Pun notwithstanding, solar is hot.

Solar Power 2006 this week in San Jose, California was, by virtue of its 9,000 person attendance, the largest business-to-business and business-to-consumer solar expo and conference in U.S. history.

The show had five times as many registrants as last year, and 55 percent of this year's attendees were from outside the traditional "solar chain" of manufacturers, distributors, and installers, according to organizers. The finance sector alone accounted for more than 300 delegates, representing name-brand technology venture capital firms such as Kleiner Perkins and investment banks like J.P. Morgan and Morgan Stanley.

"The financial industry was here, government was here, entrepreneurs from Silicon Valley were here and the public was here," said Rhone Resch, president of the Solar Energy Industries Association. "Solar is no longer a curiosity; it is an industry."

Seats filled for keynote addresses >>

There was a level of optimism not seen in solar for the last twenty years. Many pundits and vendors agreed the stars were aligning for solar, with less expensive technologies, increasingly limited supply of fossil fuels and a confidence that historic subsidies in the industry weren't even going to be necessary for long.

"Explosive growth" in the industry could come in the next few years, said Vinod Khosla in a keynote address. Khosla is major solar investor widely considered to be one of the most successful venture capitalists in the world. And "I'm not asking for subsidies, I'm saying we'll compete," he said.

Subsidies were examined a panel discussion with leading solar venture capitalists. In another telling metric, it was often tough to find seats at the panels. Rarely have we ever seen people turned away from breakout sessions by capacity crowds, but that was the case here.

Activities rotated around the show floor, which, despite the odd geeky component vendor, featured more actual, shipping products than simply the emerging technologies of years past.

Urecon hawked pre-insulated pipe >>

Across the aisle, Sharp touted new consumer photovoltaic panels, streamlined mounting hardware and a new consumer marketing thrust; its towering two-story booth suggested this wasn't your father's solar show >>

Bless the vendor (there's always one) that splurges on a popcorn machine ... in this case, kudos to Power-One, purveyors of fine DC-DC and AC-DC power conversion products >>

When open, the floor itself was always busy, even without free food >>

Among the more interesting announcements were dueling assertions from SunPower (NASDAQ: SPWR) and Kyocera Solar (NYSE: KYO), each claiming leadership in photovoltaic solar cell efficiency. While neither had formal news at the show, flexible thin film solar vendors Konarka and XsunX (OTCBB: XSNX) were among companies getting significant buzz in the sessions. Nor could you go far at the show without seeing or hearing about performance monitoring startup Fat Spaniel Technologies, whose technology was featured by many solar vendors on the show floor. The company had just closed a $7M first round.

As always, vendors and others hosted their own events outside the conference. Attendees, investors, press and analysts mixed it up one night at a local restaurant, courtesy of a PR firm representing a number of companies at the show.

Thomas Dinkel, VP sales (L), and Richard Eckman, co-founder and director of operations (R) of Fat Spaniel Technologies illustrated that they're neither fat nor canine >>

Brian Gallagher, Delaware Million Solar Roofs Coordinator (L), Christopher Cook of SunEdison (C) and Adam Browning of the Vote Solar Initiative (R) got friendly >>

The show itself culminated in an address by California Governor Arnold Schwarzenegger - who's become something of an action hero for the industry, given that California is now home of the largest solar energy program in the country.

The Republican governor received ovations several times for his passage of environmentally friendly regulations.

"This is really incredible," he said. "I feel the energy here, I feel the electricity but it's solar energy I feel here."