Is MIT's Latest Solar 'Breakthrough' All Hype or a New Hope?

• MIT
• solar power
• alternative energy
• hydrogen

The Storage Breakthrough

Hydrogen is often thought of as a fuel for hydrogen cars, but its role is actually much broader: It's a way of storing energy. That's particularly attractive for solar power, the great weakness of which Kanan and Nocera, in their Science paper, call "the diurnal variation in local insolation"—in other words, the fact that the sun goes down each night.

It's worth noting that Nocera's current experiments didn't use solar energy—they simply ran off electricity from the grid. That's actually an advantage, since it means the same technology could be used to make hydrogen with wind turbines or other renewable sources like hydropower.

In Nocera's solar-based scheme, photovoltaic (PV) panels on a home would provide its residents with electricity during the day, while at the same time splitting water into hydrogen and oxygen. When the sun goes down, a fuel cell would combine the stockpiled molecules to continue to provide power. MIT's press release predicts that, within 10 years, "electricity-by-wire from a central source will be a thing of the past."

The problem of how to store solar energy—or any energy at a large scale—is very real. Batteries are simply too expensive and don't yet have enough capacity. The Andasol solar thermal plant in Spain will test one interesting option later this year: Liquid heated by its mirrors will be stored in what is essentially a giant Thermos, so that the plant can continue to generate six hours of electricity each night. Abengoa recently announced a similar plant in Arizona; thermal storage will power the air-conditioning usage peak that continues after sunset in the Southwest.

Nocera's scheme has several advantages, though. Because it can work on a small scale, it's suitable for distributed power in homes. Hydrogen is also versatile enough to be used in other applications, such as fuel-cell cars.

Next Steps

There's no question that finding a clean, cheap and efficient way of making hydrogen would be transformative—which is why the Department of Energy's Hydrogen Program is funding literally dozens of possible ways of doing it. The question is which one will be cheapest and most efficient.

Nocera says that, with the publication of these results, he's confident that scientists and engineers will rush to advance the design, pushing it toward practicality within the next 10 years. He may be on target, except that virtually every one of the hydrogen-production projects funded by the DOE has entertained similar hopes; otherwise they never would have obtained funding.

The next move for Nocera's team will be to build a more efficient version of their current device—one that reduces the physical distance between the two electrodes. Then they plan to design a version that is actually powered by PV panels. "The basic science is done," Nocera says, referring to the new catalyst. "Now it's engineering."

That, unfortunately, is the stage at which innumerable great ideas for alternative energy sources have met their demise. That includes earlier attempts to mimic photosynthesis by using the sun's energy to produce hydrogen—research that experienced a vogue in the 1970s when early proof-of-principle experiments showed promise. In that case, the engineering didn't work out.

Of course, that doesn't mean it won't work out this time, or that the new results aren't cause for enthusiasm. "The only people this isn't good news for is people who dig oil out of the ground," UC Irvine's Heyduk says. Mallouk's endorsement was even more direct: "I already e-mailed [Nocera] this afternoon to see whether the new catalyst would work in my system."

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