system accomplished

System Accomplished focuses on unique design or installation problems and how they were solved. if you have solved a difficult installation problem, we want to hear about it. Email smasia@solartoday.org.

Washington’s largest solar array, a 782-kilowatt (k W), 2.5-acre PV array, is on the rooftop of an event center adjacent to CenturyLink Field.

installer Surmounts Snags at Seattle Stadium

FiRST & GoAL

Bono, or a non-compliant disconnect switch? Seattle-based McKinstry, contractor for the solar photovoltaic (PV) system on the rooftop of CenturyLink Field Event Center, isn’t saying which made for the more memorable installation experience.

CenturyLink Field (formerly Qwest Field) is the home of the NFL’s Seahawks and Major League Soccer’s Sounders, and the location of frequent large-scale events. As of late June, it’s also the site of a 782-kilowatt (k W), 2.5-acre PV array. The Solyndra system, on the rooftop of an event center adjacent to the stadium, hit the grid as Washington’s largest.

Besides a space-themed U2 concert, McKinstry had to accommodate for a number of other events during the nine-day panel installation. The Seahawks cheerleaders — the “Sea Gals” — held a function, and there were shows at the WaMu Theater and soccer and baseball games to be worked around. “At times, the site was very busy with traffic and people coming and going to events,” said John McBride, project manager at McKinstry. “It did extend the actual delivery of the panels by around four or five days.

McBride worked closely with First & Goal, the field operator, to work out a delivery schedule based around everything going on. “We took our deliveries as early in the morning as we could — by about 6:00, 6: 30 a.m. By noon, we were pretty well offloaded from the truck, with the product up on the roof,” he said.

The crew, consisting of two install teams of three people, four panel transporters, a crane operator, bell man and two flaggers, averaged 375

panels delivered and installed per day, with a peak delivery of 468. The self-ballasted, non-penetrating Solyndra panels, chosen because of the freshly renovated white “cool roof,” simplified the installation, allowing for half the team to be comprised of apprenticeship labor.

Approximately a month into the project, but before the panels arrived, McKinstry became aware of compatibility issues with the disconnect switches. As originally designed and approved, the system featured a 1,200-amp switch for each of its two Power-One inverters. McBride came across a white paper that suggested the planned design could fail to break the DC power from the inverter — a potential safety hazard to maintenance crews. By using multiple 600-amp, three-pole disconnect switches per inverter, which increased the DC arc gap, the redesign corrected the issue. Without compromising the construction schedule, it was approved by the city of Seattle within days.

Completion of the system gives Seahawks’ owner and Microsoft co-founder Paul Allen another green stadium under his belt. In 2010, the Rose Garden, the arena of Allen’s NBA team, the Portland Trail Blazers became the first pro-sports stadium to achieve LEED Gold certification.

The CenturyLink Field system will output 830,000 kilowatt-hours of electricity annually. That offsets 380 tons of carbon emissions, equivalent to planting about 71 football fields of trees. — MikE koShMrl