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Comment by londons_explore | Hacker News Reader

Electric and Hydrogen trucks today struggle because a truck needs a huge amount of energy to go somewhere.

If that energy could be reduced, the problem would be far easier.

Here is a free idea for anyone working on this problem:

Make it more aerodynamic. EU trucks today have flat fronts and flat back. They're super aero-inefficient. US is better but not much. The flat front and back are primarily to meet maximum length regulations, which are to allow them to navigate small streets. Bypass all this by having an inflatable front and back that auto-inflate to make a pointed front and back when going over 40 mph on a straight road. Use the same kind of construction as a SUP-paddleboard - ie. 15 psi air and thousands of cords for shape. When the truck slows down, have the whole lot deflate to leave a flat front/back.

This will ~halve energy requirements for long distance trucking, which, considering fuel/energy is ~30% of the cost of shipping goods, is a massive financial win, as well as being good for the environment!

The main barriers will be regulatory. You'll have to persuade lots of government agencies to let you run trials of such things on the road. Trucks have pretty strict regulations, and you can bet 'stick a massive inflatable on the front' is going to mean you can't meet some of them, so will need exceptions to those regulations. That in turn will mean your truck can only drive in some states or regions, which will reduce its utility.

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> Electric and Hydrogen trucks today struggle because

...pollution and carbon emissions haven't been priced correctly for decades.

Now that's changing, and ICE trucks are starting to struggle, starting at the last mile, low weight, urban end of the scale, but inevitably expanding outwords.

It also explains why the 50% savings you mention haven't already been taken advantage of with ICE trucks. The costs of developing and deploying that technology (mostly related to a political fight with the people who sell the fuels and therefore really dislike efficiency and clean air) hasn't been worth the savings available.

The people who sell the fuels have approximately zero influence over the people who sell the trucks. Truck manufacturers try to optimize overall operating costs because that's the primary metric their customers look at. Adding active aerodynamic surfaces to trucks would cut fuel consumption slightly, but nowhere near in half (as londons_explore suggested); that's simply not plausible. And it would be another thing to break.

>The people who sell the fuels have approximately zero influence over the people who sell the trucks

I wish that were the case:

https://www.thetruthaboutcars.com/2022/05/gas-war-republican...

> Last week, a group of Republican attorneys general decided to sue the Environmental Protection Agency (EPA) over its decision to reinstate the waiver allowing California to set its own limitations on exhaust gasses and zero-emission vehicle mandates that would exceed federal standards.

What's your point? That article isn't relevant to my previous comment. Nothing is stopping truck manufacturers from increasing fuel efficiency. They're free to do so, regardless of whether or not California imposes emissions requirements that are stricter than the federal standard.

Somehow I have a hard time trusting “thetruthaboutcars.com” as a trustworthy, unbiased source.

That site isn't too bad, but the article is almost completely unrelated to the point that was raised.

Republican attorneys concerned about the EPA overstepping its authority (right or wrong) don't sell the fuels or sell the trucks.

I'd argue they do.

Big Oil lobbies government hard to not price in externalities (carbon tax).

Therefore diesel is cheaper than it might be under a carbon tax. Truck manufacturers optimise max length & volume, so flat front and back, rather than diesel efficiency.

>Truck manufacturers optimise max length & volume, so flat front and back, rather than diesel efficiency.

I don't think they do optimize volume, because they could certainly have larger trailers.

The correct metric seems to be diesel consumed per kg/cargo mile.

> I don't think they do optimize volume, because they could certainly have larger trailers.

No they cannot, at least in Europe. The outer dimension of trucks are regulated, such that street planners know what to plan for and truckers know they can pass a street.

People think ya can pop a wind farm anywhere, but ya have to be able to drive the 100m plus single piece blades there, they don't fit on regular trucks, and doesn't always go as planned.

https://www.abc.net.au/news/2019-09-19/wind-turbine-blade-bl...

Exactly, the benefits are fairly marginal. Its a bit like those foldout truck tails, they do have a marginal benefit but they cause truckers enough pain that many avoid them.

Back in the day the people working to shut down electric street cars were the same people making and selling cars and buses and tires and oil for the oil changes: https://en.wikipedia.org/wiki/General_Motors_streetcar_consp...

Oh yeah, because batteries and solar panels contain the long term pollution they create in their price right? All of these prices have a lot of factors involved and none of them are actually related to their pollution aspect. In fact pricing things ONLY in carbon emissions as people would like to do nowadays is maliciously deceiving.

Batteries and solar panels are (broadly) affected by the same carbon fees and pollution regulations as other products.

Yes, those fees should be higher, and pollution regulations should be even stricter, but if they were, (which they should be!) it would only further speed the uptake of solar and batteries, because they are less polluting than their rival technologies.

> In fact pricing things ONLY in carbon emissions as people would like to do nowadays is maliciously deceiving.

