Electric semi-trucks. My vision.

I always assumed battery swap would make sense for the big boys...

The main problem is the weight of the batteries which would be much more than the weight of the engine (the drive train would still be there, unless the motors were placed inline with the axles the way the are in subways). Remember that you'd have to design a truck that could drive all day without stopping to charge. Also many truck drivers wouldn't put up with a 75 mph speed limit.

Trucks have a limit per axle between 8,000 kg and 10,000 kg depending upon the jurisdiction. Every bit of mass that isn't cargo can't be charged for. Now there are some types of trucking (furniture vans for example) that are volume constrained rather than weight constrained. These could benefit from being electrified, but they are in the minority.

The real answer to this is more trains and fewer trucks.

Having just completed a 2600 mile round trip ,Sarasota to Dallas much of it overnight, I was surprised at the number of trucks in rest stops sitting idling while their occupants got some rest. One can certainly envision those trucks charging instead of idling.

Yes, there will be electric trucks in the future. EVs of all sizes.
Just a note however, you referring to the tractor which is not a "semi-truck". It is a tractor with semi-trailer.
~Larry

My dream is for a fully autonomous, battery powered RV so I can travel the country in retirement in 30 years. I don't see that as an impossibility...

Larry93535 said:

Yes, there will be electric trucks in the future. EVs of all sizes.

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I don't doubt that for an instant as batteries become more energy dense.

A good friend of mine is a truck driver, and we've discussed this at length, even to the point of considering a prototype... but it's not worth it right now.

With current tech it's just not going to happen. At a minimum the thing would need a true 700 mile range (not "ideal miles"), fully loaded. It could be done with enough batteries, but the weight of those batteries is now weight that he can't haul, which defeats the purpose.

Plus would need to be able to recover that power consistently and conveniently. At a best case scenario overnight. So we're looking at something like at least 100kW charging continuously for many hours to recover. Not even a current supercharger could do 100kW for 10 hours *continuously* without burning up the cabling.

Then there are tandem drivers where they basically don't ever have to stop (couple of hours per day) like when they put my P85D on a truck last December and had it cross-country in 2 days. No way at all to do this with current battery tech.

Basically, just as is the case with every EV, batteries need to get much much better and much more energy dense per unit of weight. When a 5MWh pack can fit under the hood of a truck and weigh barely more than the diesel equivalent setup, then we'll see how it goes. But that's not happening any time soon.

Battery-swap would basically be a necessity. Which means the various makers would have to standardize and truck stops would need swap equipment.

Long-haul OTR trucks is where hydrogen fuel cells actually start to make a little sense. Granted, electrified freight trains make even more sense. Especially once we free-up the tracks by clearing off the obsolete coal and oil cars which are currently clogging the US rail network!

Bangor Bob said:

Battery-swap would basically be a necessity. Which means the various makers would have to standardize and truck stops would need swap equipment.

Long-haul OTR trucks is where hydrogen fuel cells actually start to make a little sense. Granted, electrified freight trains make even more sense. Especially once we free-up the tracks by clearing off the obsolete coal and oil cars which are currently clogging the US rail network!

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It would be extremely difficult to carry enough hydrogen tanks on a typical semi to allow the distances necessary. Where trucks are weight constrained with batteries, they are space constrained with hydrogen.

Not to mention, with current costs, it would cost around $200,000 for a FC capable of putting out an equivalent amount of hp of current diesel engines. And I'm not sure, with the way power is delivered, that you wouldn't need a much bigger FC than equivalent diesel engine.

There is a lot of oil from the Bakan on trains these days, but goods traffic cross country shipping from Asia to Europe is a major percentage of traffic too.

The problem that has to be faced with any electric vehicle is that fossil fuels are the best concentration of energy we have in a transport energy source. Gasoline is 33 KWh/gal and diesel almost 38 KWh/gal. Compare that to the Model S battery pack which has a volume of 96 gallons (365L) and holds 90KWh of energy. If you could replace the batteries in the Model S with an energy source as dense as gasoline, the energy rating of the battery pack would be 3.22 MWh and the range would be around 9475 miles on a charge.

The Model S has the equivalent of about 3 gallons of gasoline for fuel, only .933 KWh/gal of space. It only gets 270 miles out of a charge because it uses that energy far better than any ICE engine can.

