FLYWHEEL BATTERIES Presented by 14X41A0313 14X41A0314 14X41A0315

Contents Introduction Flywheel technology Principles Block diagram Flywheel Energy Storage(FES) Main components Function and operation Stored energy Energy density Working of flywheel Applications Advantages

Introduction A flywheel, in essence is a mechanical battery simply a mass rotating about an axis. When short-term back up power is required the rotor’s inertia allows it to continue spinning and the resulting kinetic energy is converted to electricity. They may still prove to serve us as an important component on tomorrow’s vehicles and future energy needs.

Flywheel technology Integrates the function of a motor, flywheel rotor and generator into a single integrated system. The motor, which uses electric current from the utility grid to provide energy to rotate the flywheel, spins constantly to maintain ready source of kinetic energy. The flywheel rotor spin in a near frictionless environment, created by active power’s patented magnetic bearing technology.

Principles The efficiency in the chamber is further enhanced by the creation of a rough vacuum, which reduces drag on the spinning flywheel. As power is transferred to load, the flywheel’s speed decreases. Additional current is then supplied to the field coil to ensure that the voltage output remains constant throughout discharge. This enables the flywheel system to provide ride through power during power disturbances.

Flywheel Energy Storage(FES) FES works by accelerating a rotor to a very high speed and maintaining the energy in the system as rotational energy. 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. Most FES systems use electricity to accelerate and decelerate the flywheel, but devices that directly use mechanical energy are being developed.

Main components A typical system consists of a rotor suspended by bearing inside a vacuum chamber to reduce friction. First generation FES system use a large steel flywheel rotating on mechanical bearings. never use carbon fiber rotor. Magnetic bearings are sometimes used instead of mechanical bearings, to reduce friction.

Function and operation Flywheel smoothen out variation in the speed of the shaft caused by torque fluctuations if source of driving torque is fluctuating. It is also used to provide continuous energy in system. It is also used to supply intermittent pulses of energy transfer rates that exceed the abilities of its energy sources.

Stored energy Stored energy = sum of kinetic of individual mass elements that comprise the flywheel. Kinetic Energy = 1/2*I*⍵2 where, I=moment of inertia i.e., ability of an object to resist changes in its rotational velocity ⍵= rotational velocity(rpm) I=K*M*R2 (M=mass; R=radius) K=inertia constant(depend on shape)

Energy density The maximum density of a flywheel rotor is mainly dependent of two factors. Rotor’s geometry Property of Material used The relation is where, E - kinetic energy of the rotor [J] m - the rotor's mass [kg] K - the rotor's geometric shape factor [dimensionless] - the tensile strength of the material [Pa]   - the material's density [kg/m3]  

Working of flywheel

Applications Transportation Uninterruptible power supplies Laboratories Aircraft launchers system Pulse power Grid energy storage Wind turbines

Advantages Provide continuous energy when energy source. Flywheels have very high output potential and relatively long life. flywheel are relatively unaffected by temperature extremes. The lifetime of the flywheel is almost independent of the depth of the charge and discharge cycle. No periodic maintenance is required. Short recharge time.

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