I don't think anyone is suggesting this, though it may actually be better overall than not pricing carbon at all, so it's an interesting thought experiment.

Don't let perfect be the enemy of good...

The EU is already on this with new regulations. As of 2022 european trucks can be upto 90cm longer if the extra space is used for aero bodywork. The DAF XG+ is the 1st truck that uses a 60cm longer nose to get improved aero. It will be interesting to see what other truck manufacturers will do with these new EU rules.

https://www.daf.com/en/news-and-media/news-articles/global/2...

The lowest hanging fruit is likely going to be adding a second trailer behind the first and increasing the horsepower while simultaneously reducing speed.

Ontario, Canada made this tradeoff a couple years back on very specific motorways. There are dedicated places for super-long road trains to lash-up, drive, pull over, and disassemble between London, Toronto, and Montreal. These combinations are only allowed to drive a max 90km/h speed which further reduces fuel use and permits easier passing by standards trucks and cars.

Sounds like trying to convert a truck to work like a train. Why not just more trains?

Trains require dedicated rails, and increasing traffic on rails requires modern signalling infrastructure, both which are a lot more expensive to build and take decades. At least if the UK is anything to go by.

Road trains use existing infra, aren’t as constrained in destinations, and don’t take decades to roll out.

Don’t get me wrong. More rail is a good thing. But we also need more road trains too.

It's all of this but mostly the flexibility. Rail is a centralized service with unpredictable schedules. Once a truck is full it can be shipped, but rail poses an additional bottleneck. Plus then you also need a driver on the other end anyway to pick up and deliver the trailer.

Rail should absolutely be used more frequently. It just isn't well integrated with trucking right now.

In India we have Ro-Ro (or whatever it is called now) where trucks are loaded onto trains and transported over long distance, fast and cheap. Then the roads take them last 100 km or so, in the heartlands (or wherever the destination). Best of both worlds.

We do the same thing in the US for more long haul things. Also we ship a lot of intermodal containers this way.

The big issue is speed. Individual trucks moving trailers is insanely fast. Semi's are commonly moving at 110km/h here in the states. The US is highly dependant on JIT shipping so any changes to slow this down would have huge economic impacts (which we saw with covid).

Roads don't just emanate out of nowhere either. They must be built and maintained, or they become useless. I doubt building new highways really takes much less time than building new railways.

We wouldn't need to build new highways for this. We'd just be changing how we use existing ones (replacing existing road traffic with more efficient road traffic).

Which will wear down bridges and streets far faster. There have been experiments with extra long trucks in Germany, but so far they haven't resulted in extended regulations. Longer trucks have severe limits of manouverability in small cities.

As far as I know, German trucks are already limited to 90 km/h

Above 7.5t on the Autobahn 80km/h, outside cities 60km/h. Fines start at 10km/h over, so they're usually going 89 and 69 though...

> Fines start at 10km/h over

This is not correct. A distinction must be made between:[1]

a) Driving up to 15km/h too fast outside of a city/village for more than 5 minutes or in two cases after departure is fined with 140 EUR.

b) Exceeding the speed limit once for a short time by up to 10 km/h outside a town or village is finded with 30 EUR. (11-15km/h: 50 EUR; 16-20km/h: 140 EUR; ...)

There is a tolerance applied to the measurement of 3km/h for under 100km/h and 3% above 100km/h. That should take into account the inaccuracy of the measurement; however, it does not guarantee that you get away with driving 83km/h in the autobahn, because the measurement might be a little inaccurate to your disadvantage.

[1] Source: https://www.bussgeldrechner.org/lkw.html (in German)

An absolutely horrible idea for safety outside of the autobahn. There are many distributive roads where over taking safely is impossible with two trailers in front of you.

The autobahn??? The highway between London and Montreal is 4-8 lanes, what's the issue?

I too used to have fun googling the scores of patents envisioning these ideas: https://patents.google.com/?q=inflatable+aerodynamic+truck&o... - the fun part is figuring out which energy crisis or recession they emerged from (post-1971, post-9/11, post-2008, etc.)

here's a few:

- https://patents.google.com/patent/WO2013182618A1/en

- https://patents.google.com/patent/US20170158260A1/en?q=B62D3...

- https://patents.google.com/patent/US4088362A/en

> Make it more aerodynamic. EU trucks today .... and flat back

Definitely go touch up your aerodynamics :) The flat back is actually not as bad as you think for speed these trucks moving at. It creates a circular vortex that makes a high pressure zone.

* Asterisks apply. Ask representative for details. Commentors on HN will comment that I over-simplified.

Aerodynamics are important but unless all the roads are flat like a railway (which, of course, is infeasible) they really only impact trucks driven at high speeds with light loads. Of course any 5 or 10% savings on fuel is very helpful, and most North American companies have used aerodynamic skirts and shapes to minimize resistance, but when you're hauling 80,000lbs the density of air in front of you is dwarfed by the rolling resistance of the load behind you.

