RMK Solar: Snyder’s of Hanover
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Snyder’s-Lance, a snack food manufacturer with plants across the US and in Ontario, Canada, recently commissioned a 3.546 MW PV array located at its Hanover, Pennsylvania, facility. RMK Solar was contracted to complete the design and construction of the project, which features a 3 MW array interconnected with the company’s manufacturing facility service and a 546 kW array interconnected with a recently completed R&D facility. The total energy generated on-site offsets approximately 30% of the campus’s annual consumption.
RMK’s initial design called for one array that would be interconnected with the manufacturing facility’s existing service. However, as RMK worked with local utility First Energy to establish the interconnection agreement, it discovered that the largest PV array that could be connected to a single service was 3 MW. This limitation required design changes to accommodate both the utility’s and the customer’s requirements.
SMA Sunny Central HE inverters and medium-voltage transformers were specified to allow direct connection to the plant’s 13.2 kVac service. The transformers were located close to the inverters to reduce the required conductor size by increasing the transmission voltage. The switchgear used for the utility interconnection was custom designed by Square D.
Given the large area required for the array and the slope variations on the site, RMK could not perform the excavation needed to create a relatively flat field for mounting the array. As a result, driving the racking system’s piles required meticulous attention to position the array to precisely follow the contours of the land.
Upon completing the test pile installation and soil testing, RMK found that the hilly terrain had high amounts of shale. Initially, this suggested that a large number of piles would not reach their required depth. Custom trailers were developed and equipped with punching, drilling and cutting tools to modify the affected piles. Fortunately, only several dozen piles out of 2,700 required modification, and the addition of concrete footers was avoided.
Another challenge was the need to bore under a state highway. The PV array is located on the opposite side of the highway from the interconnection point. The bore hole had to be carefully placed because the required path was close to existing township water mains and other utilities. A directional bore was successfully located without incident.
RMK designed and installed a custom monitoring system that employs RS-485 and Modbus communication between the inverters and the Shark 100S revenue meters. Current transducers were installed to monitor each individual source-circuit combiner box. All monitoring devices were routed back to a main PLC using fiber optics. The customized solution allows RMK Solar to have web access to all live and historical data and also permits a remote on/off control of the entire system’s main switchgear.
“The Snyder’s of Hanover solar project faced many up-front challenges due to the size of the system. Our engineering team worked closely with the utility company to design a single system that would feed two services and meet all utility requirements.”
—Jason Dorta, RMK Solar
DESIGNER: Robert H. Kline, president, RMK Solar, rmksolar.com
LEAD ENGINEER: Jason Dorta, solar design engineer, RMK Solar
DATE COMMISSIONED: May 2011
INSTALLATION TIME FRAME: 160 days
LOCATION: Hanover, PA, 39°N
SOLAR RESOURCE: 4.2 kWh/m2/day
HIGH/LOW DESIGN TEMPERATURES: per Solar ABCs Solar Reference Map: 91°F/5°F
ARRAY CAPACITY: 3.546 MW
ANNUAL AC PRODUCTION: 4,453 MWh
MODULES: 15,092 SCHOTT PERFORM POLY 235, 235 W STC, +4.99/-0 W, 7.78 Imp, 30.2 Vmp, 8.42 Isc, 37.1 Voc
INVERTERS: 3-phase, 13.2 kVac service, seven SMA Sunny Central 500HE-US, 500 kW, 600 Vdc maximum input voltage, 330–600 Vdc MPPT range; four copper 200 V:13.2 kV 1,000 kVA transformers total; two inverters per transformer (typical)
SUBARRAYS: 14 modules per source circuit (3,290 W, 7.78 Imp, 422.8 Vmp, 8.42 Isc, 519.4 Voc); 22 strings per source-circuit combiner (72.4 kW, 171.2 Imp, 422.8 Vmp, 185.2 Isc, 519.4 Voc); seven combiner circuits per inverter (506.7 kW, 1,198 Imp, 422.8 Vmp, 1,296 Isc, 519.4 Voc); seven subarrays total
ARRAY INSTALLATION: Ground mount, Schletter FS System racking, 180° azimuth, 39° tilt
ARRAY STRING COMBINERS: 49 Cooper Crouse-Hinds, CCBS22F20, 15 A fuses
SYSTEM MONITORING: Custom-designed PLC-based monitoring system