solar installations
CHuCk NELSON
BIPV Crowns Historic Retrofit
A REdEvELOPEd AIR FORCE HANgAR WITH BuILDING-
INTEGRATED PHo ToVoLTAICS HIgHLIgHTS SOLAR’S
POTENTIAL AT dENvER’S MIxEd-uSE SELF-STORAgE PROJECT.
By GINA R. JoHNSoN
It was, in architect Jim Hartman’s words, a hard nut to crack.
The Lowry Air Force Base in Denver, built in
1938 and comprising two massive hangars, had
been shuttered in October 1994 due to military
cutbacks. Even as Hangar 1 became home to an
air and space museum, developers struggled with
Hangar 2. One by one, plans to redevelop it as a
condo building or senior apartments or to simply
level it were discarded. Finally Hartman’s development company, Hartman Ely Investments, with
partners at Larimer Associates, hit on the idea of a
mixed-use project. The centerpiece of the Lowry
Dining District: Hangar 2, redeveloped as a super-efficient self-storage facility and crowned by solar
panels to simulate the facility’s original skylights.
It’s unusual to get approval to put photovoltaics (PV) on a historic landmark, but Hartman
had a proposal that appealed to the Landmark
Preservation Commission: to use building-inte-grated PV (BIPV) panels to replicate the appearance of three rows of skylights on the old hangar’s
Pv System Highlights
Hangar 2 at Lowry, Denver
Site Details
Average Solar Resource: 4.55 kilowatt-hours/square meter/day
Average High/Record Low Temps:
46°F–88°F ( 8°C− 31°C)/minus 24°F (minus
31°C)
Latitude: 39. 8 degrees north
System Details
Concept Architect, System Developer:
Hartman Ely Investments, with Larimer
Associates
Designer, Integrator: Martifer Solar USA
Array Capacity: 106 kilowatts
Annual AC Production: 148,343 kilowatt-hours
Panels: 504, 210-watt crystalline panels
from Suntech
Inverters: PV Powered 110-kilowatt
inverter
Array: 36 strings of Suntech STP210s
Array Combiners: Solectria
System Installation: BIPV modules on
Unistrut racking attached to existing
curved metal deck roof. Varying tilts,
144-degree azimuth
System Monitoring: DECK Monitoring
Platform
Installation Time Frame: Three weeks in
August 2010
Cost and Incentives
BIPV system with Suntech panels: about
$498,000
Federal cash grant: ($149,000)
100% depreciation bonus: ($148,000)
Xcel utility rebates: ($200,000)
Xcel REC payments: 6. 5 cents/k Wh
Total cost after incentives: $0
34 March/April 2012 SOLAR TODAY solartoday.org
gina R. Johnson ( editor@solartoday.org) is
SOLAR TODA Y’s editor/associate publisher.
southeast-facing roof. The project required close
coordination with the commission and systems
designer/integrator Martifer Solar to ensure the
panels looked like skylights.
Hartman believes the 106-kilowatt BIPV
system is one of the nation’s largest. It helped
that his firm had designed another BIPV project
using architectural canopies, featuring custom-made glass panels and structural silicone mounting solutions. That experience smoothed the way
with the Hangar 2 project and its unique mounting challenges.
The first obstacle Martifer Solar faced was
repairing the hangar roof. The installation team,
led by Chuck Nelson, did significant restora-
tion to repair leaking and loose metal panels.
Said Hartman, “I don’t know how many tens of
thousands of screws the Martifer guys had to use,
because the old roof is literally a bunch of sheets
of metal deck.”
Simulating the old skylights meant installing
three, 275-foot-wide (84-meter-wide) bands of
PV panels across the hangar roof — more than
500 210-watt Suntech panels total. Each band of
panels crosses over a roof expansion joint, which
required a break in each strip.
Complicating the installation, the old electrical room was located on the north side of the
building, clear across the hangar from the south-facing panels. That meant thousands of feet of
conduit to connect the arrays to the inverter.
Installers used high lifts inside the building to
install conduit on the underside of the 90-foot-
high (27-meter-high) roof.
Outside, the crew faced a steeply sloped
roof surface and occasional very windy conditions. “When putting the racking and panels on
the roof — especially the lowest strip, which is
the steepest part of the roof — they were using
rock-climbing gear and literally rappelling down
the roof to stay safe,” Hartman recalled. What’s
