MINNEAPOLIS – Xcel Energy soon will begin testing a cutting-edge technology to store wind energy in batteries. It will be the first use of the technology in the United States for direct wind energy storage.

Integrating variable wind and solar power production with the needs of the power grid is an ongoing issue for the utility industry. Xcel Energy will begin testing a one-megawatt battery-storage technology to demonstrate its ability to store wind energy and move it to the electricity grid when needed. Fully charged, the battery could power 500 homes for over 7 hours.

“Energy storage is key to expanding the use of renewable energy,” said Dick Kelly, Xcel Energy Chairman, President and CEO. “This technology has the potential to reduce the impact caused by the variability and limited predictability of wind energy generation. As the nation’s leader in distributing wind energy, this will be very important to both us and our customers.”

Xcel Energy has signed a contract to purchase a battery from NGK Insulators Ltd. that will be an integral part of a project. The sodium-sulfur battery is commercially available and versions of this technology are already being used in Japan and in a few US applications, but this is the first U.S. application of the battery as a direct wind energy storage device.

The 20 50-kilowatt battery modules will be roughly the size of two semi trailers and weigh approximately 80 tons. They will be able to store about 7.2 megawatt-hours of electricity, with a charge/discharge capacity of one megawatt. When the wind blows, the batteries are charged. When the wind calms down, the batteries supplement the power flow.

The project will take place in Luverne, Minn., about 30 miles east of Sioux Falls, S.D., with the battery installation beginning this spring adjacent and connected to a nearby 11-megawatt wind farm owned by Minwind Energy, LLC. S&C Electric Company will install the battery and all associated interconnection components. The battery is expected to go on-line in October 2008.

Partners in the project with Xcel Energy include the University of Minnesota, the National Renewable Energy Laboratory, the Great Plains Institute and Minwind Energy, LLC. Xcel Energy is testing emerging technology and energy storage devices as part of its overall Smart Grid strategy, which modernizes and upgrades the grid to allow for easier integration of renewable energy sources.

The project has been selected to receive a $1 million grant from Minnesota’s Renewable Development Fund, pending Minnesota Public Utilities Commission approval this spring.

Xcel Energy (NYSE: XEL) is a major U.S. electricity and natural gas company with regulated operations in eight Western and Midwestern states. Xcel Energy provides a comprehensive portfolio of energy-related products and services to 3.3 million electricity customers and 1.8 million natural gas customers through its regulated operating companies. Company headquarters are located in Minneapolis. More information is available at www.xcelenergy.com.