Colorful concentrators: The colored plastic sheets illustrate a way to concentrate sunlight. Combinations of advanced organic dyes made into similar sheets could make solar concentrators more practical.
Kevin Bullis
A more efficient way to concentrate sunlight could reduce the cost of producing solar power.
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.
Integrating solar cells into building materials could make solar power more attractive to homeowners.
A new way to concentrate sunlight could make solar power competitive with fossil fuels.
Forgive my ignorance -
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!
You're absolutely right, this system does not do any of the actual "conversion" in the light-to-electricity sense. What they've developed is technology to channel the light to the edge of the plates, where you would then have your photovoltaic device. The trick is that you could filter off select parts of the spectrum and then channel them into PV's designed specifically to handle them.
this is really encouraging. i believe mkogrady makes a valid point worth considering and i was thinking along the same lines myself. if you can start a fire with a 50-cent magnifying glass, why is it so difficult to focus this awesome power onto something that won't catch fire yet will harness it? like colored glass! i mean the magnifying glass obviously multiplies the collective potential far greater than mirrors, and i believe it would be a good place to look for future experimentation within this model. as mk suggests i also believe incorporating a layer of magnifying glass above these others, and combining this with the current movable array designs, would skyrocket efficiency and bring this to viability a lot sooner, which i'm sure we mostly agree we sure do need, like, yesterday.
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...
The problem with concentrating light via a magnifying glass, or Fresnel lens, is that you have to aim it at the sun in order to get the effect.
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.
Maybe a fresnel lens MADE of colored glass that actually filters and focuses only the spectrum you want!
Moving parts aside, it places more energy per pixel than send it to the edge of the glass itself.
This has been a long time coming.... the concept of using basic photonic technologies such as waveguides (as in this example) or photonic crystals seems to have been lost on a lot of solar researchers. Over the years we've gotten much better at manipulating light on the micro and nanoscale using photonics and plasmonics respectively, however little of these ideas seem to have seeped into solar cell research.
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.
Globe99: "This has been a long time coming.... the concept of using basic photonic technologies such as waveguides (as in this example) or photonic crystals seems to have been lost on a lot of solar researchers."
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
By waveguide - do you mean something like a fiber optic channel to contain and control the delivery of the light or energy?
Yes. The term "waveguide" refers to a broad class of materials, ranging from fiber optics to thin films of polymers (in this case) to nanostructured strips of metal on a dielectric. The purpose of all of these is to channel and transport light in certain defined directions.
wiki -- http://en.wikipedia.org/wiki/Waveguide_%28optics%29
paradigm-shift that the solar field has needed
I agree with that this is the paradigm-shift that the solar field has needed. Modules like the one they describe would be so much more practical than the traditional panel.
Very interesting approach.
Whether or not this will work will depend on key issues like:
- Durability; how do the dyes hold up over time?
- Cost; dyes are probably cheap but the entire module has to be cheap as well.
- Concentration factor; how many times can light be concentrated using this method? If it's really big (say 500x) then high efficiency exotic cells can be used, lowering total cost per Watt considerably. I suspect though, that the maximum achievable concentration will be much lower.
Also, I have a question: does this work with diffuse light as well as direct insulation? It looks like it does.
It does work with diffuse light, which is one of the main selling points. It's related to the fact that these systems don't require tracking mechanisms.
The best way to describe the concentration factor possible in this system is through something called "flux gain," which is equivalent to how much more power a solar cell produces when it's connected to the concentrator. The researchers project that 30 centimeter sheets can multiply the power by about 50.
Thanks. 50x isn't as high as I'd hoped. Uneconomical for GaAs multijunction. But more than good enough for high efficiency silicon technology. Sliver Cells maybe, if they hurry up with their production rate.
Has there been any discussion to use larger panels to get a larger multiple?
Is there any technical limitation where increasing the concentration/panel size provides diminishing returns?
This seems very exciting and it would be great to find any way to use the higher efficiency cells. Especially the GaAs cells at 40%.
What would it take to get GaAs cells cost effective?
Power generating window and Skylights
I see this technology as being directly applicable to large window skylights.
Right now skylights come in all different type of shapes and sizes from small individual windows to large complex shapes covering huge indoor rooms. Most are tinted anyways. Even if adding this technology increase the price of the skylight by 20% to 100% that may still be acceptable to many home and business owners. Resorts, business, and homes in remote regions may especially find this attractive because of the high variable in electricity cost, but I don’t see this as replacing electricity, only as a supplement. Some people may find it attractive even if it only produced enough electricity to run a single fan.
I strongly think these researchers should license the manufacturing process for the special glass (or plastic) to anyone they can. They should also have a list of suppliers who can build the photovoltaic cells that go on the edges. The goal is to make the plastic easy to come by in any needed size, and let the larger photovoltaic industry take advantaged of the features of this special concentrator.
Also they could license the plastic material to plastic manufactures because I think they could sell it as a special material that may be used in special applications like clubs, bars, and so on.
Thanks
Brian Glassman
www.TechRD.com
Commercialization
Innovation Management
Here are some pictures of skylights
http://www.skylightwindows.net/skylightwindows.htm
http://www.majorskylights.com/technical/
I don't see any mention on how to handle the heat generated, would this not require some kind of cooling system if the efficiency of the collector is multiplied X times?
The collector essentially filters out unneeded wavelenghts, so there wouldn't be too much heat to deal with. A very low cost passive cooling device should do.
organic dyes as solar collectors
This concept was pioneered by Nobel prize winner Ahmed Zewail at Caltech in the late 1970's --about 1977 as I remember. I had the pleasure of working with him for several months in 1978, on another project. Fluorescing dyes were incorporated in plastic sheets (perhaps Plexiglas or Lucite). The broad visible solar spectrum was absorbed by a mix of dyes that absorbed and fluoresced at lower frequencies, while the radiation was reflected to the edges of the pane of plastic. Then the photovoltaic collector was attached to the edges of the pane. So the system acted as a spectral and optical concentrator. As I remember, it was turned over to the Jet Propulsion Laboratory to optimize the concept for architectural appeal as well as solar electric conversion efficiency.
According to someones analysis, for say the US, you could potentially generate 3TWe from a very large solar farm in the SW desert.
link: http://www.ez2c.de/ml/solar_land_area/
He is assuming 8% efficiency. What kind of efficiency could we get using this technology, and thus what kind of potential yield with such an installation?
What am I missing with regards to the feasibility of such a scenario?
I did not see any mention of the amount of energy that is lost by the dyes. What % of energy gets to the edge of the panels?
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javs
97 Comments
A Barrier to this Potential Breakthrough
The electric power industry regulations have a strong barrier to the development of the resources of the demand side. For the better solar collector to be integrated to power system planning, operation and control a new market architecture and design is required to eliminate said barrier.
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."
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nekote
139 Comments
Re: A Barrier to this Potential Breakthrough
EWPC: Electricity Without Price Controls
EPAct: Energy Policy Act
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javs
97 Comments
Re: A Barrier to this Potential Breakthrough
Thanks.
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