December 5th, 2008 · No Comments

By John DeFore

Scientists at Rensselaer Polytechnic Institute believe they’ve made another step toward the economic viability of solar power with a coating that allows “near perfect” absorption of sunlight.

The Institute recently announced results of a project funded by the Department of Energy and the Air Force’s research department, in which researchers led by Shawn-Yu Lin developed a new anti-reflective coating for solar cells that captures 96.21% of the sunlight hitting them — a huge boost over the light-gathering abilities of uncoated silicon cells, which reflect about a third of incoming light.

That’s news of a sort that might make an engineer jump for joy. But a second aspect of the discovery, which is detailed in a paper published by the journal Optics Letters, should wow even ordinary folks who have daydreamed about solar energy: Lin’s coating might make worries over the angle of the sun a thing of the past.

While today’s solar installations must be placed in areas that get maximum direct sunlight — meaning only certain parts of your roof will work well, and that large-scale installations require electricity-consuming motors that move panels in sync with the sun’s path — the seven-layer coating Lin’s team has developed should mean panels can be positioned at any angle and absorb nearly all the light hitting them. Seven layers of silicon dioxide and titanium dioxide nanorods are stacked up in the coating, each of which gathers light from a certain angle, and working together they have the effect of “bending” sunlight toward the material below.

While the innovation only affects how much light gets to the actual energy-generating cells that are coated, not the efficiency of those cells, researchers say that the coating “can be affixed to nearly any photovoltaic materials for use in solar cells,” so that new, more efficient photovoltaics can benefit from it as well.

Lin has told reporters that, pending negotiations with manufacturers, the coating could be on the market within two or three years, and that it shouldn’t cost more than two to four percent above the cost of today’s solar cells.

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