There is currently one gigawatt of concentrating solar power (CSP) plants under construction in the United States.

The 500-MW Blythe CSP plant obtained a $2.1 billion DOE loan guarantee. Construction is underway on the-30 MW Alamosa CPV plant, with expected completion in 2011. There is a concentrating solar (combined CSP and CPV) pipeline of over 9 GW in the U.S.; more than 2.4 GW have signed power purchase agreements. In total, 1,100 MW of CSP and CPV are now under construction in the U.S.

But the continued progress of that growth is shaky, given the political realities of the country and the massive amounts of capital such projects require.

That could be the takeaway from a recent briefing by the Solar Energy Industries Association (SEIA), called to highlight the economic contributions of large-scale plants in the Southwest, with price tags running into the billions.

The federal loan guarantee program, currently under fire in many budget negotiations, is a main driver in these massive projects. Fred Morse, senior advisor, US Operations, for Abengoa Solar, said the company last December closed the financing for its 280-megawatt Solana CSP plant to be built in Arizona, which has a $1.45 billion loan guarantee by the Department of Energy.

“This large power plant would not have been possible without the loan guarantee,” he said. Private financing wouldn’t work, simply. “Financial markets today are not able to provide the kind of debt that these very large projects need,” he added.

Morse said the contract terms banks could offer, in length and interest rates, would not make the projects viable. Also, due to their size, even a consortium of lenders would not be able to provide enough capital.

Solana has a 30-year power purchase agreement with Arizona Public Service and now has 350 construction workers now on the site, and that will increase to 1,500 to 1,700 jobs. When operating, 85 to 100 workers will be employed. So far, $600 million in components from 14 states have been purchased. John Mulligan, director public policy and regulatory affairs for BrightSource Energy, echoed many of the same points.

 The Ivanpah CSP project is rated at 392 megawatts in the Mojave Desert in California. It, too received a loan guarantee, this one for $1.6 billion loan.

“In our case Ivanpah is a $2.2 billion project procuring supplies from 16 states and we expect our domestic spend to be well in excess of 50 percent,” he said.

But the long-term prospects could be damaged by inaction. “From a business perspective, these are capital intensive, long-term projects from permitting to online that take multiple years and a lot of money,” Mulligan said. “Given that amount of time and money, you really need that policy certainty in order to attract capital and reap the benefits.”

But loan guarantees are controversial, with Congressional hearings now focused on allegations of favoritism in the case of Solyndra, in addition to the objections associated with excess government spending.

“There’s a lot of pressure on the program. We stand by it and believe that the program pays real dividends and hopefully it will be continued,” he said.

Continuation will be needed. BrightSource has a pipeline of 2,600 megawatts for Pacific Gas &Electric and Southern California Edison. Tom Kimbis, vice president for strategy and external affairs, said there has been 31 percent growth in solar manufacturing in the first quarter of 2011 compared to 2010. If that rate continues, “the U.S. could be the largest market in the world in two to three years.”