> when you're hauling 80,000lbs the density of air in front of you is dwarfed by the rolling resistance of the load behind you.

Isn't this only true up until around 50-55 mph? IIRC, at the speeds truckers see in the US, especially on rural highways, aero dominates.

Where I live, trucks are governed to 105km/h (approx 65 mph) and frequently companies cap them lower than that, so it's not like they are driving around at 75mph. No company could afford the fuel bill.

I'm not saying aerodynamics isn't important, but only that significant changes need to be made that smooth the transition between road and rail so that single truck/trailer combinations aren't being used for stupid trips across the continent that could easily be accomodated by rail and are only used for local deliveries.

However, making rail responsive enough to tie into the just-in-time manufacturing sector is more difficult than it should be.

> so it's not like they are driving around at 75mph.

Plenty are in the US. A lot of people from other countries don't appreciate just how much open space there is to cover here.

Cars yes, but with diesel over $5.00+/gallon there are very few trucking companies that will allow their drivers to go over 65 mph. It's simply too expensive.

The ones you see driving around at 70+mph are usually owner-operators who don't have their trucks governed.

Owner operators are very common, I think.

Anecdotally, as someone with a lot personal experience driving an RV down the road capped at 65mph, I get passed all the time by big trucks. I do see plenty that are likely governed at 65 though.

Bypass all this by having an inflatable front and back that auto-inflate to make a pointed front and back when going over 40 mph on a straight road

In the U.S., many tractor trailers have something similar, but they fold out on the back and underneath the trailer to make the rig more aerodynamic.

Example: https://www.fleetequipmentmag.com/wp-content/uploads/2015/03...

I've never seen any fold-out attachments for the front, so there's probably not much to be done there, except for the roof of the cab, which often has a built-in fin/wing/whatever to help air get over the trailer.

A flat front isn't a major issue at all - the most aerodynamic shape is roughly a teardrop - and the "front" of a teardrop is mostly flat anyway.

It's the backend and the wake you cause that is the major problem.

Seems like more often than not I see them folded up, not in use. Even with the price of diesel. I wonder how much they save?

Maybe 5% at best? Probably less, given that there's always some time spent at lower speeds too.

They are not allowed in all states/areas. So you might be someplace where they are not allowed, or close enough that there isn't a good place to stop and put them back out. I see them in use all the time, but that is a reflection of where I live.

I suspect flat fronts and backs are driven by length restrictions?

IIRC this is why cab over designs decreased in the US (length requirements were relaxed): https://www.quora.com/Why-are-Cabover-trucks-for-the-most-pa...

This is completely wrong.

Energy isn't the problem. A small corner(100mix100mi) of the Nevada desert, or Spain can power the entire United States/Europe. The problem is storage and transport. Hydrogen solves that.

People are so obssessed about efficiency. They're completely missing the point. You don't need to be that efficent when your source of electricity of effectively unlimited.

Isn't hydrogen pretty hard to store and transport? It's pretty corrosive and escapes through seals readily, and needs to be compressed.

You don't have to store and transport it in pure form as gas. You could use e.g. some carrier medium (or whatever is the right English term).

You mean a liquid hydrogen carrier pathway like liquid ammonia. That seems possible, but requires extra plants and equipment, and obviously you still have to store H2 if you want to burn it in an engine in a vehicle.

Ammonia, the most likely carrier you're talking about has its own set of issues. It burns rather cool so will require new engine designs to overcome this. Also the engine must run efficiently or will produce nitrous oxide gases, hence smog. Lastly, and one of the bigger risk for end users is ammonia is a highly aggressive irritant. While gasoline/diesel can be bothersome in low concentrations, ammonia will send you running and choking. I personally think it will lead to consumers being more afraid of it and lead to adoption issues.

There are attempts being made to store Hydrogen as 'green ammonia' which hopes to totally eliminate those issues:

https://www.abc.net.au/news/2021-10-11/queensland-hydrogen-t...

Alternate idea (which could be enabled by tele-op trucks) - make trucks go slower. Make them stick in the right couple lanes and give them a lower speed limit.

Momentum is a massive benefit that trucks try to leverage. I fully support truck lanes though, as cars are generally the cause for losing momentum on on ramps etc.

Separating different types of traffic could be a good idea, but there's no free lunch in physics. Higher speeds require more energy, period. Heavier loads require more energy, period. Wasting momentum due to curvy roads or traffic is inefficient, but higher speeds don't somehow make up for that.

Maybe speed limits are the wrong idea - you probably do want trucks to be able to speed up above their cruising speed before going up a hill. But dedicated lanes and tele-op could set up an incentive structure that favors a lower speed without any laws.

