(word processor parameters LM=8, RM=75, TM=2, BM=2) Taken from KeelyNet BBS (214) 324-3501 Sponsored by Vangard Sciences PO BOX 1031 Mesquite, TX 75150 There are ABSOLUTELY NO RESTRICTIONS on duplicating, publishing or distributing the files on KeelyNet except where noted! October 30, 1993 POWERING.ASC -------------------------------------------------------------------- Citation-> Popular Science, Jan 1989 v234 n1 p66(3) COPYRIGHT Times Mirror Magazines Inc. 1989 RINGS OF POWER There's been a nuclear attack. An incoming warhead has just struck a key U.S. defense site and knocked out the region's power grid, leaving the country's ground-based missile-defense system without power. In the meantime, the United States has less than 10 seconds to fire laser weapons at the next round of incoming missiles. Where will the power come from? An emergency electrical generator takes 15 minutes to spin up, and power is required instantly. The solution: tap into giant energy-storage rings that can deliver an awesome 1,000 megawatts to the lasers within 30 milliseconds. These storage rings do not exist yet, but the Strategic Defense Initiative Organization (SDIO) plans to build a football-field sized prototype by the end of 1994. The heart of the undergound ring, called a superconducting magnetic energy-storage (SMES) ring, is a superconducting coil cooled by liquid helium to temperatures nearing absolute zero. AT those temperatures the coil will have no electrical resistance, and the current can be stored almost indefinitely. Energy storage rings could also serve an important role for utilities. By storing excess power generated during off-peak hours and releasing it into the grid during peak hours, the ring could increase utility efficiency. Experts believe that a SMES unit could be built almost anywhere, and because it would have no moving parts, it would be easy to maintain. And if efforts succeed in developng high-temperature superconductors [July '87, April '88], refrigeration costs will drop substantially, making a SMES system more practical in smaller sizes. "I've been trying for eighteen years to get funding to build a SMES for a large utility," says Roger Boom, director of the University of Wisconsin's Applied Superconducting Center in Madison. A portly man with glasses and a fringe of gray-white hair, he was not dissuaded when the funds did not materialize. But then came SDIO with new reasons for investing in the technology. "We need a system that will provide about one gigawatt of power Page 1 available immediately when the battle starts," explains Capt. Paul Filios, technical adviser to the Defense Nuclear Agency (DNA), the agency overseeing the SMES project for SDIO. "We can't get that kind of power straight from the power grid. For one, the grid might not be there after an attack. And secondly, we need the energy equivalent of what a nuclear power plant produces in a fraction of a second." The actual figures are classified, but a free-electron laser weapon [Dec. 87] would require at least 1,000 megawatts of electricity in 3/100 of a second. The heart of a SMES is the current-carrying conductor that is coiled around the ring 550 times. The number of coiled conductors varies from one to four, depending on the design. Each conductor is composed of tens of thousands of 27-millimeter-wide filaments made from superconducting niobium-titanium alloy and embedded in copper. In Boom's design, these filaments are embedded in unalloyed, extremely pure aluminum, a soft material about the consistency of toothpaste that is an extremely good conductor. If the superconductor warms up slightly and becomes resistant, the high- purity aluminum will carry the current. Keeping it cool Another conductor concept being developed by Bechtel National in San Francisco uses a ropelike cable of superconducting strands contained in a stainless-steel tube. The voids in the tube are filled with liquid helium to keep the conductor at 1.8 degrees Kelvin (minus 456 degrees F). To ward off warm-up in Boom's design, the coil will be surrounded by a vacuum vessel that acts like a giant thermos bottle with superfluid liquid helium inside. Moving outward from the thermos, several heat shields are cooled to temperatures progressively higher than 1.8 degrees K and further protect the coil. In November 1987 SDIO (through DNA) awarded two $15-million contracts to develop plans for a test SMES unit. One contract went to Ebasco Services in New York and the other to Bechtel. One company will be chosen in the spring of 1990 to build the device. It will have a 300-foot diameter and be capable of storing about 20 megawatt-hours of electricity--enough to power 1,000 100-watt light bulbs for 200 hours. The model must operate in two modes: fast discharge for the ground-based laser (400 to 1,000 megawatts for 100 seconds), and slow discharge for utility applications (10 to 25 megawatts for two hours). The design must also solve less obvious problems. When the SMES is first cooled down to super-low operating temperatures, the entire ring, including the coil and aluminum support structure, will shrink several feet and tend to move inward toward the ring's center. But if the ring needs maintenance, the liquid helium will be drained out and the ring will warm up, causing it to expand. To accomodate strain on the coil, the ring must have some radial leeway. One idea championed by Boom's group is to have two conductors and an aluminum support structure between them ripple radially around the ring (see drawing). "The nodes of the ripple will be fastened through struts to the rock wall," says Boom. "When the coil cools down, those nodes stay fixed while the radius between the ripples contracts." Page 2 Terry Walsh, Bechtel's project manager, finds fault with this rippled support design. "As the coil cools down it's going to be pulling against the point where it's restrained," he says. Walsh is concerned that these high-stress points will cause strain on the conductor as well as dangerous hot spots from friction. He says that Bechtel is studying an alternative approach in which a telescoping support structure absorbs coil shrinkage and expansion. Ring sharing The benefits associated with SMES are wide ranging. "With SMES, the utility can operate all plants continuously at one hundred percent efficiency," says Boom. And in the event of a generator failure, "the power control equipment can prevent a blackout by switching the unit from charging to discharging in thirty milliseconds," he adds. Boom also says that SMES could make it simpler for utilities to buy power from intermittent alternate energy sources, such as cogenerators and wind and solar power plants. Where would a SMES site be located? "It depends on what the facility is going to be used for," says Filios. Although a laser weapon probably would not be located right next to an electric utility, it would be more economical if the two shared a SMES. The reason: A SMES is only economical if it's used continuously. Otherwise, the savings from generating efficiency are lost to the costs of refrigerating the coil. a large 5,000-megawatt-hour facility would require a 1-1/2-mile-diameter exclusion zone, so populated areas are out. This is because as the superconductor cools down it generates strong magnetic forces. The aluminum ring must also be buried in a bedrock trench to counterract these forces. Although the free-spending military has firm plans for SMES, the trick in persuading a frugal utility to build is to reduce operating costs. One way of achieving this is with the new generation of high-temperature ceramic superconductors. "Without refrigerating cost constraints, smaller SMES units could be economical," says Boom. So far the current-carrying capacity of these warmer superconductors is not high enough to be useful in a SMES facility. But the pace of developments in the field lends credence to their possible use in the future. Boom is optimistic that economical SMES rings could have even more exotic applications: storing energy for space platforms or powering rail guns or tanks. (Refer to 4THSTATE on MHD power generation systems on KeelyNet) -------------------------------------------------------------------- If you have comments or other information relating to such topics as this paper covers, please upload to KeelyNet or send to the Vangard Sciences address as listed on the first page. Thank you for your consideration, interest and support. Jerry W. Decker.........Ron Barker...........Chuck Henderson Vangard Sciences/KeelyNet -------------------------------------------------------------------- If we can be of service, you may contact Jerry at (214) 324-8741 or Ron at (214) 242-9346 -------------------------------------------------------------------- Page 3