Isolux Corsan and Soltec: Kayenta Solar Facility
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The Kayenta Solar Facility represents the first utility-scale solar power plant in the Navajo Nation, located at the gateway to Monument Valley, 300 miles north of Phoenix. The technically challenging project took shape on sacred land, stewarded by a reverent nation. Strict project criteria required that most of the construction team be members of the Navajo Nation, that they preserve the natural landscape during installation and that they effectively restore it if the plant is removed when it reaches the end of its operational life.
The Navajo Tribal Utility Authority (NTUA), which provides utility services for the Nation, contracted Isolux Corsan as the EPC firm to oversee the installation of this landmark 37.6 MWdc project. Isolux relied on the technical expertise of its partners, including Soltec, which supplied and installed the PV trackers during the harsh desert winter. Soltec recruited and trained 188 members of the local community, representing 98% of the installation workforce, in record time—only 3.5 months.
Another critical condition of the Kayenta Facility was to limit earth grading and other environmental impacts while achieving the greatest possible yield per acre. To maintain the natural environment during installation, Soltec supplied its SF Utility single-axis tracker with land-use features that minimize all civil works and optimize yield density for maximum land utilization. The trackers used in Kayenta required only 10,864 driven-pile foundations for the 37.6 MWdc plant. Additionally, a slope tolerance of 17% north-south, a short-step tolerance of 120 feet and contour tolerances to ±0.66 feet significantly reduced the need for grading.
Other noteworthy aspects of the Kayenta project include the following: The team optimized the layout of the length and the width of inner roads, resulting in fewer trenches and saving 23 miles in alternative wire management. They also used a unique cabling solution to locate the PV Wire homeruns inside the trackers’ torque tubes, substantially reducing labor hours required for trenching, trays and hanging cables. Lastly, the wireless mesh communication network used on-site allowed the team to streamline installation, reducing communication wiring and conduits by 80%.
NTUA established a power purchase and renewable energy credit agreement with Arizona’s Salt River Project Power District. Revenue from the Kayenta project is helping NTUA extend electricity to several communities on the reservation, significantly raising the standard of living for its families, some of whom have never before had electricity delivered to their homes. The Navajo Nation plans to bring more renewable energy capacity online as NTUA prepares to sunset a coal-fired power plant in northeastern Arizona.
“The Navajo Nation has always had to purchase energy from the outside. Now we can sell electricity and environmental attributes to other parties. This project gives us the opportunity to bring outside dollars in and contribute to the financial strength of the Navajo economy.”
—Walter Haase, general manager, Navajo Tribal Utility Authority
EPC firm: Isolux Corsan, isoluxcorsan.com
INTEGRATOR: Soltec, soltec.com
DESIGNER: Antonio José Ros, mechanical design manager, Soltec
LEAD INSTALLER: Javier Carpio, director of operations, Soltec
DATE COMMISSIONED: June 2017
INSTALLATION TIME FRAME: 6 months total, 3 months for tracker installation
LOCATION: Kayenta, Navajo County, Arizona, 36.7°N
SOLAR RESOURCE: 6.3 kWh/m2/day
ASHRAE DESIGN TEMPS: 98.6°F 2% average high, 15.8°F extreme minimum
ARRAY CAPACITY: 37.6 MWdc
ANNUAL AC PRODUCTION: 76,037 MWh
MODULES: 87,856 Jinko Solar JKM320PP-72, 320 W STC, -0/+3%, 8.56 Imp, 37.4 Vmp, 9.05 Isc, 46.4 Voc; 30,096 Jinko Solar JKM315PP-72, 315 W STC, -0/+3%, 8.48 Imp, 37.2 Vmp, 9.01 Isc, 46.2 Voc
INVERTERS: 10 GPTech WD3 Inverter Stations with 3.6 MWac capacity each; 1,000 Vdc–rated input (1,100 Vdc maximum input), 670–950 Vdc MPPT range, inverters positioned in two rows of five units, each row with independent entrance to the 24.9 kV side of the 66.9/24.9 kV substation
TRACKERS: 1,552 Soltec SF Utility independent-row single-axis trackers, 2 by 38 portrait module configuration, 120° tracking range, asymmetric backtracking, self-powered with battery backup, wireless mesh network communication
ARRAY: 19 modules per source circuit (for 320 W modules: 6,080 W, 8.56 Imp, 710.6 Vmp, 9.05 Isc, 881.6 Voc); eight, 12 or 20 strings per combiner (for 20-string combiner: 121.6 kW, 171.2 Imp, 710.6 Vmp, 181 Isc, 881.6 Voc); 37.594 MWdc array total
ARRAY COMBINERS: 321 Renovagy combiner boxes with eight, 12 or 20 strings each, polyester enclosure, SPF Type fuses, S6000 DC UL disconnect switch
ARRAY INSTALLATION: Ground mount with single-axis tracking, 10,864 driven-pile foundations
SYSTEM MONITORING: Custom SCADA system by Isolux Ingenieria