected in different series and parallels, resulting in battery modules and battery packs.

　　(Schematic diagram of lithium battery energy storage system)

　　A 1 MW energy storage system will have about 3,000 batteries (take 100 Ah as an example), which is about the capacity of about 80,000 batteries in 10 Tesla electric vehicles, because the capacity of the single cell used by Tesla is not high.

　　Pack: Many battery cells can be stringed and combined together to form a module. A battery module usually has at least 100 batteries, which is more convenient to manage. The pack factory is responsible for the assembly technology and process of this section. When they make the module, they will establish the first layer of small battery management system, and also design the fire protection mechanism to prevent the burning between the battery cells. This part is also one of important rings to pass international safety certifications such as IEC and UL.

　　Battery cabinet and battery management system (Rack and BMS): 14~21 strings of battery modules are put away like a drawer, which is a battery cabinet. In order to manage battery cells and modules, a higher-level battery management system is required to give battery commands, it knows how to act. BMS is a real-time monitoring system composed of electronic circuit equipment. It can monitor the voltage, temperature, SOC, SOH status of cells and battery packs. The battery management system will check the status of each battery cell from time to time and try to maintain the balance between the battery cells.

　　Power Conditioner (PCS): It is the key to connecting the battery cabinet and the grid application. It can be converted in both directions. Discharge is to convert the DC power of the battery into the AC power of the grid, and charging is to convert the AC power of the grid into the DC required by the battery. energy and store it. The power conditioner needs to connect various communications between the battery management system and the energy management system, and the complexity of the collection and transmission is quite high.

　　Energy Management System (EMS): Whether it is energy saving, energy creation, energy storage, or smart system integration, as long as it involves the integration of many electrical equipment, power generation equipment, and energy storage equipment, an energy management system is required. Energy systems are no exception.

　　In the energy storage system, the energy management system is a complete monitoring system covering the controller. In addition to managing when the power regulator is charged and discharged, it also includes monitoring the ambient temperature and humidity of the battery storage, fire protection system, access control system, etc., which is equivalent to the brain of energy storage system.

　　The energy management system needs to be able to communicate with the battery management system and power conditioner. If the scheduling is not good, there may be loopholes in the safety design, which is one of the reasons for the fire accident of energy storage batteries in South Korea.

　　Energy storage system and system integration (SI): The energy storage system is not like an electric vehicle, and more often requires a customized design. After all, each application scenario that requires an energy storage system is different. Therefore, it is necessary to choose a system integrator to assemble and operate the entire energy storage system effectively. A system integrator typically develops an energy management system to ensure that the various parts it purchases perform well.