The Department of Energy has already given out nearly $17 billion in stimulus package funding, and that's set to nearly double by year's end, said Matt Rogers, the senior advisor to Energy Secretary Steven Chu who's in charge of keeping track of those billions of dollars.

Eager would-be recipients should stay tuned, as "we've got a very exciting fall," he said Tuesday at the Renewable Energy Finance Forum-WEST conference in San Francisco.

Still, some DOE stimulus funding sources are flowing faster than others, as was noted by observers of the slow progress for a $6 billion DOE loan guarantee program for clean energy generation and transmission projects.

With a host of upcoming announcements, the DOE should boost its stimulus handouts to nearly $30 billion in the coming months, Rogers said. That's out of about $90 billion the department has responsibility for giving out under the stimulus package signed into law in February.

That's a pretty fast spending clip for a big government bureaucracy – though not as fast as the $1.2 billion per week, half-done by Labor Day pace Rogers set out for the DOE back in May (see Stimulus Money Going, Going...)

The money is coming across an array of programs, from renewable energy tax credits, grants and loan guarantees to cash infusions for electric and plug-in hybrid car makers, battery makers, smart grid deployments and carbon capture projects.

Among the announcements so far are $2.4 billion for auto battery and electric drive projects, nearly $1 billion in cash grants in lieu of tax credits for renewable power generation projects, and billions of dollars in block grants being given out to states for energy efficiency projects.

Of the money handed out, about $700 million has been reported as spent, Rogers said, though the DOE sees about a three-month lag in that reporting.

But for every lucky grant winner, there will be reluctant losers.

Take the $3.9 billion available for smart grid stimulus grants, which have seen up to $14.6 billion in applications, according to the Wall Street Journal. The DOE is expected to start announcing winners of those grants in mid-November, but with requests more than triple the number of dollars available, there are sure to be some disappointed utilities out there (see Green Light post).

And then, other DOE stimulus programs seem to be stuck in limbo. That description may apply to the DOE's so-called 1705 loan guarantee program, which seeks to use $6 billion to guarantee an estimated $60 billion in private-sector loans to help renewable power generation and transmission projects get underway, according to some comments at Tuesday's conference.

The DOE opened up the first round of applications for roughly half that loan guarantee program in July (see DOE Looks for Submissions for $30B Renewable Energy Loan Guarantees).

But since then, the process has stalled, said Tim Newell, senior advisor for private equity firm U.S. Renewables Group. Why is that? In short, the DOE wants to be more aggressive with the lending plans, and the White House's Office of Management and Budget – which has a mandate to protect taxpayers' money – isn't nearly as eager, he said.

"The perception from the private sector is that there is some conflict between DOE and their very aggressive plans to work closely with the capital markets" to loan the money backed by DOE guarantees, Newell said, "and skeptics at OMB who would prefer to see the program move more slowly, and with less ambition."

How well the DOE, OMB and private lenders work out their differences will likely drive the success or failure of that loan program, said Jonathan Yellen, managing director of global principal finance for Deutsche Bank.

That success or failure, in turn, "could seriously affect the amount of capital flowing to renewable projects," he said.

Of course, the stimulus package was meant to be spent quickly to boost jobs and economic growth, so the DOE is under pressure to spend quickly.

But after the stimulus comes the letdown. The green technology sector will face "the biggest cliff we've ever faced" in reduced federal financial support once the tens of billions of dollars directed toward green tech in the stimulus bill runs out in the next year or so, said Dan Reicher, Google's director of climate change and energy initiatives.

The possibility that Congress won't be able to pass a carbon cap-and-trade law by year's end, as many greentech companies and investors hope, could also drag on the sector, Reicher noted (see Green Light post).

And the global economic recession has driven down prices for fossil fuels, making it harder for renewable energy to compete, noted James Metcalfe, global head of power and utilities for UBS Securities.

Still, developments such as last week's IPO of lithium-ion battery maker A123 do provide some optimism for the sector, Reicher noted in comments after his speech (see A123 Closes Above $30: 50% Jump on IPO).

The boost in VC greentech investing in the third quarter, as reported by Greentech Media analyst Eric Wesoff this week, is another bright spot (see Green Light post).