No thanks. Try driving on highway truck route like I-5 where there are only 2 lanes in each direction. Even when the trucks stick to the right lane that still results in long delays as everyone else tries to pass on the left. Slowing the trucks down even more will just cause further delays, road rage, and dangerous driving.

Oh, don’t worry. We’ll add more sensors and real-time monitoring to passenger cars so we’ll becable to punish those doing road rage. We’ll also put a hard speed limit in place which will be enforced electronically by the car itself.

We will then eliminate all old cars by raising taxes on them beyound what any sane person would pay.

It’s coming. Total control.

Or just do it where it makes sense and don't do it on two lane roads. Doesn't have to be an all-or-nothing policy. Many roads already have lower speed limits and lane restrictions for trucks. That could easily be expanded where it makes sense.

> Even when the trucks stick to the right lane that still results in long delays as everyone else tries to pass on the left.

I'm always amazed in the midwest what a difference there is between traffic in states that have (and actually enforce!) a "get out of the left lane" law vs states that don't.

I-80 across the eastern half of Iowa in particular is exhausting to drive on, because a lot of people camp in the left lane and clog up traffic. That leads to desperate and aggressive driving to get around these silly bottlenecks, which kills fuel efficiency and makes the roads more dangerous.

>I'm always amazed in the midwest what a difference there is between traffic in states that have (and actually enforce!) a "get out of the left lane" law vs states that don't.

Those laws are unAmerican: they're about people doing what's best for the common good, instead of being selfish, and that's completely contrary to American ethics and mindset. That's why Americans generally hate those "keep right except to pass" signs and ignore them.

I know you're trolling, but those keep right except to pass laws are actually more common in right-leaning states with a lot of empty space. Which kinda undermines your trolling.

Turns out many cars and trucks are more efficient at 65mph (120km/h) than 55mph (100km/h). There are a lot of fixed losses, and ideal engine RPM is critical for efficiency.

Going too slow is definitely inefficient for non-hybrid cars and trucks, but the optimal speed for most vehicles is certainly not higher than 55 MPH.

Average fuel economy for cars and light trucks decreases 12% going from 50 to 60 MPH: https://www.energy.gov/eere/vehicles/fact-982-june-19-2017-s...

Heavy trucks are the exception, they are typically designed for an operating point of 65 MPH. However, there are huge losses above that speed. No reason for a heavy truck to be going 70 or 75 MPH.

The American Trucking Association actually endorses a nation 65 MPH speed limit for trucks, which they say would save 280 million gallons of diesel per year: https://www.fleetowner.com/emissions-efficiency/article/2166...

Really? The graphs I have seen put the optimal ICE car speed at about 30-50 mph depending on car aerodynamics. For EVs it is probably even lower as drag dominate earlier.

The Tesla Model 3's computer's range calculator gives a max efficiency at 22mph.

In my gasoline car, max efficiency is at 29 mph, or 35 if it's dark, cold and raining (energy use of lights, fan and wipers is minimised by driving faster so you need the lights for fewer hours to go the same distance)

or or, hear me out, become switzerland and get serious about doing freight logistics with trains

I think that's exactly what the likes of Nikola and Tesla are doing with their trucks.

From what I understand, battery electric trucks exist in pretty much every size and weight class right now ranging from huge dump trucks used in the mining industry, long range trucks to more medium and small size trucks. Hydrogen may have a role to play with some of these.

But the decision as to use hydrogen is more a cost consideration than it is a functional necessity. The reason there are not a whole lot on the road is that cost wise, it doesn't make that much sense to go for hydrogen. Hydrogen is expensive to source, difficult to handle, there hardly any fueling stations, you need complex systems on the truck, heavy tanks, etc. It adds up to a lot of cost and limitations for not a whole lot of benefit.

As for this particular truck, it does not look like it's particularly impressive in terms of torque, range, etc. 400km range is well below the 500 mile range that Tesla is advertising for the Tesla Semi (with a ~500kwh battery). That's 2x the range (and a bit). The normal range also has a better range with about half the battery.

What is interesting is that hydrogen fueling takes a bit of time. It's not like fueling a truck with diesel. You need to squeeze a lot of hydrogen through some heavy duty pipes at very high pressure. That takes time.

People always complain that charging batteries takes so long. Well, 20 minutes of fueling time for hydrogen is also substantial and at the lower end of the scale of what a lot of EVs can do in terms of 0 to 80% charging already. There are already chargers being designed that will charge trucks at over 1MW. So, if you have 500kwh of battery, you might get it charged in about 30-40 minutes. That's a lot of range depending at what rate you are cruise (typically nowhere near the maximum capacity of the motor).

