From the new Supercharger announcement this week:

[R0b_]

I noticed the nice little artist's rendering showing the proposed new supercharger sites. Obviously we don't expect them all to look like that, but it got me thinking.

If they DID make the covered stalls with solar power and tossed in some of their industrial battery packs, would that even help at all? I'm no engineer, but given the approximate surface area to be covered in solar panels, how much (best case) energy could they harvest and store in powerpacks? Would that offset enough of the demand to lower their overall costs of providing electricity? Would their costs to supply the equipment exceed the benefits? I know they don't have to pay retail obviously but still there would have to be a rather significant up front expense to doing this.

Oh, and I LOVE the "lounge" idea as drawn, I'd assume bathrooms on site and possibly renting the facility as a "convenience store" so it would be just like a modern day gas station and you could rest up and get snacks while charging.

 

[arg]

There's various ways of looking at this.

The original supercharger concept (from the launch of the system) was that sites would have solar canopies plus batteries and that would provide most of the energy (realistically it would have to have been topped up by a small grid connection, but that's much better both economically and environmentally than a huge grid connection). At the time, a big site was 4 stalls and a small site was 2 stalls. At that sort of site, the numbers just about added up - with only a few stalls, and assuming no overcrowding/queueing, you can't actually serve all that much traffic: to have a reasonable chance of finding a free stall when you turn up at random, stalls have to be empty a lot of the time (I'm presenting a handwaving argument, but the subject has been well covered mathematically). So a stall spent most of its time empty, with the panels charging the battery, and when the odd car turns up it draws down from the batteries - the short gulps of power from a few cars charging average out over the day to nearly match the continuous low power from the panels.

However, once you get to much larger numbers of stalls the maths turns around - the peak and the average come much closer together (at a given level of 'quality of service' or risk of having to wait). Now you have the prospect of many stalls occupied almost continuously, with just a small pool of empty ones to handle new arrivals, and the panels make a relatively insignificant dent in the power drawn. The canopy over one space plus related pedestrian areas might perhaps generate 4-5kW when the sun is shining; the cars in the space draw 50-100kW, day and night. This hugely improves the economics of the sites, but means the solar only makes a small contribution.

The recent change towards accepting Superchargers for local users rather than just for long distance tilts things a little bit back the other way - with long distance drivers, the load is spread throughout the day and night (though obviously with some peaks), while if it's providing charging for locals who don't have the ability to charge at home then there will be much bigger peaks at commute times, and stalls sitting idle the rest of the day.

I still think you'd be lucky to get even as much as 10% of the energy from panels over the stalls.

This doesn't mean the canopies aren't worth doing - shade/shelter is a useful amenety for the users, and it's probably cheaper to put canopies over the stalls than put solar panels anywhere else: the canopies are going to need only marginally more structure than the average ground-mount panel you might have in a solar farm, and putting them at the supercharger site saves on the grid connection you would otherwise need for the solar farm along with losses in transmission. So if solar panels anywhere make sense, then ones at a supercharger site are a better deal.

 

[wayner]

And the canopies can reduce the amount of snow clearing that has to be done - but if the snow packs onto the panels that will not be good. I have had to back my car right into a snow bank to be able to get close enough for the SC cord to reach.

 

[MorrisonHiker]

They could build solar farms in addition to the canopies. Solar farms can be much larger and while the power wouldn't go directly to the Superchargers, it would offset the use of power consumed at Superchargers.

 

[wayner]

But solar farms wouldn't necessarily have anything to do with the SCs. And if you cared about GHG emissions then you would put the solar farms in locations with lots of coal generation today so that we aren't fueling our cars with coal, rather than near SCs.

 

[MorrisonHiker]

But solar farms wouldn't necessarily have anything to do with the SCs. And if you cared about GHG emissions then you would put the solar farms in locations with lots of coal generation today so that we aren't fueling our cars with coal, rather than near SCs.

They can't put enough solar on every Supercharger site. They can build solar farms in each municipality to offset usage at each Supercharger site. Any solar power generation would be better than no solar power.