lorenfb
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Re: Tesla Semi Truck

Thu Mar 08, 2018 10:41 pm

RegGuheert wrote:
lorenfb wrote:Where are the data to conclude this, i.e. an energy consumption of at least 300 kWh (over 250 miles) - less than a mile/kWh?
It's from the link to the article which is same link that I provided for the estimate of 630 kWh the other way fully loaded. I should have linked it in that comment, as well.


Thanks for the info and link.

Since you have most likely gathered the data relating to an economic analysis of operating costs for an EV semi versus a diesel ICE semi,
exclusive of factors such as maintenance, insurance, energy costs (electricity vs diesel fuel), etc., here are a few questions:

1. What is the generally accepted typical energy usage per mile (miles/gal) for a diesel rig (tractor & typical fully loaded trailer)
traveling at 60mph on a level highway?
2. What is the assumed miles per kWh for the semi in #1, given these components;
a. Rolling Resistance Losses - RR = k * V
b. Drag Losses - DL = k * V^3
c. Energy Conversion Efficiency of the diesel ICE, - assumed to be a little better than a gasoline ICEV (@ about 60%), assume 75% for diesel?
3. What is the assumed miles per kWh for an EV semi assuming RR & DL are the same for a diesel ICE semi traveling under the same
conditions and assuming about +95% energy conversion efficiency for the EV semi?

A simple solution to #3;
1. Assume 38 kWh per gallon of diesel fuel.
2. Assume RR + DL = energy output of diesel = .75 of diesel fuel energy input
3. Then miles/kWh for the EV semi = miles/gal (diesel mileage) X (EV conversion efficiency) / (kWh/gal X diesel conversion efficiency),
or simply MPG (#1) X .95 / (38 X .75)
4. Assuming a diesel ICE under conditions of #1 with an MPG = 5 miles/gal (bad assumption?) then;
EV semi miles/kWh = .167 miles/kWh
5. If one assumes that the diesel is only 50% efficient versus 75%, then the EV semi miles/kWh becomes .5 miles/kWh

Your range number from the quotation is 250/300 or .833 miles/kWh for an unloaded tractor & trailer not necessarily on level
terrain and not necessarily at 60 mph. So what data have you found that realistically compares the two vehicles based on
just efficiencies, exclusive of the key factors; the energy cost differential, maintenance, etc.? I may have missed a post of yours,
so what calculation data, e.g. present cost per kWh for a EV semi, have you been assuming in this thread?

Notes:
1. Diesel fuel is presently at about $4/gal which amounts to about $.10 / kWh.
2. Unknown weight delta between power train of diesel semi (ICE, gearbox & diff) versus EV semi (battery for same range &
motor/motors/controllers).
3. Potential loss of cargo capacity delta, i.e. EV battery size delta over ICE power-train.
4. Charging infrastructure and delivery costs per trip.
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

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RegGuheert
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Re: Tesla Semi Truck

Fri Mar 09, 2018 5:13 am

lorenfb wrote:2. Assume RR + DL = energy output of diesel = .75 of diesel fuel energy input
Diesel trucks achieve a Carnot efficiency of 75%? Hardly.

I have already calculated the relative per-mile costs for fuel for the Tesla Semi when compared to a standard diesel truck, with references:
RegGuheert wrote:The DOE requires new trucks to achieve at least 7.2 MPG on level ground while some companies have demonstrated economy as high as 9.9 MPG with a 65,000-lb. load. If we go with the 7.2 MPG number and put diesel fuel at $3.00/gallon, we get a per-mile fuel cost of about $0.42/mile. Tesla has promised truck fuel for $0.07/kWh and efficiency better than 2 kWh/mile. That comes to about $0.12/mile, or a savings of $0.30/mile! (I will note here that Elon Musk said "wholesale price" in his presentation, so I'm not exactly sure what that means.)
SageBrush has an excellent post which includes all Class 8 semi per-mile costs and you can see that the fuel costs match my estimates very closely (image from this reference source):

Image

Even if my estimate for the per-mile fuel cost for the Tesla Semi is low by 100% (which I highly doubt), there are still huge savings for the trucking companies in there. In fact, many trucking companies will be able to further reduce their fuel costs with the Tesla Semi by manufacturing their own fuel on-site using photovoltaics. I expect that as trucking companies begin to electrify their fleets, we will see them investing in photovoltaics to cover their facilities and possibly their parking lots in order to lock in lower fuel costs for the long term.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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RegGuheert
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Re: Tesla Semi Truck

