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On Rooftops, A Newly Attractive Form of Solar Power

It may not be attractive to your pocketbook, but at least it'll look slick: Dow Chemical has unveiled a new solar rooftop shingle that converts the sun's rays to electricity. The shingles work just like solar panels, but without the bulky (and ugly) mounting systems used to attach panels to regular roofs.

Not a company to dream small, Dow says the solar shingle market could reach $5 billion by 2015, and $10 billion by 2020.

Dow's shingles will have some other advantages over traditional solar panels, at least according to the company. For one, they'll take less time to install, so the installation costs could be reduced by half or more.

They also may be easier for roofers to figure out than mounting arrays, and for a newly constructed house, they should be even cheaper to put in than for a retrofit.

Costs are also coming down for the solar cells themselves. A couple weeks back, I wrote about Global Solar, which is providing the solar tech to Dow. The company has topped 10 percent efficiency for its production thin-films, and is busy trying to shave pennies off the production cost.

And there should be some stimulating competition within the solar shingle market. Another company, SRS Energy, has a curved shingle it calls the Solé Power Tile. I'm used to seeing Spanish-style tiles in red hues, but there is something uniquely attractive about them solar-panel blue. Here's one view (much more at Inhabitat):

Unfortunately, it looks like Dow has been ducking questions that have to do with the cost per watt on the solar shingles. Maybe it's just too early to tell, but it could be that the pitch and direction of different roofs means that cost per watt often ends up being higher than solar panels.

Taking the SRS Energy roof pictured above as an example, it's easy to see how solar shingles could be a waste of money.

In the northern hemisphere, south-facing roofs tend to get the best sunlight, while the other three cardinal directions aren't as good; installing panels on them is a waste of money. The angle is also important (though less so for thin-films). And in the case above, there's a rather egregious problem, in that some parts of the building block sunlight from reaching other parts.

You won't hear it addressed by any of the companies involved, but solar shingles can also cause heat problems, because they're flush with the house (solar panels are elevated). At one point last year, an analyst noted that some early installations had even burst into flame, although the companies he named denied it when I contacted them.

In short, there's a lot yet to be worked out for solar shingling. And in terms of the competitive market, BIPV will have to compete not only with solar panels, but also with the "white roof," which reflects some of the light that hits it back into space (though it's not necessarily white).

A white roof doesn't produce energy for the home, but it could help keep houses in hot areas cool. And as an environmentally-friendly alternative, it's a lot cheaper than solar paneling.

All the options, though, are great for homeowners. When all is said and done, roofs that just keep the rain out may be the one option that disappears.

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