The biggest thing Tesla has done is prove that electric cars are feasible, despite the limitations of current battery technology. But those are real limits that drastically limit the applications. We don't have any known technologies in the lab that will get dramatically better energy concentration in batteries. There is a tremendous amount of research, but it's going to take a while. Even if a discovery was made tomorrow, it would be at least 10 years before it was on the market. It takes at least 5 years of evaluation in the lab to prove the new technology is viable, then another 5 to prove it will work as a mass market product as well as develop production techniques.

ratsbew said:

A single "battery railcar" could hold 200,000lb of batteries. I'm thinking that having one or a couple battery cars behind the locomotives might be a feasible thing to do. The locomotives could be essentially unchanged since they already have most of the electrical components.

Of course, most locomotives carry about 5000 gallons of diesel fuel which at 38kWh/gallon that gives 190MWh of batteries to replace a 5000 gallon tank.

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One of the problems would be making enough batteries. Tesla today uses 10% of the entire planet's lithium ion battery production for the Model S. The Gigafactory is scheduled to deliver enough batteries for about 500,000 cars a year, maybe a little more now they have done some redesign. To produce 10 million electric cars a year would require 20 Gigafactories. That's just cars with about 50-90 KWh per car. A railcar with 200,000 pounds of batteries would suck up enough batteries to build several thousand cars. Enough batteries for a semi truck would consume enough batteries for 50-100 cars.

Then there is the problem of charging the batteries. With supercharger technology it takes about 40-50 minutes to get 70 KWh into a Tesla battery. Try charging a 1 MW battery. Commercial vehicles only make money when they are moving stuff around. Having to shut them down for long periods to recharge them would be unacceptable in most cases.

Companies like UPS and FedEx have shown some interest in electric vehicles for their delivery vans. That can be feasible because the vans are only used part of the day and return to the same depot every day.

In some areas locomotives can draw electricity from overhead power lines or powered rails, and that is done for light rail in many places. Powered rails is too dangerous in places where the rails can't be protected from people wandering by, but overhead can work in some places. However, the train will stall if it loses connection with the power lines.

Even if someone built 20 Gigafactories to produce that many batteries, the world may hit a lithium shortage. Ores rich in usable lithium are not that common. There is a dry lake in Bolivia very high in lithium salts that could be a major supplier of lithium, but even if the resources were found, it would take a while to get production up to levels high enough to supply all those factories.

There are a lot of things that are feasible on a small scale that will take a massive effort to scale up to a point where they truly displace fossil fuels. Even if we have a 100% commitment from everyone to do it tomorrow, it would still take a very long time to implement. Probably a few decades at minimum.

I have been thinking a lot about this too over the years. Assuming the trucks are driver-less, you wouldn't need a tractor.
Mechanically, you could have one Model S drive unit per trailer and a few Model S battery packs hung flat under each trailer, number variable with range needed per trip. Here is where battery swap would make more financial sense than in passenger cars.
A side benefit with batteries at the bottom is a little lower COG so that the trailers can carry more speed through curves, saving time and energy.

Without the weigh of the tractor, there is obviously more payload and battery weight available for the trailers. Being self driving, trailers need not be mechanically coupled. However, they can "team up" at speed on the highway to reduce drag and so improve range. Imagine 100 in a row driving a few inches apart. Resulting frontal area would be 1% of that of a single trailer...

Olle said:

I have been thinking a lot about this too over the years. Assuming the trucks are driver-less, you wouldn't need a tractor.
Mechanically, you could have one Model S drive unit per trailer and a few Model S battery packs hung flat under each trailer, number variable with range needed per trip. Here is where battery swap would make more financial sense than in passenger cars.
A side benefit with batteries at the bottom is a little lower COG so that the trailers can carry more speed through curves, saving time and energy.

Without the weigh of the tractor, there is obviously more payload and battery weight available for the trailers. Being self driving, trailers need not be mechanically coupled. However, they can "team up" at speed on the highway to reduce drag and so improve range. Imagine 100 in a row driving a few inches apart. Resulting frontal area would be 1% of that of a single trailer...

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I'm all for tech and self driving... but I thknk self driving semis are a long way off. It'll take decades of validation in the regular auto market before an autonomous truck is going to be possible or accepted by the public.

