The Open Table and SolarWinds IPOs, along with massive stimulus dollars, seem to be finally brightening the mood among investors.

"I'm optimistic," said Alain Harrus at Crosslink Capital eariler this week. He predicted one or maybe more greentech companies might try to go public in late 2009 and early 2010. Why? Despite the downturn in the economy, the federal government, local governments and several investor-owned utilties clearly support the industry. Governments will provide loans and utilities will be willing customers for smart grid technologies and solar equipment. Indirectly, utilities will also help industries like wind. Overseas, you see much of the same picture. The United Kingdom is issuing leases for offshore wind farms as a way to reduce coal consumption and increase employment and exports. Australia lacks water, so it wants to boost its water technology industry.

When asked, most investors speculate that Silver Spring Networks (which used to be named Real Time TechComm) could be one of the first to go public. The company has large contracts with PG&E and it can farm out a lot of its basic manufacturing to contract manufacturers. Relatively low capital expenses and a secure deal with a large customer: those are two things that were absent when A123 Systems put forth its plans for an IPO. But don't hold your breath: people have been waiting for the S-1 from Silver Spring for weeks, but it has yet to be filed, as far as a search tonight shows. Is it being prepared? Probably, but it's not public yet.

If Silver Spring does go public, it will underscore an interesting trend. So far, traditional VCs have not played a huge role in the 'big' green IPOs. First Solar was funded by a member of the Walton family for nearly two decades before going public. SunPower got life support from T.J. Rodgers and Cypress Semiconductor. Energy Recovery, the desalination outfit that went public last year, was funded by Norwegian investors. So far, the only two really big clean IPOs that have had VC money have been EnerNoc and Comverge. Like Silver Spring, both are smart grid companies.