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Sci Tech
Flywheel batteries come around again
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Flywheel batteries can improve power quality by storing energy near the load (where it is needed), ready to take up the slack anytime the main power feed is temporarily interrupted by lightning hitting a transformer.
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THANKS TO advances in composite materials and magnetic bearings, flywheel batteries are looking for a variety of applications: high-speed trains, hybrid buses, stealth planes, orbiting space stations, and reliable electric power.
The trouble with electricity is that it is very difficult to store: it takes a 400-pound automotive battery to store the energy contained in one pound of gasoline.
Unlike coal and oil, which are easily stockpiled, electricity therefore has to be generated where and when it is needed.
But that situation is changing as flywheel batteries capable of storing much more energy in much less space get ready for prime time. The results were published in the journal IEEE Spectrum.
Unlike old-fashioned flywheels heavy metal wheels rotating at fairly low speeds these modern devices are lightweight and rotate at extremely high speeds, in the vicinity of 50,000 rpm.
To withstand such high speeds, they are made of advanced composite materials and are supported by magnetic bearings in which there is no actual metal-to-metal contact.
Instead, the rotating masses are held in place by carefully controlled magnetic fields.
According to the researchers, flywheel batteries are starting to be deployed in several more areas, including power quality improvement, transportation, and military and also in aerospace applications.
Flywheel batteries can help improve power quality by storing energy near the load (where it is needed), ready to take up the slack anytime the main power feed is temporarily interrupted by lightning hitting a transformer, for example. Such a battery can carry the load for the time needed to get an emergency generator going.
The result: uninterrupted power and relief from the maddening frustration of computer crashes caused by brief power outages. Flywheel batteries are also a good match to several hybrid vehicle schemes, including high-speed trains and buses.
Now they are not practical for passenger cars as they would require flywheels smaller than can be constructed today. Like ordinary commercial vehicles, military transport is also becoming electrical.
Not only are these vehicles adopting electric propulsion (which, among other advantages, allows them to operate in a quiet, `stealth,' mode), they are also relying increasingly on electrical and electronic weapons systems.Some of these systems draw tremendous amounts of electrical power for short periods of time, a job for which flywheel batteries are well suited but which tends to ruin ordinary batteries.
Batteries are also used in orbiting spacecraft to store energy while the craft is in the sunlight for later use when it is in shadow.
Flywheel batteries can store energy more efficiently than any other ordinary batteries, and they have an additional, unique, advantage: their spinning rotors can be used as gyroscopes to help stabilise the craft in its flight.
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