Wind Power Is A Valuable Renewable Energy Source; But How Do You Capture The Power Of The Wind And Use It Later? Xcel Energy Has A Test Project In Minnesota That The Company Hopes Will Provide Some Answers.
If there is one thing the Midwest has in abundance, it is wind. A study published in April 2009 by the American Wind Energy Association showed that Minnesota and Iowa were among the top four producers of wind energy in the United States in 2008, along with Texas and California. So it stands to reason that Xcel, already the country's biggest wind-power provider, is testing the storage of wind energy in batteries at Luverne, Minn. The Luverne project is the first of its kind in the country.
One of the biggest drawbacks of wind energy is its unpredictability. According to Frank Novachek, director of corporate planning for Xcel Energy, not knowing whether the wind will blow or how strong it will be makes providing a consistent supply of power to the energy grid difficult without using an alternative energy source. "It's hard to get much penetration of wind power onto the grid without using compensating technologies," he says, adding that to compensate for natural drops in the wind, the company uses natural-gas power units to pick up the load when the wind dies down.
The Luverne test project will not require any other form of power generation. When the wind blows, the sodium-sulfur (NaS) batteries that Xcel is using for this project will be charged. When there is little or no wind, the batteries will supply the grid with electricity. "The batteries will act as a sort of shock absorber between the wind and the grid," says Novachek. Fully charged, the batteries could supply one megawatt of energy, enough to supply 500 homes for seven hours.
Versions of this wind-power storage technology have been used in Japan, but this is the first time these batteries have been used to store wind power in the United States. Nevertheless, they have a high storage capacity, can be constantly charged and recharged, are already used commercially in other applications and can store energy on a large scale.
"We weren't trying to pick the technology we would use from here on out. We picked one that we could learn from," says Novachek. "But we wanted something with a demonstrated reliability so we wouldn't have so much technology risk in our investment." The company expects to get some preliminary results in the first part of next year on how effectively the battery can store wind energy and move it to the grid when needed, but the testing period will continue through 2010.
MINNESOTA'S POTENTIAL
Novachek says that Minnesota's wind resources are among the best in the Midwest, but Xcel Energy also chose to locate the project in the state because it could hook its project up to an 11-megawatt wind farm at Luverne owned by Minwind Energy, a company that Xcel has partnered with before. "There's no requirement for the battery storage facilities to be physically tied to a wind farm, but we thought that proximity to a wind farm was important for this early demonstration to get the concept across to people early on," he says.
The project will also receive $1 million in grant funding from Minnesota's Renewable Development Fund, set up to promote the startup and expansion of renewable-energy projects in the state. "The state of Minnesota has been very supportive and is very interested in energy storage as a way of getting more wind energy onto the grid," says Novachek.
The Great Plains Institute, a nonprofit organization that promotes the production and use of renewable and low-carbon energy throughout the Midwest, is also supporting Xcel's Luverne project. "Our interest is for the public benefit this could deliver," says Rolf Nordstrom, executive director of the institute. "We want to bring together enough different interests - technology experts, elected officials, utility regulators and other non-governmental organizations with similar interests - to discuss the technology tested here, what the commercial barriers to entry are and whether there are any unintended consequences."
Xcel is going to assess the results of this test project and of other demonstrations that it has under way, including wind-to-hydrogen and solar-to-hydrogen test projects at the National Renewable Energy Laboratory in Colorado, before it determines how they might be used commercially.
However, Novachek points out that if wind energy storage does become a commercial reality one day, power generated from wind could easily exceed Minnesota's renewable-energy mandate, which requires that a minimum of 25 percent of energy in the state must come from renewable sources by 2025. "That would certainly be beneficial to the Midwest economy and to Minnesota in particular," he says.
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