A multi-state consortium of southwestern energy utilities issued a request for proposals today for a 250 megawatt concentrating solar thermal power plant.

The Southwest Energy Service Provider's Consortium for Solar Development said the plant would be owned by a third-party with consortium members each signing long-term power purchase agreements.

The power purchase agreements will have a maximum term of 30 years.

The consortium is made up of Arizona Electric Power Cooperative, Arizona Public Service (NYSE: PNW), Southern California Public Power Authority, Arizona's Salt River Project, UniSource Energy (NYSE: UNS) subsidiary Tucson Electric Power, and Minnesota-based Xcel Energy (NYSE: XEL).

The group said the project is expected to be located in either Arizona or Nevada, and would be the largest solar power plant in either state.

A concentrating solar thermal plant uses the sun to heat a liquid that can directly or indirectly drive a turbine.

Proposals are due March 19, 2008, with the final bidder to be selected in June. The consortium hopes to have a facility in operation by the end of 2012.