Energy storage technology is classified according to the storage medium. Energy storage systems can be divided into mechanical energy storage, electrical energy storage, electrochemical energy storage, thermal energy storage, and chemical energy storage. The application forms of mechanical energy storage include pumped storage, compressed air energy storage, and flywheel energy storage.
Mechanical energy storage system
Pumped storage: The surplus electricity generated during off-peak hours is used to pump water, which serves as a liquid energy medium, from a low-situated reservoir to a high-situated reservoir. During peak electricity demand, the water in the high-situated reservoir flows back to the lower reservoir, driving a water turbine to generate electricity.
Compressed air energy storage: The surplus electricity during low-load periods of the power system is used to drive an electric motor which compresses air and stores it in a closed underground cavern serving as an air storage chamber. When the power generation capacity is insufficient, the compressed air is mixed with oil or natural gas and burned in a combustor to drive a gas turbine for power generation.
Flywheel energy storage: It stores energy in the form of kinetic energy using a high-speed rotating flywheel. When energy is needed, the flywheel decelerates, releasing the stored energy.
Electrical energy storage system
Supercapacitor energy storage: It achieves a high capacitance by using a double-layer structure composed of activated carbon porous electrodes and an electrolyte.
Superconducting energy storage: It is a device that stores electrical energy using the zero-resistance property of superconductors.
Electrochemical energy storage system
Lead-acid battery: It is a storage battery with electrodes mainly made of lead and its oxides, and sulfuric acid as the electrolyte.
Lithium-ion battery: It is a type of battery that uses lithium metal or lithium alloy as the negative electrode material and non-aqueous electrolyte solution.
Sodium-sulfur battery: It is a secondary battery with metallic sodium as the negative electrode, sulfur as the positive electrode, and ceramic tubes as the electrolyte separator.
Flow battery: It is a high-performance rechargeable battery in which positive and negative electrolytes are separated and circulated.
Generation side
To increase the dispatchability of renewable energy sources and avoid wasting excess solar and wind energy. Achieve smooth output power of renewable energy sources, reduce the impact on the power grid, and improve the utilization of output power transmission lines. Application scenarios: photovoltaic power generation, wind power generation, and other renewable energy sources.
Transmission side
To provide frequency regulation and peak shaving for the power grid. Actively achieve active and reactive power output to improve power quality. Application scenarios: power plants, renewable energy power stations.
Distribution side
To improve the self-consumption rate of photovoltaics, self-balance the load, and reduce energy exchange between the system and the power grid. When the power grid has faults, the system can operate independently to ensure load power supply. Application scenarios: microgrids, distributed generation for self-use.
Consumption side
To benefit from time-of-use electricity pricing, improve load characteristics, reduce electricity costs, and basic charges. Reduce the impact of peak loads on the power grid. Application scenarios: high-energy-consuming enterprises and important backup power sources for the country, industries such as electrolysis, electroplating, and metallurgy, transportation sectors such as electric vehicles, light railways, and subways. Power consumption in data centers, communication base stations, port operations, remote mountainous areas, etc. Used as important backup power stations for governments, hospitals, and military command centers. Essential energy storage technology for office buildings and households. Alleviating the increased capacity demand caused by the charging of electric vehicles.
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