Enerparc: Holdrege Solar Center

Located 5 miles outside Lincoln, Nebraska, the 4.68 MWdc Holdrege Solar Center is the largest solar installation in the state and a multimegawatt deployment of Solar FlexRack’s TDP Turnkey Tracker system. The project team includes Enerparc, an international solar development company with its US operations based in Oakland, California. Enerparc has developed more than 1.6 GW of PV capacity worldwide and performs O&M for 1.1 GW of PV assets. With 30 years of experience as a general contractor for large-scale projects, Golden, Colorado–based New Energy Structures Company (NESCO) led the on-site construction. In addition to supplying trackers for the project, Solar FlexRack, a division of Northern States Metals, assisted the team with project-specific engineering, analysis, planning and field support. The Holdrege Solar Center is an example of effective collaboration that maximizes on-site productivity.

Early planning efforts mitigated many on-site challenges, but some conditions could not be avoided, such as the dramatic spring weather swings typical of the prairie state. Construction crews dealt with high winds, seasonal rain, thunderstorms and extreme heat. While Nebraska ranks 48th nationally in installed PV capacity, Enerparc reported that it was still able to hire almost 40% of the Holdrege Solar Center’s construction crew locally. The PV plant is located on an active agricultural site with a center pivot irrigation system. The project’s scope included relocating and reconfiguring the irrigation infrastructure in advance of the solar installation to allow agriculture to continue in the areas outside the PV array. The project utilizes approximately 25% of the site for PV generation. The remaining 75% is used for agricultural activities.

Site-specific challenges included the rolling topography, which required a combination of civil engineering and earthwork to support a foundation design compatible with the tolerances of the independent-row tracker system. Layout challenges included avoidance of adjacent wetlands, terrace systems and areas with steep topography. The Solar FlexRack service team worked closely with the installation team well in advance of construction to minimize the impact of these on-site project variables.

NESCO deployed 15,333 Heliene PV modules on 269 Solar FlexRack TDP Turnkey single-axis horizontal trackers, and 60 Sungrow 60 kWac 3-phase string inverters provide power conditioning. Installers aggregated the outputs of the individual string inverters at low-voltage ac panelboards and switchboards. Transformers allow the collected ac sources to interconnect with the site’s 15 kV medium-voltage substation. The electrical design includes integrated relays that ensure PV output operability within utility-required generation parameters, as well as programming for protective settings.

“We selected Solar FlexRack TDP Trackers based on our previous successful experience with Solar FlexRack, and especially because of the great turnkey services packaged with the product, ensuring a smooth installation. Once again, we were not disappointed.”

—Florent Abadie, CEO, Enerparc


DESIGNER: Paul Corteza, project engineer, Enerparc, enerparc.com

LEAD INSTALLER: Ben Searl, construction manager, New Energy Structures Company, nesco-us.com



LOCATION: Holdrege, NE, 40.4°N

SOLAR RESOURCE: 5.3 kWh/m2/day

ASHRAE DESIGN TEMPS: 95°F 2% average high, -7.6°F extreme minimum



Equipment Specifications

MODULES: 15,333 Heliene 72P 305, 305 W STC, +4.99/-0 W, 8.29 Imp, 37.06 Vmp, 8.73 Isc, 45.51 Voc

INVERTERS: 15 kV medium voltage substation interconnection, 3-phase 277/480 Vac collection system; 60 Sungrow SG60KU-M, 60 kW, 1,000 Vdc maximum input, 300–950 Vdc MPPT range

ARRAY: 19 modules per source circuit (5,795 W, 8.29 Imp, 704.1 Vmp, 8.73 Isc, 864.7 Voc), 14 source circuits per inverter, typical (81.1 kW, 116.1 Imp, 704.1 Vmp, 122.2 Isc, 864.7 Voc), 4.68 MWdc array total

ARRAY INSTALLATION: Tracked array, 269 Solar FlexRack TDP Turnkey single-axis horizontal trackers, ±45° tracking rotation range

SYSTEM MONITORING: Locus Energy supplied and commissioned DAS hardware, software and performance analytics, including inverter-direct monitoring and revenue-grade metering

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