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Powerhouse: Building-Integrated PV for Asphalt-Shingle Roofs

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Shingle.jpg

Dow Powerhouse shingles are installed like regular asphalt shingles, making them easy for roofers to handle and eliminating the need to have an electrician on the roof.

Photo: Dow Solar

By Paula Melton

The long-anticipated rollout of Dow Solar’s Powerhouse photovoltaic (PV) shingles has finally begun, with a handful of pilot installations in Michigan and an agreement with Colorado homebuilder D.R. Horton, which will install the systems on new homes in a Denver suburb.

The Powerhouse shingle is designed to be installed by roofers and integrate seamlessly into a typical asphalt-shingle roof. For the foreseeable future, the systems will be available only through handpicked homebuilders and authorized dealers—primarily roofing companies.

Domestically manufactured thin-film

The shingles incorporate copper indium gallium selenide (CIGS) thin-film cells with 12% conversion efficiency made by Arizona-based Global Solar and are manufactured at a Dow Solar plant in Midland, Michigan.

Kate Nigro, global communications and brand leader at Dow Solar, declined to comment on the long-term competitiveness of thin-film solar products given the plummeting cost of more efficient crystalline PV panels imported from China—a situation that has been putting U.S. factories out of business. However, Dow is not marketing the shingles as a low-cost alternative to crystalline; the major selling points are aesthetics and ease of installation.

Capacity and aesthetics

Because the shingles integrate with the rest of the roof, each array is customized based on the home’s orientation and roof style. Nigro claims that wattage per square foot is “not a metric that’s relevant to a roofing solution,” but she said a typical new home could readily support up to 5 kW of capacity. The company also declined to provide performance ratings for the shingles, claiming that testing conditions don’t reflect the benefits of thin-film, such as the ability to perform well in lower light.

Dow anticipates that homeowners’ associations will accept the shingles more readily than they accept roof-mounted crystalline panels. According to Melissa Wahl, co-owner of Cobblestone Homes, which has piloted the Powerhouse technology on two net-zero-energy demonstration projects in Michigan, about half of the people who come to tour the pilot homes need to have the shingles pointed out to them. “If they didn’t pick up on that right at the get-go, we’ve done something well,” Wahl said. “Some people do notice them because there is a sheen.”

One trade on the roof

VisionZero.jpg

The "Vision Zero" pilot home in Midland, Michigan, has a Powerhouse PV array on the roof. According to the builder, visitors to the pilot projects often don't even notice the solar shingles.

Photo: Dow Solar

“We’re very excited about our installation process,” said Nigro. “It’s the same type of work as installing an asphalt roof.” The company offers a training program to explain how to read the customized layout diagram and how to plug together and nail the solar shingles. The electrician does not need to be present during the installation and never has to go on the roof at all, which “simplifies the entire process,” she explained. Online videos of Powerhouse installations show the roofers casually walking on the installed shingles, and the company says the product can withstand rain, wind, and hail.

“The simplicity of installation is just amazing,” said Wahl. She added that because the shingles are part of the roof rather than an addition to it, transitions between a typical roof-mounted PV system and the roof itself are eliminated; the array “provides its own flashing.” The shingles in one row are plugged together to make a “string,” and then the wires at the end of the row are dropped into the attic through a small hole that is completely covered by a shingle, she explained. The electrician comes later to install the junction box indoors. “Durability-wise, we feel very comfortable with the product,” she added.

There are some quirks with installation, the most obvious one being that nail guns cannot be used for the Powerhouse shingles (they can still be used for the asphalt shingles surrounding the PV array). Instead they are hand-hammered through holes clearly marked “nail here” in both English and French. Wahl told EBN that the extra time needed for installation was negligible.

Cost and service life

According to Nigro, a Powerhouse array adds $10,000–$15,000 to the installed cost of a typical asphalt-shingle roof, after incentives. The company is carefully choosing markets, aiming for areas where payback time will be five to twelve years. Powerhouse shingles come with a 20-year warranty that reflects their expected service life. Asphalt shingles can be replaced without removing the array.

For more information:

Dow Solar

www.dowsolar.com

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November 29, 2011