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The new windows will be formed of stacked tinted thin plates of glass which each target a specific wavelength of light, which they gather and emit intensely to cells at their edges.  (Source: Donna Coveney)

An artistic rendition detailing how the new system could easily be applied to existing panels to make them more efficient.  (Source: Nicolle Rager Fuller, NSF)

Marc Baldo, associate professor of electrical engineering and computer science (left), and Shalom Goffri, postdoc in MIT's Research Laboratory of Electronics (right), show off examples of the new solar window layers.  (Source: Donna Coveney)
A new solar design will soon be able to contribute significantly to powering city buildings

There is much ongoing research into making photovoltaic solar power, common among commercial business and residential installations, more efficient.  While many focus on the cells themselves, MIT researchers are focusing on a different approach by changing the places where cells can be deployed and how light gets to them.

MIT researchers built upon previous research into colored dyes from the 1970s and created special glass panels.  Each panel absorbs a different wavelength of light and carries it to solar cells.  The result: the first potentially viable solar windows.

The new research is reported in the July 11 issue of the journal Science.  In it, the researchers detail how the build up their novel "solar concentrator".  Explains Marc A. Baldo, leader of the work and the Esther and Harold E. Edgerton Career Development Associate Professor of Electrical Engineering, "Light is collected over a large area [like a window] and gathered, or concentrated, at the edges."

By clustering solar cells around the edges of the specially prepared sheets of glass, the new method provides a unique alternative to expensive rooftop solar cells.  They are also much more efficient than their rooftop brethren.  The special glass panels concentrate light 40 times standard sunlight before delivery directly to the cell.  Further different designs to absorb different wavelengths are available, so by using windows with several stacked glass panes, absorption can be optimized across the entire visible wavelength.

The system is so simple to manufacturer that the inventors expect it to be deployed within 3 years at little cost over standard window costs.  Furthermore, it can be added to existing solar panels to help concentrate sunlight for virtually no additional cost, and would increase their efficiency by a modest 50 percent, according to the authors.

Baldo's team includes 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.  The U.S. Department of Energy (DOE), a sponsor of the research is very pleased with their progress.

Dr. Aravinda Kini, program manager in the Office of Basic Energy Sciences in the DOE's Office of Science, states, "Professor Baldo's project utilizes innovative design to achieve superior solar conversion without optical tracking.  This accomplishment demonstrates the critical importance of innovative basic research in bringing about revolutionary advances in solar energy utilization in a cost-effective manner."

In the paper, Professor Baldo addresses current methods for improving efficiently, stating that, "track the sun to generate high optical intensities, often by using large mobile mirrors that are expensive to deploy and maintain.  He comments that additionally "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."

As he points out, even methods today considered to promote efficiency are clumsy and expensive.  His team's process is extremely simple in comparison with no moving parts.  The windows are painted, in essence, with a series of two dyes.  Combined, the dyes absorb light of a specific wavelength and then retransmit it at the edges of the window. 

The previous work in the 1970s involved a similar principle but lost too much energy during transportation.  The MIT engineers were able to take their expertise in lasers and organic light-emitting diodes and apply it to making a mixture of two special dyes which work much better.  Says Jon Mapel, "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."

The research was sponsored by the National Science Foundation in addition to the DOE.  Professor Baldo is associated with MIT's Research Laboratory of Electronics, Microsystems Technology Laboratories, and Institute for Soldier Nanotechnologies.

Mr. Mapel, Mr. Currie and Mr. Goffri have founded a company Covalent Solar, which looks to make good on the researchers' promise to bring the technology to market within 3 years.  The company is progressing nicely, winning the Energy category ($20,000) and the Audience Judging Award ($10,000) in MIT's $100K Entrepreneurship Competition.  The new design is especially heavy to the tinted-glass heavy urban settings and follows a trend of incorporating wind and solar power into less obtrusive urban-ready designs.

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RE: Sounds intriguing..
By masher2 on 7/17/2008 10:12:17 AM , Rating: 2
Another problem may be the lifetime of the organic dyes being used here. Any organic chemical breaks down over time, especially when exposed to strong light.

RE: Sounds intriguing..
By JasonMick on 7/17/2008 10:28:39 AM , Rating: 3
Yea, but how much time? Depending on the chemical structure it could be a few hours, a few days, a few years or a few decades.

I'm guessing these engineers have sufficient chemistry backgrounds to realize and consider this issue. I'm guessing they'd be offering a lifetime at least comparable to current photovoltaic breakdown/weathering lifetimes by the time they bring this to market.

It seems you're implying that this might breakdown in a couple years or less.

I might be surprised, but a team of top MIT researchers don't strike me as stupid enough to make that kind of mistake.

RE: Sounds intriguing..
By Spuke on 7/17/2008 11:11:34 AM , Rating: 2
I might be surprised, but a team of top MIT researchers don't strike me as stupid enough to make that kind of mistake.
They didn't say either way so it's all an assumption. I guess I need to read the journal to find out.

