Intensifying the Sun  

Technology Review has a new article on concentrating solar PV - Intensifying the Sun" - a "new way to concentrate sunlight could make solar power competitive with fossil fuels".

In his darkened lab at MIT, Marc Baldo shines an ultraviolet lamp on a 10-­centimeter square of glass. He has coated the surfaces of the glass with dyes that glow faintly orange under the light. Yet the uncoated edges of the glass are shining more brightly--four neat, thin strips of luminescent orange.

The sheet of glass is a new kind of solar concentrator, a device that gathers diffuse light and focuses it onto a relatively small solar cell. Solar cells, multilayered electronic devices made of highly refined silicon, are expensive to manufacture, and the bigger they are, the more they cost. Solar concentrators can lower the overall cost of solar power by making it possible to use much smaller cells. But the concentrators are typically made of curved mirrors or lenses, which are bulky and require costly mechanical systems that help them track the sun.

Unlike the mirrors and lenses in conventional solar concentrators, Baldo's glass sheets act as waveguides, channeling light in the same way that fiber-optic cables transmit optical signals over long distances. The dyes coating the surfaces of the glass absorb sunlight; different dyes can be used to absorb different wavelengths of light. Then the dyes reëmit the light into the glass, which channels it to the edges. Solar-cell strips attached to the edges absorb the light and generate electricity. The larger the surface of the glass compared with the thickness of the edges, the more the light is concentrated and, to a point, the less the power costs.

Baldo, an associate professor of electrical engineering, published his findings recently in Science. On their basis, he projects that his solar concentrators could be made big enough for the electricity they help generate to compete with electricity from fossil fuels. Indeed, says Baldo, panels equipped with the concentrators "could be the cheapest solar technology."