The post last week about the current challenges of solar investments elicited a bunch of comments from colleagues -- split between yea or nay. Meanwhile, last week saw yet another wave of general media coverage of the "bubble" in cleantech, such as this Boston Globe article. And we continue to see some high-profile "venture capital" investments of eyebrow-raising magnitude, such as SunEdison's raise this week (see below), and rumors going around the industry of multiple thin-film solar fundings underway at valuations in the hundreds of millions or even over a billion dollars... You know, the kind of thing that, if you're only checking the headlines, would make you think there's a bubble in cleantech. So it's worth noting yet again what we wrote about a year ago, when all this talk started: If there are bubbles in some sub-sectors of cleantech (a big "if"), that really doesn't indicate a general bubble across the sector. There are still plenty of great investment opportunities in cleantech, and it seems like the number is growing, not declining. It's admittedly a small data set, but at least at one firm, @Ventures, we're seeing plenty of attractive early-stage deals across the various sectors of cleantech -- energy, water and materials. Deals at reasonable valuations, with strong management teams and decent long-term growth prospects. Companies like GE are raising their revenue targets (and thus their need to acquire technology solutions) for cleantech markets. And while macroeconomic conditions are putting a damper on exits in 2008, bankers expect that cleantech IPOs will lead the re-opening of the exit window when it occurs. It's for subscribers only, but it's very much worth checking out Venture Capital Journal/European VCJ's recent Cleantech Report if you can get a copy. It's a very good overview of what's going on in the sector, touching on the breadth of investment opportunities, and taking a good balanced point of view that gets beyond the general media headlines. A nicely-done primer and update. And the following passage seems particularly relevant:

"So far, however, enthusiastic projections aren't reflected in the early funding data. For all the buzz cleantech has generated, it hasn't attracted anything near the early stage funding levels that Internet and telecommunications drew a decade ago. Even today, despite all the media attention focused on cleantech, Internet investments continue to exceed cleantech by a substantial margin."

It's worth reiterating: Yes, it's entirely possible that there are bubbles within certain narrow sub-sectors of cleantech venture capital. And yes, despite the incredible breadth and variety of uncorrelated sub-sectors within "cleantech", it's possible that at some future date there could be overall over-investment across these categories. But we're a long way from that point. We're only at the earliest stages of a period of "creative destruction" of incumbent energy, water and materials markets that are measured in the trillions of dollars in size. Cleantech continues to be only a small portion of venture capital investments. Cleantech, broadly defined, is going to be an attractive venture capital sector for a long time to come. Deals from the past week:

• GTM's Funding Roundup had details on the raises by SunEdison, Marrone Organic Innovations, and Climos, as well as on Suntech's strategic investment in Shunda Holdings.

• Michael Kanellos reports that Hum Cycles has raised an angel round of financing.

• It's not really a venture deal, but it's worth noting Masdar's $2B bet on making thin-film solar in Abu Dhabi.

• Sapphire Energy has raised $50mm from ARCH, Wellcome Trust and Venrock, to develop algae-to-gasoline.

• BT Imaging, an Australian company which is developing inspection tools for solar cell manufacturers, closed an A$3mm Series A led by Allen & Buckeridge Venture Capital, with participation from UniSeed.

Other news and notes: Google is reportedly teaming up with Ormat... Another article describing the increasing interest of limited partners (LPs) in cleantech... Here's a funny column on the subject of VCs and IPOs... DTE Energy and the University of Michigan are teaming up on the DTE Clean Energy Prize... A nice article on how student ideas and efforts can impact markets... Finally, green astroturf?