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Taking backup power underground

Sat, 11/30/1996 - 7:00pm
Roger Brown

Once considered little more than a technical curiosity by some engineers, it now appears that backup electrical power from high-speed flywheel technology could be a viable option for telecommunications network providers within the next 12 to 18 months.

After more than a year of development, Cambridge, Mass.-based SatCon Corp. debuted its flywheel-based uninterruptible power supply during a power industry conference in early October, aiming the new product squarely at cable TV and telecom network operators who for years have had to rely on cumbersome and unreliable lead-acid batteries for backup power when commercial power suffered an outage.

SatCon, which demonstrated the flywheel at Intelec '96 in Boston, intends to repeat the demonstration at the Western Cable Show in Anaheim later this month.

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The concept has moved from technological promise to a real product.

But already, several top-level cable TV engineers are excited about the flywheel's possibilities and intend to be among the first to field test the units. "I'm very gung-ho on the project," says Bill Bauer, who heads tiny WindBreak Cable in Nebraska, but who is considered to be one of the industry's most forward-thinking engineers. "It appears to be a strong, viable way of doing things."

Nick Hamilton-Piercy, senior VP of engineering and technology at Rogers Cablesystems, is likewise optimistic — and looks forward to the day when he can cease purchasing batteries that often don't work as advertised without a lot of maintenance.

Other operators who intend to test, and perhaps deploy the units, provided they can be manufactured for about $2,000 per unit and deliver the necessary specifications (1 kilowatt of power for two hours), include: Cox Communications, Comcast, Tele-Communications Inc. and Buford Cable, among others. In fact, SatCon officials say they already have letters of intent amounting to about $11 million in equipment, or roughly 5,000 units.

How it works

SatCon first burst on the cable TV scene in January 1996, when company VP and chief technical officer Richard Hockney delivered a paper on flywheel technology at the SCTE's Conference on Emerging Technologies. The presentation surprised many and had others curious but doubtful that the solution could work economically.

SatCon is leveraging its research from various space program contracts it has worked on over the years. That work was designed to control spacecraft attitude and momentum control. The challenge to convert that knowledge into this product chiefly consisted of engineering out costs, something the company claims it has done.

It (the $2,000 per unit price tag) is an aggressive target, but we're confident we can do it," says Peter LeBlanc, business development manager for SatCon's Energy Systems Division. "There are challenges, but it's what we're driving toward."

The $2,000 figure comes from the projected 10-year cost of buying lead-acid batteries and maintaining them, according to Hamilton-Piercy.

Since the first of the year, the concept has moved from technological promise to a real product. In fact, the company demonstrated a working prototype, showing how when commercial power is cut off, the spinning flywheel converts its stored kinetic energy to electrical energy that can power a network node.

The unit is said to last at least 20 years, with scheduled maintenance necessary only every seven to 10 years to keep the unit operating efficiently, according to Bauer, who has seen the company's working prototype.

The flywheel module, which is designed to spin at a steady 30,000 revolutions per minute, is stored in an underground concrete vault for safety reasons. The flywheel itself is made of a fiberglass-like composite to insure safety to craftpersons as well as the general public.

A lot of people think that this thing could explode and become shrapnel if it's made of metal," says Bauer, who notes that those concerns should be obviated now that the flywheel has been re-designed to be made of fiberglass and spins on magnetic, not mechanical, bearings. Tests are already underway at SatCon to determine exactly what happens when the flywheel module fails, but the unit should just delaminate, or "end up looking like cotton candy," says Hamilton-Piercy.

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Bauer believes that a network monitoring system also provides new benefits to him and his cable colleagues. Through internal sensors, software can show how much energy has been stored, how much is left (if the unit has gone into a backup mode), the speed at which the flywheel is spinning, and other information. "This is the first time we can really find out what's going on with our power," he notes.

Although the technology has been designed for cable and telecom networks, it has application elsewhere in such systems. In fact, Bauer intends to eventually gang several flywheels to provide backup power to his headend. "It (the flywheel) will replace the batteries we currently use," Bauer emphatically states. "And with the cable industry getting into the telephony business, we have to be able to provide reliable service. This gets us there."

This is the best alternative that's come forward so far," says Hamilton-Piercy, who notes other options include fuel cells and large generators. "The flywheel still seems to be the best, easiest to deploy" option.

Will two hours of backup be enough? With most cable operators backing off full-scale lifeline telephony deployment for the time being, Hamilton-Piercy says it ought to be plenty. Research has shown that 95 percent or more of all outages have a duration of four hours or less.

While SatCon is busily doing final design work and preparing for full-scale mass production of the unit, it's already working on an installation manual as well. "This is way past emerging technology," he notes. "It's much further along than most people realize."

Maybe not for long.

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