TomT said:
Who cares. The fact that they are putting in charging stations is all that really matters!
mkjayakumar said:
Given that a solar panel setup of this size will generate no more than 40-50kWh per day, the Tesla's supercharger setup will generate enough juice for no more than one Model S per day, or even less. So Tesla's claim that they are generating power for free, or generating power enough to offset the charging done in a Supercharger station is facetious..
The thing is, the Supercharger, to be cost-effective, requires very intermittent use. You couldn't really install more EVSEs with that array if you wanted to come out with a net profit, even allowing for the fact that you hope to do most of your generation at peak rates and much of the charging off-peak. Since Tesla is going to let S owners use the Superchargers for free, there's no incentive for owners to try to take trips off peak.
Still, kudos to Tesla for showing that it can be done, albeit a practical capability for large numbers of EVs requires much larger arrays. For example, I measured the parking space for full size cars in a local lot: 19' (from the center line between rows) x 9' between side lines; compact spaces tend to be 7'6" or 8' wide instead, and a foot or two shorter. Using the larger space, you've got about 15.9m^2 of flat surface above the space; let's assume no more than 15m^2 practical, and probably less. The typical 200W module puts out around 120Wpeak/m^2, so each space will generate at most 15 x 120 = 1.8kW, or enough to charge L1 for that space under peak sun conditions. To charge L2 at 3.3 kW, you'll need 2+ spaces per car (assuming 86% charging efficiency). For L2 at 6.6, 10 or higher kW, just multiply the number of spaces as needed
Naturally, not all spaces will be occupied by PEVs or at all times, but it does give an idea of just how much public space will be needed _just for car charging_ using PV.
Shopping malls and especially sports arenas with acres of ground level parking lots strike me as good spots where this could be cost-effective. My local mall doesn't have any, but about 1/4 mile away the local community college has installed solar arrays over most of their lots to offset their own hotel usage, but they also have a couple of EVSEs albeit not located at the arrays.