Energy storage is the process of storing excess energy. Energy storage is an important part of the power system's "generation-transmission-distribution-consumption-storage" process, and it is the foundation for building new energy microgrids. In the power system, energy storage technology can be used in various fields such as power generation, transmission, distribution, and end-user applications.
Energy storage system absorb the fluctuations of renewable energy generation or smooth the output power of renewable energy generation. They track the generation plan and follow the ramping of renewable energy generation. They assist wind and solar power generation in becoming partially dispatchable power sources, enhancing their controllability. In areas with high penetration of renewable energy generation, excess wind and solar power can be stored to reduce curtailment and improve the penetration rate and economics of renewable energy. Stored energy can be used as spinning reserves to provide power to the grid whenever necessary, reducing the need for conventional backup power and improving their efficiency.
The intermittency of renewable energy generation increases the likelihood of line overload and congestion. Energy storage devices located in different places can provide ancillary services, optimize power flows, and alleviate or resolve line overloads and congestion, reducing losses in lines and networks. They can also postpone the construction and commissioning of new lines. When disturbances or accidents occur in the grid, solar energy storage system can serve as frequency-regulating power sources, assisting in improving the security and stability of the grid operation and increasing the margin of grid safe operation. They can also serve as emergency backup power sources or black start power sources for the grid.
In an isolated microgrid or when a microgrid is separated from the connected distribution network, energy storage devices become essential equipment to ensure the continuous and stable operation of the microgrid. They enhance the power quality, keeping the voltage within the qualified or appropriate range. They can be used to regulate the frequency of microgrids and maintain frequency stability during transitions and for long-term energy management. Energy storage is particularly important for an isolated microgrid equipped with a significant amount of wind and solar power generation, such as an island. Mobile energy storage devices can be quickly transported to blackout areas during regional accidents and connected to the grid to shorten the blackout time and improve power supply reliability. For example, using energy storage devices such as batteries and flywheels in combination with reactive power compensation devices can improve power quality.