pv magazine has sent an email to Tesla asking for comment and will update once we have new information.
At first glance, the “70MW” value on a 43 acre rooftop seems like a strong number. The structure is projected to have a 1.9 million square foot footprint. Roughly, 100,000 PV modules – if lain flat, and fairly tight – would fill that space up. A high-efficiency product from solar panel partner, Panasonic at 325W would allow for a 32.5MW installation, under half of the projected 70 MW project.
Per Tesla’s description of the project:
GF1 is an all-electric factory with no fossil fuels (natural gas or petroleum) directly consumed. We will be using 100% sustainable energy through a combination of a 70 MW solar rooftop array and solar ground installations. The solar rooftop array is ~7x larger than the largest rooftop solar system installed today.
Reading into that quote, we see an out for the rooftop being less than 70 MW – in combination with a ground installation. A rule of thumb for ground based projects I’ve been involved in is about 1 MW per 4-5 acres – putting the project potential at a much smaller 8-11 MW potential.
The current world’s largest PV rooftop installation on a single roof is an 11.5 MW plant in India on a 42 acre rooftop. That rooftop is part of a larger 19.5 MW, 82-acre project spread across eight rooftops.