NationMaster - Encyclopedia: Flywheel energy storage

Flywheel Energy Storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy. The energy is converted back by slowing down the flywheel. Image File history File links Download high resolution version (768x1024, 262 KB) Summary G2 Flywheel Module, NASA Image http://space-power. ... Image File history File links Download high resolution version (768x1024, 262 KB) Summary G2 Flywheel Module, NASA Image http://space-power. ... R0t0r is from efnet ... Spoked flywheel Flywheel from stationary engine. ... The rotational energy or angular kinetic energy is the kinetic energy due to the rotation of an object and is part of its total kinetic energy. ...

Most FES systems use electricity to accelerate and decelerate the flywheel, but devices that directly use mechanical energy are being developed.^[1]

Advanced FES systems have rotors made of high strength carbon-composite filaments that spin at speeds from 20,000 to over 50,000 rpm ^[2] in a vacuum enclosure and use magnetic bearings. Such flywheels come up to speed in a matter of minutes, rather than the hours needed to recharge a battery.^[2] A magnetic bearing is a bearing which supports a load using magnetic levitation. ...

Main components

A typical system consists of a rotor suspended by bearings inside a vacuum chamber to reduce friction, connected to a combination electric motor/electric generator. Look up Vacuum in Wiktionary, the free dictionary. ... Look up generator in Wiktionary, the free dictionary. ...

Rotor

First generation flywheel energy storage systems use a large steel flywheel rotating on mechanical bearings. Newer systems use carbon-fiber composite rotors that have a higher tensile strength than steel and are an order of magnitude lighter. The steel cable of a colliery winding tower. ... This article does not cite any references or sources. ... Tensile strength isthe measures the force required to pull something such as rope, wire, or a structural beam to the point where it breaks. ...

Bearings

Magnetic bearings are necessary; in conventional mechanical bearings, friction is directly proportional to speed, and at such speeds, too much energy would be lost to friction. A magnetic bearing is a bearing which supports a load using magnetic levitation. ... A bearing is a component used to reduce friction in a machine. ... friction is the force that opposes the relative motion or tendency toward such motion of two surfaces in contact. ...

The expense of refrigeration led to the early dismissal of low temperature superconductors for use in magnetic bearings. High-temperature superconductor (HTSC) bearings however may be economical and could possibly extend the time energy could be stored economically. Hybrid bearing systems are most likely to see use first. HTSC bearings have historically had problems providing the lifting forces necessary for the larger designs, but can easily provide a stabilizing force. Therefore, in hybrid bearings, permanent magnets support the load and HTSC are used to stabilize it. The reason superconductors can work well stabilizing the load is because they are good diamagnets. In hybrid-bearing systems, a conventional magnet levitates the rotor, but the high temperature superconductor keeps it stable. If the rotor tries to drift off center, a restoring force due to flux pinning restores it. This is known as the magnetic stiffness of the bearing. Rotational axis vibration can occur due to low stiffness and damping, which are inherent problems of superconducting magnets, preventing the use of completely superconducting magnetic bearings for flywheel applications. Despite its name, high-temperature superconductivity still occurs at cryogenic temperatures. ... Levitating pyrolytic graphite Diamagnetism is a form of magnetism which is only exhibited by a substance in the presence of an externally applied magnetic field. ... Flux pinning is the phenomenon where a magnets lines of force (called flux) become trapped or pinned inside a superconducting material. ...

Since flux pinning is the important factor for providing the stabilizing and lifting force, the HTSC can be made much more easily for FES than for other uses. HTSC powders can be formed into arbitrary shapes so long as flux pinning is strong. An ongoing challenge that has to be overcome before superconductors can provide the full lifting force for a FES system is finding a way to suppress the decrease of levitation force and the gradual fall of rotor during operation caused by the flux creep of SC material. Flux pinning is the phenomenon that magnetic flux lines do not move (become trapped, or pinned) in spite of the Lorentz force acting on them inside a current-carrying Type II superconductor. ...

