Tesla Model S Plaid Fast Charging Results Amaze: Analysis


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A. J.
Dec 8, 2019
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Tesla X LR+, Lexus SUV, Toyota SR5, Toyota Landcruiser
EE (Retired)
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But we're in the same ballpark. Thats good. Technically you could fit 2-3 kW of solar on a CT with a custom expandable roof. I already have a simple design for that.
Let's assume you have 3 kW of solar available. Maybe in the Centre you could get 7 hrs FSE (full sun equivalent) in a day. That gives you 21 kWh/day = 42 miles of range in a CT. That would be enough for me but is it enough for you? My experience with Oz is that once away from the cities things are more than a couple of tinnies apart.

So given we have 800 EVs in town, lets say worst case half are driving in the same period of the day. Then of the rest lets say 25% are parked and connected to a 10kW bi-directional V2G charger. Thats within a househol connection budget without an upgrade (42A). That would be around 200 vehicles x 10kW so 2MW of charge capacity which is enough to run 8x 250kW SC stalls simultaneously.
With 800 vehicles you'd have an annual demand of .350*9000*800 = 2.52e+06 kWh/yr which is 6899.38 kWh/da. = 287 kWh/hr. This means that whatever your collective power source is now it is going to have to be upgraded to collect 2520 MWh per year more than it does now. That's 3150 kWh/yr per vehicle or 8.62 kWh/day. This can be collected by a 2 kW system as long as you have 4.3 hr FSE. If everyone did this there would be no additional demand on the municipal system. If all charging was done on the municipal system it would have to install 6899.38/5 = 1379.88 kW of panels (assuming 5 hrs/da FSE) and the batteries to smooth the load.

Whether the additional panels are installed by the municipality or by the yeomanry the community will need 2520 MWh more solar per year just for the cars.

If as above we assume that only 40% of cars charge at a SC, we end up with 3.2MWh of energy required in the same period that only 25% of EVs are connected to a V2G. So thats 3.2MWh/200=16kWh of battery cycling (plus losses) per day to keep the SC chargers powered.
To be realistic about it there aren't going to be any SC in a town with a population of a couple of thousands unless it is on a major route like the A8. The Alice doesn't have any, the Isa doesn't either nor does Darwin. You will find the occasional CHAdeMO (which will charge a Tesla) but these aren't much faster than the 3ø destination chargers.

Not bad at all. In ballpark figures that validates the viability of using V2G to power SC charging in small capacity grids. Technically that scales up and down with population too. Is there something we missed?
I'm afraid I just don't see V2G having a place in this. We've noted how much extra sun energy would need to be collected and noted that most of it will need to be stored. The best place for it to be stored is in a static battery bank operated by the utility. Then each owner goes home and plugs in whenever he wants to just as is done in places connected to a national grid. Or he goes to a charging station whenever he wants or needs to. The downside here is the imposition on the resources of the local utility. Equally convenient from the users point of view would be a system where he has his own 2 kW (8 panels) system with enough battery to smooth the loading. He would then have to charge when the sun shines and charge several hours to get 40 miles or so. This can get expensive and he has to charge when the sun shines, He could be relieved of the time and money requirements if entrepeneurs built charging stations on this same design but with more panels and bigger buffers. With V2G you are essentially shuffling charge from Tom's vehicel to Freds and then on to Ralphs, each time losing to conversion efficiency. The main disadvantage is that Tom has to be on line and charging when the sun shines. Not only Tom but enough cars to absorb the output of the newly installed arrays. IOW with V2G the battery may not be there when it is needed. This applies both to the storage demand and discharge demand.

Beyond all that Tesla is not currently interested in V2G whether because they understand the shortcomings from an engineering perspective or because it potentially competes with their storage business or a combination of the two.