Saul Griffith opened with "awesome" and Amory Lovins ended by "firing-up" jaded delegates.
Griffith, the huggable hirsute MacArthur "genius", told the audience: "The future we are going to create can be spectacularly beautiful and interesting."
He then proceeded to show off a few of his inventions - by turns brilliant and bizarre - from his Makani Power company.
A carbon fibre wind turbine aeroplane that takes off autonomously and generates 6-8kw by doing 200mph barrel rolls at 5,000 feet.
It's certainly innovation, and there's certainly room for such blue sky thinking that may never be practical enough to reach commercial scale. But Griffith, a great fan of robotic technology, is chasing MWs with this technology.
"This is pretty radical," Griffith admitted. "You need a good reason to do this. We're projecting about 3c/kwh subsidised. Twice the capacity factor of existing wind tech. This looks like a fabulous technology for offshore. We originally had Google funding. We've since got ARPA-E funding to prove out all of the remaining things."
He wasn't clear on now much money he is chasing to fund the next stage of development, but the money spent on this project so far made the VCs in the room inhale sharply.
"This sounds wild, this is expensive. You don't get much change from $20m to get where we are here today. You're still a lot of money away from the MW machines.
"I'm not sure this is something you can do with venture financing," he admitted, sending a wave of relaxation through the audience.
"You do need public private partnerships to do this. Government funding in the early hard R&D stages and large corporates to help this through to commercial technology. Conceptually this is proven out but there is still a long way to go from 20kw wind that fly 24 hours to MW [machines] that fly 20,000 hours."
Then he showed one of his more recent designs in a "my job is more fun than your job video" - a robotic tracking heliostat for concentrated solar applications that performed at better than .1% precision and would reduce costs by 20% compared with traditional heliostats and increase performance by 30%.
It's a compelling technology proposition when heliostats accounting for roughly one-third of solar thermal costs.
But although ARPA-E's EnergyInnovation Summit in DC last month may have been ready for Otherlab's fluidic heliostat arrays, the forum's audience less so.
Griffith said they were pursuing the "typical R&D financing" with the DOE and ARPA-E, but also working with corporate partners on developing this technology.
"The cost models are excellent so I call up a friend in a top tier VC firm and say I've got this killer technology and he says, well there's a serious turd in the punchbowl this year, come back in a couple of years. This was about two weeks after Solyndra happened."
But just as investors were beginning to slouch in their seats again, Griffith gave them a shot in the arm with cost projections for his solar technology.
"It needs $3-$4m to get it to the stage where you're doing small real world rooftop tests. And then $20m plus to make this into a commercial technology. These numbers are larger than traditional VCs are ready for. I still don't think we've solved the funding problem for early stage energy technologies."
Griffith buoyed the audience, finally by telling them to be "awesome".
"Attack the customer at points of infrastructure change and let's make the world awesome again," he said. "Can everyone think that what we're doing is awesome? You are awesome! If your 10 year old doesn't think what you're doing is awesome, you're telling them the wrong story. As a group we've got to make it more exciting again."
Amory Lovins, just as awesome, also bearded but a bit less huggable, closed the two days of shop talk with an introduction to the new book from the Rocky Mountain Institute, Reinventing Fire.
Lovins said: "America's public energy conversation boils down to this, would you rather die of a) oil wars, b) climate change or c) nuclear holocaust, or d) all of the above or e) none of the above. What if we could make energy do our work without working our own undoing? What if we could have fuel without fear? Could we reinvent fire? Fire made us human; fossil fuels made us modern. Now we need a new fire that makes us safe secure healthy and durable.
"This has now been made possible. We humans are creating a new fire, not dug from below but flowing from above."
But the real message for the Cleantech Group's 10th anniversary forum in San Francisco arrived early in the proceedings from Wal van Lierop, co-founder of Chrysalix ventures in Vancouver.
He addressed the launch party with a gentle slap in the face. Cleantech, he said, was merely a marketing exercise and we are now witnessing a mainstreaming of clean energy.
He said that the 2008 global economic crisis had caused a shakeout in cleantech, which was a good thing. And since then, we've seen the rise of cleantech in China.
We've also seen the switch almost overnight to the prospect of cheap natural gas prices in the US for the foreseeable future.
What does this mean for cleantech 5.0, he asked? Cleantech will become less visible, creating a new club of green elephants (incumbents). He also said that there was a convergence between the hydrocarbon energy industry and the clean energy industry, as the oil and gas companies seek technology solutions to mitigate the impact of shale gas, overcome environmental barriers and produce more sustainably.
Technology will be used to clean up the hydrocarbon industry, he said.
It might not be the end of cleantech as we know it yet, but perhaps next year's forum will be all about convergence, marking a critical stage in the maturation clean energy.