Parasitic losses such as friction, hysteresis, and eddy currents of both magnetic and conventional bearings in addition to refrigerant costs can limit the economical energy storage time for flywheels. However, further improvements in superconductors may help eliminate eddy current losses in existing magnetic bearing designs as well as raise overall operating temperatures. Even without such improvements, however, modern flywheels can have a zero-load rundown time measurable in years. In short, Parasitic Loss is a loss that a parasite consumes from its host which may or may not be beneficial to the host. ... friction is the force that opposes the relative motion or tendency toward such motion of two surfaces in contact. ... Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history. ... As the circular plate moves down through a small region of constant magnetic field directed into the page, eddy currents are induced in the plate. ...

Physical characteristics

For the basic physics of a flywheel, see Flywheel#Physics. Spoked flywheel Flywheel from stationary engine. ...

Compared with other ways of storing electricity, FES systems have long lifetimes (lasting decades with little or no maintenance^[2]), high energy densities (~ 130 W·h/kg, or ~ 500 J/g, and large maximum power outputs. The energy efficiency (ratio of energy out per energy in) of flywheels can be as high as 90%. Since FES can store and release energy quickly, they have found a niche providing pulsed power (see compulsator). Energy density is the amount of energy stored in a given system or region of space per unit volume or per unit mass, depending on the context. ... A compulsator is the short name for a compensated pulsed alternator, a form of power supply. ...

Applications

Transportation

In the 1950s flywheel-powered buses, known as gyrobuses, were used in Yverdon, Switzerland, and there is ongoing research to make flywheel systems that are smaller, lighter, cheaper, and have a greater capacity. It is hoped that flywheel systems can replace conventional chemical batteries for mobile applications, such as for electric vehicles. Proposed flywheel systems would eliminate many of the disadvantages of existing battery power systems, such as low capacity, long charge times, heavy weight, and short usable lifetimes. In Vancouver, BC, flywheels were used in buses to retain their electric power when disconnected from overhead lines ^[3]; they may also have been used in the experimental Chrysler Patriot, though that has been disputed ^[4]. This does not cite any references or sources. ... A Gyrobus is an electric bus that uses flywheel energy storage, not overhead wires like a trolleybus. ... Yverdon-les-Bains is a town in the Vaud canton of Switzerland, located on the northwestern shore of Lake Neuchâtel. ...

Recently, there has been a new incentive to develop continuously variable transmissions (CVTs) for use in the new kinetic energy recovery systems (KERS) proposed for Formula One motor racing. (In 2009, F1 is introducing new rules that will lower the environmental impact of the sport. Part of this is to recover deceleration energy that can be stored for acceleration.)^[1] The continuously variable transmission (CVT) is a transmission in which the ratio of the rotational speeds of two shafts, as the input shaft and output shaft of a vehicle or other machine, can be varied continuously within a given range, providing an infinite number of possible ratios. ... Formula One - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... Environmental impact analysis is conducted to determine the likely human environmental health impact, risk to ecological health, and changes to natures services that a proposed or ongoing project may bring, or is bringing. ...

Flywheel systems have also been used experimentally in small electric locomotives for shunting or switching, e.g. the Sentinel-Oerlikon Gyro Locomotive. Larger electric locomotives, e.g. British Rail Class 70, have sometimes been fitted with flywheel boosters to carry them over gaps in the third rail. 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.^[2] Modern three-phase AC locomotive (DBAG Class 152) A GG1 An electric locomotive is a locomotive powered by electric motors which draws current from an overhead wire (overhead lines), a third rail, or an on-board storage device such as a battery or a flywheel energy storage system. ... A modern US switcher, an EMD SW1500. ... This article or section does not cite its references or sources. ... 20002 at East Croydon, 13 December 1967. ... Third rail at the West Falls Church Metro stop in Washington, D.C., electrified to 750 volts. ... The University of Texas at Austin (often referred to as The University of Texas, UT Austin, UT, or Texas) is a doctoral/research university located in Austin, Texas. ...

