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How Does a Flywheel Work

What is a flywheel?
Vehicles and electrical power benefit from a particular metal disk-shaped object that one could say comes somewhat close to the physically impossible idea of “perpetual motion”. Flywheels are rotational mechanical devices which often have teeth and store energy by rotating near-continuously. The flywheel obtains this rotation by having a torque (the rotational version of force) applied to itself to the flywheel, and due to that almost continuous motion, the device stores kinetic energy. Kinetic energy is the energy form associated with motion, which in this case can be calculated by halving the product of the flywheel's “moment of inertia” and its angular or rotational velocity, which is then released as the flywheel applies its own torque to a mechanical load, transferring its energy to that load. Flywheels, for this reason, are important components in motor vehicle engines, and are also shown to be of use in electricity generation.

 How does a flywheel work?
The flywheel's application to vehicle engines will be used to explain how it works, and the operations in this explanation can be applied in some way to the flywheel's operations in other applications. In a vehicle engine, the flywheel is connected to the engine's crank shaft and in modern vehicles is lubricated with hydraulic fluid to reduce friction on the wheel. During the four-stroke engine cycle, while normally the crankshaft would be subject to fluctuations in the energy supplied to it, thus causing a fluctuation in its rotation, the flywheel acts as a continuous supply of energy due to its ability to near-continuously rotate and store energy, and then transfer that energy to the crankshaft by applying a torque to the shaft. This allows the pistons connected to the shaft to be more consistent in their own motion, which ensures the smooth operation of the vehicle overall. The main reason for the flywheel's ability to almost continuously rotate is its high moment of inertia (a quantity found using the wheel's mass and radius), which translates to a high resistance to any change in its rotational speed. In car and truck engines, the flywheel is engaged by the engine's starter, which is the mechanism that allows the car to start operating. This electrically pushes a small gear onto the flywheel and crank shaft (thus applying a torque to the flywheel and crank shaft) to initiate their rotation and get the engine running.

Uses of the flywheel
As explained before, flywheels are used in motor vehicle engines to reduce the fluctuations in energy supplied by the engine's power source to the crank shaft, which allows the vehicle to be operated without worrying about it going through an unintentional cycle of slowing down and speeding up. Flywheels, however, also can be used in electricity generation. The flywheel, when engaged, can store significant amounts of kinetic energy as it rotates, and when needed, this stored energy can be released into the system by slowing down the wheel. A company known as Beacon Power is dedicated to exploiting this technological potential; their design for the flywheel with regards to electrical power involves sealing the flywheel in a vacuum chamber, and levitating the wheel with permanent magnets and an electromagnetic bearing to significantly reduce friction being applied to the wheel, which in turn increases its ability to rotate almost continuously, which allows it to effectively perform its function of storing energy.