Home energy storage system can be used for wind or photoelectric energy storage. It is the ideal green energy storage product of the smart grid and other industries. Taking the most common solar energy storage as an example, the electricity generated by photovoltaic power is supplied to the household load, while the excess electricity is stored in the energy storage battery. When there is no light, the energy in the energy storage battery is used for the load. Home energy storage system can provide power for ordinary families, small business districts, areas facing a shortage of energy, areas with frequent natural disasters, areas with unstable power or isolated islands off the grid, residential buildings, public facilities, small factories and so on. Home energy storage system has the characteristics of safety, high efficiency and simple operation. Home energy storage system is simple to assemble and convenient to operate. At present, home energy storage system is divided into two types, one is grid-connected home energy storage system, the other is off-grid home energy storage system.
Grid-connected home energy storage system consists of five parts, including solar cell array, grid-connected inverter, BMS management system, battery pack and AC load. The system adopts the hybrid power supply of photovoltaic and energy storage system. When the power supply is normal, the photovoltaic grid-connected system and the power supply are used to supply the load. When the utility power is cut off, the energy storage system and photovoltaic grid-connected system jointly supply power. The grid-connected home energy storage system can be divided into three working modes: Mode 1: photovoltaic provides energy storage and surplus electricity is connected to the grid; Mode 2: photovoltaic provides energy storage and some users use electricity; Mode 3: photovoltaic only provides partial energy storage.
The off-grid home energy storage system is independent and has no electrical connection with the grid. Therefore, the whole system does not need a grid-connected inverter, and the photovoltaic inverter can meet the requirements. The off-grid home energy storage system can be divided into three working modes: Mode 1: photovoltaic energy storage and user electricity (sunny day); Mode 2: photovoltaic and energy storage batteries provide users with electricity (cloudy day); Mode 3: energy storage battery provides power for users (in the evening and rainy days).
At present, the mainly used energy storage devices are BMS battery management system, photovoltaic grid-connected inverter and energy storage inverter. How to choose batteries for home energy storage system? At present, most household energy storage systems use safe and high-performance lithium iron phosphate batteries. Compared with lead-acid batteries, they have the characteristics of long service life, small size, light weight, environmental protection and no pollution. In addition, the battery design ideas are different in different application scenarios. Normally, there are 3 common application scenarios, self-generation and self-use (high electricity charge or no subsidy), peak valley electricity price, and standby power supply (unstable power grid or important load).