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Monday, November 22, 2010

PowerHouse Solar Shingle Is Clever. But Is It A Good Idea?

by Lloyd Alter

dow powerhouse solar shingle display photos

95% of roofs in America are asphalt shingles that are cheap, fossil fuel based, heat absorbing and don't last very long; then they are hard to get rid of. They have been called "a disposable roofing system that is difficult to dispose of." But did we say they were cheap? Dow Chemical decided if you can't beat'em, join'em and has developed the Powerhouse solar shingle, which John showed us last year. It just got UL approval and can now prepare to go to market in early 2011.

But is this a good idea?

dow powerhouse solar shingle display closeup photo

One has to admire the way they have figured this out; roofers are often not the sharpest knives in the drawer and they have spelled it out clearly, not only putting in nail holes, but clearly saying "nail here". The connection from one shingle to the other is similar to a USB plug and lines the shingles up nicely. Then the connection is covered up by the next row.

dow powerhouse solar shingle display assembly photo

There are endpieces to finish it off nicely. Dow says in their press release:

Breaking the traditional barriers to residential solar adoption - complexity, affordability and aesthetics - this technology offers the missing link needed by the energy industry to drive solar adoption across the U.S., and will bring the possibility of safe and reliable solar power to American households.

Asphalt shingles are rated by supposed years of life, in 25 and 35 year grades. They are, hands down, the cheapest roofing in existence. But those lifespans are under perfect conditions; a south facing roof will start deteriorating, drying out, curling and breaking up from the day it is installed. You don't buy an asphalt roof, you rent it. Along with vinyl siding and PVC windows, it is one of the reasons that American housing is so cheap and so shoddy. And according to Energy Secretary Chu, we are supposed to be installing white roofs, not black.

So is it a good thing to integrate an expensive solar system into such a cheap roof? Or should it be independent, so that the roof can be replaced without affecting the solar collectors? How does the heat generated by being part of a black roof on top of a hot attic affect the performance and lifespan of the solar panel?

dow powerhouse solar shingle display installation photo

And while those connections are simple and straightforward, in this installation I count 182 of them, all permanently inaccessible after the roof was installed. They will be baked and frozen, wet and dry. Finally, I have to note that solar photovoltaics are supposed to be installed at latitude-appropriate angles, facing due south. How much efficiency is lost by putting them on a roof that is only vaguely close to either?

Philip Proefrock described Tedd Benson's open building system:

"The principle is to maintain a separation between the different aspects of the building in order to be able to make repairs and do upgrades with a minimum of interference with other elements of the building.....Much in the same way that we need to conserve resources for the use of future generations, the buildings we build today will also be used and re-used well into the future, and a longer-term approach to building is another part of building green."

The Powerhouse solar power system appears to be the antithesis of this. It is a cleverly designed system; it will be cheaper and almost foolproof to install. But that doesn't necessarily make it the right thing to do.

More at PowerHouse by Dow

More solar shingles:
Sunslates: Solar Powered Shingles
Dow Steps Out Into The Sun With POWERHOUSE™ Solar Shingles
Sharp Electronics, Multi-Crystal SPV Integrated Roof Tiles