Tesla has announced their long awaited Tesla Semi, along with a surprise: a new version of the Roadster.
The Semi is a class 8 truck. Class 8 are the biggest trucks in regular use on the roads. They're used for long haul trucking, dump trucks, cement trucks and so forth. The prototypes they've showed have a slick aerodynamic cab and a close-coupled trailer. My suspicion is the trailer will revert to the more conventional ones in most cases. It has a center driving position in the cab, two large touch screens, and software that controls the independently powered wheels to prevent jackknifing. He says it'll have 400 mile range, and a new, bigger than supercharger that they call a megacharger, which supposedly can charge the battery in half an hour.
400 mile range implies something between 600 and 1000 KWH of battery. The biggest batteries sold with Teslas now are 100KWH. Mine has an 85KWH battery, which others have discovered actually puts out more like 81KWH.
Charging a 1000KWH battery with J1772 protocol at 80 amps (e.g. HPWC) will take approximately 50 hours.This is obviously not suitable for a commercial truck. A conventional 125 KW supercharger brings this down to 8 or 9 hours, but Tesla is not presently selling these for commercial installation. They showed the truck side of the receptacle for charging the truck with a "megacharger", which appears to have 8 holes in it, each a little smaller than the present charge orifice. The present supercharger cable is pretty close to the limit of what a relatively frail adult can handle. 8 of them all at once is likely beyond what even Hafþór Björnsson could handle. (He's the actor/strongman that plays "The Mountain that Rides" on Game of Thrones). The strands might be connected individually, but more likely this connection is handled by a machine, such as the one Tesla demonstrated a few years ago.--the truck drives close enough to the charger and the cables are moved into place by a large robot arm.
Anything less than about 400KW is unsuitable for long haul trucking. Long haul truckers may drive 11 hours in a 14 hour day. 400 miles is only about half of that. So they need to charge twice a day, and in the case of drivers who share their truck, they may need to charge more than that. This may be adequate for a lot of Class 8 truck applications though: Cement trucks and dirt trucks spend a big part of their day loading and their routes are often start and stop and stay close to home. Trucks being used to move containers around within container terminals tend to spend well over half their day waiting in line. A 100KW charger may well be adequate for these. Tesla may choose to sell something resembling an existing supercharger for these applications, where the trucks spend their off duty time hooked to the charger. And they may not need much more than an 20KW HPWC for trucks that serve local chains, like grocery stores, where the truck spends a half hour or more loading or unloading for every 20 minutes actually on the move. But long haulers need more
I'm estimating about 1000 truck stops around the US. Tesla would need to install megachargers at a large number of these. A megacharger installation would resemble existing diesel refueling stations in that the chargers will need to be drive-through, like gas stations. There will need to be enough of them at each location that nobody has to wait too long--remember that 14 hour limit. The interesting part though is that the transformer for each megacharger plug needs to be about as big as a 12 bollard supercharger. They can do the same charger sharing, so a 12 megacharger station needs transformers the size of that needed fo 72 individual supercharger bollards. Enough to power hundreds of houses
Interestingly though, on the scale of our national demand, it's not that big a deal. 250*12*400,000 is only 100MW. 25-50 of those big windmills.
adenda 18Nov17:
https://www.dailykos.com/stories/2017/11/17/1716536/-Further-thoughts-on-Tesla-s-EV-Truck-announcement-from-a-former-fleet-owner
No comments:
Post a Comment