Project description

As a result of the increase in PV systems in private households, the need for decentralized energy storage capacity to relieve the grid is increasing. In addition to poor economic efficiency, chemical energy storage systems have other disadvantages - such as difficult recycling and aging-related capacity losses.

The Solar Flywheel project was a feasibility study for a low-loss, low-cost flywheel storage system. A system design with a storage unit with an energy content of 5 kWh and a peak power of 2.2 kW was developed. A steel rotor and standard individual components contribute to the low-cost approach.

A supercritical operating strategy was made possible by a silicone suspension of the roller bearing, which significantly reduced self-discharge. Axial bearing loads were minimized by means of magnetic weight compensation, which made it possible to downsize the bearing and thus achieve a reduction in losses. The concept was validated using scaled component tests.

The system design of the draft developed in the project allows the flywheel storage to be used in different areas of application. The storage capacity can easily be varied with minor modifications. With regard to the energy content, it is possible to scale the rotor and the associated system components to the required size.

The Solar Flywheel project has shown that a low-cost, low-tech solution for a stationary flywheel for day-night storage of renewable energy is possible. However, further research into the cost-dominating components is necessary for future competitiveness.


Project partner

  • Institute for Machine Components and Methods of Development - Graz University of Technology
  • Institute of Electrical Measurement and Measurement Signal Processing - Graz University of Technology