Flywheel Energy Storage - An Opportunity for the Automotive Industry and Beyond

This publication summarizes the major results of 7 years of research in the field of flywheel energy storage systems (FESS) for automotive applications conducted by the Institute for Machine Elements and Methods of Development at the Graz University of Technology. It was shown that the use of FESS for load leveling and break energy recuperation for vehicles operating in urban areas may reduce fuel consumption by more than 20%. Despite the seemingly simple physical principle behind this mechanical energy storage concept, practical and cost-efficient solutions, which are suitable for mass production in the automotive industry, are still missing. A systematic analysis revealed the components responsible for the economic success or failure of this storage technology. A holistic approach was necessary, which did not only consider the energy storage device itself, but also the entire (hybrid-)vehicle and the greater supersystem.
Within several research projects technical solutions for critical components such as bearing concept, low-cost rotor design and burst containment were elaborated and validated using special test setups. Besides a significant cost reduction, approaches for improved inherent safety and reduction of self-discharge were achieved. This makes FESS relevant for applications beyond the automotive industry, such as the storing of solar energy, which can then be used to charge electric or plug-in hybrid vehicles.