Velocitel Energy Solutions: BP Solar Pico Rivera Towne Center
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Velocitel Energy Solutions contracted directly with BP Solar to install a 561 kW PV array at the Pico Rivera Towne Center, a large retail mall in southeastern Los Angeles, California. The design team had to consider extensive existing rooftop conditions, including 198 skylights, and the relocation of hundreds of feet of HVAC gas and condensation pipes, as well as 350 new roof penetrations and attachment points.
The rooftop skylights presented two challenges: providing fall protection for workers and accommodating an irregular array layout. Prior to mobilization, fall protection railings were erected around every skylight. Twenty-eight separate subarrays comprised the array layout, and installation crews needed to double and triple check the subarray locations before beginning to install each one. The roof was split into three zones, with a separate installation team dedicated to each zone. Teams worked from south to north, panelizing the modules for mounting to the SunLink supports at workstations that migrated south to north along with the installation progress.
Due to seismic considerations, the designers were required to locate 10 to 15 attachment points to the building per subarray. These followed an irregular pattern due to the segmented array layout. A team of roofers preceded each array installation crew. The roofers cut holes in the roof membrane and insulation down to the corrugated metal roof deck at points identified by a surveyor. The roofers then attached cylindrical stanchions to the roof deck and flashed the penetrations with TPO single-ply roofing membrane that followed the membrane manufacturer’s published specification.
The electrical side of the installation faced its own set of challenges. The utility transformer that fed the store switchgear was an older unit that needed to be replaced. However, the utility was not aware that shutting down the transformer during the PV system interconnection was too dangerous in the transformer’s current state. Just hours before the scheduled outage, after weeks of preparation and the scheduling of a 1 MW backup generator and refrigeration trucks—as well as teams from BP Solar, Blue Oak Energy, Southern California Edison, Velocitel, SASCO and the building owner—the utility canceled the shutdown due to the unsafe conditions inside the transformer. The interconnection had to be rescheduled for after the transformer was replaced. Several weeks later, the interconnection was successfully completed during a 2am outage that had no negative impacts on the stores’ operations.
Ultimately, despite the challenges, the installation was completed within budget and on schedule to the satisfaction of BP Solar and the building owner.
“The complex nature of this installation required the expertise of many different trades. Electricians, plumbers, roofers, surveyors, civil contractors, fencing contractors, safety consultants, utility workers and retail managers all worked together to deliver the project. It was a true team effort.”
—Morgan Vickery, Velocitel Energy Solutions
DESIGNER: Jayme Garcia, PE, electrical engineer, Blue Oak Energy, blueoakenergy.com
PROJECT MANAGER: Morgan Vickery, Velocitel Energy Solutions, energy.velocitel.com
DATE COMMISSIONED: August 2010
INSTALLATION TIME FRAME: 68 days
LOCATION: Pico Rivera, CA, 34.1°N
SOLAR RESOURCE: 5.66 kWh/m2/day
HIGH/LOW DESIGN TEMPERATURES: per solarabcs.org/permitting/map: 88°F/36°F
ARRAY CAPACITY: 561 kW
ANNUAL AC PRODUCTION: 905.5 MWh
MODULES: 3,300 BP Solar 3170N, 170 W STC, -3%/+5%, 4.8 Imp, 35.6 Vmp, 5.2 Isc, 44.3 Voc
INVERTERS: 3-phase, 277/480 Vac service, two Schneider Electric Xantrex GT250-480, 250 kW, 600 Vdc maximum input, 300–480 Vdc MPPT range
ARRAY: 12 modules per source circuit (2,040 W, 4.8 Imp, 427.2 Vmp, 5.2 Isc, 531.6 Voc); 139 source circuits on Inverter One (284 kW, 667.2 Imp, 427.2 Vmp, 722.8 Isc, 531.6 Voc); 136 source circuits on Inverter Two (277 kW, 652.8 Imp, 427.2 Vmp, 707.2 Isc, 531.6 Voc)
ARRAY INSTALLATION: SunLink Roof Mounting System installed on single-ply thermoplastic olyphen (TPO) membrane, 213° azimuth, 20° tilt
ARRAY STRING COMBINERS: 24 Steven Engineering String Combiner, 9 A fuses
SYSTEM MONITORING: National Semiconductor/Energy Recommerce RECtrack 3