Working principle of flywheel energy storage
Flywheel energy storage system is a kind of energy storage device with electromechanical energy conversion, which breaks through the limitation of chemical battery and realizes energy storage by physical method. The electric energy and the mechanical kinetic energy of the high-speed flywheel are transformed and stored by the electric / generator reciprocal two-way motor, and different types of load interfaces are connected by frequency modulation, rectification, constant voltage.
During the energy storage, the electric energy is transformed by the electric power converter to drive the motor to run, and the motor drives the flywheel to accelerate rotation. The flywheel stores the energy in the form of kinetic energy to complete the energy storage process from the electric energy to the mechanical energy conversion, and the energy is stored in the flywheel body of high-speed rotation. After that, the motor maintains a constant speed until receiving a control signal of energy release; During the energy release, the high-speed rotating flywheel drives the motor to generate electricity, and the current and voltage suitable for the load are output by the power converter to complete the energy release process from mechanical energy to electrical energy conversion. The whole flywheel energy storage system realizes the process of power input, storage and output.
What are the characteristics of flywheel energy storage
The flywheel energy storage uses the motor to drive the flywheel to rotate at high speed, and converts the electrical energy into mechanical energy for storage. When necessary, the flywheel drives the generator to generate electricity. The flywheel system operates in a high vacuum environment, which is characterized by no friction loss, small wind resistance, long service life, no impact on the environment, almost no maintenance. It is suitable for power grid frequency modulation and power quality assurance. The disadvantage of flywheel energy storage is its low energy density. The cost of ensuring the safety of the system is very high, which can not show its advantages in small occasions. At present, it is mainly used to supplement the battery system.
Compared with other energy storage methods, flywheel energy storage system (FESS) has many advantages, such as high energy density, high efficiency, high instantaneous power, fast response, long service life, and the installation site is not limited by geographical environment. It is one of the energy storage technologies with a promising future, and has a very broad application prospect.
Application of flywheel energy storage
1. Battery free maglev flywheel energy storage UPS
(1) Under the condition that the mains power input is normal, or the mains power input is low or high (within a certain range), UPS can stabilize and filter the mains power through its internal active dynamic filter, so as to provide high-quality power guarantee to the load equipment, and charge the flywheel energy storage device. UPS uses the built-in flywheel energy storage device to store energy.
(2) In case that the quality of mains power input fails to meet the normal operation requirements of UPS, or in case of mains power input interruption, ups will convert the mechanical energy stored in flywheel energy storage device into electric energy, and continue to provide high-quality and uninterrupted power guarantee to load equipment.
(3) In case of internal problems affecting the operation of UPS, UPS switches to bypass mode through its internal static switch, and the municipal power supply directly provides power guarantee to load equipment without interruption.
(4) In the case that the mains power input is restored to power supply, or the mains power input quality is restored to meet the normal operation requirements of UPS, switch to the mode of mains power supply through ups immediately, continue to provide high-quality and uninterrupted power support to the load equipment, and continue to charge the flywheel energy storage device.
2. Electric vehicle battery
At present, with the improvement of environmental protection awareness and the contradiction between global energy supply and demand, it is an important trend for the development of automobile industry in the world to develop energy-saving and alternative energy vehicles to reduce environmental pollution. The automobile manufacturing industry has turned its attention to the development of electric vehicles. To find a new type of battery with high energy storage density, short charging time and appropriate price is the key for electric vehicles to have greater mobility and compete with gasoline vehicles, while flywheel battery has the characteristics of clean, efficient, fast charging and discharging, and no pollution to the environment, which is widely valued by the automobile industry. It is predicted that the flywheel battery will be a research hotspot in the electric vehicle industry in the 21st century.
3. Uninterruptible power supply
UPS is widely used in communication hub, national defense command center, industrial production control center and other places because it can ensure uninterrupted power supply and power quality. At present, UPS is composed of rectifier, inverter, static switch and battery pack. But at present, the battery usually has the requirements of working temperature, working humidity, input voltage, and discharge depth. At the same time, the battery is not allowed to close and open frequently. The flywheel has the advantages of large energy storage, high energy storage density, fast charging and unlimited charging and discharging times, so it has a good application prospect in the field of uninterruptible power supply system.
4. Uninterrupted power supply of wind power system
Because of the instability of wind speed, wind power users have difficulty in using. The traditional method is to install the diesel generator, but because of the special requirements of the diesel engine itself, it can be stopped within 30 minutes after starting. The wind often breaks for seconds, minutes. Not only the diesel engine starts frequently, which affects the service life, but also the diesel engine works at the same time after the fan restarts, which will cause the electric energy surplus. Considering the energy storage of flywheel. Charging is fast, so many foreign research institutions have introduced energy storage flywheel into wind power generation system. In the United States, flywheels are introduced into the wind power generation system to achieve full peak regulation. The generating power of flywheels is 300kW, and the energy storage of large capacity flywheel is 277kw / h.
5. High power pulse discharge power supply
In order to avoid the huge waste and reduce the air pollution, the United States is studying a kind of Maglev linear motor bracket (also known as space elevator) to launch the space shuttle, which requires a huge power, but the discharge time is very short, so it is obviously unreasonable to reduce the energy provided by a huge store system. The flywheel energy storage system can achieve this.