Another interesting aspect is that these hydrogen trucks have a 72 kwh battery. That's because fuel cells are not that easy to throttle up and down. So, instead it's basically a battery electrical truck with a smallish battery and a complicated hydrogen generator. Swap it out for a diesel or petrol engine and you have a hybrid truck. Swap that out for a proper battery and you have a proper battery electric truck. Same engine, just a larger battery and lot less complexity.

The reason the battery is relatively large is because they are powering a 350kw motor with a 160kw hydrogen setup. It would not be able to operate that engine at its full power. And when you are driving up a mountain, you need a bit of a buffer since you are depleting faster than you can charge it so it needs to be able to sustain high power levels for a bit.

I have a hybrid with a little battery and a small gasoline engine like this... The 'mountain problem' is real. If I drive up a long hill when fully loaded, the electric bit runs out, and the gasoline engine is really undersized. You end up limping along on the highway at 25 mph with the engine revving like crazy and your foot on the floor.

I could imagine the trucking industry might even have different models with different ratios of battery to fuel cell to motor depending on the terrain of the places it's likely to drive.

This is why big rigs have so many gears. It lets them maintain maximum power in a wider range of situations. That way they can actually reach the level of power that gets them up to speed (and more efficient RPMs) in situations like that.

I've driven big rigs. I've driven up mountains fully loaded (80,000lbs total). MOST trucks will struggle to drive up a moderate incline at that weight.

I've been in the Smokey Mountains and crawling up a hill at under 20mph.

People do not realize how little horsepower many trucks have - they're often comparable to mid-size sedans!

Tons of torque, of course, but getting up a grade is a function of total energy, not just torque.

https://www.youtube.com/watch?v=R-xqfqcgNAE

As a long haul driver, what is your opinion on replaceable battery packs?

Assume we had these stops every 500-400km (or miles..), and you could do 4-5 hours driving per pack, and the on-site replacement process takes like 2 minutes (excluding the detour and approach time, of course..)

Not the person you asked but...

Look at any ad for OTR jobs. Notice the emphasis on miles, the more the merrier. It's rare for an ad to specify less than 3k miles per week. High miles aren't only an incentive, but a requirement.

Now consider several things. Drivers are paid mostly by the mile. Federal regulations dictate 11 hours of driving time daily, with a mandatory 30 minute break after 8 hours ( or 6 not long ago). On duty hours are limited to 14. As things are now, pulling into a truckstop often takes about 30 minutes after waiting in the fuel line, fueling, etc. Weighing/scaling new loads also takes time and this is necessary often. Toward the end of a shift even with the assistance of apps, parking can take significant time to find too, especially on the east coast. If a driver follows regulations, a mid-trip stop will be made for a cursory vehicle inspection, especially of tires. Many companies govern speed between 62-65mph - and this causes myriad clusterfucks of ungoverned drivers trying to pass the governed drivers. Remember, miles are dollars, and many factors stand in the way. Driving through Atlanta, or any similar monstrosity is a regular one. Detention is another, and this is a really big one that has inspired me to quit on the spot.

I could bloviate about the all that sucks in the world of trucks, but I'm quite certain that the primary element that impells the 18 wheeled slave is money. Any thing that gets in the way of those miles is discouraging. The whole experience is discouraging for me.

Much improvement could come to the industry, but mostly in theory rather than practice. I suspect anything that makes it all even slightly worse won't be too warmly welcomed. Personally, I'd probably keep doing it if I could make a bit less and ruin myself a bit less in the process. I don't want to run 3700 miles every week, 4 weeks out and 3 days home. But when I start my day, I only stop for weigh stations, at 8 hours, and to hold my piss bottle still.

So, maybe, if it was 2 minutes.

Time is money while driving. If I stop on the side of the highway to jump out and pee, I lose a GUARANTEED minimum of 15 minutes. (even if the piss-stop was under a minute) It is a bizarre phenomenon that I could never rectify, or articulate precisely HOW it happens.

When you are driving, you constantly are doing math. Miles (or Kilometers) converted into minutes until the next turn, and also final destination. Then you try to fit that into how much time you have left in your day.

A 2 minute battery change will always take longer then 2 minutes off of your driving time. Filling up with diesel takes ~10-15 minutes. Pulling into the truck stop, grabbing more coffee or tea for your thermos, going to the bathroom, all combine make you lose 30-45 minutes. It's not the individual item times. It's the accumulation. Accelerating, decelerating, traffic, etc.

The job of Driving a truck is almost impossible to make a living at in Canada if you do it legally. Now with all trucks having an onboard electronic log-book, I'd never even try.

I was wrong, but in a way that brought out interesting and informative conversation. So in a way, I was actually right.

No, this is why big rigs make the same amount of maximum power at all points along the hill.

The reason hybrids have less power mid way up a hill is that they use the combined output of two power sources: the engine and motor(s). When hybrids deplete their battery, the only power remaining is the output from the engine. This mode of operation is unique to hybrids. The state-of-charge management software in hybrids attempt to mitigate this, but their batteries are only so big.

