Xcel Energy: Wind-to-battery project a success so far

Xcel Energy says a project in southwestern Minnesota that transfers power generated by wind turbines onto a large battery pack is working as hoped.

Xcel started the project in 2008, to determine how battery-storage technology could help the utility store energy from renewable sources in the future. If done efficiently, energy generated by wind power at off-peak times could be stored in batteries and be available on the electricity grid during periods of high demand.

Batteries could also become an important part of dealing with the intermittency of wind and solar energy and could make the electric grid more reliable, officials said.

But the project in Luverne, located about 30 miles east of Sioux Falls, S.D., is not ready to be expanded.

Frank Novachek, director of corporate planning for Xcel Energy, said that while preliminary tests show the technology works, more tests will be conducted by University of Minnesota researchers in the next year to predict how long the battery will last. Researchers will also continue evaluating the technology.

The price of the batteries, which are the size of two semi-trailers and weigh 80 tons each, would also have to drop before Xcel expands use of batteries, he said.

"For broad deployment, we will have to have much lower cost energy storage devices than we have now," Novachek said. "It does appear that that will be the case moving forward."

The battery pack in Luverne is capable of powering 500 homes for more than seven hours.

Novachek said information gathered from the project will help Xcel officials make decisions about energy storage in the future, as the utility moves toward adding more wind and solar generation facilities.

"We wanted to test it there because we have interests in using storage to help us with grid stabilization," he said.

Making wind energy more efficient is also a goal. The tests in Luverne showed 75 percent efficiency with the battery.

"We are increasing our ownership in wind ourselves, and so we're wanting to look at what the value might be in using a battery as an integral part of the wind farm to shape the output of the wind farm directly," Novachek said.