finance-commerce.com
August 3, 2010
Apparently, you can charge a sodium-sulfur battery with energy from the wind and then draw on that battery power to charge an electricity grid. Those, at least, are the preliminary results that Xcel Energy released Tuesday from its wind-to-battery storage project in southwest Minnesota. In other words, so far, the renewable-energy-related technology works.
The Achilles heel of renewable energy like wind and solar is that it's cyclical-stronger at different times during a 24-hour period. So, utilities like Xcel Energy are investing in finding ways to store renewable energy so that it can be used constantly, like coal-fired power. In October 2008, Xcel Energy began testing battery-storage technology to demonstrate its ability to store wind power, then draw on the battery power to supply the electricity grid when needed-its first use of the technology in the U.S, for direct wind-energy storage. "We have proved that this technology can perform the functions of storage that we were looking for to help us manage the variability of wind power on our operating system", said Frank Novachek, Xcel Energy's director of corporate planning.
Novachek said Xcel Energy executives are "greatly encouraged" by the results of the wind-to-battery storage test. Preliminary results indicate that the battery can shift wind power from off-peak generation to peak battery power availability; reduce the need to compensate for the variable nature of wind power generation; support the transmission grid system by providing voltage support; and responding instantly to real-time imbalances between electric generation and available power load.
Xcel Energy's test project has been conducted near Luverne in southwestern Minnesota, with power from the nearby 11-MW wind farm owned by Minwind Energy LLC. The wind farm charges a total of twenty 50-kW battery modules that, combined, are roughly the size of two semi-truck trailers and weigh 80 tons. The battery, which Xcel Energy purchased from Tokyo-based NGK Insulators Ltd., now enters a Phase II period of testing to determine the technology's chemical makeup and measure the economic potential of selling battery power for the electrical grid.
Novachek said the chemical testing, which will be conducted by University of Minnesota staff, will help determine the number of charging cycles the battery is capable of delivering. NGK Insulators initially told Xcel Energy executives that the battery should be capable of 5,000 cycles, which, considering usage of the battery over the last year, would mean the sodium-sulfur cell would last about 15 years.
In addition to NGK, partners in the wind-to-battery project include Chicago-based S&C Electric, the University of Minnesota, the Golden. Colo.- based National Renewable Energy Laboratory, the Minneapolis-based Great Plains Institute, Minwind Energy and Arlington. Va.-based Gridpoint Inc. Novachek said that Xcel Energy is considering a solar version of the Minnesota wind-to-battery test in Colorado just south of Denver International Airport.
That test, which could begin as soon as late 2010 or early in 2011, is designed to test the variability of solar power in Colorado. "The (solar) application is different because solar output can drop drastically", said Novachek. "We've observed a solar output drop from 100% to 20% within one minute". That means that any solar battery backup system must be ready to provide a quick burst of electricity to compensate during sharp power spikes caused by such non-dramatic events as a cloud drifting in front of the sun. The utility's testing of emerging technology and energy storage devices is part of its Smart Grid strategy, which upgrades the power grid and allows easier integration of renewable energy sources.
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