Editor's note: The future of cleantech technologies will be further discussed at VERGE @ Greenbuild, November 12-13 in San Francisco.

The cleantech industry, at least as the term has come to be defined, is about a dozen years old. That’s adulthood, if not middle age, in technology years, and it hasn’t exactly been a charmed life. The markets for clean energy, transportation, water, and materials have evolved in fits and starts. There’s been a lot of hype, an impressive amount of progress, and a great deal of pushback in the form of political controversy and an industry shakeout that is natural to every emerging technology.

Ron Pernick and Clint Wilder have been watching it all from their perch at Clean Edge, a 12-year-old research and advisory firm focusing on clean technology. (Note: Pernick and I co-founded the company in 2000, though in recent years I have been involved primarily as an advisor.) Five years ago, the two co-authored The Clean Tech Revolution, one of the first books to frame the cleantech business opportunity. Now comes the sequel, Clean Tech Nation: How the U.S. Can Lead in the New Global Economy. It takes stock of the cleantech marketplace and what it will take for the United States to be a competitive player in the years ahead.

I recently talked with Pernick and Wilder about the state of cleantech, the political reality, and the outlook for cleantech markets overall. Here's an edited version of that conversation.

Joel Makower: Things have changed a lot since your last book. I was wondering if we could start off by getting your take on the state of cleantech since The Clean Tech Revolution.

Ron Pernick: The biggest change has been the politicization and partisanship of cleantech. I think if you look at the city level, at the state level, there's a lot of support for cleantech, but I think when you get to the federal level, and right now if you look at the national campaign that's being waged, both clean and green have become, in many ways, four-letter words. So, that's one of the huge shifts.

The other big shift is on the industrial side of the equation. While all of these venture capitalist-backed companies are getting funding, not all of that has come to fruition. On the other hand, the large industrials, from GE to General Motors to Siemens — that's where we're seeing a lot of activity now. We're looking at numbers that show it's becoming an increasingly large, double-digit percentage of major corporate and large government activity.

So, for us, five years later, whatever you want to call cleantech — green tech, sustainable tech, advanced energy, whatever — the industrials have embraced it and they see it as their next major push.

Clint Wilder: To me, a big historical moment in this industry was Total's purchase of the controlling interest in SunPower. So you have one of the world's largest oil companies saying, "Hey, we're in the energy business, and these guys at SunPower have assets that we see as key to our role as an energy company moving forward in the next decade and century." I think you will see that with a lot of other large companies, saying, "We're not looking at this election cycle or this particular government loan to whatever company. We're looking at cleantech as a long-term business proposition.”

Next Page: A matter of policy