With its ability to store a massive amount of kinetic energy, the humble flywheel is a marvel of mechanical engineering in the midst of a technological resurgence.
The potter’s wheel offers an early example of the flywheel in use, while engineers of the Islamic Golden Age were responsible for bringing it to the realm of agriculture. The 11th-century scholar and botanist Ibn Bassal, who wrote extensively on agronomy, applied the principle of the flywheel to the noria (a water wheel used to scoop up into an aqueduct) and the saqiyah (when a noria is powered by an animal).
During the Industrial Revolution, flywheels were heavily deployed in steam engines, with Scottish pioneer James Watt and English inventor James Pickard in particular being responsible for this integration. The latter’s decision to install a simple crank that worked in conjunction with the flywheel greatly increased the efficiency of its function.
Going to war
The flywheel soon had military applications. John Adams Howell, an American Civil War veteran who made many innovations in ordnance, invented a self-propelled torpedo in the 1880s that was powered by a 60 kg flywheel. The flywheel was spun to 10,000 rpm by a ship’s steam turbine, with its gyroscopic effect helping the torpedo maintain a straight course with minimal wake. The Howell torpedo was soon replaced by a superior model developed by English engineer Robert Whitehead.
The 20th century saw various attempts to harness the flywheel’s inherent energy boon, to varying degrees of success.
One of these attempts was made by the Swiss engineering firm Maschinenfabrik Oerlikon, which in the 1940s and 50s attempted to commercialise flywheel propulsion in public transit. The gyrobus used flywheel energy storage as an alternative to the overhead wires used in trolleybuses. A single large flywheel approximately 1.6 m in diameter was installed in fleets and deployed in locations including Switzerland and modern-day Kinshasa, Democratic Republic of the Congo. The system could reach a top speed of up to 60 kph.
Despite the inherent advantages in cutting down on pollution by not using fossil fuels, and in forgoing the use of overhead wires, the gyrobus proved unsustainable due to the weight of the flywheel itself (1500 kg) and the danger to users from its high rotation (3000 rpm). The gyrobus in Kinshasa was also a victim of its surrounding environment, with the wheel exposed to rust caused by the humid climate, and the limited number of routes with sufficient tarmacked road constraining the vehicle’s movements.
Only with the material science breakthroughs of later decades would the flywheel become viable for wider implementation in transport.
Fast forward to the 21st century, and flywheel technology has seen a renaissance driven by innovations in motorsport and energy storage.
Formula 1 vehicles were first allowed to use a kinetic energy recovery system (KERS) in the 2009 season, marking a turning point along the road of flywheel innovation as several Formula 1 teams and automakers began testing KERS integration. A KERS stores the kinetic energy generated during braking, stores it in a flywheel and deploys it during acceleration to avoid reliance on the engine. The KERS is also called a regenerative braking system owing to the way it recovers part of a vehicle’s kinetic energy which would otherwise be lost to friction during braking.
Energy assets
Meanwhile, the US-headquartered Amber Kinetics has integrated the flywheel into an energy storage unit. Its flywheel spins at a lower speed, approximately 50,000 rpm slower than a flywheel in Formula 1, and can maintain its rotation for longer owing to highly efficient magnetic bearings and vacuum systems. Critically, the system has been designed to discharge across a much longer period than that found in motorsports – hours rather than seconds – moving the consideration of flywheels from short-term power assets to long-term energy assets.
A hybrid system from Amber Kinetics that combined four 32 kWh flywheels was installed at a farmstead in Armidale, NSW. The system powers the workshop shed with three-phase power, operates completely off the grid, and was designed to integrate with the facility’s existing solar and battery setup.
This article was originally published in the May 2025 edition of create with the headline ‘Spin cycle’.
