Evolving Toward High Efficiency

Greening
WrEF 2012

Dow solar

Dow solar’s Powerhouse building-integrated photovoltaic (biPV) shingles made their commercial debut in Denver last fall, but the company was coy about technical specifications. we sat down with ceo jane Palmieri in february to learn more.

seth Masia
first of all, Palmieri said, future growth
depends on solar being sold as a con-
sumer product. so Powerhouse will be
sold not through traditional solar install-
ers, but through mainstream roofers and
homebuilders. it is designed to handle like
a conventional
asphalt shingle
— tossed onto a
roof in bundles
and nailed down
through a water-
tight membrane.
and so, for the
first generation
of production,
Dow chose not a
rigid, relatively fragile crystalline silicon
technology, but a copper-indium-gallium-
selenide (ciGs) thin film on a light, flexible
plastic substrate. Dow buys the plastic
modules from existing ciGs manufactur-
ers, then laminates them into a standard
12-by-36-inch shingle shape. Palmieri
notes that the ciGs technology is improv-
ing rapidly, and the company hasn’t
Jane Palmieri

announced a specific efficiency because
that’s been a moving target. it’s gone from
9 percent to more than 11 percent within
the past year, and is headed for 13 percent
as the company ramps up to full-scale pro-
duction at a larger plant in Midland, Mich.
at 11 percent, a three-square-foot
shingle would produce 25 peak watts.
the homebuilding company D.r. horton
is now installing 3-kilowatt (kw) Pow-
erhouse systems on new-construction
homes in the Denver area. that would
require 120 shingles covering 360 square
feet ( 33 square meters).
Powerhouse shingles plug together.
the only cable run required is off the end
of the string to a central inverter (from
Kaco or emerson). the first three retail
dealers, who plan to sell the product for
reroofing projects, are academy roofing
(Denver), b&M roofing (frederick, colo.)
and D&D roofing (commerce city, colo.).
and, according to Palmieri, ciGs is not
the final word. Powerhouse may evolve
into a high-efficiency gallium-arsenide
product. — SE TH MaSIa

the colorado convention center (ccc) — site of the world renewable energy forum (wref 2012), May 13-17 — has been generating solar power since 2008. the 300-kw array on the south roof (see cover photo) uses 1,310 230-watt sunPower modules feeding three satcon three-phase inverters. installed with a nonpenetrating ballasted rack by Namasté solar, the system provides 14 percent of the building’s electricity year-round, and up to 23 percent during air-conditioning season (see the data log at bit.ly/helGgd). another 25 percent of the building’s electric load is carried by wind power.

LEED: in May 2010, the ccc received leeD: existing building operations and Maintenance certification.

Waste and Water: ccc has an advanced waste-handling process that diverts 48 percent of its refuse from landfill to compost, recycling and donation programs. in colorado’s high-prairie climate, water use is a critical issue, so the ccc landscaping uses native drought-resistance plants to reduce irrigation load by 75 percent. water-saving measures are used throughout the complex.

Air Quality and Carbon Offsets: Drivers of delivery and passenger vehicles should note that Denver’s anti-idling ordinance is strictly enforced. Visitors are invited to use the two bike share stations ( bcycle.com). and attendees may purchase carbon credits on site to offset the carbon footprint of travel to wref 2012.