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Flywheels are the ultimate green energy storage machines. They store energy mechanically, like a wind-up toy, so they don’t involve large quantities of lead, acid, or other environmental hazards, and they have a much longer lifespan than conventional batteries. That makes flywheels an ideal storage format for sustainable energy, but until recently their full potential wasn’t exploited. Early versions were heavy, difficult to maintain, and not very efficient compared to lead-acid batteries.
Pentadyne Power has come out with a new GTX flywheel that represents the kind of next-generation improvements that are pushing the technology into more widespread use. It combines lightweight carbon fiber components with magnetic levitation to achieve a level of energy efficiency that competes favorably, pound for pound, with conventional lead-acid batteries – and shows how the new developments are beating old school flywheels at their own game.
One of the fastest emerging uses for flywheels is to provide instant, seamless power to data systems in case the primary system suffers an interruption (flywheels need no time to warm up). Pentadyne notes that flywheels also eliminate conventional battery hazards such as leaks, explosions, and of course disposal issues. That makes them ideal for sensitive facilities including hospitals, laboratories, and military installations. Another emerging use is in harvesting energy from braking systems that would otherwise go to waste, for example in rail systems and shipping yards (a market that is already being tapped by another next-generation flywheel company, Vycon).
The “heart” of the new flywheel is a multi-layer carbon fiber composite cylinder with a titanium hub, which is much lighter than the large steel discs used in older technology. It is also stronger, which enables the GTX to store more energy in a smaller space. Older flywheels also rotate on steel bearings which must be replaced every few years. Pentadyne’s flywheel uses magnetic levitation instead. That eliminates the high-maintenance bearings. By eliminating friction from the bearings, the magnetic system saves a huge chunk of energy that would otherwise be needed to keep the flywheel cool. A patented vacuum bumps the energy efficiency up further by reducing aerodynamic drag (flywheels need a vacuum to minimize drag) without the use of a mechanical pump.
Flywheels knock the ball out of the park when it comes to sustainability, but as Pentadyne’s website notes, until recently the technology has not been competitive with batteries in terms of energy efficiency. The GTX could mark a tipping point. It uses about the same amount of standby power as a conventional lead-acid battery bank and it generates far less heat, which in turn can help lower cooling costs at data centers. It can also tolerate greater temperature extremes, and according to Pentadyne it has close-to-zero maintenance costs and a longer lifespan.
Porsche has just announced that it’s introducing a flywheel hybrid model that uses a Kinetic Energy Recovery System (KERS) — featuring a 40,000 rpm flywheel in the passenger’s seat — to provide a quick blast of power to the front wheels. Formula 1 announced a changeover to KERS last year. With the high profile, high performance car market adopting flywheels, there’s bound to be a growing interest in developing more advanced versions of the technology for other applications as well.
Image: Weight by patrick swint on flickr.com.
Tina Casey specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. You can also follow her on Twitter @TinaMCasey and Google+.