Capacitor energy storage refers to the technology of storing electrical energy using capacitors. Currently, capacitor energy storage is widely used in electric vehicles, wind and solar power generation energy storage, power quality regulation in power systems, pulse power supplies, and more.
Based on different energy storage mechanisms, capacitor energy storage can be divided into the following two categories:
1. Electric Double Layer Capacitance: Electric double layer capacitance arises from the opposing charges caused by the directional arrangement of electrons or ions at the electrode/solution interface. In an electrode/solution system, an electric double layer forms at the interface between the electron-conducting electrode and the ion-conducting electrolyte solution. When an electric field is applied to the two electrodes, the anions and cations in the solution migrate towards the positive and negative electrodes, respectively, forming an electric double layer on the electrode surface. After the electric field is removed, the positive and negative charges on the electrodes attract the oppositely charged ions in the solution, stabilizing the electric double layer and generating a relatively stable potential difference between the positive and negative electrodes.
2. Faraday pseudocapacitance: This refers to the underpotential deposition of electroactive materials on the electrode surface and near-surface or in the bulk phase, resulting in highly reversible chemisorption-desorption and redox reactions, generating capacitance related to the electrode charging potential. For Faraday pseudocapacitance, the charge storage process includes not only storage on the electric double layer but also redox reactions between electrolyte ions and the electrode active materials.
The main form of capacitor energy storage is supercapacitor energy storage. A supercapacitor energy storage device primarily consists of a supercapacitor bank, a bidirectional DC/DC converter, and corresponding control circuitry. Its 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.
Supercapacitors are a new type of electrochemical energy storage device that falls between traditional capacitors and batteries. Compared with traditional capacitors, they have higher energy density and electrostatic capacitance in the range of thousands to tens of thousands of farads; compared with batteries, they have higher power density and ultra-long cycle life. Therefore, they combine the advantages of traditional capacitors and batteries and are a chemical power source with broad application prospects.
It primarily utilizes the electric double layer formed by charge separation at the electrode/electrolyte interface, or the Faraday "quasi-capacitance" generated by rapid redox reactions on or inside the electrode surface, to store charge and energy. Therefore, supercapacitors feature fast charging speeds, excellent high-current discharge performance, ultra-long cycle life, and a wide operating temperature range. A supercapacitor energy storage device mainly consists of a supercapacitor bank, a bidirectional DC/DC converter, and corresponding control circuitry.