To be fair, most vehicle types have similar problems but they're a result of heat rather than battery exhaustion. In a pure battery EV you can run into thermal limits: drawing too much power for too long overheats the motor and batteries. Same thing happens in ICE vehicles, though I think the difference between max continuous power and max instantaneous power tends to be greater in EVs.

It always surprised me that gasoline engine manufacturers didn't cut down on the size of the radiator and cooling stuff to save money, and then say "you can only be full throttle for 1 minute at a time, and after that it will reduce to 60%". In a typical car use case, it's very very rare to be at full throttle for over a minute.

It can happen if you're going up a long hill or towing something. Probably no car company wants their car to be known as "the car that can't make it up a hill without the radiator boiling over" even if it doesn't actually happen all that often.

They have to have some wiggle room for high ambient air temps that happen in some places, and it’s cheaper to build one car than build a different one for each climate zone. If you go to a high performance driving event at a racetrack on a hot day, you’ll occasionally see cars that overheat.

> Well, 20 minutes ... a lot of EVs can do in terms of 0 to 80% charging already

How long will the battery last if you do that cycle twice per day every day though ?

3-5 years at best? Depreciation on the battery over that lifetime is a meaningful issue, tbh.

You need to think in miles not cycles. How many hundred thousands of miles will the battery last until it needs replacing? Most ice trucks kind of do up to about three quarters of a million miles before they head for the scrap yard. Maybe a bit more if you take good care of it. By that time they will have consumed hundreds of thousands of dollars worth of fuel and needed lots of maintenance to replace lots of its moving parts.

Batteries look pretty good when you consider that you can charge them a few thousand times before they degrade to below 80% of their original capacity. Electricity is of course not free but can be sourced a lot cheaper than diesel. The savings on that probably create a pretty nice budget for replacing the entire truck. But it might be cheaper to replace the battery and drive it for another few hundred thousand miles.

The economics of this don't favor diesel engines. That's why electrical trucks and vans are so much in demand right now with companies operating fleets of these commercially.

>As for this particular truck, it does not look like it's particularly impressive in terms of torque, range, etc. 400km range is well below the 500 mile range that Tesla is advertising for the Tesla Semi

Ah yes, the classic comparison of a real product versus something Tesla says on a website splash page.

Both the Hyundai and the Tesla are in the prototype phase.

I was thinking about this yesterday. We should probably start allowing active aerodynamics in racing, especially electric racing like Formula E.

Active aerodynamics are under-utilized. We start to see them, but they could be used much more, as break or turn assist, etc.

Imagine a car with retractable wheels. Only have a couple (or single) "bike" (narrow) wheel(s) for propulsion at highway speed, rely on aerodynamic controls for the rest, and on lift if necessary. Deploy aerobrakes and lower both the body and wheels in case of an emergency braking.

Such a system would be much more complex, but it could probably be engineered to be as safe as current cars (with aditionnal self- checks, attention to failure modes, etc).

I am not sure how much energy could be saved, but it's probably substantial. Plus people would finally have their "flying" cars (make them jump over detected obstacles too!).

There probably are some low-hanging fruits too, like deployable wheel covers for people who do not want to sacrifice low-speed aesthetics.

So, not exactly the ideas you're talking about, but the racing world is increasingly exploring outside of the aero that FIA/F1 et all have allowed.

Check out this fancar that set a new course record at Goodwood this year: https://www.youtube.com/watch?v=xtvT2XYlcOY

For anyone unfamiliar, a fan car uses motor driven fans to actively create a low pressure zone under the car, while also reducing the low pressure drag bubble behind the car. This particular one is all electric and quite compact.

It's very fast, and yes footage of it looks weird, almost artificial, because its sustaining grip through corners that rivals F1 cars, with the torque of electric. Running full tilt the fan system creates about 2000 kg of downforce. But the neat thing is you can flip a switch and then the thing just becomes a Nissan Leaf with a really crazy body kit. So some future "track day" car based on this concept would be surprisingly practical.

I think the future of auto racing in a pure electric era is going to be surprisingly bright.

Anyhow, not really relevant to talking about making big trucks more efficient, but thought you'd find it interesting.

> But the neat thing is you can flip a switch and then the thing just becomes a Nissan Leaf with a really crazy body kit. So some future "track day" car based on this concept would be surprisingly practical.

This car is really cool, I'm not going to argue against that for a single second. But your suggestion of a "practical track day car" is missing the fact that there are two things making this crazy fast: huge downforce and ridiculously low weight. It weighs less than half of what a Nissan Leaf does, has a single seat, no storage for anything, no aircon etc. etc.

