Borrego Solar: Palmer Metropolitan Airfield

The 6 MW Palmer Metropolitan Airfield installation is the largest Department of Energy Resources (DOER)–qualified brownfield project under the Massachusetts SREC II solar energy incentive program. The SREC II program promotes the positive reuse of sites cleaned up under Massachusetts Department of Environmental Protection supervision. Prior to qualifying the solar installation, the state remediated Palmer Airfield after 75 years of airfield operations dating back to the 1920s. Massachusetts caps projects such as the Palmer Airfield at 6 MWdc.

Multiple entities benefit directly from the project. The Town of Palmer will receive real and personal property tax revenue valued at approximately $2 million over the 20-year project term. Three public entities—the Town of Leicester, the Town of Spencer and Worcester State University—will together purchase all the net metering credits from the energy that the project generates, resulting in millions of dollars in energy savings for these entities over the 20-year terms of the agreements. Finally, the landowner, JenJill of Wilbraham, Massachusetts, which purchased the site and paid for its cleanup, will benefit from the long-term ground lease.

Borrego Solar designed and built the system, and negotiated and finalized off-taker agreements with the Town of Leicester and the Town of Spencer. Syncarpha Capital financed, owns and operates the Palmer Airfield facility. Renewable Energy Massachusetts, with assistance from Syncarpha Capital, gained site control and negotiated the lease with the landowner, performed all project development functions including permitting, initiated the National Grid interconnection process, cemented Worcester State University as a key energy off-taker and secured the DOER’s SREC II Brownfield Qualification designation for the site.

The most difficult aspect of the Palmer Airfield project was the management of site logistics. The project has “Frankenstein” elements. The team had to account for, sort, install and commission eight module types. While 1,000 Vdc would have been the optimal system design voltage, Syncarpha Capital had a variety of safe-harbored 600 Vdc–rated modules that it preferred to utilize. Borrego determined that SMA Tripower inverters had a wide enough MPPT window to permit their use in both 600 Vdc and 1,000 Vdc source-circuit configurations on-site. Therefore, the installation team deployed the stored Canadian Solar and Suniva modules in 600 Vdc configurations and the newer 1,000 Vdc–rated Yingli modules in 1,000 Vdc configurations. Florence Electric played a central role in the project’s success by managing and tracking the various module models and the specific rack purlins required to mount them.

Despite the challenges of incorporating different modules, workers completed the project’s construction 7 weeks early. J. Bates and Son, the subcontractors, facilitated the presence of experienced workers on-site 7 days a week when necessary, enabling completion of the project well within its projected time line. This Palmer Airfield installation highlights the benefit of choosing reliable, high-quality construction partners and an EPC contractor that has those relationships in place.

“Throughout the duration of the project, all parties involved continuously maintained a keen focus on executing the project scope of work within the project schedule, while also maintaining a high level of quality control and assurance. Our civil contractor, J. Bates and Son, and our electrical contractor, Florence Electric, worked in partnership with Borrego Solar to control overruns and stay within the budget.”

— Matt Martunas, Borrego Solar


DESIGNERS: John Lagasse, development senior design engineer, and Aharon Wright, operations senior design engineer, Borrego Solar,

LEAD INSTALLERS: Matt Martunas, project manager, and Robert Vessichio, site superintendent, Borrego Solar



LOCATION: Palmer, MA, 42.2°N

SOLAR RESOURCE: 3.8 kWh/m2/per day

ASHRAE DESIGN TEMPS: 84.2°F 2% average high, -4°F extreme minimum



Equipment Specifications

MODULES: 156 Canadian Solar CS6P-235M (235 W STC, +5/-0 W, 7.82 Imp, 30.1 Vmp, 8.34 Isc, 37.2 Voc), 533 Canadian Solar CS6P-240M (240 W STC, +5/-0 W, 7.95 Imp, 30.2 Vmp, 8.46 Isc, 37.3 Voc), 330 Canadian Solar CS6X-285M (285 W STC, +5/-0 W, 7.89 Imp, 36.1 Vmp, 8.40 Isc, 44.7 Voc), 20 Canadian Solar CS6X-290M (290 W STC, +5/-0 W, 8 Imp, 36.3 Vmp, 8.51 Isc, 44.7 Voc), 926 Canadian Solar CS6X-295M (295 W STC, +5/-0 W, 8.11 Imp, 36.4 Vmp, 8.63 Isc, 44.9 Voc), 1,820 Suniva OPT250-60-4-100 (250 W STC, +5/-0 W, 8.44 Imp, 29.6 Vmp, 8.98 Isc, 37.7 Voc), 3,341 Suniva OPT255-60-4-100 (255 W STC, +5/-0 W, 8.5 Imp, 30.2 Vmp, 9.05 Isc, 37.9 Voc), 13,851 Yingli Solar YL300P-35b (300 W STC, +5/-0 W, 8.37 Imp, 35.8 Vmp, 8.86 Isc, 45.2 Voc); 20,977 modules total

INVERTERS: 3-phase 13.2 kV medium-voltage interconnection; four SMA America SC800CP-US, 800 kW nominal output, 1,000 Vdc maximum input, 570–820 Vdc MPPT range, 360 Vac rated grid voltage; 70 SMA America Sunny Tripower STP-24000TL-US, 24 kW rated output, 1,000 Vdc maximum input, 450–800 Vdc rated MPPT range, 150–1,000 Vdc operating voltage range, 480/277 nominal ac voltage

ARRAY: 63 SMA STP-24000TL-US inverters are deployed with the following safe-harbored modules and source-circuit configurations: Canadian Solar CS6P-235M, Canadian Solar CS6P-240M, Suniva OPT250-60-4-100 and Suniva OPT255-60-4-100 configured in 13-module source circuits; Canadian Solar CS6X-285M, CS6X-290M and CS6X-295M configured in 11-module source circuits; two SMA SC800CP-US inverters with 174 19-module Yingli Solar YL300P-35b source circuits; two SMA SC800CP-US inverters with 173 19-module Yingli Solar YL300P-35b source circuits; seven SMA STP-24000TL-US inverters with five 19-module Yingli Solar YL300P 35b source circuits; 5,999.93 kWdc array total

ARRAY INSTALLATION: TerraSmart TerraFarm non-ballasted racking, 180° azimuth, 30° tilt

SOURCE CIRCUIT COMBINERS: 17 SolarBOS CDK350C-24A-15-N3 AFCI Combiners, 350 A, 24 inputs, 15 A fuses; 17 SolarBOS CDK350C-32A-15-N3 AFCI Combiners, 350 A, 32 inputs, 15 A fuses; 63 SolarBOS FDK100-6-15-N14 Disconnect Combiners, 100 A, 6 inputs, 15 A fuses; seven SMA CU-1000-US-10 DC Connection Units

ARRAY RECOMBINERS: Four SolarBOS RCK-07-300BM-N3R, 300 A breakers

SYSTEM MONITORING: AlsoEnergy performance monitoring and portfolio management

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