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. Flywheel is a mechanical device with a significant moment of inertia used as a storage device for rotational energy. Flywheels resist changes in their rotational speed, which helps steady the rotation of the shaft when a fluctuating torque is exerted on it by its power source such as that caused by a piston-based (reciprocating) engine, or when an intermittent load, such as the motion of a piston pump, is placed on it.

Construction and Operation of Flywheel Energy Storage

A typical Flywheel Energy Storage system consists of a rotor suspended by bearings inside a vacuum chamber to reduce friction, connected to a combination electric motor/generator. Modern flywheels use carbon-fiber composite rotors that have a higher tensile strength than steel but are an order of magnitude less heavy. Magnetic bearings are sometimes used instead of mechanical bearings, to reduce friction. High-temperature superconductor (HTSC) bearings however may be economical and could possibly extend the time energy could be stored economically.

Most Flywheel Energy Storage systems use electricity to accelerate and decelerate the flywheel, but devices that directly use mechanical energy are being developed. Flywheels can be used to produce very high power pulses. A small motor can accelerate the flywheel between the pulses. Recently, flywheels have become the subject of extensive research as power storage devices for uses in vehicles and power plants, to make flywheel systems that are smaller, lighter, cheaper and have a greater capacity.

Flywheel Vs Battery Energy Storage

Compared with other ways of storing electricity, Flywheel Energy Storage systems have long lifetimes (lasting decades with little or no maintenance; full-cycle lifetimes quoted for flywheels range from in excess of 105, up to 107, cycles of use), high energy densities (100-130 W·h/kg, or 360-500 kJ/kg), and large maximum power outputs. The energy efficiency (ratio of energy out per energy in) of flywheels can be as high as 90%. Typical capacities range from 3 kWh to 133 kWh. Rapid charging of a system occurs in less than 15 minutes.

Applications of Flywheel Energy Storage (FES)

  • Flywheel-powered heavy vehicles such as GyroBuses (Gyrobus is an electric bus that uses flywheel energy storage), Flywheel-powered Trucks and Cranes.
  • Flywheel-powered motor vehicles are used as high-speed cars or racing cars.
  • Flywheel Locomotives & Electric Trains – Flywheel systems have also been used experimentally in small electric locomotives for shunting or switching. Eg., Gyro Locomotives, which are electric locomotives with Flywheel Energy Storage.
  • Flywheel Uninterruptible Power Supply (UPS) – Flywheel power storage systems are in production, and 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 for data centers as they save a considerable amount of space compared to battery systems.
  • Flywheel Energy Storage for Laboratory Experiments for testing heavy electric equipment.
  • Flywheel Grid Energy Storage System for grid energy storage in power plants.Momentum Wheel is a type of flywheel useful in satellite pointing operations, in which the flywheels are used to point the satellite’s instruments in the correct directions without the use of thruster rockets.
  • Friction motors used to power many toy cars are simple flywheel motors.