As of September, of the $34 billion loan portfolio for low-carbon energy and green automobiles, only about 2 percent had been lost; the other 98 percent had either been repaid or was on track toward repayment, according to the department.

That failure, alongside a few other high-profile bankruptcies, made the program a Republican punching bag for years, but overall, the program yielded a high rate of success.

The last round of renewable-energy project loans in 2009-11 included big solar and wind power-generating projects (not to mention a half-billion for the infamous Solyndra solar-panel manufacturing flop).

The Energy Department is getting closer to issuing loan guarantees for green-energy projects for the first time in years. DOE on Wednesday issued a draft call for applications for up to $4 billion in financing for renewable-energy and efficiency projects.

Now DOE has less money to play with on the renewables front and is focusing more heavily on how to help commercialize other kinds of green technologies beyond big power projects.

The department is focusing on projects that integrate renewable power into the grid and help store it; next-wave biofuels; projects to "enhance" various existing facilities (think, for instance, adding power production to a dam that doesn't do it); waste-to-energy projects; and energy-efficiency proposals.

Peter Davidson, who heads DOE's loan office, said the goal is to finance projects that deploy technologies that are "market-ready," "catalytic," and "replicable."

With the clock winding down on the Obama administration, Energy Department officials have been moving more aggressively to use their remaining lending authority in the financing program, which was born in a bipartisan set of energy bills in 2005 and 2007 but has fallen out of favor with Republicans.

In addition to the new renewables effort, last year DOE solicited applications for petroleum- and coal-related projects that trap carbon emissions. It's also rebooting the loan program to spur manufacturing of high-tech vehicles and components.

"We are really just going all out to put these resources to work," Davidson said in an interview.

But Davidson also said that the department is doing its due diligence. The draft solicitation issued Wednesday is going out for public comment, and he said that the office has been making the rounds on Capitol Hill to discuss its efforts. Congress has 45 days to weigh in.

Davidson said he expects the final version of the renewable-energy project solicitation to arrive in the June-August time frame, and that projects could win approval as soon as the end of 2014 but more likely next year.