Professor Keith Pullen

The problem

Balancing electrical supply with consumption is a challenge for power grids. An added difficulty is maintaining the balance across different timescales – from milliseconds to seasons. Sustainable grid management solutions need to manage intermittent supply from sources, including renewables. New technologies with long-term durability are needed to manage these demands.

The solution

Keith PullenGyrotricity Ltd, a spin out from City, University of London, has developed a new technology for kinetic energy storage. . The technology is based on a flywheel, a steel rotor that stores energy that can be converted to electrical energy and released quickly on demand.

Gyrotricity’s flywheel is made using thin layers of laminated steel. As a result, it is more durable and safer than single-mass steel flywheels, as any potential damage can be easily contained. The company has also designed an electrical motor generator that lasts for up to 25 years, and is used for transmitting and retrieving power from the flywheel. Combined, the systems provide a lightweight and cost-effective solution to energy storage in the grid.

The Gyrotricity flywheel has two to four times greater energy density than conventional steel flywheels. High power, at the megawatt scale, can be provided by having flywheels connected in banks in containers. Gyrotricity is currently designing and testing these in the laboratory and at customer sites.

Professor Keith Pullen, Chief Technical Officer, holds the patents for the laminated flywheel technology. He draws on over twenty years of expertise in the field as he supports Gyrotricity in bringing its solutions to market.


  • 2017:  Rail Safety and Standards Board funded development of the Gyrotricity flywheels in rail.
  • 2018: Awarded funding from the Department for Business, Energy and Industrial Strategy Energy Entrepreneurs Fund.

Professor Pullen was awarded a 2018 Enterprise Fellowship to support him in refining Gyrotricity’s flywheel technology and bringing it to market.


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