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Thursday, July 10, 2008 A Better Solar CollectorA more efficient way to concentrate sunlight could reduce the cost of producing solar power. By Kevin Bullis
Looking to make solar panels cheaper, MIT researchers have created sheets of glass coated with advanced organic dyes that more efficiently concentrate sunlight. The researchers, whose results appear in this week's issue of Science, say that the coated glass sheets could eventually make solar power as cheap as electricity from fossil fuels. The researchers show that the glass sheets can reduce the amount of expensive semiconducting material needed in solar panels and provide a cheap way to extract more energy from high-energy photons, such as those at the blue end of the spectrum. "This could be the cheapest solar technology," says Marc Baldo, a professor of electrical engineering at MIT. "And I think one day, it could be competitive with coal." The simple, flat sheets of glass have a number of advantages over previous solar concentrators, devices that gather sunlight over a large area and focus it onto a small solar cell that converts the light into electricity. Solar concentrators in use now employ mirrors or lenses to focus the light. Because the new glass sheets are lighter and flat, they can easily be incorporated into solar panels on roofs or building facades. They could also be used as windows, which, connected to solar cells, could generate electricity. What's more, mirrors and lenses require mechanical systems for tracking the sun to keep the light focused on a small solar cell. These tracking systems add cost and can break down over the decades that solar panels are made to be in service. The flat glass concentrators don't require a tracking system. Instead of using optics, the glass sheets concentrate light using combinations of organic dyes specially designed by Baldo and his coworkers. Light is absorbed by the organic dyes coating one side of the glass sheet. The dyes then emit the light into the glass. The glass channels the light emitted by the dye to the edges of the glass, in the same way that fiber-optic cables channel light over long distances. Narrow solar cells laminated to the edges of the glass collect the light and convert it into electricity. The amount of light concentration depends on the size of the sheet--specifically, the ratio between the size of the surface of the glass and the edges. To a point, the greater the concentration, the less semiconductor material is needed, and the cheaper the solar power. The challenge of using organic dyes as solar concentrators has been that the dyes tend to reabsorb much of the light before it can reach the edges of the glass. Baldo overcame that problem by using dyes that don't absorb the light that they emit. For example, a dye might absorb a range of colors in the light spectrum, such as ultraviolet through green, but emit light in another color, such as orange, which the dye cannot absorb. |
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Cheaper Solar Power
06/23/2008
Comments
javs on 07/11/2008 at 10:34 AM
32
I am partially repeating what I said earlier. The article is a good contribution to TR readers about one of the most important kinds of uncertain generation... The EWPC article Uncertain Generation is Here to Stay takes the idea into the context of the Third Industrial Revolution. . . . . . . With regard to solar distributed generation, please read the EWPC article Nanosolar Breakthrough and the Old Paradigm. Research for scheduling and integrating ... solar power to power systems planning, operations and control, will be part of the next stages. . . . . . . To understand what to do first in the wider, and highly uncertain, legislative and regulatory context, TR readers should consider reading the EWPC article Leadership Answers What to do First, whose summary is "The answer to the question of what to do first is for the global power industry to get out of the wrong jungle to produce a EWPC based EPAct as soon as possible. That is the kind of leadership needed to face the inevitable fundamental changes required to significantly reduce today’s legislative and regulatory uncertainty."
nekote on 07/11/2008 at 11:35 AM
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EPAct: Energy Policy Act
javs on 07/11/2008 at 12:05 PM
32
mkogrady on 07/11/2008 at 12:43 PM
74
Do these died plates of glass function as stand alone converters or do they work in concert with thin panel and polysilicon wafer systems too?
Can a fresnel lens increase their potential by focusing sunlight into a smaller area and increasing the energy onto a smaller plate surface? If yes can it be adapted to work off big desert tower installations or arrays?
In any case - let us know when the IPO is coming. I'll ante up some 401K funds!
Good job and very cool!
Globe99 on 07/11/2008 at 7:44 PM
11
johnalphonse on 07/11/2008 at 3:00 PM
69
additionally, mentioning the obvious may be worthwhile for those working in the field: nothing absorbs heat quite like the color black, which absorbs all wavelengths of light...
TragicComic on 07/11/2008 at 3:47 PM
4
This means you need to have moving components, timers, etc. and can dramatically increase the cost of the device.
Essentially ou have a trade off between the cost of the PV material and the cost of the device to concentrate it.
Globe99 on 07/11/2008 at 7:36 PM
11
It's really simple: (A) the vast majority of photovoltaic elements will NOT span the entire solar spectrum, so (B) why don't you make part of the cell a device (like a waveguide) to channel that color specifically into a PV optimized to handle it?
No, solar researchers would rather just throw everything into some structurally ill-defined soup and hope for the best. Well, kudos to these guys for bucking the trend. Expect in the future to see this optimized on the nanoscale using quantum dots and/or more advanced waveguide structures.
incm79 on 07/12/2008 at 7:08 AM
1
You might be interested in a project I was involved with back in the '80s and 90s that developed the concept for what we called the Lateral Aperture design. As far as I know it was the first design for a wave guide that integrated one side as a collection surface with the internal capture of radiant energy which could then be directed parallel to the surface to multiple edges if desired. This technology doesn't use dyes, and therefore has potential for other various applications besides solar, such as fiber optics, satellite dishes, etc.
Back then if you claimed to be able to capture solar energy within a flat sheet of glass and direct it to an edge you were considered crazy. Times and attitudes change and its nice to see Professor Baldo and other researchers can take non-traditional technology and ideas forward without being committed. There are some pages on the Lateral Aperture research at: http://research.atspace.org/index.html
zig158 on 07/12/2008 at 5:14 AM
44