If you tried to make it approach the practicality of a Nissan Leaf while still being performant, you would not just need more space and weight for the practicality, but you'd end up tripling the weight since you would also need a much bigger battery pack to keep the runtime at the current ~30 minutes on a track, bigger motors to keep the acceleration high when you're dragging that weight, much wider tyres to enable cornering at these speeds, etc. etc. Then you're no longer killing hypercars but rather maybe matching a Bugatti Veyron, and you might as well just go for standard aero so you don't have the 120 dB (!!) fan noise inside the cabin.

Nope. There's already a variety of track cars in this weight class, including road legal ones. Check out Palatov motorsports for example. This compact but high performance format is indeed very practical and in fact in very high demand, at least for race car crap. If you can spend the same amount of money as you would on a track built 911 for something considerably higher performance, a lot of people will.

Sure you can get very lightweight two seater road legal track cars. You can even slap an Exocet kit on an MX-5 and get that for very cheap.

But you said "Nissan Leaf". A five-seater car that can fit a full baby stroller plus a bit of luggage in the trunk. That is fully incompatible with being a lightweight track car.

Can you not understand I was being figurative vs so literal? This behavior is so common and so very tiresome here. Read charitably.

I'm sorry, but then I don't understand the point of the original comment. As we agree, you can already buy a lightweight two-seater track car with very good performance for quite cheap. I understood the point of your original comment to be that with active aero devices we could now have something far more practical, like a Nissan Leaf, but still having very good track performance. If that was not the point, then what is the new thing you think is going to be enabled by active aero?

There was some truly fantastical stuff imagined in the 1950s [1]. I’m particularly fond of the GM “Firebird” self-driving jet-turbine cars [2]. They prominently featured various winglets. Not sure if they were there just for futuristic looks and jet-age appeal or if they were intended for the kind of use you describe.

[1]: https://youtu.be/cPOmuvFostY

[2]: https://en.wikipedia.org/wiki/General_Motors_Firebird

Meh, no. Essentially all the aero stuff you see in racing, including active aero and fans and stuff, is to increase downforce. Which is absolutely useless, unless you're going more than 150 km/h (90 mph) while cornering hard.

Take the active spoiler on a Tesla Model X for instance - it is 100% a toy for people who enjoy the Transformers aesthetic. I don't think there are published numbers for it, but the Porsche Panamera which has a substantially more agressive spoiler is reported to produce a whopping 7 kg downforce at 250 km/h (150 mph), decreasing substantially at lower speed.

In the ordinary cars that actually need spoilers - famous example is the Audi TT - it's in order to fix crappy airflow giving lift at high speed, that is caused by the design of the car being optimized for looks rather than aero.

And aerobrakes?? Anything that's not big enough to cover 4 highway lanes is completely ineffective at speeds below 100 km/h (60 mph). It would be substantiallt more useful to install boat anchors.

I was interviewing with people in Berlin who wanted to make trucks go in caravans to save on fuel. I don’t know if it went somewhere beyond idea.

The song Convoy references this - https://www.youtube.com/watch?v=Sd5ZLJWQmss - on the US interstates trucks will kind of "naturally" form convoys and the lead truck will swap off now and then; the rest will "draft" behind it.

It saves a small but noticeable amount of fuel.

This is an example of bahnization - the tendency of every transportation method to evolve into a train.

I looked up bahnization hoping it was a real concept. Did you just coin it?

The concept is widespread, but to my knowledge there isn't a name for it. Bahnization is meant to be a play on carcinization, the tendency for things to evolve into crabs.

I heard they even want to electrify them and put them on rails, then they'd run electrical cables on top of the rails so they wound't need batteries. This would be hyper disruptive

That’s not web3, someone has to maintain the rails, that’s centralized. Imagine crypto-trucks assembling into a train through smart contracts.

Electrified freight rail has prevailed in Europe, but mostly because the European rail system is optimized for passenger travel which favors faster and shorter electric trains. America freight trains are several times longer than European freight trains, use double stacked containers (which don't fit under the wires Europe uses) and run slower. This makes them disruptive to passenger rail, but also more efficient. As a consequence of these factors, America moves a much greater percentage of its total freight tonnage by rail than Europe, which relies more on trucks.

So in short, electric freight trains are not 'disruptive'; they don't compete with diesel freight trains unless you have enough political pressure to prioritize passenger trains above diesel freight trains.

You need to consider sea and river transport if you compare Europe to the USA for freight. A big chunk of the bulk goods market (coal, stone/ore, grain) is moved by water in Europe: https://www.researchgate.net/figure/Modal-Split-of-Freight-T...

