Flywheel technology past, present, and 21st Century projections

This paper describes the present status of flywheel energy storage technology, or mechanical batteries, and discusses realistic future projections that are possible based on stronger composite materials and advancing technology. The origins and use of flywheel technology for mechanical energy storage began several 100 years ago and was developed throughout the Industrial Revolution. One of the first "modern" dissertations on the theoretical stress limitations of rotational disks (isotropic only) is the seminal work by Dr. A. Stodola whose first translation to English was made in 1917. The next big milestones were during the 1960s and 1970s when NASA sponsored programs proposed energy storage flywheels as possible primary sources for space missions. However, it was not until the 1980s when microelectronics, magnetic bearing systems and high power density motor-generators became enabling technologies. The next decade proved that a mechanical battery could surpass chemical batteries for many applications.