New Approach to Solar Concentrators

Researchers at MIT (see post below)
have developed a novel way to concentrate sunlight for solar cells that
doesn’t involve mirrors and tracking mechanisms. They use a system of
glass and coatings to guide and collect light at the edges of the pane
where solar cells can be positioned. Team leader Marco Baldo explains
their innovation in the video.

His group uses an organic solar concentrator, as reported on in Science.

“Light is collected over a large area [like a window] and gathered, or concentrated, at the edges,” explains Baldo.

As a result, rather than covering a roof
with expensive solar cells, the cells only need to be placed around the
window’s edges. An added benefit is that the focused light increases
the electrical power attained from each solar cell “by a factor of over
40,” according to Baldo.

MIT’s solar concentrator entails a mixture of two or more
dyes coated onto a flat panel of glass or plastic. The dyes work
together to absorb light across a range of wavelengths and, then,
re-emit it at a different wavelength and transport nearly all of it to
the pane’s edges. Solar cells placed around the panel’s edges then pick
up this concentrated light energy.

Similar solar concentrators were developed in the 1970s by
impregnating dyes in plastic. The idea was abandoned, however, because,
among other things, too much light was lost en route and never
reached the edges. MIT has overcome this obstacle by mixing the dyes in
specific ratios and applying the mixture only to the surface of the
glass, allowing some level of control over light absorption and
emission.

Says Jon Mapel, an MIT research team member:

“We made it so the light can travel a much longer
distance. We were able to substantially reduce light transport losses,
resulting in a tenfold increase in the amount of power converted by the
solar cells.”

MIT’s solar concentrator improves on concentrators in use today. Baldo notes,

“[Existing concentrators] track the sun to generate high
optical intensities, often by using large mobile mirrors that are
expensive to deploy and maintain. Solar cells at the focal point of the
mirrors must be cooled, and the entire assembly wastes space around the
perimeter to avoid shadowing neighboring concentrators.”

Baldo says his team still needs to improve the concentrator’s
durability and efficiency (estimated at 6.8 percent) before it can be
taken to market. He estimates these changes and more can be
accomplished within three years. He even has plans to adapt MIT’s
concentrator so it can be added to existing solar-panel systems to
increase their efficiency by 50 percent at minimal cost. He says this,
in turn, will substantially reduce the cost of solar electricity.

In addition to Jon Mapel, Baldo’s research team also includes
Michael Currie and Timothy Heidel, also graduate students in MIT’s
Department of Electrical Engineering and Computer Science. The team’s
fifth member is Shalom Goffri, a postdoctoral associate in MIT’s
Research Laboratory of Electronics.

Mapel, Currie and Goffri have started a company, Covalent Solar, to develop and commercialize the new technology. Earlier this year Covalent Solar won two prizes in the MIT $100K Entrepreneurship Competition. The company placed first in the Energy category ($20,000) and won the Audience Judging Award ($10,000).