Flywheel Kinetic Energy Storage: Energy in Motion

by Chad Redman

Rapidly spinning masses known as flywheels are used for energy storage in a wide variety of applications, including transportation, sport, and grid level electricity. Focusing on grid solutions, flywheel energy storage systems (FESS) comprise massive rotors magnetically suspended in a stator, which acts as a motor when the flywheel needs to be spun up and a generator when the kinetic energy of the flywheel needs to be converted into electricity. Through the use of magnetic bearings and a vacuum chamber for the flywheel housing, FESS are highly efficient for short-term energy storage. Continue reading

Trackside Flywheel Energy Storage in Light Rail Systems

by Emil Morhardt

Light rail systems, like hybrid electric vehicles, use their electric engines to generate electricity when they are slowing down, a process called regenerative braking. In hybrid electric vehicles, the energy usually gets stored in lithium-ion batteries, which work well because they are comparatively light weight and not overly bulky. If neither of these were constraints, then flywheels or supercapacitors would be a better choice because they can deliver power faster and they take much longer to wear out. Of the two, flywheels are lighter, less bulky, cost less, and have longer lives according to a study by the UK Rail and Safety Standards board (Kadim 2009). If they are installed alongside the tracks rather than on the trains, weight and bulk are not very important but cost and lifetimes still favor flywheels. Continue reading

Flywheel Versus Supercapacitor for Running a Small Electric Ferry

by Emil Morhardt

When we think of all-electric cars, we think lithium-ion batteries because they are lightweight and have a high power density. For ships, light-weight doesn’t matter so much, and it turns out there are types of shipping routes that don’t need very much energy storage: think ferries, specifically the plug-in ferry Ar Vag Tredan (the “electric boat” in Breton), a zero-emission passenger ferry crossing the Lorient roadstead 56 times a day. When parked between trips it can recharge its supercapacitor more-or-less instantly (that’s a main feature of supercapacitors—that and their ability to discharge their power equally quickly to meet any need for power the ship may have.) How would a flywheel energy storage system work compared to the existing supercapacitor? That’s the question asked in a new paper by Olivier et al. (2014). Continue reading