Published Saturday March 1, 2014: Updated August 12, 2014
Every Car An Electric Car
Imagine a hypothetical world where every car on the road today was a Tesla Model S electric car with a 300 mile range. Would this create some real problems with charging infrastructure?
For starters, 97% of all miles driven are well within the range of a 150 mile round trip. So for all commutes and trips under 300 miles, nearly every driver could charge their car at home. If they installed an increasingly affordable a PV solar array on the garage roof, all the car’s fuel would be free. For a large percentage of current EV drivers, (myself included), this is already the case. If you can enjoy the energy independence and convenience of charging at home for free, why not?
BTW, in Utah, a solar array the size of a parking space will collect enough solar energy in a year to power an electric car 12,000 miles.
In this very possible and reasonable example, public charging stations would not be needed most of the time.
It is only the occasional road trips and extremely long commute commutes that will need supercharger stations.
Supercharging stations located inside
city limits will only be needed for the occasional traveler passing
through or for someone who got caught off guard with a lower than
expected charge and is in a hurry.
Destinations will also have charging stations but they could be the more common L-2 chargers that can literally be installed anywhere 240VAC is available.
A fast charge at a 120kW Tesla supercharging station takes 40 minutes to fill up.
How will all the cars be able to fill up if there are only a few charging stations?
Currently, with only 6 stalls at a charging station, even if cars arrived in perfectly spaced increments to charge up, you are still looking at a wait time of 6 minutes 40 seconds before a stall opens up. Throw in a few dozen more cars and it quickly skyrockets to hours of wait time. How will this problem be solved?
And what about those occasional holidays and weekends where it seems like everyone is driving 300, 400, 500 or 600 miles to head to the lake, the beach or Las Vegas baby? How will the supercharger network handle high traffic, long distant travelers?
Just as in the early days of the automobile, when there were only a few gas stations connecting the country, Tesla’s supercharger network is also in its infancy. It was only in early 2014 that the first coast to coast connection was completed. By the end of 2015, these stations will literally dot the landscape. But would that be enough if every car were electric?
Let’s assume on a particularly busy Friday afternoon, before a weekend event, that 10,000 electric cars are leaving Salt Lake City, bound for Las Vegas on I-15, 427 miles away.
Assuming everyone charged up before leaving, each car will need to make 1 stop at a supercharger station before continuing on to Las Vegas.
With only 6 stalls at a typical Tesla charging station, assuming each car arrives in evenly spaced increments to charge up, effective wait time is 6 minutes 40 seconds before another stall opens up and the next car can begin charging.
In the 7 hours that it takes to drive to Las Vegas (with a charge in the middle), only 54 Tesla cars could make the journey due to the bottleneck at the charging station. Not very good is it. Of course in a 24-hour period, that would increase to 216 cars. But since traffic flow is not continuous for every hour of the day, that is not a realistic assumption. Plus, every car is heading down for the same event, leaving within a few hours of each other. For this exercise we will limit the charging window to only 6-hours.
Now imagine, instead of only 6 charging stalls at this sole super charger station, there were 120 (5 rows of 24 stalls). With a 40 minute charge time, that would effectively allow 1 car to leave and 1 car to enter every 20 seconds, bringing the throughput to 1080 cars in 6 hours.
That is much better but still only covers 10% of the cars needing a charge.
If one massive charging station is good, then why not add 10 more of them? If there were 10 super-deluxe sized supercharger stations located around the mid-way point between the two cities, that would increase the throughput to 10,800 cars in a 6-hour period.
With 1200 charging stalls to choose from, (spread across 10 charging stations at multiple freeway exits), how do you find an open stall?
Since the cars are smart and the super chargers are smart, you don’t have to. Your car and the charging stations have already worked that out for you. You car issues a fast-charge request to the station and by the time you arrive, a reserved stall is open and waiting for you to pull in and begin charging. In this hypothetical scenario, the next available stall is at station 42, stall 11B near the Starbucks, Walgreens and a Subway sandwich shop. How nice would that be to know exactly which stall is available before you arrive?
How to renewably power all those fast chargers?
A single fast charger draws up to
120kW. 1200 of these fast charging stalls would draw 144 MW of
power. Many of the Tesla supercharger stations currently in use have
a PV solar canopy (and soon, grid storage as well), that supplies
most if not all the power they need. To power 144 MW for 6 hours
continuously only with PV panels (assuming 12 watts per sqft), would
require 413 acres of PV panels and even more if you add access rows
in between them. Fortunately there is more than ample space in
remote areas between city centers for a solar array this size and
since these super charger stations could be located right next door,
all this power doesn't have to travel through miles of transmission lines to reach its destination.
Cost of a station?
For easy math, lets assume each PV powered super charger stall costs $1 million a piece.
Super charger stall ~$50,000
180 kW PV array (large enough to cover continual use at a stall for 6-hours a day) $600,000
Grid tied storage sufficient to cover reduced traffic needing a charge at night when sun isn't shining (sufficient for 17 overnight charges) ~$450,000
In windy locations, large wind power generators would supplement the solar panels. Excess power would go directly to the on-site grid storage.
Naturally the regular electric grid (ideally comprised of additional sources of renewable power) would provide backup power during winter months or long periods of dark, cloudy days.
At 1 million dollars a piece, the 1200 super charger stalls at this large supercharging complex would cost $1.2 Billion.
Now imagine 1000 other massive supercharging sites located across the United states, each connecting cities 350-450 miles apart. This massive venture to pull off charging every long-distant driving car on the road would cost $1.2 Trillion. To put that into perspective for you, that is $800 Billion less than what the United States spent defending its oil interests in Iraq over the last decade.
After making this investment, all the fuel would be free, home-grown, non-polluting and renewable. The only costs at this point would be for maintenance.
Charging equipment would have an estimated life span of 20-100 years.
This exercise could also be applied to all the semi-trucks currently on the roads. Each truck-stop could also be a supercharger station for big rigs. Since federal law mandates that truck drivers limit their continual driving hours, these truck stops could integrate fast charging stations (for a quick fill-up, dinner and bathroom break) and 6-12 hour slow charging stations while the driver rests up.
Now, remind me again why we think we still need oil for fuel?