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Solar-power researchers at the Massachusetts Institute of Technology (MIT) have been very busy in their labs lately, and not without significant fruits for their labors. Two projects promise to elevate solar power from an expensive and cumbersome alternative to an affordable and unlimited energy source.

SOLAR POWER GOES GREEN-LITERALLY!
Relying on the process of photosynthesis occurring in plants for inspiration, MIT Professor of Energy Daniel Nocera has found what he calls “the nirvana of what we’ve been talking about for years.” His process for storing solar energy requires no more than natural, non-toxic materials that provide power both day and night.

“Now we can seriously think about solar power as unlimited and soon,” he says. Along with postdoctoral fellow Matthew Kanan, Nocera employs the sun’s energy to split water into hydrogen and oxygen gases. Afterward, the gases recombine within a fuel cell, forming carbon-free electricity.

At the heart of the process is a unique catalyst comprising cobalt metal, phosphate, and an electrode placed in water for separating oxygen gas from water (Fig. 1). A second catalyst such as platinum separates the hydrogen gas.

When electricity from a solar cell or any other source travels through the electrode, the cobalt/phosphate catalyst forms a film on the electrode and produces oxygen. Paired with a hydrogen catalyst, the system replicates the water-splitting reaction that commonly occurs during plant photosynthesis.

Electrolyzers, components that split water with electricity and are commonly associated with industrial applications, are currently available. However, they are expensive and require non-benign environments foreign to the conditions under which photosynthesis operates.

According to Nocera, “The new catalyst works at room temperature, in neutral pH water, and it’s easy to set up. That’s why I know this is going to work. It’s so easy to implement.”

Funded by the National Science Foundation and the Chesonis Family Foundation, Nocera’s research falls under the umbrella of MIT’s Solar Revolution Project. The end goal of this venture is to make large-scale deployment of solar energy a reality within 10 years. For more information, e-mail Nocera at nocera@mit.edu.

WINDOWS THAT WORK-LITERALLY!
MIT’s Esther and Harold E. Edgerton Career Development Associate Professor of Electrical Engineering Marc A. Baldo not only sees through windows, he also foresees powerful potential around their edges. He and his researchers have found an alternative to large solar panels for harnessing solar power, an approach that may enable common windows to power a home or office.

Using optical techniques developed for lasers and organic light-emitting diodes (OLEDs), the researchers have created a solar concentrator that allows some measure of control over light absorption and emission. The MIT concentrator consists of a mixture of two or more dyes in specific ratios that the researchers apply or paint onto a pane of glass. The dyes absorb light hitting the glass across a range of wavelengths. Then, the dyes re-emit light at different wavelengths and transport it across the pane to small solar cells at the edges (Fig. 2).

“Light is collected over a large area and gathered or concentrated at the edges. Rather than covering a roof with expensive solar cells, the cells only need to be around the edges of a flat glass panel,” Baldo says. “In addition, the focused light increases the electrical power obtained from each solar cell by a factor of over 40.”

Baldo and his team claim that their system is simple to manufacture, and they forecast commercial availability within three years. Of particular note, their system can interface with existing solar-panel systems to offer a 50% efficiency boost at minimal cost. For further details, contact Baldo via e-mail at baldo@mit.edu.