Flywheel

In particular, assuming the flywheel's moment of inertia is constant (i.e., a flywheel with fixed mass and second moment of area revolving about some fixed axis) then the stored (rotational) energy is directly associated with the square of its rotational speed.

Once suitably abstracted, this shared principle of energy storage is described in the generalized concept of an accumulator.

As with other types of accumulators, a flywheel inherently smooths sufficiently small deviations in the power output of a system, thereby effectively playing the role of a low-pass filter with respect to the mechanical velocity (angular, or otherwise) of the system.

Common uses of a flywheel include smoothing a power output in reciprocating engines, flywheel energy storage, delivering energy at higher rates than the source, and controlling the orientation of a mechanical system using gyroscope and reaction wheel.

Flywheels are typically made of steel and rotate on conventional bearings; these are generally limited to a maximum revolution rate of a few thousand RPM.

[1] High energy density flywheels can be made of carbon fiber composites and employ magnetic bearings, enabling them to revolve at speeds up to 60,000 RPM (1 kHz).

[2] The principle of the flywheel is found in the Neolithic spindle and the potter's wheel, as well as circular sharpening stones in antiquity.

[3] In the early 11th century, Ibn Bassal pioneered the use of flywheel in noria and saqiyah.

[4] The use of the flywheel as a general mechanical device to equalize the speed of rotation is, according to the American medievalist Lynn White, recorded in the De diversibus artibus (On various arts) of the German artisan Theophilus Presbyter (ca.

[3][5] In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine, and his contemporary James Pickard used a flywheel combined with a crank to transform reciprocating motion into rotary motion.

[7] For a given flywheel design, the kinetic energy is proportional to the ratio of the hoop stress to the material density and to the mass.

Increasing amounts of rotation energy can be stored in the flywheel until the rotor shatters.

[8] Calculation of the flywheel's moment of inertia can be more easily analysed by applying various simplifications.

For example, if the moments of inertia of hub, spokes and shaft are deemed negligible, and the rim's thickness is very small compared to its mean radius (

[citation needed] A shaftless flywheel eliminates the annulus holes, shaft or hub.

It has higher energy density than conventional design[9] but requires a specialized magnetic bearing and control system.

[11] A superflywheel consists of a solid core (hub) and multiple thin layers of high-strength flexible materials (such as special steels, carbon fiber composites, glass fiber, or graphene) wound around it.

[12] Compared to conventional flywheels, superflywheels can store more energy and are safer to operate.

[13] In case of failure, a superflywheel does not explode or burst into large shards like a regular flywheel, but instead splits into layers.

The separated layers then slow a superflywheel down by sliding against the inner walls of the enclosure, thus preventing any further destruction.

[citation needed] The first superflywheel was patented in 1964 by the Soviet-Russian scientist Nurbei Guilia.

Flywheels used in car engines are made of cast or nodular iron, steel or aluminum.

[16] Flywheels made from high-strength steel or composites have been proposed for use in vehicle energy storage and braking systems.

The efficiency of a flywheel is determined by the maximum amount of energy it can store per unit weight.

If the hoop stress surpass the tensile strength of the material, the flywheel will break apart.

In other applications, such as an automobile, the flywheel operates at a specified angular velocity and is constrained by the space it must fit in, so the goal is to maximize the stored energy per unit volume.

For example, a flywheel is used to smooth the fast angular velocity fluctuations of the crankshaft in a reciprocating engine.

In unstressed and inexpensive cases, to save on cost, the bulk of the mass of the flywheel is toward the rim of the wheel.

The purposes for that application are to improve the power factor of the system or adjust the grid voltage.

But the basic ideas here are the same, the flywheels are controlled to spin exactly at the frequency which you want to compensate.