ItsNotAboutTheMoney
Well-Known Member
That mostly assumes continuous use of the DC fast charger. When nobody's charging, the solar panels' output would either be wasted or go elsewhere. Flipped around, using batteries, which you mention (dismissively?) would enable capturing and storing a smaller solar array's output for later delivery to cars. It would take more complex calculations, including estimates of usage at a fast-charging site, to estimate how many solar panels and how much on-site storage would be needed to make a site more-or-less self-sufficient in energy needs. This would, of course, be a statistical analysis, and so would inevitably be off for days with heavy or light use, very sunny vs. very cloudy days, seasonally, etc.
All that said, I find it hard to believe that solar canopies at DC fast charging sites would be likely to provide enough energy to offset the use at that site, unless that use was very light. That's not to say that such installations are useless, though. If we as a society want to increase the use of solar power (as I believe we should), then the solar panels have to go somewhere, and atop canopies to help protect drivers from the elements when they charge their cars is one of many places they can go that will have minimal negative impacts. (Compared to cutting down a forest simply to install solar panels, for instance.)
Forget self-sufficiency. It's about saving money.
PV canopy + battery is a way to lower maximum power draw from the grid, lowering their demand charges.
It also has the advantage of being built-in backup power to keep the site running during outages without backup generators.. No so much to charge vehicles (although it can charge some), but to avoid the site going offline.
Also worth noting that in a lot of places people travel more during sunny summer weather, so additional solar generation during long days will help with some of the seasonal variation.
And, as you note, there are practical benefits to canopies.