Renewable energy to be stored in floating flywheels

Better magnets can help store renewable energy from solar cells and wind turbines in magnetic flywheels. The new technology for energy storage could help remove one of the really big obstacles to further distribution of renewable energy. Innovation Fund Denmark is investing DKK 12 million in the project.

2017.11.06 | Peter F. Gammelby

WattsUp Power in Hvidovre already produces flywheel systems for energy storage. Using better magnets, they will be able to store energy for much longer periods.

The cubes around the rotor are permanent magnets. Photos: WattsUp Power A/S

Energy storage is one of the major challenges of the twenty-first century, as well as being a prerequisite for utilising the full potential of renewable energy in power supply. A solution could be to store energy from sources such as wind turbines and solar cells as kinetic energy in flywheels, so power is also available when the sun is not shining or when there is no wind. Researchers at Aarhus University and a number of private companies have now joined forces to optimise and further develop this technology.

The principle behind a flywheel is that a magnetic field is used to keep a heavy cylinder afloat in vacuum containers. By adding power – such as energy from a wind turbine – the flywheel is pushed into motion. As long as the wheel rotates, it stores the energy that first started it off. The kinetic energy can subsequently be converted to electrical energy when there is a need for it, and energy is thus stored. Because the flywheel floats on magnetic bearings and there is no wind resistance, energy loss is minimised and the wheel can keep on rotating until the energy needs to be used.

Room for major improvements

The technique of storing energy in floating flywheels – flywheel energy storage (FES) – has been known for many years, and it is already used in some parts of the USA. This includes evening out fluctuations in New York’s power supply.

The advantage of the technology is that the flywheels are rapidly ‘charged’, they can release large amounts of energy very quickly, and they are expected to have a much longer service life than batteries. In addition, the materials in the flywheels do not have an adverse effect on the environment and, in principle, they can be reused indefinitely. They do not take up very much space. A 30 kWh unit, corresponding to the needs of a single-family house with solar cells on the roof, is about the size of a bucket.

However, there is still a significant barrier to be overcome before the flywheel technology can solve the problem of storing renewable energy. Flywheels lose energy so rapidly that they cannot be used for long-term energy storage. They have a significant self-discharge rate of only ten minutes, and are therefore not a real alternative to modern batteries at present.

... with nanosized magnets

The project will improve existing technology, enabling the floating cylinder to be held in place in the air by new nanomagnets, where all dimensions – right from the atomic structure and up to the millimetre scale – will be very precisely controlled. The flywheels will be designed in such a way that they can store energy for up to twenty-four hours.

If the researchers succeed in breaking the code to an inexpensive and efficient way to store energy, they will contribute significantly to making the world independent of fossil fuels such as coal, oil and gas. The new technology will also create growth and employment in both energy storage and energy efficiency.

The challenge of controlling nanomagnets has been in focus in recent years at the Department of Chemistry, Aarhus University. The new nanomagnets will be composed of different materials, and the combination will improve the magnetic properties.

To achieve the best results, researchers at the Department of Engineering will calculate the best possible mix ratio. The Danish Technological Institute will ensure that the mechanical and corrosive properties of the new magnets comply with the necessary requirements prior to being launched on the market.

Large-scale production of the new magnets will take place in collaboration between Haldor Topsoe and Sintex, while Grundfos and WattsUp Power will focus on applications in engine and flywheel technologies, respectively.

For more information, please contact

Associate Professor Mogens Christensen, Department of Chemistry and iNANO, Aarhus University, 8000 Aarhus C,, +45 6177 07451

Professor Henrik Myhre Jensen, Department of Engineering, Aarhus University, 8000 Aarhus C,, +45 4189 3215

Centre Director Nikolaj Zangenberg, Danish Technological Institute, 8000 Aarhus C,, +45 7220 2494

R&D Director Søren Dahl, Haldor Topsoe A/S, 2800 Kgs. Lyngby,

Development & Innovation Manager Peter Kjeldsteen, Sintex A/S, 9500 Hobro, +45 9657 4395

Specialist Badrinath Veluri, Grundfos A/S, 8850 Bjerringbro,

CEO Martin Speiermann, WattsUp Power A/S, 2650 Hvidovre,, +45 4026 2610

Innovation Fund Denmark’s investment: DKK 12 million

Total budget: DKK 17 million

Duration: 4 years

Official title: Novel Magnets for Flywheel Energy Storage – MAGFLY

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