Energy storage technologies can be classified into three categories according to their energy storage methods: physical energy storage, chemical energy storage, and electromagnetic energy storage. Physical energy storage mainly includes pumped hydro storage, compressed air energy storage, and flywheel energy storage. Chemical energy storage mainly includes lead-acid batteries, lithium-ion batteries, sodium-sulfur batteries, and flow batteries. Electromagnetic energy storage mainly includes superconducting energy storage, capacitor energy storage, and supercapacitor energy storage.
1. Superconducting energy storage
Superconducting energy storage is named so because superconducting magnets can continuously store electromagnetic energy without energy loss by circulating current under zero resistance, and they can operate even under short-circuit conditions. The advantages of superconducting coils are that they can store energy for a long time without loss and can also release it instantaneously; they have high energy storage capacity; they can be excited by a low-voltage power supply; the device is small in size, saving on conventional power transmission and transformation equipment and reducing power transmission and transformation losses.
2. Capacitor energy storage
Capacitor energy storage refers to the technology of storing electrical energy using capacitors. The mechanism of capacitor energy storage is based on double-layer capacitance and Faraday capacitance, with supercapacitor energy storage being its primary form. Supercapacitor energy storage devices mainly consist of a supercapacitor bank, a bidirectional DC/DC converter, and corresponding control circuitry. The core technology lies in the voltage equalization topology and control strategy within the supercapacitor bank, as well as the topology and control strategy of the bidirectional DC/DC converter. Capacitor energy storage has been widely applied in electric vehicles, wind and solar power energy storage, power quality regulation in power systems, and pulse power supplies.
3. Supercapacitor energy storage
Supercapacitor energy storage is developed based on the electrochemical double-layer theory. It can provide powerful pulsed power. During charging, the electrode surface, in an ideally polarized state, attracts oppositely charged ions from the surrounding electrolyte solution, causing them to attach to the electrode surface and forming a double charge layer, thus constituting a double-layer capacitor. In power systems, it is often used for short-term, high-power load smoothing and peak power applications related to power quality, such as starting support for high-power DC motors and state-of-the-art voltage restorers, to improve power supply levels during voltage dips and transient interference.
