Borrego Solar: Sacramento International Airport

The 7.9 MW Sacramento International Airport solar project is the largest on-airport solar facility in California. Commissioned in December 2017, the installation consists of a 15-acre east site on the airport’s Aviation Drive and a 20-acre north site located near the runway. Between the two sites, Borrego Solar installed more than 23,000 LG solar modules mounted on NEXTracker self-powered independent-row trackers. The arrays will provide enough energy to offset a projected 30% of the airport’s electricity demand, enough to power 1,600 homes annually.

The airport took advantage of a PPA mechanism with NRG Energy, which enabled the airport to deploy solar without any capital outlay. Under this financial structure, NRG owns and operates the facility and sells electricity to Sacramento International Airport at a reduced rate. The airport pays for the PPA through savings from electricity costs. Projected cost savings from the project are an average of $850,000 annually throughout the 25-year PPA term.

Regulatory requirements for public airports across the country are unique and can pose significant challenges for solar power plant developers. To comply with California Environmental Quality Act requirements, Borrego conducted an owl survey on the north site, and it followed the requirements of the National Environmental Policy Act since this is a federal project. Additionally, the Federal Aviation Administration requires the performance of glare studies for any type of solar project at or in close proximity to an airport, as well as updates to these studies throughout the project life cycle if there are any design changes.

NEXTracker’s support team provided Borrego Solar with specialized design, project engineering and on-site tracker installation and O&M training. Asphalt on the 15-acre east site and irregular soft soil on the 20-acre north site complicated project development. NEXTracker assisted Borrego’s installation team in driving shortened piers on the east site, where 3 inches of asphalt blanketed the area. The project team installed 13,281 modules on the north site and 9,956 modules on the east site. The typical design configuration deploys 76 modules per independent tracker row.

The airport’s electrical infrastructure is a customer-owned campus electricity loop, typical for large-load customers such as airports, colleges and some corporate campuses. Integrating the solar project’s five SMA central inverters into the system required two independent medium-voltage connections using three Eaton Cooper Power distribution transformers (two on the north site and one on the east site) to step up the aggregated inverter outputs for medium-voltage transmission.

“The Sacramento airport installation was a major success despite complexities associated with a project of this scope and navigating the security intricacies of constructing at an airport. Our success was due to comprehensive planning and implementation of Borrego core principles in regard to design, installation and logistics. Working through the interconnection process with SMUD was a fantastic experience, due to daily communication and even a gear inspection via video-conference from the Eaton factory. I was extremely impressed by SMUD’s ability to keep to a tight timeline that was necessary for the PPA owner.”

—Nick Clemens, Borrego Solar

Overview

DESIGN: Torsten Christian, development design engineer, Borrego Solar, borregosolar.com; Benjamin Walter, electrical engineer, Borrego Solar; David Dutil, structural engineer, Borrego Solar; Tarn Yates, applications engineer, Borrego Solar

INSTALLATION: Nick Clemens, project manager, Borrego Solar; Darin Flick, field operations manager, Borrego Solar

DATE COMMISSIONED: December 2017

INSTALLATION TIME FRAME: 245 days

LOCATION: Sacramento, CA, 38.7°N

SOLAR RESOURCE: 5.04 kWh/m2/day

ASHRAE DESIGN TEMPERATURES:  98.6°F 2% average high, 26.6°F extreme minimum

ARRAY CAPACITY: 7.9 MWdc

ANNUAL AC PRODUCTION: 5,900,000 kWh 

Equipment Specifications

MODULES: 23,237 LG Electronics LG340S2W-G4, 340 W STC, +3/-0%, 9.02 Imp, 37.7 Vmp, 9.54 Isc, 46.4 Voc

INVERTERS: Three SMA SC800CP-US, 800 kW–rated output, 1,000 Vdc maximum input, 570 Vdc–820 Vdc MPPT range; two SMA SC2200-US, 2,200 kW–rated output, 1,000 Vdc maximum input, 570 Vdc–950 Vdc MPPT range

ARRAY: 19 modules per source circuit (6,460 W, 9.02 Imp, 716.3 Vmp, 9.54 Isc, 881.6 Voc), 20 source circuits per combiner (129.2 kW, 180.4 Imp, 716.3 Vmp, 190.8 Isc, 881.6 Voc), 7.9 MWdc array total

ARRAY INSTALLATION: NEXTracker NX Horizon single-axis trackers, self-powered independent-row design, 120° (±60°) tracking range, 180° array azimuth

ARRAY SOURCE CIRCUIT COMBINERS: 63 SolarBOS CSK320-20-15-N4, 15 A fuses

ARRAY RECOMBINERS: Three SolarBOS BEK-09-400-N3, 300 A breakers

SYSTEM MONITORING: Locus Energy LGate data acquisition platform

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