Large commercial aircraft have been mostly autonomous for many years. When I started at Boeing, the 747-400 had just started production (late 80s). The joke was the modern flight deck had a crew of two, a pilot and a dog to bite the pilot if he touches anything. The pilots are basically there to stand by if something really bad happens that the computers haven't been programmed to handle, which does happen occasionally, but pilot error, deliberate acts by a pilot, or acts of war account for the bulk of airliner crashes in the last few decades.

Where I worked was a testing lab where engineering testing was done on all the electronics destined for the aircraft. They also had a lab for testing out new cockpit arrangements. Several people told me that they could easily go to one pilot with no problem, the real reason there were still two people on the flight deck was people were queasy with the idea of only one crew. This was all before 2001. Today people would be more concerned with security if someone tried to hijack the plane.

In any case, the public as well as regulators are going to want a human watching over the machines for a while yet. Especially very big machines that share the road with passenger vehicles.

A train of truck trailers going down the highway has the problem that they block an entire lane for a long distance. You get a mile long truck train in the right lane and a slowpoke doing less than the speed limit in the left on a two lane highway and you have a traffic jam stretching into the next state.

ratsbew said:

EVs are obviously the future. My question is can heavy trucks be electrified? Here is my brief analysis.

The truck can rid itself of the heavy engine, fuel tank and drivetrain. Place a motor equivalent to Tesla's "big" motor on each rear axle for a total of about 1000 horsepower. Gear the motors for a top speed of 75mph. Under the hood would provide enough volume for about 500kWh of batteries. An additional 200kWh could probably fit in other areas for a total of about 700kWh on the truck.

I don't know what the Wh/mile would be, but I'm guessing about 2000 Wh/mile. This would give a range of about 350 miles which brings me to the trailer.

A standard truck trailer's roof is 53' x 8.5' which gives 450 square feet. According to this map from energy.gov a typical square foot (I chose central Missouri as a typical location) provides 450 Watt hours per square foot per day. 450x450 = 200kWh/day. If each trailer has 200kWh of battery capacity then the battery could be charged from flat to full in a single day of sitting on a lot. Additionally, during a 12 hour shift of driving, the trailer would provide it's original charge of 200kWh plus the extra 200kWh that is generated over the course of the day for a total of 400kWh. Keep in mind that in the southwest you can get as much as 600Watt hours per square foot per day which would boost the amount generated.

700kWh on the truck plus 400kWh from the trailer gives 1.1MW/hr and dividing that by my estimated 2000Wh/mile gives about 550 miles. Assuming a 12 hour shift of driving that's only about 45mph so it may be necessary to have more battery capacity.

Regen going downhill would be an enormous benefit. I don't know if the dual motors would even be able to keep the truck's speed under control assuming about 130kW of braking (taken from Model S's 65kW of regen times two motors).

This is a relatively unorganized stream of thought, but I hope the truck makers are looking into this. There is already a well established network of truck stops so charging might be less of a factor than one would think.

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We had a discussion like this about a year ago:
What are the technical barriers to large battery-electric trucks?

In it, I suggested a ~450 kWh pack - 4 model S packs, similar to the current pallet batteries, attached to a pair of classic S motors driving the two drive axles through extra reduction gears as an adequate replacement for most purposes provided suitably scaled supercharging is available.

However, doing long distance over the road trucking with BEVs is unlikely to make sense overall - it doesn't really make sense now with diesel trucks except for our political landscape. We really should be investing our money into an expanded and upgraded rail network with overhead catenary lines and doing most of our long distance shipping that way, using trucks only to move goods to/from the nearest railheads.

A modern diesel-electric train moves about three times the cargo miles per gallon of fuel that a state of the art diesel truck does, and the electric difference would presumably be even greater since you don't have to haul the battery pack around...
Walter

wdolson said:

...
Companies like UPS and FedEx have shown some interest in electric vehicles for their delivery vans. That can be feasible because the vans are only used part of the day and return to the same depot every day.

....

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Others have articulated the difficulties with long haul trucking being electrified - no need to say more there. I think that this comment shows us a path towards increasing electrification of commercial vehicles. Like many such things in life, there will be a gradual process of technology improvement leading to a larger and larger range of vehicles that can be electrified in an economical and effective fashion.

