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ArsTechnica wrote:At the American Association for the Advancement of Science meeting, the morning started off with a panel discussion that was intended to provide some insights into where we should be focusing our research efforts when it comes to the production and use in energy. To set the stage for that, many of the speakers described the challenges we face in coming to grips with the energy needs we'll be facing in the next several decades. As was the case with several other recent analyses, the raw figures can provide a lot of reasons for pessimism, as we'll reach some pretty severe limits if we simply try to extend current technology. Referring to current tech, Los Alamos' John Sarrao said, "very exciting things are happening , yet you can't get there from here."

Caltech's Nate Lewis described the "there" in some detail. Right now, the world's energy consumption is in the 15TW range, and everyone expects that to double every few decades. Under an optimistic assumption that we can implement efficiency measures that cut our needs in half, that still means we ideally need to come up with about 15TW of generating capacity that doesn't emit carbon. That's going to take building a Gigawatt-sized nuclear reactor a day for forty years, which means that nuclear's not going to do it, at least not alone. Even at 100 percent use and efficiency, most of the renewable sources—wind, hydro, biomass—won't get us much more than a Terawatt. In Lewis' view, that meant that, while we shouldn't ignore the other technologies, our only real option is solar, where an hour's worth of incoming solar radiation can power the globe if it could all be harvested.

For the US alone, we'll be looking at supplying about three Terawatts of power. Lewis said that solar thermal is now the cheapest way to supply electricity on utility scales, but even the recent announcement of a huge solar thermal build will simply provide a bit more than a gigawatt when complete several years from now, nowhere near the pace we need. Alternately, we'd need to be installing a million roof installations a day (assuming about 10 percent efficiency)—and then start covering all our roads with solar roofs. Unfortunately, most photovoltaics are using materials like Cadmium-Telluride mixes that simply aren't available in the kind of quantities we'd require. Even if the entire world's annual supply is given over to solar equipment and optimistic efficiency estimates are used, it's simply not going to supply our power needs.

Meeting the challenges with nanotech

That set of depressing figures set the stage for the focus of the talks: if our current approaches won't work, what should we be working on in the research labs? The basic message (with a few exceptions) is that we have to focus on new ways of harvesting solar power, and figure out how to store and distribute it efficiently, and what next-generation technologies might provide that.

The easy model, according to Lewis, is nature, which harvests sunlight using cheap and abundant elements like iron, and stores it in easily transportable chemical compounds. The recent solution of the structure of Photosystem II has allowed us to make chemical compounds that mimic its active site. The problem, however, is that even the most efficient plants only operate at about two percent efficiencies.

Both Lewis and Berkeley's Paul Allivisatos felt the answers would lie in nanomaterials. Conventional silicon photovoltaics require single, large crystals, which are hard to generate. Although we're just developing the ability to manufacture nanoparticles, Allivisatos felt that, ultimately, small particles would be easier to make than large crystals. These particles have some interesting properties related to the fact that they're often smaller than the typical wavelength of electrons in the parent material. To an extent, this allows electrons to ignore boundaries between neighboring particles, and boundary effects at semiconductor-electrode interfaces. It's possible that these nanoparticles wouldn't even require careful ordering, which Lewis suggested could ultimately lead to materials like photovoltaic paint.

Allivisatos said that nanoparticles can be formed that harvest far more of the energy in each photon, by structuring materials to ensure that some of the energy that's normally lost as heat gets used to knock an electron free instead. Other nanoparticles are being used to directly split water in his and Lewis' lab.

Solar thermal didn't come out of this analysis looking that great; its efficiency is two orders of magnitude lower than photovoltaics, and it currently requires lots of moving parts. But Lewis said that materials scientists are about 3/4 of the way to having materials that convert heat to electricity at a rate where their use in solar thermal devices would make sense. In addition to eliminating the moving parts, these materials would have a huge economy of scale, as they could replace the moving parts in heating and refrigeration applications, as well.

So from the generation side, there were several key messages about where we should be putting our money: go with solar, increase efficiencies using nanoparticles, find a way to use cheap and abundant raw materials, and think seriously about thermoelectric materials.

Moving and storing the power

Producing the power is only part of the problem; the fossil fuels we've built our energy infrastructure around are easy to transport and store. Electrons aren't, and we don't currently have an efficient way of converting them to fuels. And, if we're relying on solar, as Lewis put it, "he that cannot store will not have power after four."

Yet-Ming Chiang of MIT talked about the potential of battery storage, and he started his talk with a slide that showed the relative sizes of the US automotive and electric industries, which indicated they were about the same; the battery industry, in contrast "is about the size of a lug nut," Chiang said. That needs to change, because batteries can have applications in both.

Chiang shared figures that showed the effect of replacing our current auto fleet with one filled with plug-in hybrids that have a 40-mile range: imported oil would drop to 1980s levels, and carbon emissions to 1990s levels, all by 2030. He argued that we already have good funding and research mechanisms for bringing new battery tech to market—he pointed to his own use of DOE money to develop olivine-based batteries, which went from initial funding to 20 metric tons of production in five years.

What we do need, he argued, is to develop the ability to to vastly expand the manufacturing capacity for the latest battery technology. If we can, he argued, we can start putting the batteries to use for storage on the grid, which has a similar set of response time and power flow needs as vehicle batteries. Test projects, with 2MW of rack-mounted batteries in a portable trailer, are already being tested in the field.

John Barrao of Los Alamos talked about moving the power from renewable sources around the grid efficiently using superconductors. He showed figures indicating that the average US power customer experiences 214 minutes of outages a year, at a cost of $79 billion to our economy; the equivalent figure for Japan is six minutes a year. Superconductors, he argued, should have an important role in modernizing the US grid. We're now on the second generation of superconducting wires, which have reached lengths of up to a kilometer.

Barrao didn't point to any specific area of superconducting research that had more or less promise than others, but he highlighted how there's been an explosion of new classes of materials developed in recent years, which he ascribed to our ability to identify basic properties—a layered structure, variable valence states—that have allowed us to identify materials that hold promise. "Our paradigm shift has been moving from superconducting by serendipity to superconducting by design," he said. The more we fill in the range of materials that work, the better shape we'll be in to pick those materials that have the properties we need for manufacturing and deployment.

These were not the only topics covered in this session—an Indian researcher described his country's consideration of various breeder reactor designs, and someone from Argonne labs took the session on a quick tour of all our energy options—but these were the talks that seemed to provide the strongest hints of where our energy research will be going. Allivisatos ended the session with a note of optimism: "the best and brightest minds want to work on this stuff," he said, "the first thing we have to do is just not screw it up."