Flywheel energy storage is an energy storage technology that uses a reciprocal two-way motor (motor/generator) to achieve mutual conversion between electrical energy and the mechanical energy of a high-speed rotating flywheel. Flywheel energy storage is different from traditional chemical energy storage and is a purely physical energy storage technology.
The concept of flywheel energy storage in the modern sense was first proposed in the 1950s, and then in the 1970s, the U.S. Energy Research and Development Agency (ERDA) and the U.S. Department of Energy (DOE) began to fund the application and development of flywheel systems. Japan and Europe have also successively carried out research and development of related technologies and products. After entering the 1990s, due to the maturity of magnetic levitation, carbon fiber composite materials and power electronic technology, flywheel energy storage has truly entered a period of rapid development.
Since the 1990s, Piller in Germany and Active Power in the United States have successively launched commercial flywheel products. Today, flywheel products based on permanent magnetic levitation and electromagnetic levitation bearing technology have been relatively mature, and their stability and reliability have been greatly improved. Thousands of products have been put into formal commercial operation around the world, and the application fields mainly include enterprise-level UPS, power frequency modulation, aerospace, military and other fields. Flywheel energy storage products can be divided into many types from different angles. If it is divided from the speed of the flywheel rotor, it can be divided into low-speed flywheel products and high-speed flywheel products.
In low-speed flywheel products, the rotor is mainly made of high-quality steel, and the edge linear speed of the rotor generally does not exceed 100m/s. Such products can use mechanical bearings, permanent magnetic bearings or electromagnetic bearings. The power density of the entire system is low. The power and energy of the energy storage system are mainly improved by increasing the mass of the flywheel.
The rotor speed of high-speed flywheel products can reach more than 50,000 revolutions per minute, and the linear speed of the rotor edge can reach more than 800m/s. Such a high speed requires high-strength materials, so glass fiber, carbon fiber, etc. are mainly used as the main materials for manufacturing the rotor. Mechanical bearings cannot be used in such products, but permanent magnet, electromagnetic or superconducting bearings can only be used. At present, the research and application of permanent magnet and electromagnetic bearing in some countries have been relatively mature, and the latest research hotspot is high-speed flywheel products based on superconducting magnetic levitation.
Currently, companies that can provide flywheel commercial products globally include Active Power, Beacon Power, Piller, Flywheel Energy System and many other companies. There is a big gap between China and the international advanced level in this field.