Xcel Energy, America's largest utility buyer of wind power, has issued a request for proposals (RFP) for approximately 2200 MW of generation supply for its Colorado customers, to be installed between now and 2015. Although the RFP is an open-source request, the Minnesota-based utility has set aside 700 MW for wind power to help Xcel meet legally binding green energy targets in Colorado. Xcel says it will also consider acquiring up to 600 MW from solar thermal generation with storage capability or natural gas backup. Although all energy sources can bid, Xcel limits coal fired bids to those from facilities that capture and sequester at least half their carbon dioxide emissions. Full proposals are due April 10, with the winner to be announced by the end of the year. An independent evaluator selected by the Colorado Public Utilities Commission will review proposals.