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Evolving Toward High Efficiency
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.
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
— tossed onto a
roof in bundles
and nailed down
through a water-
and so, for the
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
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
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.
10 May 2012 SOLAR TODAY solartoday.org
Copyright © 2012 by the American Solar Energy Society Inc. All rights reserved.