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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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Sounds intriguing..
By FITCamaro on 7/17/2008 9:44:06 AM , Rating: 2
Two questions though:

What is the cost?

How much energy are we talking for a typical house and all the windows being of this type? They say they're more efficient than roof-top panels. But while they may be more efficient, windows are only on one side of the house. So the power generated by the cells in a window will heavily depend on the time of day. Roof top panels have the benefit of being in the sun from dawn to dusk.

RE: Sounds intriguing..
By skarbd on 7/17/2008 9:55:01 AM , Rating: 2
I think in office blocks they could be very intriguing.

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! ;)

RE: Sounds intriguing..
By peldor on 7/17/2008 10:45:31 AM , Rating: 2
A vertical plate is a poor orientation for collecting solar power anyway until you get to very high latitudes.

RE: Sounds intriguing..
By Solandri on 7/17/2008 1:32:42 PM , Rating: 2
That's kinda the point of this idea. Surfaces which are poorly oriented are uneconomical for solar collection because right now we plaster the entire surface area with PV cells. This idea is to take something which is much cheaper than PV, cover the surface with it, and put a thin line of PV cells on the edge where it collects the solar energy striking the surface.

RE: Sounds intriguing..
By peldor on 7/17/2008 3:50:08 PM , Rating: 2
It's not like concentrated PV hasn't been done before. If concentrated PV isn't economical now, mounting it at a bad angle isn't a step forward.

RE: Sounds intriguing..
By Solandri on 7/17/2008 3:59:07 PM , Rating: 2
Concentrated PV wasn't economical because you have to move the mirrors on motorized gimbals to track the sun. It might not have been too bad if the sun took the same path through the sky every day, but it doesn't, its path changes with the time of year. The mounting and maintenance costs (and complaints when they pointed the wrong way) got too high.

These are completely passive and immobile.

RE: Sounds intriguing..
By SiliconJon on 7/20/2008 2:03:35 PM , Rating: 2
If the cost were truly low then the cost of a lack of optimized angling could be countered. I have my doubts about the consumer seeing this application done cheaply, if it can be done at all in the near future. But to theorize of the ends rather than the means, if I could purchase power producing windows all around my house for half of what it would cost* to mount a solar panel unit to my roof and the windows produce more than 50% of what the roof unit could produce then it would be a winner of an idea economically, and one hell of a winner aesthetically and maintenance wise.

* This cost being calculated by the difference between installing comparative non-power producing windows, not compared against the cost of not replacing or installing windows.

RE: Sounds intriguing..
By DeepBlue1975 on 7/17/2008 11:29:10 AM , Rating: 2
I think this will end up being targeted to large buildings rather than houses.
Doesn't make too much sense to me, having something like this in a place where maybe only 20-30% of the exterior surface is covered with glass.

RE: Sounds intriguing..
By Moishe on 7/17/2008 1:37:04 PM , Rating: 2
I agree. Plus most people have either awnings or some sort of porch or trees precisely for the purpose of blocking sun, which saves a TON on energy. Of 18 windows in my house, only two are unprotected. One of those is a fairly small window.

RE: Sounds intriguing..
By Solandri on 7/17/2008 3:39:42 PM , Rating: 2
I don't think you understand the breakthrough here. The big deal isn't that they can use windows to collect solar energy. The big deal is that they can collect solar energy over a large area without covering that entire area with PV cells. It's like using mirrors to concentrate the sunlight onto a smaller device (PV or steam generator) to generate electricity. Except you don't have to polish the mirrors or aim them to track the sun.

In other words, instead of having to cover your roof with a $20k array of PV solar panels, you can cover it with $1k in treated glass panels with $1k in a thin PV arrays at the edges. (Numbers made up but you get the idea.)

RE: Sounds intriguing..
By JonnyDough on 7/18/2008 12:03:42 AM , Rating: 2
20-30% of the surface of your house is QUITE viable.

This idea is meant to be implemented as a PART of an overall solar package, it will likely never be able to completely power any building, not even 100 years from now. A few volts here and there add up fast. The most economical solution for home energy will in fact be integrating low-cost solar cells into every building surface. Siding, roofing, windows. This is just the start and it's only ONE of the building blocks needed to get rid of the grid. I applaud their research.

RE: Sounds intriguing..
By omnicronx on 7/17/2008 3:22:49 PM , Rating: 2
What is the cost?

I don't think it matters, here in Toronto there are a few sky scrappers that have all of their windows gold plated for insulation. If a company is willing to gold plate their windows, I see no reason as to why they would not want to use them in this situation, as long as it saves them money in the long run of course.

RE: Sounds intriguing..
By JonnyDough on 7/18/2008 12:07:05 AM , Rating: 2
Sky scrappers eh? I wasn't aware the Canadians were all aboot scrounging for old satellites for gold. Go Canada!

