Flywheels have recently become popular in the Uninterruptible Power Supply [UPS] business for short term power outages and research has been done into its use for automobiles. There are several advantages to the flywheel technology over the lead-acid batteries in UPS’s, including higher efficiency, a longer lifespan, and a smaller size, not to mention the reduction in safety and disposal issues that exist with the lead-acid battery UPS's.
The universe of flywheel stocks is small, with only two publicly traded companies, both of which trade on NASDAQ. The older of the two companies is Active Power Inc. (ACPW) which was founded in 1992 and is based in Austin, Texas. They manufacture and sell power products that are battery free such as their CleanSource UPS, a battery-free uninterruptible power supply utilizing flywheel technology. The company is debt free with year-over-year quarterly revenue growth of 27%.
Beacon Power Corp. (BCON) was founded in 1997 and is based in Wilmington, Massachusetts. Their primary product is Smart Energy matrix, a flywheel-based energy storage system used by electrical utilities for electric grid regulation. This company is also debt-free but has a 9% year-over-year revenue reduction.
Disclosure: Author does not own either of the above.
ACPW vs. BCON 1-yr chart