RE: Sounds intriguing..
By Spuke on 7/17/2008 11:13:46 AM , Rating: 2
Here's the original article:

RE: Sounds intriguing..
By masher2 on 7/17/2008 11:18:34 AM , Rating: 3
> "It seems you're implying that this might breakdown in a couple years or less. I might be surprised, but a team of top MIT researchers don't strike me as stupid enough to make that kind of mistake. "

Prepare to be surprised then:

Although the new dyes are not as fragile as the ones used in the 1970s, they still have a lifetime of only about three months, Baldo told New Scientist. "That by itself is not good enough, but it's on the way."

RE: Sounds intriguing..
By JasonMick on 7/17/2008 11:31:15 AM , Rating: 3
I'm not surprised. Notice I said that when this is RELEASED in three years I expect them to have worked out any issues and for it to have a decent lifespan.

As the lead researcher Baldo states in the article you refer to, right after your quoted portion in fact, "That by itself is not good enough, but it's on the way."

There's ways to dramatically modify organic chemicals to extend their life without impairing their functionality, it just takes more research.

RE: Sounds intriguing..
By masher2 on 7/17/2008 11:52:47 AM , Rating: 4
But your article says this is expected to be deployed within three years. Solving the problem of organic dye lifespan could easily take far longer than that. Which is why I said the lifespan issue is probably the largest problem of all.

RE: Sounds intriguing..
By SiliconJon on 7/20/2008 1:53:16 PM , Rating: 2
Another technology touted as ready or near ready that is nowhere of the sort. This political malfeasance of our science is disgustipating. A life span of 3 months is useless in a permanent application, and while the breakthrough is a great stepping stone it is nowhere near the top of the stairwell.

RE: Sounds intriguing..
By DBRfreak on 7/17/2008 11:20:09 AM , Rating: 3
I'll disagree.

Without knowing the entire team's academic background, it's impossible to say for sure, but as electrical engineers, I'll assume that their undergraduate coursework in chemistry stopped at general/inorganic 2. If they had an undergraduate degree in chemical engineering, then the situation is obviously different, but being able to predict or know the lifespan of complex organic molecules is the domain of trained chemists, which the article indicates the team is not.

However, the people who did the original work with the dyes in the 70's might have an idea. MIT is full of bright people, but there's a huge difference between a Sc.D in Electrical and a Ph.D in Chemistry.

RE: Sounds intriguing..
By Silverel on 7/17/2008 12:07:35 PM , Rating: 2
Looking at the diagram, it seems the dye is on the outside of the window. So, every three months, you go out and apply a treatment to your windows maybe?

Something like that would make sense to me. Sell the windows once time, and make tons of profit off the dye. It'd make good business sense for companies that want to support it as they would have a solid product that would be re-sold forever.

RE: Sounds intriguing..
By plinkplonk on 7/17/2008 12:53:58 PM , Rating: 2
i think the only problem with that is that they want to have multi-layer windows which can absorb light across the whole spectrum. I would guess once these had been layered up you wouldn't take it apart again to apply the dye to each layer?

RE: Sounds intriguing..
By Moishe on 7/17/2008 12:41:51 PM , Rating: 4
I think this is a very valid question.
For all we know it could last 5-10 years and they could be willing to simply accept replacement windows or panes every now and then as part of the cost involved.

Until we hear otherwise, there is no reason not to question.
MIT guys are smart, but I've seen smart guys do very stupid things. I've also seen smart guy products marketed by people who are not smart and have no qualms about fudging the facts

RE: Sounds intriguing..
By Spuke on 7/17/2008 2:02:04 PM , Rating: 2
You ever had a windows replaced? Low E "glass" can be pretty expensive by themselves. I'd imagine these would cost more than that.

BTW, will these windows still meet the same energy efficiency ratings as Low E?

RE: Sounds intriguing..
By nstott on 7/18/2008 1:38:15 AM , Rating: 2
As much as it pains me to say, I have to side with Jason on solar energy being worthwhile for R&D. While it might not be cost effective now, that will change with more research time and money. Expect leaps in the technology.

That being said, Masher is right about organic dyes - they degrade with exposure to light. While at the said institution, we did research to replace IR-emitting laser dyes used for bioimaging during surgery with biofunctionalized IR-emitting inorganic nanocrystals. While the dyes bleach out after only a few seconds, the nanocrystals lasted for the entire duration of the surgery (on rats and pigs, not people). One big selling point of using inorganic nanomaterials in various applications is robustness/lifetime. Now, these window panels will most definitely last a lot longer than seconds, but efficiency will drop with time. Applications like OLEDs have significantly long lifetimes but do experience color bleaching/fading over time.

Speaking of solar energy, Nanosys is developing decorative solar roof tiles made with inorganic nanorods that they claim will be as efficient as fossil fuels (claim made back when gas was below $2/gallon). I hope they succeed as it will significantly increase my yearly royalties.

As for MIT researchers being stupid, you will likely see a few people walking around campus with S.P.A.M.I.T. t-shirts if you visit (Stupid People At MIT - a joke support group/club).

P.S. Jason, you're completely wrong about AGW. Quit being a natural process denier! ;)

"Death Is Very Likely The Single Best Invention Of Life" -- Steve Jobs

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