Tuesday, July 6, 2010

Green Tech: Replacing Batteries with Flywheels

Via economist.com (Technology Babbage Blog) -


The new generation of batteries, based on lithium-ion cells, are lighter and can store far more juice. Unfortunately, they are a good deal pricier and need lots of cooling. Lithium is a reactive, inflammable metal. Unless the temperatures and voltages within individual cells are monitored carefully, lithium-ion batteries can suffer “thermal runaway” and explode—as has happened on numerous occasions with similar batteries used in laptops and mobile phones (see “Less bang for your buck”).

Moreover, supplies of the metal are far from abundant, and are located in countries not necessarily friendly to America: the biggest reserves are in Bolivia, China and Russia. Then, there is the issue of charging a plug-in car overnight. In most places, the electricity delivered during off-peak periods comes from dirty coal-fired power stations—rather negating the point of having a zero-emission vehicle in the first place.

The answer, in your correspondent’s view, is to get rid of those pesky battery packs and replace them with flywheels. Buses and trains have experimented with such devices for decades, and huge strides have been made recently in using them to add zip to road cars. For that, thank Formula One motor racing.

Your correspondent has long argued that this sport’s relentless demand for the ultimate in lightness and performance—with scant regard for cost and endurance—has removed it so far from everyday motoring as to leave little scope for transferring technology from the exotic to the mundane. That, though, may be about to change. It now seems that the same technologies which make racing cars go ever faster—the endless pursuit of stiffness, lightness and greater power from smaller engines—are precisely the ones that will be needed more and more to reduce carbon footprints and dependence on oil.


In a recent endurance race, a Porsche 911 GT3 R hybrid racing car that used a Williams flywheel system capable of boosting output at the wheels by an extra 160 horsepower and weighing just 47kg (instead of a battery system two or three times heavier) achieved 25% better fuel economy than conventional versions of the car. Now, Land Rover and Williams are working on a tiny flywheel design that can be mass produced for under $1,500, and used instead of batteries in hybrid family cars.

Besides finding their way into road vehicles, high-momentum flywheel systems are being investigated as ways of storing energy collected from intermittent sources such as wind and solar power, and for responding quickly to increases in demand that are now dealt with by switching on stand-by generators fuelled by natural gas. Beacon Power, a firm based in Massachusetts, is building a 20-megawatt plant in Stephentown, New York, that uses 200 flywheels to stabilise the local grid in this way.

Back on the road, flywheel hybrids that cut both fuel consumption and greenhouse-gas emissions by 30% or more appear to be only three or four years away. When they arrive, today’s coal-fired electric cars will look decidedly dirty by comparison. Roll on the day.

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