Idle First Solar Plant Will Produce Solar Power Anyway

First Solar’s giant new manufacturing plant in Mesa, Ariz., isn’t turning out any solar panels these days, not with its opening delayed indefinitely while the company – the whole solar sector, actually – works to rebalance supply and demand. But the idle Mesa plant will be making solar energy by the end of the year, anyway.

That’s because a 4.1-megawatt array – the largest rooftop system in sunny Arizona – has been installed on top of the massive buiding, according to developer Blue Oak Energy.

First Solar Mesa rooftop

First Solar manufacturing plant, Mesa, Ariz. (image via Blue Oak Energy)

“The system covers approximately 900,000 square feet of rooftop area, using nearly 55,000 advanced thin-film photovoltaic (PV) solar modules manufactured by First Solar,” Blue Oak said in a statement.

Yeah, that would have been an interesting story if they weren’t First Solar panels.

We usually encounter First Solar modules in sprawling ground-mounted utility-scale systems, like Agua Caliente in Arizona, the largest operating photovoltaic plant in the world, not on rooftops. That’s because thin-film panels, while potentially offering cost advantages, need more space to make up for their lower efficiency. But there’s more than a loyalty argument to be made for deploying them on a big roof in Arizona: While thin-film modules are generally rated less efficient than crystalline silicon solar modules, the advantage can swing to thin-film in sustained hot weather because their power output suffers less of a decline.

Plus, in addition to producing electricity, the system on First Solar’s roof will also serve as something of a lab, Blue Oak said: “The solar electric system was engineered to support the development of new test procedures, wiring methods and other innovative approaches to advance PV technology. An outdoor inverter test pad provides a flexible testing area where inverters and other equipment may be switched and relocated with ease.”

At 4.1 MW the system is very big; it’s in the size neighborhood of several of the large warehouse systems installed in the past couple of years in New Jersey, but doesn’t nearly measure up to the biggest of the big, the 9 MW system on the Gloucester Marine Terminal in Jersey.

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.