Xcel Energy's Wind-to-Battery Test Shows Promise

August 11, 2010

In its quest to store wind energy and move it to the grid, Xcel Energy has reached a milestone in its preliminary tests of a one-megawatt (MW) battery-storage technology system, the company announced on August 3. The Wind-to-Battery Project showed it was possible to reduce the need to compensate for the variability of wind generation, Xcel Energy said. It is the first U.S. use of the sodium sulfur battery-storage technology as direct energy storage, according to Xcel Energy. The small demonstration project was part of the company's research into how to integrate unpredictable renewable energy into the grid. Begun in October 2008, the research is being conducted with a battery installation in Luverne, Minnesota, that is connected to a nearby 11-MW wind farm. Twenty 50-kilowatt battery modules in the demonstration weigh approximately 80 tons and are able to store about 7.2 megawatt-hours of electricity, with a charge/discharge capacity of one megawatt. Fully charged, the battery could power 500 homes for more than seven hours.

The preliminary test results indicate this technology can shift wind energy from off-peak to on-peak availability, and can support the regional electricity market by responding to real-time imbalances between generation and load. The system could provide voltage to the transmission grid, which would contribute to system reliability, according to Xcel Energy. Testing will continue to see how the battery system handles larger amounts of wind energy transfers to the grid. The next phase of the project will determine the potential cost effectiveness of the technology. A final report for the project, which received a $1 million grant from Xcel Energy's Renewable Development Fund, is expected in summer 2011. See the Xcel press release and the Wind-to-Battery report (PDF 2.94 MB). Download Adobe Reader.