Flywheel Technology Explained

What is a flywheel?

You may not be familiar with the modern interpretation of a flywheel, but you have certainly come across the technology before.   Think of a dynamo on your bike, steam locomotives, or even the potter’s wheel.  Flywheel technology dates back further than the Industrial Revolution and flywheels have been used in many industries for centuries.  In recent years, flywheels have been used in Formula 1 race cars, satellites and even buses.  So, what’s the deal with the flywheels of today?  What benefit do they have on our day-to-day lives and how do they work?

A flywheel is basically a mechanical battery that stores kinetic energy in the form of a rotating mass.  Imagine an elevated bicycle wheel.  Now spin it.  It will continue to spin for some time, effectively storing the energy that you’ve just inputted.  That, in its most basic form is how a flywheel works.  As energy goes into the system, the flywheel begins to spin.  The more energy that we put into the system, the quicker the flywheel will spin.  Similarly, the quicker you try and spin a bicycle wheel, the quicker it will go.  When energy is required, the flywheel is slowed down.  We convert the kinetic energy back into electrical energy and give it back to the grid.  This can be used to light our homes, power our phones and charge our cars!

What is the difference between a flywheel for a vehicle and a flywheel for the grid?

Flywheels in Formula 1 cars form part of the KERS (Kinetic Energy Recovery System) and are very small but very fast.  The flywheels we now see in hybrid buses were developed from this technology.  As the vehicle brakes, the flywheel absorbs energy and then provides extra power when the vehicle accelerates.  This increases the efficiency of the vehicle and reduces carbon emissions.  Flywheels for grid storage on the other hand are much larger in size (both physical and energy and power capacity) and weight.  The basics remain the same but the specifications and requirements of the technology change with the application.  A flywheel in a bus for example only needs to provide power for a few seconds, whereas a flywheel for on the grid needs to be able to provide power for much longer (minutes to hours).

Why do we need flywheels?

Where to begin?  We have published a more in-depth answer to this question in our post Why We Need Storage.  The short answer to this question is that currently, storing electricity is very difficult to do on a large scale.  The energy industry does not have the luxury of reservoirs to use when demand increases and therefore has to balance generation and demand on a second-by-second basis.  This is not an easy task and doing so currently costs the National Grid over £1 billion annually.

We love green energy!  You have wind, solar, hydro and biomass amongst others that generate clean, carbon-free energy.  However, one of the pitfalls of renewable energy is that the sun doesn’t always shine and the wind doesn’t always blow when you need it.  And it is for this very reason that balancing demand and generation is becoming increasingly more difficult.

Currently, we can store electricity on a large scale via pumped storage sites such as Dinorwig in North Wales, but this is not enough.  So where do flywheels come in?  During times when generation is greater than demand, flywheels can store the excess energy for use during a period when demand is greater than generation.  This can allow wind and solar farms to continue generating even when there is no demand and maximise the amount of clean generation in the energy mix.

At OXTO, we want to facilitate the uptake of renewable generation and help transition the UK and countries worldwide into low-carbon countries.  How do we do that?  Flywheel energy storage.


If you have any further questions, please get in touch!

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