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A flywheel is a cylinder that spins at very high speeds, storing kinetic (movement) energy.
How It Works
A flywheel can be used to store energy by combining it with a device that operates either as an electric motor that accelerates the flywheel to store energy or as a generator that produces electricity from the energy stored in the flywheel.
The faster the flywheel spins, the more energy it retains. Energy can be drawn off as needed by slowing the flywheel.
Modern flywheels use composite rotors made with carbon-fiber materials. The rotors have a very high strength-to-density ratio, and rotate in a vacuum chamber to minimize aerodynamic losses. The use of superconducting electromagnetic bearings can virtually eliminate energy losses through friction.
Advantages
Flywheels are able to charge and discharge rapidly, and are little affected by temperature fluctuations. They take up relatively little space, have lower maintenance requirements than batteries, and have a long life span. Flywheels are relatively tolerant of abuse — for example, the lifetime of a flywheel system will not be shortened by a deep discharge.
Disadvantages
Power loss is faster than for batteries.
Applications
Flywheels are particularly suitable for power quality control. No large-scale applications of the technology have been made.
High-temperature superconducting flywheels (funded by DOE) are currently under development. Such systems would offer inherent stability, minimal power loss, and simplicity of operation as well as increased energy storage capacity.
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