Giant Magnet Keeps Bulbs Bright

If you're driving somewhere between the coast and Anchorage in the future and get stuck behind a trailer-truck carrying what looks to be a mammoth cigar, don't cuss--- the 70-foot long, 400,000-pound object may soon keep you out of the dark.

That object, a huge magnet in its protective housing, may soon become part of a unique superconducting magnetic energy-storage system in Alaska, the first of its kind to be installed in any power utility worldwide. In 1997, the magnet is scheduled to head from its design headquarters in Virginia to Anchorage Municipal Light and Power, where engineers will connect it to the power system.

According to Moe Aslam, chief engineer at the Anchorage utility, the magnet will make power pulsating through the Alaska Intertie (the linked electrical grid from Homer to Fairbanks, also known as the Railbelt) more stable by instantly correcting momentary drops or increases in voltage or frequency caused by generator problems within the system.

When a large power generator malfunctions today, system engineers "shed load." During load shedding, the electrical utilities are forced to black out sections of a city until the system can be stabilized.

With the new system, load shedding should be much more infrequent, Aslam said, because stored energy within the magnet will instantaneously kick in to make up for the lost or malfunctioning generator. Even a few seconds of voltage or frequency drop can be harmful to computers and motors.

A major advantage of the magnet system is that it can correct power fluctuations within two milliseconds, or two-thousandths of a second. Conventional power system back-ups such as water-driven generators take at least one minute to reach their full power, and by that time power customers are usually searching for candles. The magnet system is capable of providing 30 megawatts of energy for up to one minute, which should be more than enough time for other on-line generators to respond, Aslam said.

The system is huge, but the theory is simple. The magnet will be housed in a chamber called a cryostat, which is filled with liquid helium. The liquid helium will maintain a temperature of about five degrees Kelvin (-450 degrees Fahrenheit), or very close to absolute zero, the temperature at which molecules stop vibrating. In a medium that cold, electrical current runs almost unhindered through certain metals. This lack of electrical resistance creates a device known as a superconductor.

The magnet will be wound with a superconducting coil of niobium-titanium alloy, which will create a powerful magnetic field. This magnetic field produces a direct-current electrical charge, which the magnet stores until the electricity is needed. A power conditioning system changes the direct current into alternating current, which then can be applied to the power grid.

The magnet won't eliminate power outages altogether, though. Local problems like heavy snow and cars colliding with power poles will still turn out the lights. But generator problems, which Aslam estimates happen about once a month, will be cut down considerably.

The monster magnet is being manufactured in Lynchburg, Virginia, by Babcock and Wilson, a defense contractor. The federal government is picking up a large part of the estimated $25 million price of the system, through a grant co-written by Anchorage Municipal Light and Power and Babcock and Wilson. The Department of Defense is interested in the magnet, Aslam said, because its performance will be studied for other superconducting magnetic energy-storage uses, such as for powering submarine propulsion or laser weapon systems.

The Alaska magnet will travel here in 1997, probably by barge and then on a mammoth trailer to Anchorage Municipal Light and Power. So, be patient during the resulting traffic jam; that big cigar may actually save you time in the long run.