See-Through Solar Hack Could Double Panel Efficiency

If there's one thing most people know about solar cells, it's that they are too expensive.
Now, MIT researchers think they may have found a way to double the performance of solar arrays with cheap dyed glass and some tricks borrowed from fiber optics.

Their so-called solar concentrator could be placed on top of existing solar arrays. It could capture some wavelengths of visible light and guide them to high-voltage solar cells on the edges of the array, while still allowing the infrared light that largely powers current solar systems to pass through.

"If you stick one of these on top of existing solar panels, we think we could nearly double the performance of these systems with minimal added cost," said Marc Baldo, the lead researcher on the work.

The new research, published tomorrow in the journal Science, is another major advance in solar energy, a field that's received renewed interest due to concerns about climate change and rising fossil fuel prices. The new MIT technology marries the science behind two of the most promising ways of harnessing solar energy: light concentrators and thin-film solar cells.
Companies like SolFocus, which has raised $95 million, are using mirrors to concentrate sunlight on small amounts of photovoltaic cells. They can generate a lot of power, but rely on expensive sun-tracking mirrors. Another hot research area of solar research is thin-film solar, which uses dyes to print solar cells on cheap plastic. Putting the two technologies together could be a new way of making solar power cheaper. Current PV generation costs about 20 cents per kilowatt hour, several times more expensive than coal, wind and natural gas power generation.

If Baldo's technology scales up and can get past the inevitable engineering hurdles, it could help drive that kilowatt hour price closer to the market price for electricity, which would undoubtedly drive uptake.

"If they can solve the engineering issues, then this would very much help with the efficiency and cost of solar cells," said Marc Bünger, research director at Lux Research.

Baldo's concentrators consist of a simple piece of glass coated with dye. The glass concentrates the sun's rays by directing light almost like a fiber optic cable does. Sunlight enters the glass and is absorbed by the dyed molecules in the glass. When the dye molecules reemit the energy, it enters waveguides that send the waves to the edges of the glass.

Fundamentally, Baldo said that his organic concentrators, so named because their dyes contain carbon, help solve a fundamental problem that solar arrays have had: They have two very different functions that require different types of materials.

"Solar cells have got to absorb light and generate electricity and what we tried to do was separate those functions," Baldo said. "It doesn't make sense to use a really beautiful electronic material like silicon in huge fields to absorb light. Lots of things can absorb light, like paint."
Using a cheaper material to do the light absorbing allows the most efficient energy generating materials to be used in much smaller quantities.

Beyond driving costs down, the see-through nature of his technology means that it could integrated into buildings or products. That gets designers and architects excited but Baldo's not so sure that's the most effective way of deploying the concentrators.

"You could put them on plastic and roll it up. You can tune the color to what you'd like. Architects get really excited about this stuff," Baldo said. "But as an engineer, I'm not sure how cost effective it is to to do solar windows."

Because the technology is simple and inexpensive, Baldo thinks it will be easy to manufacture and could be deployed in the field within three years. Towards that end, colleagues of his at MIT have spun out a new company, Covalent Solar, to commercialize the technology.

via Wired