Uninterruptible power supply

Flywheel power storage systems in current production (2001) have storage capacities comparable to batteries and faster discharge rates. They are mainly used to provide load leveling for large battery systems, such as an uninterruptible power supply and for maintaining power quality in renewable energy systems. Developers of such flywheel energy storage systems include Hitec Power Protection, Active Power, AFS Trinity, Beacon Power, Piller, Powercorp and Pentadyne. Precise Power has a novel written-magnetic-field, inverter-less, slow-speed-flywheel, constant-frequency, UPS system with a model that can clutch start an engine for continuous backup. Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... An uninterruptible power supply (UPS), uninterruptible power source or sometimes called a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available. ... Power quality is a term used to discuss events on electric power grids that can damage or disrupt sensitive electronic devices. ... World renewable energy in 2005 (except 2004 data for items marked* or **). Enlarge image to read exclusions. ... Piller may refer to: Anton Piller order, court order which provides for the right to search premises without prior warning Janine Piller, politician of the Canadian province of Newfoundland and Labrador Michael Piller, television scriptwriter and producer Category: ...

Laboratories

A long-standing niche market for flywheel power systems are facilities where circuit-breakers and similar devices are tested: even a small household circuit-breaker may be rated to interrupt a current of 10,000 or more amperes, and larger units may be have interrupting ratings of 100,000 or 1,000,000 amperes. Obviously 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 off building power. So typically such a laboratory will have several large motor-generator sets, which can be spun-up to speed over some minutes; then the motor is disconnected before a circuit-breaker is tested. Other similar applications are in tokamak and laser experiments, where very high currents are also used for very brief intervals. A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot. ... Experiment with a laser (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: Light Amplification by Stimulated Emission of Radiation. ...

Amusement Ride

The Incredible Hulk roller coaster at Universal Studio's Islands of Adventure features a rapidly accelerating uphill launch as opposed to the typical gravity drop. This is achieved through powerful traction motors that throw the car up the track. To achieve the brief very high current required to accelerate a full coaster train to full speed uphill the park utilizes several motor generator sets with large flywheels. Without these stored energy units the park would have had to invest in a new substation and risked browning out the local energy grid every time the ride launched.

Advantages and disadvantages

Flywheels are not affected by temperature changes as are chemical batteries, nor do they suffer from memory effect. They are also less potentially damaging to the environment, being made of largely inert or benign materials. Another advantage of flywheels is that by a simple measurement of the rotation speed it is possible to know the exact amount of energy stored. However, use of flywheel accumulators is currently hampered by the danger of explosive shattering of the massive wheel due to overload.

One of the primary limits to flywheel design is the tensile strength of the material used for the rotor. Generally speaking, the stronger the disc, the faster it may be spun, and the more energy the system can store. When the tensile strength of a flywheel is exceeded the flywheel will shatter, releasing all of its stored energy at once; this is commonly referred to as "flywheel explosion" since wheel fragments can reach kinetic energy comparable to that of a bullet. Consequently, traditional flywheel systems require strong containment vessels as a safety precaution, which increases the total mass of the device. Fortunately, composite materials tend to disintegrate quickly once broken, and so instead of large chunks of high-velocity shrapnel one simply gets a containment vessel filled with red-hot sand. Still, many customers of modern flywheel power storage systems prefer to have them embedded in the ground to halt any material that might escape the containment vessel.

When used in vehicles, flywheels also act as gyroscopes, since their angular momentum is typically of a similar order of magnitude as the forces acting on the moving vehicle. This property may be detrimental to the vehicle's handling characteristics while turning. On the other hand, this property could be utilised to improve stability in curves. Two externally joined flywheels spinning synchronously in opposite directions would have a total angular momentum of zero and no gyroscopic effect. (Strictly speaking, they would exert a huge torqueing moment around the central point, trying to bend the axle. However, if the axle were sufficiently strong, no gyroscopic forces would have a net effect on the sealed container, so no torque would be measured externally.) A gyroscope For other uses, see Gyroscope (disambiguation). ... This gyroscope remains upright while spinning due to its angular momentum. ... Torque applied via an adjustable end wrench Relationship between force, torque, and momentum vectors in a rotating system In physics, torque (or often called a moment) can informally be thought of as rotational force or angular force which causes a change in rotational motion. ...

Contents

Main components

Rotor

Bearings

Physical characteristics

Applications

Transportation

Uninterruptible power supply

Laboratories

Amusement Ride

Advantages and disadvantages

See also

References

Contents

Main components GA_googleFillSlot("encyclopedia_square");

Rotor

Bearings

Physical characteristics

Applications

Transportation

Uninterruptible power supply

Laboratories

Amusement Ride

Advantages and disadvantages

See also

References

Main components