MIT Researchers Improve Solar Cell Performace
On July 14, 2008 in Solar News
From http://web.mit.edu/newsoffice/2008/solarcells-0710.html but found on Slashdot
This is something I am very excited for, and hopefully the rest of you are as well. Especially the fact that it can be adapted to existing solar cells without having to just switch technologies. What a very appealing and uplifting ‘invention.’
Thanks MIT!
MIT opens new ‘window’ on solar energy
Cost effective devices expected on market soonImagine windows that not only provide a clear view and illuminate rooms, but also use sunlight to efficiently help power the building they are part of. MIT engineers report a new approach to harnessing the sun’s energy that could allow just that.
The work, to be reported in the July 11 issue of Science, involves the creation of a novel “solar concentrator.” “Light is collected over a large area [like a window] and gathered, or concentrated, at the edges,” explains Marc A. Baldo, leader of the work and the Esther and Harold E. Edgerton Career Development Associate Professor of Electrical Engineering.
As a result, rather than covering a roof with expensive solar cells (the semiconductor devices that transform sunlight into electricity), the cells only need to be around the edges of a flat glass panel. In addition, the focused light increases the electrical power obtained from each solar cell “by a factor of over 40,” Baldo says.
Because the system is simple to manufacture, the team believes that it could be implemented within three years–even added onto existing solar-panel systems to increase their efficiency by 50 percent for minimal additional cost. That, in turn, would substantially reduce the cost of solar electricity.
In addition to Baldo, the researchers involved are Michael Currie, Jon Mapel, and Timothy Heidel, all graduate students in the Department of Electrical Engineering and Computer Science, and Shalom Goffri, a postdoctoral associate in MIT’s Research Laboratory of Electronics.
“Professor Baldo’s project utilizes innovative design to achieve superior solar conversion without optical tracking,” says Dr. Aravinda Kini, program manager in the Office of Basic Energy Sciences in the U.S. Department of Energy’s Office of Science, a sponsor of the work. “This accomplishment demonstrates the critical importance of innovative basic research in bringing about revolutionary advances in solar energy utilization in a cost-effective manner.”
Solar concentrators in use today “track the sun to generate high optical intensities, often by using large mobile mirrors that are expensive to deploy and maintain,” Baldo and colleagues write in Science. Further, “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.”
The MIT solar concentrator involves a mixture of two or more dyes that is essentially painted onto a pane of glass or plastic. The dyes work together to absorb light across a range of wavelengths, which is then re-emitted at a different wavelength and transported across the pane to waiting solar cells at the edges.
In the 1970s, similar solar concentrators were developed by impregnating dyes in plastic. But the idea was abandoned because, among other things, not enough of the collected light could reach the edges of the concentrator. Much of it was lost en route.
The MIT engineers, experts in optical techniques developed for lasers and organic light-emitting diodes, realized that perhaps those same advances could be applied to solar concentrators. The result? A mixture of dyes in specific ratios, applied only to the surface of the glass, that allows some level of control over light absorption and emission. “We made it so the light can travel a much longer distance,” Mapel says. “We were able to substantially reduce light transport losses, resulting in a tenfold increase in the amount of power converted by the solar cells.”
This work was also supported by the National Science Foundation. Baldo is also affiliated with MIT’s Research Laboratory of Electronics, Microsystems Technology Laboratories, and Institute for Soldier Nanotechnologies.
Mapel, Currie and Goffri are starting 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), voted on by all who attended the awards.
Fact Sheet: MIT’s solar concentrators
News release: “MIT opens new ‘window’ on solar energy”
A Q&A by the MIT research team led by Marc A. Baldo, the Esther and Harold E. Edgerton Career Development Associate Professor of Electrical Engineering, on solar concentrators.
What did we do? We demonstrated a large improvement in the performance of low-cost solar concentrators. Our new devices increase the power obtained from solar cells by a factor of over 40 without needing to track the sun. Our results are at least a factor of four better than previous results.1
Why is this important? The sun is an inexhaustible source of clean power. The major impediment to widely deployed solar-power systems has been cost. Unsubsidized solar electricity is over three times as expensive as the average grid prices for electricity derived from conventional energy sources, according to the U.S. Department of Energy. Dramatic cost reductions are needed. Clean, renewable electricity at affordable prices would be an attractive alternative to conventional electricity and the related fossil-fuel dependence, greenhouse-gas emissions and peak-time grid constraints.
What is a solar cell? Solar cells transform sunlight into electricity by using a semiconductor device, typically made of silicon. Solar cells are packaged into solar panels, which can be installed on rooftops or large fields. The solar cells are typically some of the most expensive parts of an installed solar panel.
What is a solar concentrator? Solar concentrators collect light over large areas and focus it onto smaller areas of solar cells. This increases the electrical power obtained from each solar cell. Solar concentrators can reduce the cost of solar power since more electricity is obtained per solar cell, and fewer solar cells are needed.
What is wrong with existing solar concentrators? Conventional solar 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.
What is our technology? Our devices are based on a concept from the 1970’s that was largely abandoned: the luminescent solar concentrator (LSC). Our version of this device consists of a piece of transparent glass or plastic plate with a thin film of dye molecules deposited on the face and inorganic solar cells attached to the edges. Light is absorbed by the dye coating and reemitted into the glass or plastic for collection by the solar cells.
Why did LSCs fail in the 1970’s? Two reasons: the collected light was absorbed before it reached the edges of the glass or plastic plates, and the dyes were unstable.
What precisely did you do to reduce loss of the collected light? We borrowed some ideas from lasers, introducing what is known in lasers as a four-level system. In practice, we added a small concentration of an extra dye that collected all the absorbed light from its surrounding dye molecules. We also introduced a new class of dye molecules, known as molecular phosphors, that are extremely transparent to their own light emission.
What about stability? We tested one of our devices and found that it was stable (to 92 percent of initial performance) for three months. This isn’t good enough yet for products but we are confident that the technology developed for organic light emitting devices (OLEDs) in televisions will be portable to this application.
When will these concentrators make it into production? The technology is being further developed for commercialization by Covalent Solar, a company being spun out of MIT by three of its inventors: Michael Currie, Jon Mapel, and Shalom Goffri. The team believes that it could be implemented within three years.
References
1. Currie, M. J., Mapel, J. K., Heidel, T. D., Goffri, S. & Baldo, M. A. High-efficiency Organic Solar Concentrators for Photovoltaics. Science. In Press.
I heard about this before,That will certainly drive people into purchasing solar panels for homes one day and finally dump fossil fuels
This is great!!! Does admin know of any way to invest in this company? Have they sought any private ventures? Or maybe they are looking for venture capitalists? Or will they sell their technology to the highest bidder? Do you have a way to contact them? I checked out MIT can’t find “them” or covaelent* solar.
My other comment would be what do you know about companies to invest in for solar power. I know first solar or FSLR has made a big hit by selling to companies, stock prices went through the roof.
I would like to keep in touch with Covalent Company for further exploration about dyes bying to manufacture such panels, if possible in Nepal.
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