On December 5, a panel of experts gathered at the Ferry Building in San Francisco, California, for the third Principal Voices roundtable of 2006. The guests discussed the future of alternative energy sources in front of an invited audience.

An essay about the discussion can be read here, and there is also a full transcript of the event here.

Following is a short series of key quotes from the participants:

Vinod Khosla, head of high-tech and alternative energies investment company Khosla Ventures

"I'm happy to tell you that I'm an optimist in completely believing that that time and that technology is here today. There is no economic reason -- forget the environmental considerations -- that we can't have cheaper fuels than gasoline today."

"So, we can have this alternative. Why isn't it here? The best way to explain it is that every time the price of oil changes by $4, it's worth in asset value to Saudi Arabia a trillion dollars -- for a country with a fraction of the population of California. So there are powerful economic forces focused on keeping the playing field un-level."

"If a genie gave me one wish I'd ask for a carbon tax or a carbon cap and trade system, because that would help all the alternative technologies equally and would truly be valuing the pollution that these fossil fuels are putting in our air."

"Oil constrains lots of geo-political activities that would make a lot of sense from a political point of view but can't be done because of the realities of oil."

Bill Gross, founder of high-tech companies incubator Idealab

"The total energy used by the whole planet is 15 terawatts. If you divide that by the 6.2 billion people on the planet that's 2,300 watts all day long for every person alive. But that's very unevenly distributed. There's some people with much less than that and there's us in this room that are probably using closer to 10,000, maybe if we have multiple cars 20,000 watts -- continuously, all day long for every member of our family."

"It's very exciting to be alive at a time when these technological solutions are actually in reach and the investment is going on to make that happen."

"The infrastructure that we have in place for the other energy industries was developed over a century. We are trying to repeat that in only five or 10 years. So it's hard."

"Renewable energy investors -- that was an oxymoron a few years ago. Now it's a hot topic and everybody's rushing to get in... It's great that these renewable energy technologies can actually be built as start-ups, unlike a nuclear power plant or a coal plant, that you can't do a start-up around. So the challenge is matched by the entrepreneurial fervor."

Harrison Fraker, Dean of the College of Environmental Design at the University of California, Berkeley

"I think that the challenge that we have is a whole systems integration and design problem. We have the technologies, they have been isolated into certain silos and thought about separately."

"The numbers are very, very exciting. It's possible at a scale of anything from 5,000 units to 10,000 units on about a one kilometer square to make neighborhood entirely self sufficient. By the way, if you can also pump into the grid you also make money. These neighborhoods now are energy generators and you can charge back to the grid."

"There's nothing idealistic about the things we're doing in China. We're using off-the-shelf technology. My point is that when you integrate them together and use them wisely as a whole system, they become cheaper and more cost-effective. That's the purpose for operating this way -- it's not to create some idealized community, it's trying to use existing technology in a smarter way."

Martin Roscheisen, head of solar power company Nanosolar Inc

"You feed into the electric infrastructure at the 20,000 watt level, so you deal with very different price points than with nuclear power. And you compete without subsidies at that level. You don't have to go up on 10,000 residential rooftops, which is going to be expensive one way or the other. It's one of these anchor points where solar power will increasingly become visible, and at the grid parity price points will compete with traditional energy sources."

"We're leveling the playing field in terms of competing at a clean level -- it's clearly a public policy issue... We are working very hard to do our part in terms of cost efficient solar electricity systems."