In his first 112 days as the U.S. Energy Secretary, Steven Chu has presided over unprecedented changes at the Department of Energy (DOE). The stimulus bill signed into law in February provided $39 billion to the agency–a sum that Chu acknowledges is straining the agency as it attempts to sort through proposals for distributing this money. The money is in addition to the agency’s yearly budget of about $25 billion. Most recently, President Obama’s proposed 2010 budget upped DOE’s budget by $400 million and called for increased spending on climate science and nuclear security, as well as support for many alternative-energy projects.

At a lecture at MIT on Tuesday, Chu, who won the 1997 Nobel Prize in Physics and is the former director of the Lawrence Berkeley National Laboratory, outlined his plans for reducing carbon dioxide emissions. In the near term, Chu said, the answer is improving energy efficiency. Better buildings could cut energy use in the United States by roughly one-third, he said. That would save more energy than is produced by all of the country’s nuclear-power plants, solar-power plants, and wind farms. The simple step of fine-tuning a building after it’s built–to ensure that things such as the heating, ventilation, and air-condition systems are working properly–could cut energy use in those buildings by 10 percent, according to Chu.

In the longer term, alternative energies can be a big part of the solution. But Chu noted that solar power, for one, is still far too expensive to compete with conventional power plants (except on hot summer days in some places, and with subsidies). Making solar cheap will require “transformative technologies,” equivalent to the discovery of the transistor, he said.

But Chu’s first months in office weren’t all about handing out money for new technologies. Technology Review’s energy editor, Kevin Bullis, sat down to talk with Chu about two of the most controversial decisions of the first hundred days. In an abrupt break with previous administrations, President Obama’s proposed 2010 budget eliminates funding for the controversial plan to store the nation’s nuclear waste at Yucca Mountain. The proposed 2010 budget also cuts funding for research into hydrogen fuel cells–a multibillion dollar initiative that was the focus of President Bush’s plan to develop future low-carbon-emissions vehicles. A researcher at heart, Chu discussed some of the technical solutions to storing nuclear waste and applications for fuel cells that might be more practical than using them to power cars.

Technology Review: There’s some 50,000 metric tons of nuclear waste scattered among 130 sites across the country. What are you going to do with that waste now?

Steven Chu: Yucca Mountain as a repository is off the table. What we’re going to be doing is saying, let’s step back. We realize that we know a lot more today than we did 25 or 30 years ago. The NRC [Nuclear Regulatory Commission] is saying that the dry cask storage at current sites would be safe for many decades, so that gives us time to figure out what we should do for a long-term strategy. We will be assembling a blue-ribbon panel to look at the issue.

[We’re] looking at reactors that have a high-energy neutron spectrum that can actually allow you to burn down the long-lived actinide waste. [Editor’s note: Actinides include plutonium, which can be dangerous for 100,000 years.] These are fast neutron reactors. There’s others: a resurgence of hybrid solutions of fusion fission where the fusion would impart not only energy, but again creates high-energy neutrons that can burn down the long-lived actinides.

TR: Is this to burn up existing waste? Or to deal with waste in future reactors?

SC: It could be for existing, but mostly for future waste. So we’re looking at, instead of the way we do it today, where you’re using 10 percent or less of the energy content of fuel, can you actually reduce the amount of waste and the lifetime of the waste.

TR: What about the existing waste?

SC: Some of the waste is already vitrified. There is, in my mind, no economical reason why you would ever think of pulling it back into a potential fuel cycle. So one could well imagine–again, it depends on what the blue-ribbon panel says–one could well imagine that for a certain classification for a certain type of waste, you don’t want to have access to it anymore, so that means you could use different sites than Yucca Mountain, [such as] salt domes. Once you put it in there, the [salt] oozes around it. These are geologically stable for a 50 to 100 million year time scale. The trouble with those type of places for repositories is you don’t have access to it anymore. But say for certain types of waste you don’t want to have access to it anymore–that’s good. It’s a very natural containment.

TR: Waste you know you don’t want to reprocess.

SC: Yes, whereas there would be other waste where you say it has some inherent value, let’s keep it around for a hundred years, two hundred years, because there’s a high likelihood we’ll come back to it and want to recover that.

