Flywheel energy storage is considered in this paper for grid integration of renewable energy sources due to its inherent advantages of fast response, long cycle life and flexibility in providing ancillary services to the grid, such as frequency regulation, voltage support, etc. The fundamentals of the technology and recent developments are reviewed, firstly with an emphasis on the design considerations and performance metrics. Then the progress and development trends in electric motor/generators employed in flywheel energy storage systems (FESS) are summarized, showing the potential of axial-flux permanent-magnet (AFPM) machines in such applications. Design examples of high-speed AFPM machines are provided and evaluated in terms of specific power, efficiency, and open-circuit losses in order to validate their suitability in FESS.

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Conference Proceeding

Publication Date


Notes/Citation Information

Published in 2019 8th International Conference on Renewable Energy Research and Applications (ICRERA).

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The document available for download is the authors’ manuscript version that is accepted for publication. The final published version is copyrighted by IEEE and available as: M. G. Kesgin, P. Han, N. Taran, and D. M. Ionel, “Overview of Flywheel Systems for Renewable Energy Storage with a Design Study for High-speed Axial-flux Permanent-magnet Machines,” 8th International Conference on Renewable Energy Research and Applications (ICRERA), Brasov, Romania, Nov. 3-6, 2019, pp. 1026-1031, doi: 10.1109/ICRERA47325.2019.89965

Digital Object Identifier (DOI)


Funding Information

The support of National Science Foundation NSF Grant#1809876, of University of Kentucky, the L. Stanley Pigman endowment and of ANSYS Inc. is gratefully acknowledged.