Dyeing for more solar power

The main impediment to the widespread use of solar power – clouds and nightfall aside – is the cost of the silicon cells that actually convert the sun’s rays into electricity. To keep the expense down, people have been searching for ways to minimise the size of solar panels relative to the amount of light they can harvest. Often, this is done using clunky pieces of kit called solar trackers, which tilt an array of mirrors so as to direct large amounts of sunlight onto small, high-performance cells.

An alternative now being tested is called the luminescent solar concentrator (LSC). Instead of focusing the sun’s rays on a cell, as a solar tracker does, an LSC first traps them, wherever they have come from, and then delivers them to the cell using what is known as a waveguide. No moving parts are involved. A group of MIT researchers using this technology believe it could boost a solar panel’s efficiency by up to 50 percent and formed a company, Covalent Solar, to develop the technology.

The team has spent two years identifying organic dyes, painted onto glass or plastic that can effectively concentrate the sun’s light onto solar cells, enabling them to produce more electricity from fewer cells. The dyes basically reflect the light (technically, it’s actually absorbed and then sent back out), so that some of it is trapped inside the plane of glass. With the help of a scientific principal called “internal refraction”, which is the same principal that keeps light trapped in optical fibers, the light bounces to the edges of the glass, which have been equipped with strips of solar cells that convert it into electricity.

Integrated into solar panels available today, the technology could potentially boost the amount of light the panels convert into electricity by as much as 50 percent so consumers would get more electricity for their money.

The company hopes the technology could be used for both rooftop systems and for large solar farms and even one day could be integrated into windows, where a greyish tint would let in 20 percent to 30 percent of the outside light, while simultaneously directing the light toward solar cells around the window’s edges. Covalent Solar expects to bring its first product to market in three years.

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