Fri Mar 09, 2018 5:53 am

GRA wrote:I didn't see any mention of Megachargers in the article, but I just skimmed it. Was that mentioned?
I surmised that from the fact that they drove the trucks both ways. I had thought that is the only charger available for these trucks. But it seems that at least *some* of the prototypes can be charged using Superchargers, including one of the trucks used in this demonstration:
InsideEVs wrote:At least one of the Tesla Semis en route to Fremont stopped at a Supercharger for some extra charge along the way. We now wonder, was its battery depleted?
and
InsideEVs wrote:This particular Supercharger is in Rocklin, less than 150 miles from the Gigafactory. One Semi was spotted hooked up to a Supercharger. That image has since vanished from the Internet.
So that raises a whole host of questions:

- Does the black truck contain batteries (and other electronics) from the Model 3 rather than truck batteries? That would explain it having lower range and being able to charge from a Supercharger.
- If the black truck does not contain truck electronics, does the silver truck? I'm guessing that it does.
- Did the Silver truck make the round trip without charging? It's certainly possible, but I think that charging at the Gigafactory is much more likely.
- Why was the black Semi along for this trip if it doesn't have the range? Was it because the silver Semi needed to be in a convoy in order to make the round trip?
- Will production trucks be able to charge from Superchargers? I seriously hope not, since you really don't want cars and trucks stopping at the same refueling stations.
- Will production trucks have the ability to charge from AC? If so, will they only offer three-phase charging, or also single-phase charging?

OTOH, I have to imagine that Tesla is developing their Megachargers in parallel with their trucks and that Fremont already has prototype Megachargers in place. If Tesla doesn't have a Megacharger at the Gigafactory, yet, it certainly will need one soon.
GRA wrote:Reg, like most northern CA skiers I've made the drive (both ways) many times, so I'm well aware of the elevation changes.
Yeah, that's why I called you out on characterizing this trip as "downhill".
GRA wrote:The packs should fit in a container no problem (internal width about 7'8" IIRR, although whether or not the packs can be loaded lengthwise side-by-side may be a problem), the issue will be do they have to transport special racks up the hill to stack them, if so do they fold, and what do the racks weigh? I've used (non-folding) racks similar to the one on the right end of the upper gallery row here: https://tier-rack.com/application/shipping-racks.html (the picture just left of that shows the same rack folded), but there's no way they could handle the weight of a battery pack, even if putting that much weight that high up were acceptable. A battery pack could use a much lower, stronger rack. As battery packs are dense commodities maybe stacking won't be required, and using regular dunnage (plywood, foam, pallets, inflatable bags) and shipping them in a single layer will be okay.

The other option, and one that may make sense is to haul the containers to the Livermore warehouse or else a trans-shipment warehouse at the Port (in my Teamster casual days I sometimes worked at one), and consolidate 40' container loads into 48' or 53' trailers before hauling them up the hill. It will probably depend on whether or not trailers fully loaded with packs are weight critical and can't be fully loaded in any case.
Thanks, I considered that the batteries will need racking (I'm willing to bet that they do), but I hadn't thought about getting them back up the hill. Perhaps those can be transported back up with many of them in a single load.
GRA wrote:It's a pity they weren't able to do this kind of baseline run earlier so that they could get a bad winter weather test in, because there's a good chance that they'll now have to wait until next winter for similar conditions.
You're kidding, right? I think it would be extremely foolish to make early test runs in poor weather for a large number of reasons.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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RegGuheert
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Re: Tesla Semi Truck

Fri Mar 09, 2018 6:04 am

InsideEVs linked to a couple of videos of Tesla Semis driving with trailers:





The second video is pretty funny, as it appears it was taken from a Tesla, but a Chevy Volt got in the way. I wonder if the driver of that car was also recording the Semis' drive...
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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RegGuheert
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Re: Tesla Semi Truck

Fri Mar 09, 2018 9:57 am

InsideEVs has linked to a video which highlights the noise a Tesla Semi makes when it accelerates:



That's pretty loud! Methinks they need to work on the gears to make them quieter.

