Single axis trackers on a commercial rooftop increase generation 37%


Alion Energy’s single axis tracker racking product was originally designed to be deployed in regions where heavy installation equipment was more challenging to access, but labor might be more available. One aspect of this design philosophy is that the system is light and can be easily carried and assembled, and doesn’t require metal pilings to be driven deep into the ground.

Interestingly, this carries over to commercial rooftops.

Via a post on LinkedIn, Mark Kingsley, Alion CEO, shared that a commercial real estate group had installed a standard rooftop 10º fixed tilt mono-facial solar array, as well as a competing Alion system.

The results were as expected – 37.5% greater generation on a per watt basis from the single axis tracker, on a pristine white thermoplastic roof versus standard modules.

Of course, the real breakthrough is that they were able to get single axis trackers installed on a commercial rooftop at all!

There was no information shared about the total wattage that was able to be installed on the site, however, Alion did provide pv magazine USA with a technical powerpoint covering the deployment of their product on commercial rooftops (this data-driven document is available from Kingsley upon request).

Kingsley also commented on the aforementioned LinkedIn thread with the following image showing a hypothetical rooftop situation. This project is also reviewed in greater depth in the powerpoint presentation.

Looking closely, Alion is suggesting that they can actually fit *more* modules on the rooftop – and have a higher production rate from those modules due to common nuances of rooftop installation.

The rooftop in their example has a lot of skylights, and the overall structure is not facing due south. In this configuration, Alion suggests that they can fit 4.55 MW of modules on the Maryland structure with a standard 10º installation. This system is projected to generate 1.34 kWh per watt each year.

Alion has designed a system that is 5.4 MW – a full 18% increase in wattage due to systems ability to be installed directly over skylights without needing the standard setback! Additionally, this hardware is projected to generate 1.54 kWh per watt installed per year.

In this case, that works out to 37% more electricity from the same rooftop. And when the trackers are directly attached to the roof – a 2.15 pounds per square foot dead load.

Add in one Alion’s customized robotic cleaners, and the company says the levelized cost of electricity from the system falls to 4.67¢/kWh and generates 40% more electricity than a standard rooftop solar install.

And while this rooftop was selected to show off their hardware, it’s still an interesting best case scenario for us to consider.


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