The U.S. Energy Department said it is preparing to approve more federal loan guarantees for green energy projects.

The development comes amid controversy over the Obama administration's clean energy investments, after California solar-panel firm Solyndra, recipient of a $535 million U.S. Department of Energy loan guarantee, went bankrupt last year.

Developers of about three dozen projects in the loan guarantee pipeline but that weren't approved in time for last year's Sept. 30 deadline are eligible for loan guarantees under a separate program that funds innovative clean energy projects, the department said.

Energy Department loan program chief David Frantz, in a letter Thursday to U.S. Sen. Jeff Bingaman, D-N.M., chairman of the Committee on Energy and Natural Resources and Sen. Lisa Murkowski, R-Alaska, ranking member of the Committee on Energy and Natural Resources, said the department expects to begin issuing conditional commitments over the next several months "after completing a rigorous internal and external review of each application."

Projects selected for funding would be "subject to a robust monitoring effort to ensure that taxpayers' investments are protected," he wrote.

He said the number of projects and amount of loan guarantees depends on the "government's assessment of the risk level of the projects selected."

In his letter Frantz defended the Energy Department loan program, saying it has "helped the United States keep pace in the fierce global race for clean energy technologies."

Those loans, he said, support American clean energy projects expected to provide power to nearly 3 million households and are creating tens of thousands of jobs.

In part because of private sector investment enabled through the loan program, he said, the nation's renewable energy generation has nearly doubled since 2008, with a nearly 110 percent growth in solar installations last year.

He cited NRG Solar's Agua Caliente in Yuma County, Ariz., recipient of a $967 million loan guarantee, as an example. When completed this year, he said, the project will be the world's largest solar photovoltaic installation and has already started delivering energy to the power grid.

Because of "intense" global competition, he warned, the nation "cannot afford to stop moving forward" in clean energy, noting that China offered $30 billion in government-backed financing to solar companies in 2010 alone.

Murkowski spokesman Robert Dillon told The New York Times that Murkowski had no immediate objections to a new round of loans but added that Republicans were keeping an eye on the program.

"We're always concerned when we're using taxpayer money to pay for the credit subsidy but this is money that's already been appropriated," Dillon said.