Instead of contenting themselves with the traditional venture-capital role, some greentech VCs have been acting more like project financers, said Nancy Floyd, a co-founder and managing director of venture-capital firm Nth Power.

At ThinkEquity Partners' ThinkGreen conference in San Francisco on Thursday, Floyd pointed to the slew of biofuel deals that started last year and reached a minor frenzy around September (see Biofuels Get Financing Downpour).

"One could argue that a good portion of that was for steel in the ground," she said. "Really, it should have been project finance."

Endicott Biofuels could be an example of what Floyd is talking about.

In September, the Houston-based company scored $40 million from Haddington Ventures for the construction of a "second-generation technology" refinery for biodiesel and other bio-derived products.

But times are changing, and so are venture capitalists.

One reason venture capitalists are looking to their own pocket books later in the game is because traditional project finance just isn't there for some of these deals because of the risk involved, she said.

"When you have new technology, you are going to have to tap innovative sources of capital," she said. "The risk is you put out a lot of dollars for a plant and it doesn't work."

Project-finance players are conservative and risk-averse by nature, which makes them withhold financial support until the technology has been proven at a commercial scale.

In the meantime, VCs seem to have excess capital, she said.

"I think some of these funds have so much capital that they want to put $20 to $30 to $40 million to work," she said.

That's doesn't mean venture capitalists want the project-financing role permanently.

"They will step back when project-finance people can step in," she said, meaning that she expects project financers will invest in cleantech projects once they are confident the technologies work.

Although the trend of VCs investing in projects has been the most apparent in the biofuels sector (see Are Biofuels Pushing VCs Into A New Role?), Floyd said she's also seeing it happen in other greentech areas, such as with technologies that make electricity from municipal waste.