Delivery vehicles and other in-town commercial vehicles that are used for part of the working day, and then return to a depot / garage / parking spot overnight, before going back out the next day to support work are an obvious candidate for initial electrification.

One candidate I have in mind are the fleet of yard maintenance crews running around. To really work well, you'd not only want a truck that can tow a trailer, you'd also want electric yard equipment, at a price and in a form factor that enables working all day and recharging fully overnight. Initially, something that might help these vehicles and equipment electrify is the possibility of collecting a small premium from customers that want a "green" service, though I expect that will someday soon be along the lines of the banks that wanted to charge a premium for online banking services (that ended awfully quickly - the savings to the bank for universal online banking far outweighed the revenue for a subset of the bank population using online banking services).

We're not there today, but I see the day coming soon where the daily operating expenses and maintenance of electric vehicles and equipment will put the gas powered equivalents out of business because they will be too expensive to operate.


And all of these drive demand and volume, that drives the economies of scale and further research and innovation, that lower the costs and increase the capabilities, thereby bringing ever expanding markets into first feasible range, and then to a tipping point where you have to electrify to remain viable in the market.

Another 2-5 years of Model S / X, and we may see that tipping point in the luxury sedan and SUV market. An admittedly small market, but one we can study to anticipate the effect of advancing technology and volume on other markets.

At the current level of technology, the only viable way for long haul trucks is CNG/LNG. Even hydrogen is not suitable, because despite a weight advantage, it is at a volume disadvantage. And fuel cells don't have good power density and $/kW.

What could change on the battery front is metal-air or lithium sulfur batteries, but with conventional batteries, long haul is still pretty far off. Or you get creative, like overhead wires or wireless charging on the road.

It might be easier to tackle if we think of the cargo transportation industry as 4 segments,

* short-range, small payload
* short range, large payload
* long range, small payload
* long range large payload.

and consider each segment to see if it is practical (and economical) to use electric vehicles to do the transporting.

First, a couple of arbitrary definitions:
"Short Range" is considered the distance that can be driven in an 8-hour day. Let's say that this is 500-600 miles. So we are talking about trips around town in a city, or trips from one city to another city within 500 miles.
"Long Range" is anything longer than Short Range.
"Small Payload" is considered the volume of a delivery van (certainly less than the standard 18-wheeler's trailer), or a gross weight of 25,000 lbs or less.
"Large Payload" is anything bigger than a Small Payload.

The idea here is to define a Short Range and a Small Payload in such terms that such trips with such cargo is common enough to be considered, but not so large as to tax the limits of battery technology. We-all can bicker over whether "short range" could be redefined to 525.725 miles, or "small payload" could be redefined to 127.2 1-1/2 cubic ft boxes at some other time.

Some examples of short-range, small-payload applications would be:
* delivering the local mail
* UPS or FEDex delivery trucks
* Furniture and appliance delivery trucks for local department stores
* "Really short-range and really small-payload" stuff can be handled by the Amazon.com-like drones.

Some examples of short-range, large-payload applications would be:
* cement trucks
* garbage trucks
* tow trucks
* tanker trucks from the refinery to the gas station

Some examples of long-range, small-payload applications would be:
* UPS or FEDex or mail package transport

Some examples of long-range, large-payload applications would be:
* 18-wheeler commercial transport trucks
* vehicle transport trucks
* tanker trucks from the refinery to the gas station
* moving vans

I think that its very possible for electric vehicles may handle tomorrow's short-range freight transportation needs. Self-driving (or self-flying) vehicles can deliver mail or packages, and an electric delivery truck could deliver sofas and refrigerators within a certain radius of the store. Electric garbage trucks have got to be on somebody's drawing board, although electric cement trucks may have to wait until we can accept a smaller payload due to weight. Electric snowplows? Hmmm.

Long range stuff? I dunno. It probably doesn't make sense to have a Pony Express system of swapping batteries every few hours to keep on truckin', even if they are autonomous trucks. But the hyperloop -- that may satisfy most of the long-distance cargo transport needs, without needing a driver most of the time, and without needing a bunch of battery swaps.


Intercontinental cargo that may require electric aircraft or electric ships are probably the gleam in somebody's eye, but I've never had much luck mixing salt water with electronics of any kind.


-- Ardie