Types of energy storage systems
Energy storage systems refer to systems that store energy when it is plentiful and release the stored energy to supply demand when energy demand is high. Below are some of the main types of energy storage systems:
1) Mechanical energy storage
Pumped storage: During periods of low grid load, water is pumped from a low-lying reservoir to a higher-lying reservoir using excess electricity as a liquid energy medium. During periods of peak grid load, the water in the higher-lying reservoir flows back to the lower reservoir to drive a turbine generator to generate electricity.
Compressed air energy storage: Utilizing the surplus electricity generated during off-peak hours of the power system, an electric motor drives an air compressor to compress air into a large-capacity, sealed underground cavern that serves as an air storage chamber. When the system's power generation is insufficient, the compressed air is mixed with oil or natural gas through a heat exchanger and then introduced into a gas turbine to generate electricity.
Flywheel energy storage: This method uses a high-speed rotating flywheel to store energy in the form of kinetic energy. When energy is needed, the flywheel slows down and releases the stored energy.
2) Electrical energy storage:
Supercapacitor energy storage: Ultra-large capacity is obtained by using a double-layer structure composed of porous activated carbon electrodes and electrolyte.
Superconducting energy storage (SMES): A device that stores electrical energy by utilizing the zero resistance of a superconductor.
3) Electrochemical energy storage:
Lead-acid battery: It is a type of battery whose electrodes are mainly made of lead and its oxides, and whose electrolyte is sulfuric acid solution.
Lithium-ion batteries are a type of battery that uses lithium metal or lithium alloy as the negative electrode material and a non-aqueous electrolyte solution.
Sodium-sulfur battery: a secondary battery that uses metallic sodium as the negative electrode, sulfur as the positive electrode, and a ceramic tube as the electrolyte membrane.
Flow battery: A high-performance battery that utilizes separate positive and negative electrolytes for each electrode to circulate independently.
Working principle of energy storage system
An energy storage system is a device that can collect, store, and release energy, enabling the balancing and optimized scheduling of the power system to meet the ever-changing energy demands.
The working principle of an energy storage system is as follows:
1. Charging phase: When the power grid has sufficient power supply capacity, the energy storage system loads electrical energy through the grid and converts the electrical energy into a form that the energy storage system can store, such as chemical energy, mechanical energy, thermal energy, etc., so that it can be used when needed in the future.
2. Storage Phase: When needed, the energy storage system can release the stored energy through a power-off device to meet the load demand of the power system. When the power system load is high, the energy storage system can release the stored energy to provide additional power supply.
3. Discharge Phase: The energy storage system converts the stored energy into electrical energy through an inverter and outputs it to the power system for grid use, thereby helping the power system maintain stable operation. When the power system load decreases, the energy storage system can recharge to store energy for unforeseen needs.
In summary, energy storage systems can enable energy dispatch in response to power system load changes or grid failures, improving the stability, reliability, and flexibility of the power system and facilitating the large-scale application of renewable and clean energy. Energy storage technology also helps address the mismatch between the power system and electricity demand, improving grid efficiency and sustainability.