So the real thing is, let’s get some really wise heads together and figure out how you want to deal with the interim and long-term storage. Yucca was supposed to be everything to everybody, and I think, knowing what we know today, there’s going to have to be several regional areas.

TR: That will deal with some of the transportation problems.

SC: Right. It makes it less of a problem.

TR: I know you’ve come out in favor of nuclear power. It’s been decades since any new plants have been constructed. What progress has been made so far in getting some new plants built?

SC: We’re now going to a two-step licensing. You license the generic plant, and then there’s a separate license for the site. And this helps speed along the process. Before, the way we did it is every plant was a new one.

A lot of this depends on some loan guarantee money, which will help.

TR: When might those loan guarantees become available?

SC: Well, sooner rather than later. I’m hoping within a year, but that’s just a wild guess. We’re pushing ahead. As you know, we’ve become very aggressive about trying to accelerate the loan process by a considerable amount. A factor of 5 to 10 is about the right amount. When I first came, I was told that the first loans would go out mid-2010. So they’ve now gone out, and there’s going to be another tranche of them that we’ll be vetting.

TR: No loan guarantees yet for nuclear plants.

SC: No.

TR: Are you referring to the loan guarantee to Solyndra? [Editor’s note: Solyndra is a solar company that received approval for a loan guarantee earlier this year.]

SC: Solyndra, for example. That means that there’s a commitment: if you can get the 20 percent financing, the thing’s yours. And there will be more announced this month.

TR: The hydrogen fuel-cell program has been scaled back in the proposed budget, and the emphasis has been changed from transportation to buildings.

SC: That’s right.

TR: It used to be thought, five to eight years ago, that hydrogen was the great answer for the future of transportation. The mood has shifted. What have we learned from this?

SC: I think, well, among some people it hasn’t really shifted [laughs]. I think there was great enthusiasm in some quarters, but I always was somewhat skeptical of it because, right now, the way we get hydrogen primarily is from reforming [natural] gas. That’s not an ideal source of hydrogen. You’re giving away some of the energy content of natural gas, which is a very valuable fuel. So that’s one problem. The other problem is, if it’s for transportation, we don’t have a good storage mechanism yet. Compressed hydrogen is the best mechanism [but it requires] a large volume. We haven’t figured out how to store it with high density. What else? The fuel cells aren’t there yet, and the distribution infrastructure isn’t there yet. So you have four things that have to happen all at once. And so it always looked like it was going to be [a technology for] the distant future. In order to get significant deployment, you need four significant technological breakthroughs. That makes it unlikely.

TR: So this is an example, perhaps, of picking a technology prematurely. Is there anything we’ve learned from that in terms of future policy?

SC: I wasn’t there when they started making this [decision]. I’m not sure it was deeply understood what was required. Now, having said that, I think that hydrogen could be effectively a “battery” in the sense that suppose you had a way of using excess electricity–let’s say a nuclear plant at night, or solar or wind excess capacity, and there was an efficient electrolysis way of turning that into hydrogen, and then we have stationary fuel cells. It could effectively be a battery of sorts. You take a certain form of energy and convert it to hydrogen, and then convert it back [into electricity]. You don’t have the distribution problem, you don’t have the weight problem. [Editor’s note: Storage tanks can be heavy.] In certain applications, you don’t need as many miracles for it to happen. If you need four miracles, that’s unlikely: saints only need three miracles [laughs].

TR: This application of fuel cells–is this a way, then, of addressing the variability of wind and solar power?

SC: Perhaps. I think the process we do have now that could work is pumped storage. If you have excess wind capacity, you pump water up the hill, and when the wind isn’t blowing, you could let it down into a small holding pond [using it to turn a generator]. Now, that’s only in places where you have hydroelectric facilities, so let’s say in the northern great plains, South Dakota and North Dakota, compressed air storage is something we should be looking at. The excess air is used to pump air down into a sealed cave. You use that, plus natural gas, to spin a turbine. The round trip efficiency of both of these technologies is between 60 and 70 percent of overall conversion. That’s very good for this massive-scale technology. If we’re going to go over 10, 20, 30 percent renewables that are variable, you need some storage mechanism.