True South Solar: Ashland Food Co-op
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The Ashland Food Co-op has a long history of supplying healthful organic food to Southern Oregon’s Rogue Valley and beyond. The Co-op started as a buying club in 1971 and has grown into a full-service cooperative grocery and deli with over 8,000 owners. It emphasizes locally produced, organically grown and ecologically sound products. While the Co-op has been operating a rooftop PV system for close to a decade, in 2016 it contacted Ashland-based True South Solar (TSS) to evaluate options for expanding the array.
New equipment choices, coupled with decreases in cost, can make high-density array designs that maximize annual production of rooftop systems attractive to integrators and their customers. The original Co-op array included three rows of nine modules mounted at a 30° tilt angle, with large gaps between rows to minimize interrow shading. This section of the array occupied a prime solar resource area on the building’s flat upper roof. A larger low-tilt high-density array would allow the Co-op to offset a greater portion of its annual consumption.
Initial discussions weighed relocating the original system to another area on the building or property. However, when the team compared the cost and benefit of moving the old system to that of replacing it with a new system using current modules and power electronics, it made the decision to decommission the original system. The Co-op plans to donate the equipment to the Ashland Emergency Food Bank in cooperation with TSS, which will donate the labor required to install the system at its new location.
Determining the layout of the new Co-op array was tricky due to all the rooftop HVAC equipment and required setbacks. When TSS considered the locations of the HVAC equipment, the shading and the orientation of the metal roofing panels that run roughly east-west, it determined that an array orientation of 112° with a 10° tilt was optimal. Orienting the array at 180° would have locked the attachment spacing with the spacing of the standing seams, which would have created more small subarrays, reduced the overall number of PV modules and increased labor costs. The arrays consist of nonpenetrating Sunmodo AceClamps, SnapNrack racking and Oregon-assembled SolarWorld modules.
The building’s 120/208 Vac 3-phase service and lack of space to mount inverters in the electrical room or on the building's exterior narrowed the inverter options considerably. TSS determined that HiQ Solar inverters were a great choice for the application due to their 3-phase output and mounting location flexibility. Each 5.75 kWac inverter has two MPP trackers that provide many string length options. To minimize installation complexity, TSS opted to group the six HiQ inverters together and mount them on a strut platform under the far western array. This location is close to the system’s point of interconnection and required only a short ac conduit run. Colocating HiQ inverters with two HiQ Solar AC Splice boxes allowed TSS to use the inverter ac whips to parallel the inverter output, without any additional ac raceways or wiring.
“The Ashland Food Co-op is a very integral and positive part of our community. Designing and installing a PV system for the Co-op was a true honor. It’s been a wonderful experience helping increase the size of this locally owned and operated renewable energy system.”
—Ry Heller, True South Solar
DESIGNER AND LEAD INSTALLER: Ry Heller, designer and field manager, True South Solar, truesouthsolar.net
DATE COMMISSIONED: October 26, 2016
INSTALLATION TIME FRAME: 5 days
LOCATION: Ashland, OR, 42.2°N
SOLAR RESOURCE: 4.9 kWh/m2/day
ASHRAE DESIGN TEMPS: 96.8°F 2% average high, 17.6°F extreme minimum
ARRAY CAPACITY: 39 kWdc
ANNUAL AC PRODUCTION: 45,572 kWh
MODULES: 150 SolarWorld Sunmodule Pro-Series SW 260 Poly, 260 W STC, +5/-0 W, 8.37 Imp, 31.4 Vmp, 8.94 Isc, 38.4 Voc
INVERTERS: 120/208 Vac 3-phase service, six HiQ Solar TrueString TS208-5k75 inverters, 5.75 kWac, 1,000 Vdc maximum input, 325 Vdc– 525 Vdc MPPT range, 3-phase 208 Vac output
ARRAY: 12–14 modules per source circuit, (3,640 W STC, 8.37 Imp, 439.6 Vmp, 8.94 Isc, 537.6 Voc for 14-module source circuits), two source circuits per inverter, 39 kWdc array total
ARRAY INSTALLATION: Low-profile roof mount, standing seam metal roofing, Sunmodo Standing Seam AceClamp A2N Nail Down Kit, SnapNrack 100 Roof Mount System, 112° azimuth, 10° tilt
INVERTER CIRCUIT COMBINERS: Two HiQ Solar AC Splice ACSPL-60, each combining ac outputs of three HiQ Solar TrueString inverters, unfused
SYSTEM MONITORING: HiQ Solar gateway with integrated web server, web-based string-level monitoring