Blog Post
Dow's Powerhouse photovoltaic (PV) roofing shingles are designed to integrate into a conventional asphalt shingle roof, and when Dow announced the product in 2009 they caused a lot of excitement. Two years later and they are finally on the market, but my excitement is dampened slightly, recognizing the tremendous challenges that lie ahead for any thin-film PV in today's market, especially products aimed for a depressed housing market.
The Powerhouse shingle is assembled in a recently built factory in Midland, Michigan using copper indium gallium selenide (CIGS) thin-film cells made by Arizona-based Global Solar. These cells have a conversion efficiency of 12%, which is great for a thin film, and the shingles are designed to match a conventional asphalt roof so they are barely noticeable. This latter point is important because there are some people who don't like the look of conventional PV panels--they are banned by some homeowner associations--so this building-integrated PV (BIPV) solution offers a PV option in those circumstances.
Dow is marketing this as a roofing shingle as much as PV. The shingles are hand-nailed in place by roofers specifically trained by the company. For the PV, each shingle connects to the next (if one goes out the rest still work) and then feeds through a hole in the roof that is covered by the shingle. There are no exposed wires and the shingles "provide their own flashing," according to a Michigan builder who has installed the shingles.
Up until a year or so ago, CIGS thin-film PV was considered a decent investment because of its low cost. Thin-film cannot match crystalline PV performance, of course, whose efficiency exceeds 20% in some cases, but thin-film PV offers decent low-light performance and works better at high temperatures (the kind found on asphalt roofs), so the energy gained over the course of a year can be comparable under the right circumstances.
But thin-film's cost advantage has been severely hurt by the influx of inexpensive, high-quality PV panels from China. BuildingGreen pressed Dow for specific performance and cost information, but all the company would say is the Powerhouse shingles will add $10,000–$15,000 to the installed cost of a typical asphalt-shingle roof, after incentives and that a new home could support 5 kW of capacity.
Powerhouse shingles are being rolled out in limited distribution in Denver under an agreement with homebuilder D.R. Horton and will be available in limited markets depending on local and state incentives.
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See membership options »With homebuilding at a standstill and a glut of inexpensive crystalline PV available, this is a challenging market for launching a residential BIPV roofing product, but Powerhouse has the potential to be an important PV product. Though their performance is not as good as current crystalline panels, thin-film technology is improving, and there is no reason Dow won't be able to integrate improvements into its shingles as the technology advances. And creating a PV product that integrates into a home so that it is barely noticeable is a positive step toward PV becoming a routine part of our lives.
Published November 16, 2011 Permalink Citation
(2011, November 16). BIPV Solar Shingles Angle for Space in the Residential Market. Retrieved from https://www.buildinggreen.com/news-article/bipv-solar-shingles-angle-space-residential-market
Brent,
That is exactly my point. Even Crystalline PVs often require structural upgrades depending on the age of a home adding significant costs to installing PVs. This would avoid that upcharge possibly making them competitive with Crystalline PVs from a cost perspective.
Hi Lloyd,
I think you raise valid points. We’re not fans of asphalt shingles, and BIPV does present challenges. But if installed properly there is no reason Powerhouse shouldn’t outlive the other shingles. Perhaps there will be more environmentally sound, equally inexpensive shingles—and recycling options—when it comes time to replace them. And for the electrical system, I would hope that the 20-year warranty covers any potential problems, and the modular nature of these means that one shingle can be replaced if there is a problem without impacting the rest of the system.
As for maintaining separating building components, I think Powerhouse shingles approach the problem from a different angle. Though they are nailed to the roof, when the asphalt shingles are replaced at the end of their service life the PV doesn’t have to be moved. With a conventional roof-mounted PV system the racking system has to be removed and reinstalled when the shingles are replaced, which is a huge headache. Ideally you have the yard space for one of the cool new ground-mounted AllSun Trackers that we gave a Top 10 product award to this year.
Sam, I don’t think weight will be as much of an issue as it would be with some solar thermal systems, for instance. With the weight distributed across the roof, there shouldn’t be any need for additional structural support.
In retrofit applications these may, may, just be more cost effective because I am assuming they are not significantly heavier than the asphalt shingles they replace (are they?). If that is the case the building owner may be able to minimize, or avoid altogether the expense of upgrading the structural system to carry the loads of Crystalline PVs.
I really wonder about the whole idea of these. Asphalt shingle roofs are cheap and disposable, and here you are integrating something that is expensive and permanent. Electrical connections are often the weakest part, and on one sample in a photo I looked at I counted 182 connections that will be alternately baked and frozen, sometimes on the same day.
Tedd Benson, in his open building system, is teaching us 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" and here we are nailing solar panels in as part of the roof.
I wrote about it in TreeHugger http://www.treehugger.com/renewable-energy/powerhouse-solar-shingle-is-c... and all the commenters thought I was an idiot, but I still think it is questionable.
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