Breakthrough: An Interview with Solar Power Expert Ken Zweibel

Ken Zweibel co-authored the recent attention-grabbing Scientific American piece on solar power, "A Grand Solar Plan." He is an international authority on thin film solar, is widely published (including two books), and is a popular speaker on solar policy issues.

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Compressed air has been used reliably in Germany to store energy since 1998 and Alabama since 1991. Do you it can be ramped up to an even larger scale?

Yes. These things have good size flexibility. At the smallest they can be about 10 megawatts -- the size of the gas turbine - but other than that there is no constraint on size except for the size of the cavern or aquifer that stores the compressed air, and these are of similar volume to what's already being used to store natural gas.

What about the infrastructure for transporting the electricity?

We visualized a high voltage DC distribution line from the Southwest, and visualized compressed air storage pretty much everywhere in the country.

Is there any risk of being too dependent on a single source of energy? It seems like these lines would be vulnerable to a terrorist attack, putting the whole country in trouble.

Solar itself is so distributed that there's no risk there. Blowing up individual panels would have no impact. The soft spots would be the high voltage DC and compressed air. But the loss would only be on one small part of the grid, because you need so many of these DC lines. Terrorists would have to work for days and days to have a major impact. So in fact there's no real soft spot for terrorism -- just the opposite. And it's a heck of a lot safer than our current options.

At the end of the article, you talk about how your plan for solar could not be done with a price for carbon. Why are subsidies necessary?

I think the problem is that solar is more expensive than most other low hanging fruits, yet it's the biggest part of the solution. We have to be willing to break the mold and take a chance on backing solar, and not just depend on the marketplace and regulatory influence.

We've been arguing for a large investment, but critics say the government shouldn't pick winners and losers, that it should be left to the marketplace.

You don't have to pick winners within solar. You can do a broad approach. But you have to be able to see that without the solar solution you can't do it.

What do you think of the controversial new Nature commentary suggesting that the IPCC underestimated the emissions reduction challenge by at least half? There have been attempts to discredit the authors on popular environmental blogs like Grist.

I didn't look at Grist or anything, but I find the Nature articles quite mainstream. I thought everyone knew the climate change models already assumed huge improvements in their baseline and that there were plenty of issues with double counting. The Nature articles are right. This is just the normal stair step progress to coming closer to the truth.

The New York Times recently reported that NREL has been starved for funding and equipment. You've been there for such a long time -- are you feeling optimistic about where things are headed?

I am optimistic. What the Europeans and Germans have done to stimulate the market has changed the face of PV. They've catalyzed innovation by funding entrepreneurs to do new technologies. That's what we were developing at NREL for the past 25 years. We had them in the pipeline but they weren't getting out because no one was pulling on the other end.

But I would caution that there isn't going to be another crop of innovation overnight. We've been solving some really challenging technical problems over the past 25 years. But this round of technology is enough. This will do it if we fully implement it.

Solar thermal is a lot cheaper than PV. Say more about the technological challenges with solar thermal. Could price come down low enough for China to start implementing it?

The lowest number is 16 cents per kilowatt-hour before production tax credit. And coal is, what, 5-10 cents? But the lowest cost PV is also at 16 cents. There is no separation between solar thermal and PV except at the second order level. The horse race is neck and neck. First Solar's recent announcement with Southern Cal Edison of a system that meets the California market price referent for daytime electricity is an example of that.

I know that the road map to half the cost of today's PV is very solid. Getting down to $2 per watt installed PV is going to happen. Whether it's four years or eight years I don't know, but 16 cents will soon be eight. In the meantime the problem solar thermal faces is inflation. It's made out of basic commodities like steel and glass, so it's vulnerable to increases. Still CSP is a crucial part of the future of solar energy and has some advantages with hybrid systems and thermal storage.

I think $10 billion a year over 40 years is not a lot of money, but in Washington they say there's no money for this. How do you get this done politically?

That's the key question. I'm starting the American Solar Action Plan (ASAP) to help convince the public and others that the grand solar plan from Scientific American makes sense and should be done. People aren't aware of it because it's a disruptive new technology. This is the only field I've ever been involved with where disruptive technologies get the least attention.

The issue with solar is that you're paying high capital costs. But you're avoiding the uncertainties of fuel costs, and you're getting a stream of energy at a fixed priced. As long as we can get in the same ballpark economically, people will demand solar energy, and the government will respond, just like it did in Colorado where a groundswell of public support led to a significant renewable portfolio standard.

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