They also have the following video which indicates that even the silver Tesla Semi was charging at that location, so I guess that means that either there is not yet a Megacharger at the Gigafactor or that truck does not have a 500-mile battery or both (or possibly something else).



It looks like you were right, GRA: It now appears that really was just a PR stunt, not unlike the video of the Model S self-driving in the bay-area a while back.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

lorenfb
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Re: Tesla Semi Truck

Fri Mar 09, 2018 10:41 am

RegGuheert wrote:
lorenfb wrote:2. Assume RR + DL = energy output of diesel = .75 of diesel fuel energy input
Diesel trucks achieve a Carnot efficiency of 75%? Hardly.

DOE requires new trucks to achieve at least 7.2 MPG on level ground[/url]


So my analysis was close using 5 miles/gal (S/B 7.2) & 50% efficiency (actual 45%):

A simple solution to #3;
1. Assume 38 kWh per gallon of diesel fuel.
2. Assume RR + DL = energy output of diesel = .75 of diesel fuel energy input
3. Then miles/kWh for the EV semi = miles/gal (diesel mileage) X (EV conversion efficiency) / (kWh/gal X diesel conversion efficiency),
or simply MPG (#1) X .95 / (38 X .75)
4. Assuming a diesel ICE under conditions of #1 with an MPG = 5 miles/gal (bad assumption?) then;
EV semi miles/kWh = .167 miles/kWh
5. If one assumes that the diesel is only 50% efficient versus 75%, then the EV semi miles/kWh becomes .5 miles/kWh


Tweaking the numbers (7.2 X .95) / (38 X .45) results in a EV semi having a potential typical range about .4 miles/kWh.

You didn't answer my question:

Your range number from the quotation is 250/300 or .833 miles/kWh for an unloaded tractor & trailer not necessarily on level
terrain and not necessarily at 60 mph. So what data have you found that realistically compares the two vehicles based on
just efficiencies, exclusive of the key factors; the energy cost differential, maintenance, etc.?


So is there an implication, based on your numbers versus mine, that a fully loaded EV semi's range is reduced by 50%?
That's too simplistic. Surely, one of the analyses is inaccurate, right? One always needs an accurate initial base analysis.
Last edited by lorenfb on Fri Mar 09, 2018 11:06 am, edited 1 time in total.
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

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RegGuheert
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Re: Tesla Semi Truck

Fri Mar 09, 2018 11:06 am

lorenfb wrote:So is there an implication, based on your numbers versus mine, that a fully loaded EV semi's range is reduced by 50%?
:?: :?: I have no idea where you came up with that idea. I have estimated that an unloaded BEV semi's consumption is reduced from 378 kWh when fully loaded to about 300 kWh when unloaded. That is roughly 80% of the energy consumption needed by the fully-loaded truck.

Edit: range -> consumption
Last edited by RegGuheert on Fri Mar 09, 2018 11:16 am, edited 1 time in total.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

lorenfb
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Re: Tesla Semi Truck

Fri Mar 09, 2018 11:12 am

RegGuheert wrote:
GRA wrote:The question is, how much do those battery packs weigh, i.e. what's the payload, and is this the 300 or 500 mile pack in the tractor?
That's a good question, but even fully unloaded, this trip likely required the consumption of at least 300 kWh and traveled over 250 miles.


Range = 250 / 300 as you imply? Or did you NOT clearly state what you meant.
Last edited by lorenfb on Fri Mar 09, 2018 11:18 am, edited 2 times in total.
Leaf SL MY 9/13: 70K miles, 49 Ahrs, 5.1 miles/kWh (average), Hx=70, SOH=78, L2 charges to 100% > 1000, max battery temp < 95F (35C), min discharge point > 20 Ahrs

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RegGuheert
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Re: Tesla Semi Truck

Fri Mar 09, 2018 11:15 am

RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

User avatar
RegGuheert
Posts: 6332
Joined: Mon Mar 19, 2012 4:12 am
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Re: Tesla Semi Truck

Fri Mar 09, 2018 11:22 am

Here is some more discussion on the LOADED energy estimated to get the Tesla Semi from Fremont to the top of Donner Pass:
InsideEVs wrote:Our modeling shows that the kWh burn to get to the top of Donner Pass is 587 kWh’s.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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