This is cool if...
By Loveless on 7/17/2008 9:34:31 AM , Rating: 4
you like tinted windows. Notice that the picture says "some" light gets through. Obviously, the more energy you get from this, the less light that you get through the window. It would be kind of ironic if all of the energy collected by these windows would be used to light the house during the day.

Of course, that's only a problem for people that are home during the day. Overall, I'd say that this is a very nice invention, especially considering its application to existing solar panels.

RE: This is cool if...
By FITCamaro on 7/17/2008 9:46:56 AM , Rating: 2
Good point. Of course I like the idea of some, but less light coming through. Means less glare. Besides I'm only home on the weekends anyway.

RE: This is cool if...
By nvalhalla on 7/17/2008 10:58:51 AM , Rating: 2
I think the idea is for businesses, whose windows are usually very tinted anyways. Now the energy wasted by the tinting can be absorbed and used to power the florescent lights, with some left over for the coffee makers hopefully...

RE: This is cool if...
By Etsp on 7/17/2008 1:19:06 PM , Rating: 2
Now, they never said in the article that the light that the dyes absorb would be in the visible spectrum, so there is potential that you wouldn't lose much visible light at all, and still absorb a large portion of the light. The picture in the article shows them using obvious colors, but that was probably to make it easier to demonstrate. I highly doubt that these dyes will focus on visible light.

RE: This is cool if...
By Loveless on 7/17/2008 2:38:50 PM , Rating: 2
That's a good point. I didn't consider that the light absorbed might be from outside of the visible spectrum.

However, in the picture of the two researchers, they are holding samples of the glass, and the glass is clearly orange. The very color of the glass itself indicates that it is absorbing visible light.

RE: This is cool if...
By Etsp on 7/17/2008 3:10:47 PM , Rating: 2
But like I said, that was probably done so they could demonstrate how it works, it's so much easier to understand it if you can see the effect taking place. You can describe what it does with one picture, instead of a series of similes and metaphors, punctuated with technical terms many people wouldn't be able to understand.

RE: This is cool if...
By TheOtherBubka on 7/17/2008 10:55:02 PM , Rating: 3
Okay...sorry this is going to be longish.

1. This technology does absorb visible radiation. The dyes absorb radiation and re-emit radiation of a longer, wavelength which undergoes total internal reflection (waveguides) and continues to the edges of the window where it is emitted/collected/you see it glow.

2. As you can see, the windows are colored. Most people like 'neutral' transmittance for 'windows' and not to look at the outside world in colors.

3. If they do make a 'multilayer' glass, architects need to design that into the frame of the building to support the extra weight for the skyscraper. More window weight, stronger materials, higher cost. Same for your roof in the depiction they claim.

4. Typical 'low E' windows let in about 33% of the solar radiation, absorb about 33%, and reflect about 33%. The energy they let in is highly skewed toward the visible. This technology as is, states nothing about reducing the IR that would be transmitted through the window. If they want to reflect the IR, then you are still going to need a 'low E' tehcnology behind it to keep long wavelength radiation (aka heat) in/out depending on the season. Thus higher cost compared to conventional windows. See solar heat gain. The more solar heat gain, the bigger AC units you need, then more power required to cool.

5. Yes this technology concentrates light. But only light of certain wavelengths. Let's say the dye absorbs strongly over 300-550 nm as is common in Graetzel (dye sensitized solar cells). If you absorb all of that radiation, the maximum output power available (no light getting through) is ~400 W/m^2 of glass under direct sunlight. If not direct radiation, then decrease maximum accordingly. The light is then re-emitted at a longer wavelength (less energy) plus photovoltaic diode losses in the cells and you are down to regular PV efficiencies which is where they get to. Also, if you want 30% light throughput so people can 'see through the window', take 30% off of your efficiency (roughly).

6. If you are lucky enough to be able to see the paper, you will see there were a lot of estimations in their efficiency measurements. Furthermore, this technology with 2 of the best concentrator materials known (GaInP and GaAs which are also very expensive in solar costs), was estimated to produce 6.8%.

7. Their power conversion efficiencies went down with increasing concentration and not up as conventional concentrators. Important if you consider a 1.5m x 2.0m x 3mm glass pane on a side of a building. Concentration ratio of roughly 142. Thinner glass since you can laminate this technology between them? Then higher concentration.

8. Not to say this isn't a worthwhile idea, just a long, long way to go with high promises and 'theoretical' results such as 'low cost organic PV packaging.' Yes. You will pay for expensive packaging for 1 OLED TV. But will you pay for 20 for your windows in your house? Imagine a skyscraper.

