Sun Light & Power: Hanover Page Mill Associates

Jim Gaither and Jim Gaither Jr. of Hanover Page Mill Associates wanted their new 87,000-square-foot commercial office building to have net zero electrical usage with 100% of the electrical load offset by on-site PV generation. The owners also wanted a beautiful PV system. The Gaithers contracted Sun Light & Power (SLP) as the design-build firm for the PV portion of the project. During the 2 years of design and construction, the design team reduced the PV system capacity from 633 kW to 412.16 kW as it refined the energy model and increased the energy efficiency of the planned building.

A fully attached racking system maximizes the array coverage of the available roof area. SLP installed 262.91 kW of the total 412.16 kW array on the building roof, with the majority of the remaining array deployed on two highly visible parking lot shade structures. M Bar C’s latest FIT mounting system aligns the module edges with the purlins, creating very clean lines when viewing the parking canopies from underneath. In addition, SLP painted the columns, beams and purlins the same color. Due to the unusually small size of the HiQ inverters, SLP was able to effectively hide them atop the canopy beams.

The team installed the remaining 12 kW of PV on a tall trellis structure over the main entrance to the building. SLP and the owners chose Lumos Solar frameless modules with transparent backsheets for the final array segment. Careful design of the steel substructure coupled with Lumos LSX mounting rails produced very clean visual lines. SLP designed a custom sheet-metal section to contain and hide the module leads, homeruns and Tigo Energy Dual Maximizers. The designers located the trellis array’s HiQ inverters in an electrical room to keep them out of sight. The trellis array is almost 30 feet above the ground and needed to look perfect. Scissor lifts did not allow the necessary simultaneous access for the installers to get everything visually aligned during construction, so SLP built a full scaffold platform just below the top of the trellis, allowing its installers to work comfortably and safely on the entire trellis array at once.

Early on, SLP switched the entire project from traditional wall-mounted string inverters to HiQ Solar TrueString inverters due to the limited space. Even with a painfully complex and tight layout, the electrical room did not afford sufficient space, and there were aesthetic issues with locating string inverters on a large HVAC screen on the roof. In the end, the HiQ product distributed throughout the rooftop and shade structure arrays worked perfectly.

“The ownership group we were working with was one of the unique aspects of this project. This was an engaged and actively involved ownership team who worked collaboratively with us to overcome challenges. They were involved in every level of detail, from the height of the arrays off the roof to the size of the ‘mow curb’ bases at the carport columns. It felt more like a partnership than the traditional owner-contractor relationship.”

Jon Trevor, project manager, Sun Light & Power

Overview

DESIGNER: Ben Bachelder, PV project engineer, Sun Light & Power, sunlightandpower.com

LEAD INSTALLER: Tyler Wallace, PV foreman, Sun Light & Power

NET ZERO CONSULTANT: Point Energy Innovations, pointenergyinnovations.com

DATE COMMISSIONED: October 1, 2015

INSTALLATION TIME FRAME: 75 days

LOCATION: Palo Alto, CA, 37.4°N

SOLAR RESOURCE: 4.93 kWh/m2/day

ASHRAE DESIGN TEMPS: 84.2°F 2% avg. high, 32°F extreme min.

ARRAY CAPACITY: 412.16 kWdc

ANNUAL AC PRODUCTION: 655 MWh

Equipment Specifications

MODULES: 1,312 Trina Solar Trinasmart TSM-305PD14.002 with integrated Tigo Energy dc optimizers, 305 W STC, +3%/-0%, 8.33 Imp, 36.6 Vmp, 9.5 A maximum current, 39.4 Vdc maximum voltage; 48 Lumos Solar LSX250-60M-C, 250 W STC, +3%/-0%, 8.31 Imp, 30.1 Vmp, 8.78 Isc, 37.3 Voc

INVERTERS: 277/480V service, 44 HiQ Solar TrueString TS480-8k, 8 kW rated output, 1,000 Vdc maximum input, 425–850 Vdc full-power MPPT range, dual MPPT

ARRAY: 14–16 modules per source circuit (for Trinasmart modules), 8.33 Imp, 9.5 A maximum current per string, 4.27 kW–4.88 kW per source circuit; two source circuits per inverter, 8.54 kW–9.76 kW total per inverter; Trina array total 400.16 kW; Lumos modules integrate with Tigo Energy Dual Maximizers (MM-2ES), two modules per dc optimizer; Lumos array total 12 kW

ARRAY INSTALLATION: 262.91 kW roof-mounted with custom pipe and channel racking, IronRidge XR-100 rail and module clamps; 65.88 kW mounted on shade structure 1 and 71.37 kW mounted on shade structure 2; both shade structures use M Bar C Fast Install Track (FIT) mounting system; 12 kW mounted on trellis with Lumos LSX rail; 213° azimuth, 5° tilt (all arrays)

SYSTEM MONITORING: HiQ Solar string-level and inverter diagnostics monitoring, Tigo Energy module-level monitoring, Locus Energy system-level and revenue grade monitoring

Article Discussion

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