Flywheel Energy Storage: Why It Is So Important?

Flywheel Energy Storage: Why It Is So Important?

Learn how flywheel energy storage functions and how we can utilize this technology.

It is clever to store energy using flywheels. Essentially, a giant rotor is levitated and spun in a chamber by way of magnets. Since there is very little friction, the flywheel spins continually with very little added energy input needed. The spinning rotor can then be used as a generator to draw energy from the system whenever needed.

Please read this article to learn more about flywheel energy storage.

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About 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. As a result of the energy conservation principle, the flywheel’s rotational speed decreases when energy is removed from the system and increases when energy is added.

Although most FES systems use electricity to accelerate and decelerate the flywheel, mechanical energy-based devices are currently under development.


  • incredibly effective, with a recovery rate of 80% of the stored energy.
  • Very quick to start up and transform stored energy.
  • long-lasting and free of pollution.
Flywheel Energy Storage: Why It Is So Important?


  • Limited energy storage time of around 15 minutes, making flywheels only suitable for quick, timely applications.

As a result, unlike batteries and pumped-storage systems, flywheels are more commonly used for system regulation and optimization than for ensuring long-term autonomy.

How Do Flywheels Work?

Modern flywheel energy storage devices typically consist of a cylinder, called a rotor, that is housed in a vacuum chamber that is sealed to reduce air friction. New materials, like carbon or glass fibers, or Kevlar, which can withstand extremely high speeds better than conventional metals, are frequently used to make the rotor. With magnetic levitation to lessen friction, velocity can reach 10,000 revolutions per minute (RPM) or higher.

By utilizing the motor as a power generator while the wheel is spinning at its fastest, its kinetic energy can be recovered. The flywheel’s rotational speed is gradually slowed down by this.

Flywheel Energy Storage Applications

Here, we list some of the applications of flywheel energy storage technology:

Subway Systems

Subway trains release a lot of energy when breaking and absorb an equal amount when accelerating due to their heavy weight. The Hanover, Hamburg, Los Angeles, and Rennes subway systems use flywheels to store and recover this energy, as do other networks.

An 8-kilometer-long subway line in Rennes, for instance, has a 2.5 metric-ton spinning top installed in the middle of it. The energy released during braking is not lost as heat when a train slows down; instead, the motor of the train transforms it into electricity. The third rail is then used to transmit the electricity, which is then used to accelerate the flywheel’s rotation.

Flywheel Energy Storage: Why It Is So Important?

After being recovered, this energy is used to propel the train as it leaves the station. Carefully managed train synchronization and “smart” digital technology are used to efficiently coordinate the energy flows. With this system, the Rennes metro system saves about ten days’ worth of electricity every year.

Automotive Systems

The weight and size of flywheels are major hurdles in small vehicles. Cylinders that weigh a few kilograms and spin at a high rate of 60,000 RPM are used in some systems to increase engine power. They are typically installed on Formula One race cars and give drivers an advantage when, for instance, accelerating out of bounds.

Regulating Power Grids

By balancing voltage drops, flywheels are occasionally used to stabilize power grids. In New York, for example, 200 flywheels at a small 20-megawatt power plant are capable of providing sufficient energy within a few seconds to contribute to maintaining a steady supply throughout the grid.

On a smaller scale, the same technology is applied in specialized markets to guarantee an uninterrupted electricity supply to operating rooms or server rooms, for instance. In the event of protracted power outages, flywheels can supply electricity while you wait for other, more potent sources of electrical products, such as diesel generators, to start up.

Why Are Flywheels So Crucial for Renewable Energy Storage?

Flywheel energy storage systems are seen as a key to unlocking the full potential of renewables. Flywheels are perfect for storing energy from solar and wind power because they have a large energy storage capacity and a long energy storage time. But why are flywheels so essential for storing renewable energy?

Flywheel Energy Storage: Why It Is So Important?

There are a few key reasons.

  1. First, flywheels are quick to adapt to changes in power demand, so they can supply power when it is most needed. This is particularly crucial for renewable energy sources because they can be unpredictable.
  2. Second, unlike batteries, flywheels have a long lifespan and don’t lose their effectiveness over time. This means they can be used for more extended periods of time, making them a more cost-effective solution in the long run.
  3. Third, compared to other storage options, flywheels can use less room and are lighter in weight.
  4. The last benefit is that flywheels are safe for the environment and non-toxic.

Flywheel energy storage is essential to the transition to renewable energy because of all of these reasons.


Vehicles have used flywheels to store braking energy, and they’ve also been used to stabilize electrical grids. For station-keeping purposes, the International Space Station makes use of a flywheel.

In comparison to other mechanical energy storage methods like compressed air and pumped hydro, flywheel storage has higher values for specific power, specific energy, power and energy density, lifecycle, efficiency, self-discharge rate, and energy capital costs.


How Long Can You Store Energy in a Flywheel?

Flywheel energy storage is characterized by its long lifetime (typically 20 years). A flywheel is a disk with a certain amount of mass that can spin to store energy in kinetic form.

Is Free Energy Possible With a Flywheel?

The free energy that was obtained is kept in a battery. This free energy can be used either as feedback to the motor for continuous processes or supply for external appliances. MATLAB simulation has been carried out and results have proved that this Free Energy Flywheel system is possible.

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