To Capture Lost Power, Super Solution Sought
The steel lattice towers that help carry electricity from one place to another are not a pretty sight, but there’s also an invisible problem--the power lost due to electrical resistance. Superconducting technology may be solution.
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Few people welcome the sight of those steel lattice towers that help carry electricity from one place to another, but there’s a deeper problem on the lines that’s invisible.
Conventional aluminum or copper power lines have a certain amount of natural resistance to the flow of electricity, so some energy is lost as heat during transmission. About 7 to 10 percent of the power put on the U.S. grid is wasted due to electrical resistance. That may not sound like much, but it’s enough juice to run 14 cities the size of New York.
So experts and entrepreneurs are looking at the potential of superconducting materials. These materials would allow power to zip along for miles with zero electrical resistance, but there’s a catch. The super-cables would have to be super-chilled--kept at a temperature of about -350 degrees Fahrenheit (-212 degrees Celsius)--in order to work their magic.
Scientists at the Electric Power Research Institute (EPRI), an electric industry-funded nonprofit focused on technology, said in a new report that a superconducting cable system could be ready for commercial development within a decade. Moreover, they said it’s an important technology to consider, given the challenge of greater reliance on renewable energy. Areas with great potential for wind and solar power are often in remote regions far from population centers. Super-chilled wires could efficiently shuttle thousands of megawatts of electricity from distant sites to cities, said the EPRI report.
"The reason the superconductor [system] is beautiful is it likes big,” explained Steven Eckroad, a co-author of the report. “It likes high power."
Another advantage of such a system is it would be buried underground. Proponents say that out-of-sight transmission projects would face less opposition than the traditional power towers. This month, for example, the Los Angeles Department of Water and Power dropped plans for an 85-mile, U.S.$800 million transmission line designed to convey electricity from remote solar, geothermal and nuclear plants in the southeastern California desert and Arizona. The project faced fierce opposition from environmentalists opposed to erecting 16-foot (5-meter) pylons across the Big Morongo Canyon Preserve, the San Bernardino National Forest and other preservation areas.
Of course, buried superconducting transmission lines would face their own challenges. The wires would be encased in liquid-nitrogen filled tubes to keep them cool. Refrigerators also would have to be interspersed every few miles.
Then, there’s the power conversion issue. A superconducting line would use direct current (DC), good for transmitting power over long distances. But the nation’s power system now relies on alternating current (AC) for safe low-voltage transmission of power to homes and businesses. Improvements in AC-DC power conversion make long-distance DC transmission more feasible, the EPRI report said. Some power, however, would be lost at the terminals as electricity is converted from AC to DC and back again.
But the amount of power lost when transmitting electricity on a DC superconducting system would be less than 3 percent, according to Jack McCall, director of business development at American Superconductor, a Devens, Massachusetts firm that has been working to develop a system very similar to the one EPRI envisions.
Although the EPRI study cites cost as an obstacle to deploying superconducting technology as a competitive alternative to conventional power lines, McCall said that his company’s system will cost between $8 to $13 million per mile — or about the same as a conventional overhead power line today.
American Superconductor aims to prove the technology, and at the same time tackle a vexing U.S. power grid problem. Electricity can’t go cross-country because the nation has three separate power grids—one for the East, one for the West and one for Texas. American Superconductor’s proposed Tres Amigas project, on a 22.5-square-mile (58-square-kilometer) site in Clovis, New Mexico, would unite the three grids. The project, which could cost more than $1 billion, would be privately financed and is awaiting federal approval. If it goes forward, it would be the first large-scale test of superconducting transmission technology.
"By the end of 2014, the U.S. will have a 5,000-megawatt superconductor cable running in DC that utility companies can come and look at and touch and feel and poke and prod and say, ‘Yeah, this actually works,’" McCall said.
But there are other ideas for moving power. Electric Pipeline, a start-up company in Cambridge, New York, says it has a technology for moving DC power long distances underground without superconducting material. Instead, it would use wires that contain up to 50 times more aluminum as conventional overhead wires.
Roger Faulkner, Electric Pipeline chief executive, said there would be some electricity lost, but less than on conventional power lines, and at a price that makes it a competitive alternative.
Another option, of course, is to try to get by without moving power at all. The Los Angeles power department, having abandoned its cross-desert transmission plan, is looking at constructing a huge 80-square-mile (207-square-kilometer) solar array in the dry bed of Owens Lake—the body of water drained early last century by the city aqueduct. Among the advantages city officials cite: It is close to existing power transmission.