We would be hard-pressed right now to find a study indicating a positive trend in any sector of the economy for the past two quarters, an observation you’ve no doubt made for yourself since Day One. Still, the bad news is sometimes tempered by the good, as an April report from CleanTech Group, a market research firm, shows: while the combined clean-tech venture capital investments in North America, Europe, China and India plummeted 41 percent from the last quarter of 2008 to the first quarter of 2009, most of the renewable energy investments that did occur went into solar. The news is a bit old (the report was released April 1), but I’m of the opinion that a dose of optimism never goes stale.

The combined $1 billion raised in the period ending March 31, 2009 across the 82 companies surveyed was a staggering 48 percent lower than the sum raised in the same period last year, which ought to come as a surprise to nobody. There were also no large ($100 million-sized) deals this quarter, according to the report. Yet with the U.S., Germany, Japan and other G20 nations injecting federal stimulus money into renewable energy, it’s a relief to see that the gradual movement toward increased energy efficiency, though slowed down—like nearly every other sector of the economy—hasn’t lost too much steam.

Compared to all the other renewable energies, funding for solar power came away with the least damage, with biofuels coming in at a distant second ($96 million):

During the first quarter solar companies again garnered the most attention, capturing $346 million, or more then one-third of the quarter’s total venture investment. Norsun, a Norwegian polysilicon producer, raised the most in a $72 million round led by Good Energies.

The reasons for this are manifold, according to a BusinessWeek article discussing the report:

That shows VCs are turning away from more mainstream cleantech projects — such as wind energy — in search of second-generation technology, like concentrated solar and biofuels. In part, this trend represents cleantech’s maturing: venture capitalists moving from one, well-developed, technology to another, more immature, one in search of a larger rate-of-return.

But it also shows the way VCs are investing has changed. A couple of years ago, funds would have been willing to spend millions — on their own — in untested sectors, betting the farm that their investment would pay off. Now, venture capitalists are more cautious, often investing with other funds in industries, such as solar, that are supported by lucrative, government-backed incentives.

Inevitably, VC cleantech investment will pick up as the global economy gets back on its feet. But in the meantime, investors are being circumspect where they put their money. To win backing, says one cleantech entrepreneur who declined to be named, it’s all about making your business work. “Money is out there, but only for projects that make financial sense,” he says.

As we’ve noted before (or Adam has, to be more precise), solar can make sense, even in tough times—and not just for the behemoth company sitting on its giant cash pile.