Make:

How efficient is this though. If they're windows, they have to let some light in too.

How many Watts/square meter in average sunlight would these generate. If it's like any other solar technology, it wouldn't make a dent in the lighting budget for the building it's mounted on, and it will cost more than it could save in a hundred years.

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"Imagine these windows installed onto every skyscraper in the world, they might generate enough power to fuel the whole city below."

I find this claim extremely optimistic. First off, the amount of solar energy that strikes a vertical surface like a window is much less than a horizontal surface like a rooftop (or even more if titled at an angle favorable for the given latitude).

For example, let's look at sunny New York City. In July, with your solar panels pitched at a favorable angle, a solar panel would see an average 6.0 kWh/m^2 each day. That same panel, if stuck on the side of a building would only see 2.7 kWh/m^2 each day AND that's only on the south-facing wall. You'd get even less than that on the west, east, and north side (almost nothing usable on the north side). Also, one must consider that in a dense downtown area where skyscrapers are, most of the buildings are shaded by other buildings most of the time. At the very least, the lower stories of the buildings are shaded except for an hour or two near noon.

So, rounding up to 3 kWh/m^2 and then multiplying by a generous solar system total efficiency of 20% (since solar systems only capture a fraction of the available energy from the sun) we'll get about 0.6 kWh/m^2 per day of usable AC electricity (3kWh/m^2 * 0.2 = 0.6kWh/m^2).

That is WAY less than the energy density of any office building. For example, let's say you have a computer using 100W continuously. That's 100W * 24h = 2400 Wh = 2.4kWh per day. You have just used up 4m^2 (43ft^2) of your window real estate to power a single computer.

Anyhow, I think building-integrated PV is a great idea, but let's be realistic about the scale of energy production vs. energy use.

(Please correct me if you see error in any of these calculations.)

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20% efficiency is being very generous. Organic dye cells like this are on par with amorphous silicon in the 6-8% efficiency regime. Personally, I'd be happy seeing one of every hundred skyscrapers in NYC with commerically availble Si cells (~12-14%) on their roofs.

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Posted by: Bandman on April 16, 2008 at 12:04 PM

The trick would be to produce a replacement for blacktop that generates electricity. Then those giant mall parking lots could serve a purpose. Along with streets, sidewalks, paths, etc.

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I'd be happy if anybody could produce solar electric panels that cost less than the electricity they can produce in their normal service life if you include the costs of maintenance for them too. Right now it makes no financial sense to go solar, but it does if you value the environment. Also, even if the prices were more on par with the price of electricity, the manufacturing process is still pretty harsh on the environment.

One caveat, in some cases it might be cheaper to install solar electric than run new power lines. Solar panels are very common in my area (rural New Mexico) because there is no alternative.

If you really want to change the world, consider solar heating panels. They pay for themselves in a few years and last decades.

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I disagree that it makes sense if you value the environment. Producing the panels takes a great deal of energy to begin with, plus other materials. Then at the end of the life of the panel, it's just garbage.

So there is a huge negative environmental impact in a solar panel, and I doubt it can, in its useful life, offset that.

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www.nanosolar.com

IF these guys get there ducks lined up then we would have something worth investing in for solar.

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I thought of this while in High School in the 70's. I made a presentation to PPG, Pittsburgh Plate Glass through a so-called Invention Marketing Firm. Cost me roughly $2K then. I got ripped off. Who knows if anything became of it. What is funny is I said the same thing almost 40 years ago..." would it not be cool to have a skyscrapers windows provide electricity for the whole building...every window could be a source for energy". I have seen several renditions over the years. Good luck with it!

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