Arizona’s largest solar plus storage plant starring Tesla, First Solar and NEXTracker

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Sometime in 2015, there was an engineer in Juno Beach, Florida looking at a piece of land in Pinal County, Arizona. She was mesmerized by some of the best sunlight on the planet. Across the street, Shelako’s Pecan Farm, in the other direction an electricity substation.

Then she glanced at the hardware specifications: NEXTracker single axis tracker, First Solar thin film solar panels and a Tesla battery. And it must have been at this moment that she most appreciated the beauty that was being built.

NextEra Energy has completed construction of the Pinal Central Solar Energy Center – a 20 MW solar plus 10 MW/ 40 MWh energy storage power plant. The project costs approximately $50 million, employed up to 150 people at its peak, will employ three people permanently, and spreads across 257 acres of already developed desert land.

NextEra will sell the electricity generated by the project to local utility Salt River Project Power & Water (SRP), under a 20 year power purchase agreement. The facility was built by the energy services division of Mortenson Construction.

The 20 MW-AC solar portion was built using 258,000 First Solar Series 4 PV Modules. These peak at 17% efficiency – ranging from a 110 W 15% efficient model, to the 122.5 W 17% efficient model. First Solar is shifting much of its manufacturing over to the large-format Series 6, but as the Pinal Central solar project shows, there is still demand for its smaller Series 4.

The specific model number wasn’t known at press time by pv magazine, however the range of model sizes tells us the system’s DC wattage was between 28.3 MW and 31.6 MW. The range of DC:AC ratio – 1.58 to 1.49 – is higher than the national average, however, in line with other aggressive DC:AC ratio sizings built by NextEra (some reaching towards 1.7).

The energy storage hardware was provided by Tesla. The logos on the 250kW PowerPacks aren’t adorned with their normal red lettering.

Though SRP and Tesla settled a lawsuit earlier this year dictating that SRP purchase a 25MW Tesla battery, this project and the Tesla battery was envisioned long before that lawsuit settled. A July 26, 2017 presentation by NextEra to locals extolled the value of using energy storage for the evening peak and other grid stabilization benefits.

Trade publication Transmission Hub says the project required approximately $1 million to interconnect the power plant to a nearby substation, and $3 million for the project’s new substation. The new 230 kV substation would be use exclusively by the solar plant, and that would be connected by 0.4-mile 230 kV power line to an already existing, nearby 230/500 kV substation.

First Solar’s modules are mounted on NEXTracker NX Horizon single-axis tracking system. Marketing by NEXTracker specifically focused on the First Solar Series 4 is evidence of a strong business relationship.

The First Solar Series 4 panels are smaller than standard 72 cell commercial solar panels – so four of them fit vertically. NEXTracker says each tracker row will hold up to 90 panels, meaning 25-35 kW.