RE: This is cool if...
By Etsp on 7/18/2008 12:42:57 AM , Rating: 2
1. This technology does absorb visible radiation. The dyes absorb radiation and re-emit radiation of a longer, wavelength which undergoes total internal reflection (waveguides) and continues to the edges of the window where it is emitted/collected/you see it glow.
Only if they choose to use dyes that create this effect on visible wavelengths of light when it goes into production. Because like you said
Yes this technology concentrates light. But only light of certain wavelengths.
Yes, the technology is certainly capable of absorbing visible light, but it is also capable of absorbing UV light without affecting visible light. That was the only point I was trying to make. :)

To the naysayers...
By Jackattak on 7/17/2008 12:15:27 PM , Rating: 3
I'm sure you're all right. I'm sure that this will fail and that these scientists haven't thought of any of your "liabilities."

They're only MIT scientists, after all. :rolleyes:

RE: To the naysayers...
By Spuke on 7/17/2008 2:06:24 PM , Rating: 3
They're only MIT scientists, after all.
They're also human beings which do tend to make a mistake or two every now and then.

RE: To the naysayers...
By Master Kenobi on 7/17/2008 2:59:07 PM , Rating: 2
Just because they are at MIT doesn't mean they are covering all their bases. Hence why in science everything is peer reviewed. Wouldn't be the first time one place goofed and someone else caught it.

first thought
By zaxxon on 7/17/2008 9:20:35 AM , Rating: 3
when I read the title, the first thing that went through my head was

"Windows Vista - Solar Power generation Edition"

RE: first thought
By nvalhalla on 7/17/2008 10:56:29 AM , Rating: 2
So did I! I thought "there's a solar powered version of Windows?"

RE: first thought
By deeznuts on 7/17/2008 5:55:33 PM , Rating: 2
I was thinking, damn Windows 7 doomed before it begins, they have a replacement already."

By hellokeith on 7/17/2008 3:56:40 PM , Rating: 2
You are underestimating the good-ole-boy factor. A friend of mine is an HVAC & refrigeration professional, and he says it is astounding the amount of good-ole-boy pat-on-the-back son-in-law we've-always-done-it-this-way behavior that stagnates the culture and impedes any kind of improvements. Unless the improvement comes packaged in the new model of "Big Equipment Company" product at the same or lower price than last year, it won't even be accidentally used. If Bubba at Home Depot in the contractor department can't pronounce the product name, forgittabout!

By DBRfreak on 7/18/2008 11:04:50 AM , Rating: 2
Bring it back to the most common denominator of all: money. Provide a strong enough financial incentive for Bubba to use it and he'll learn its name in four different languages.

Auto usage?
By silhrt on 7/18/2008 10:24:40 AM , Rating: 2
I remember reading that one electric car company was putting soloar panels on the tops of their cars. This did little more than recharge the car form the AC use.

Would this method, with its 40% increase, provide enough juice to recharge, say a Volt, while i am at work?

You can use the top, sides, and back for this as well. ( and if its not blocking my visible light then the front, too )

RE: Auto usage?
By epobirs on 7/21/2008 4:29:09 AM , Rating: 2
Nope, it would still be terribly little contribution to an electric car's needs. But it could increase the feasibility of a solar recharging station at your home or office by reducing the needed surface area and cost.

By CurtOien on 7/17/2008 8:25:56 PM , Rating: 2
I know this is a bit off topic but... birds run into windows because they either think they can fly right through or they get confused by reflections. Birds see ultraviolet.(I'm not sure if 100% of them do.) If a window were to absorb ultraviolet and also have something like a hatch mark pattern that would reflect some of the ultraviolet to make it appear like a chain link fence or something, I'm guessing that there would be a lot less birds slamming into windows. Any thoughts on this?

What If
By nerdboy on 7/17/08, Rating: -1
RE: What If
By excelsium on 7/17/2008 9:36:33 AM , Rating: 2
Then it would be a goldfish bowl..

RE: What If
By FITCamaro on 7/17/2008 9:44:42 AM , Rating: 5
What if you learn to spell "were"

RE: What If
By retrospooty on 7/17/2008 9:50:21 AM , Rating: 2
then you would never get laid ever again... You might as well start playing dungeons and dragons.

Your electric bill would rock though. ;)

RE: What If
By FITCamaro on 7/17/2008 10:48:06 AM , Rating: 5
That's why he wants to call it his Fortress of Solitude.

RE: What If
By SavagePotato on 7/17/2008 11:19:27 AM , Rating: 3
You might go instead for names such as the fortress of indecent exposure.

Or the fortress of stupidity.

RE: What If
By bobsmith1492 on 7/17/2008 11:20:27 AM , Rating: 2
It would be a greenhouse? I hope you live in cold climes or all your electricity would be going to your AC and fans.

RE: What If
By Moishe on 7/17/2008 12:43:13 PM , Rating: 2
Call it the fortress of love and you might be able to fix the nerd problem. I doubt it though.

RE: What If
By stryfe on 7/17/2008 5:21:57 PM , Rating: 2
As long as you don't throw stones...

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