Flywheel energy storage
Most FES systems use electricity to accelerate and decelerate the flywheel, but devices that directly use mechanical energy are being developed.[why?
][1] Advanced FES systems have rotors made of high strength carbon-fiber composites, suspended by magnetic bearings, and spinning at speeds from 20,000 to over 50,000 rpm in a vacuum enclosure.
[2] Such flywheels can come up to speed in a matter of minutes – reaching their energy capacity much more quickly than some other forms of storage.
Newer systems use carbon-fiber composite rotors that have a higher tensile strength than steel and can store much more energy for the same mass.
Since flux pinning is an important factor for providing the stabilizing and lifting force, the HTSC can be made much more easily for flywheel energy storage than for other uses.
Composite materials that are wound and glued in layers tend to disintegrate quickly, first into small-diameter filaments that entangle and slow each other, and then into red-hot powder; a cast metal flywheel throws off large chunks of high-speed shrapnel.
Angular forces may cause portions of a metal flywheel to bend outward and begin dragging on the outer containment vessel, or to separate completely and bounce randomly around the interior.
Traditional flywheel systems require strong containment vessels as a safety precaution, which increases the total mass of the device.
Still, many customers of large-scale flywheel energy-storage systems prefer to have them embedded in the ground to halt any material that might escape the containment vessel.
[17] Much of the friction responsible for this energy loss results from the flywheel changing orientation due to the rotation of the earth (an effect similar to that shown by a Foucault pendulum).
[19] When a flywheel is used entirely for its effects on the attitude of a vehicle, rather than for energy storage, it is called a reaction wheel or a control moment gyroscope.
The center axle of the flywheel acts as a single gimbal, and if aligned vertically, allows for the 360 degrees of yaw in a horizontal plane.
Full free rotation would require slip rings around each gimbal axis for power conductors, further adding to the design complexity.
To reduce space usage, the gimbal system may be of a limited-movement design, using shock absorbers to cushion sudden rapid motions within a certain number of degrees of out-of-plane angular rotation, and then gradually forcing the flywheel to adopt the vehicle's current orientation.
Strictly speaking, the two flywheels would exert a huge torqueing moment at the central point, trying to bend the axle.
In the 1950s, flywheel-powered buses, known as gyrobuses, were used in Yverdon (Switzerland) and Ghent (Belgium) and there is ongoing research to make flywheel systems that are smaller, lighter, cheaper and have a greater capacity.
battery power systems, such as low capacity, long charge times, heavy weight and short usable lifetimes.
The flywheel was composed of a titanium hub with a carbon fiber cylinder and was gimbal-mounted to minimize adverse gyroscopic effects on vehicle handling.
When partnered with a four-cylinder engine, it offers up to a 25 percent reduction in fuel consumption versus a comparably performing turbo six-cylinder, providing an 80 horsepower (60 kW) boost and allowing it to reach 100 kilometres per hour (62 mph) in 5.5 seconds.
[23] In July 2014 GKN acquired Williams Hybrid Power (WHP) division and intends to supply 500 carbon fiber Gyrodrive electric flywheel systems to urban bus operators over the next two years.
Advanced flywheels, such as the 133 kWh pack of the University of Texas at Austin, can take a train from a standing start up to cruising speed.
[30] These trials and systems store kinetic energy in rotors consisting of a carbon-glass composite cylinder packed with neodymium-iron-boron powder that forms a permanent magnet.
[7] Costs of a fully installed flywheel UPS (including power conditioning) were (in 2009) about $330 per kilowatt (for 15 seconds full-load capacity).
The enormous transient loads produced by deliberately forcing such devices to demonstrate their ability to interrupt simulated short circuits would have unacceptable effects on the local grid if these tests were done directly from building power.
Storage was 525 Wh (1.89 MJ) and could be charged or discharged at 1 kW (1.3 hp), leading to a specific energy of 5.31 W⋅h/kg and power density of 10.11 W/kg.
The Incredible Hulk roller coaster at Universal's Islands of Adventure features a rapidly accelerating uphill launch as opposed to the typical gravity drop.
Flywheels are sometimes used as short term spinning reserve for momentary grid frequency regulation and balancing sudden changes between supply and consumption.
No carbon emissions, faster response times and ability to buy power at off-peak hours are among the advantages of using flywheels instead of traditional sources of energy like natural gas turbines.
[52] Amber Kinetics, Inc. has an agreement with Pacific Gas and Electric (PG&E) for a 20 MW / 80 MWh flywheel energy storage facility located in Fresno, CA with a four-hour discharge duration.
The system was part of a wind power and flywheel demonstration project being carried out for the California Energy Commission.
