Advanced Technology Ventures announced on Tuesday that it had closed its eighth fund at a whopping $303 million.

The venture-capital firm, based in Palo Alto, Calif., and Waltham, Mass., has been known to invest in cleantech companies, along with Internet, communications and healthcare firms.

The ATV fund comes at a time when green-technology companies are seeing a surge of investments. It's also a time when the private sector might be drumming up more cash than it is able to spend.

After all, the UK-based research New Energy Finance said recently that venture-capital and private-equity firms invested $8.5 billion in clean-energy companies, a 27-percent increase from 2006, but that VCs invested only 73 percent of the funds they had raised, leaving $2 billion unspent (see Clean-Energy Fundings reach $117.3B in 2007).

With a number of venture firms closing funds for green technology within the past few months, it begs the question: How will ATV spend its $303 million?

Among many examples, Houston-based Yellowstone Capital Partners launched a $50 million alternative- and renewable-energy fund in January, a fivefold increase from its first greentech fund of $10 million in 2005 (see Yellowstone Capital Launches $50M Greentech Fund). And Expansion Capital Partners closed a $103 million fund for green technology last fall, far surpassing its original target of $60 million (see Expansion Closes $103M Fund). But VentureOne and Ernst & Young have said that investors are not overspending on cleantech startups. The median cleantech investment in 2007 was around $7.5 million, which is about the same as median deals in other sectors.

Representatives of Advanced Technology Ventures could not be reached for comment.