And India runs electric double-stack container trains, but of course it would be an enormous upgrade project to convert to this -- tunnels and bridges more than the wires: https://www.youtube.com/watch?v=yNq8lP6cfL4

The US freight railways have priced wiring their rails. It is possible to do this, and double stacked containers are not a problem (except for a few bridges that are already borderline for being high enough). Problem is it is only worth it if you have every rail electrified, just a short section in some out of the way rarely used rail that isn't wired is enough that they have to have diesel locomotives everywhere just in case they want to send that train to the one unwired track. And so it doesn't pencil out until diesel gets substantially higher and remains there.

That is according to the railroad. There are others who question the math, which is a valid thing to do, though I don't know who is right. In any case it is possible to wire all US freight, but so far nobody has done it.

Electrified rails don't prevent diesel locomotives rolling down them, so if it was cost effective right now to electrify the most active lines, they'd do it.

So far, it is not.

This is called truck platooning:

https://www.nrel.gov/transportation/fleettest-platooning.htm...

If you want to be as green as possible with today's technology the holy grail is probably LPG derived from nuclear reactor powered atmospheric carbon capture. Existing fueling infrastructure is used, low vehicle emissions since it's not a liquid when injected, retrofit is possible for every vehicle on the road today with existing and proven technology, compact fuel storage, familiarity in much of the world, the works. It's great.

Electrified highways (over head or in road) is vastly more efficient and covers the vast majority of truck pollution. Ex: https://www.volkswagenag.com/en/news/stories/2019/07/electri... or https://www.greencarreports.com/news/1127520_world-first-in-...

After that using bio or synthetic fuels, batteries, hydrogen etc are more reasonable because they need to supply vastly less energy per trip.

I don't think this is true if you factor in the Total carbon from the process of actually electrifying the roads. Its a ton of cabling made out of a ton of metal that needs to be mined.

In comparison to building 5 or more times as many nuclear reactors, vastly more of whatever fuel creating facility you want etc it’s a clear win.

I don't think it's a clear win. Because the scale of either initiative seems to be massive it warrants further study. Regardless, electrified freeways are a very interesting concept and I have never seen them anywhere yet.

Inflatable parts will need a way to ensure they can't obscure the windshield after a catastrophic failure, e.g. hitting a deer at 70mph.

(Of course you could just over-build to withstand the impact, though it would make for an interesting liability case (and interesting dashcam video) the first time a deer gets bounced off the highway and through someone's roof)

Can you give sources for the claim of how much diesel would be saved by an inflatable pad in the front and back?

Good question and one I’m curious to know as well. Parent said about “~halve” their consumption?

This is only partially related but this NASA article says with their aerodynamic technology a truck can save almost 7000 gal of diesel a year.

If we assume (just to get ballpark numbers) a semi gets about 5mpg and drives about 100k miles a year that’s about 20k gal of fuel.

Don’t truckers (at least in the US) often own their truck? I would assume that being more of a constraint than the aerodynamic tech itself

https://www.nasa.gov/offices/oct/40-years-of-nasa-spinoff/tr...

At the very minimum every truck should have an energy recuperation system for braking.

Truck brakes are wasting energy and they are dangerous because they frequently catch fire and become non operational.

I wonder about engine cooling. The radiator is at the front to catch as much of that air flow as possible. You don't really want to block it.

Modern aerodynamic designs have mechanical flaps to allow in just the necessary airflow for however much cooling is required. Hot day going up a hill - the flaps open. Cold day lightly loaded going downhill - the flaps close to reduce drag.

An inflatable cone could use the same type of mechanism

Hydrogen especially has this problem because the produces a LOT more waste heat than a pure battery-electric powertrain. One person familiar with the matter once told me the cooling system (fan, coolant pump, etc) on the heat exchanger of a fuel cell hydrogen semi truck prototype used about as much power as a Nissan Leaf.

Honestly, why not just use trollys. Adding that infrastructure would be expensive but it is more efficent then battery or hydrogen.

How will this impact braking distance?

Who cares about braking, the cone acts as an airbag!

Okay buddy, how about you let your car/truck/SUV be hit by a 150,000 lbs “airbag” and I will watch from afar to see what happens. I’m thinking pinball and the lanes as bumpers, yeah?

Why would it impact braking distance? Aside from "everything affects everything" of course. I can't see this majorly affecting the overall vehicle's momentum or braking ability at any given speed, and speed limits wouldn't change.

It would impact braking distance because if the air isn't slowing the truck down as much then it will take longer for the brakes to slow the truck down.

Oh that's a great point. It reduces drag, which would normally help braking distance. Thanks for explaining, I was genuinely having trouble thinking of how it could affect things.

That doesn’t matter much for slowing a truck down due to the high inertia. Really good low rolling resistance tires (Super Singles) should actually reduce stopping distance as they generally have a bit more contact area. You want low amounts of slippage on the tires while driving as slippage is wasted energy, which should give you more margin when you need to slow down.

Electric trucks also have a massive advantage in mountainous terrain due to ability to dump energy into the battery instead of the brakes which can and do overheat.

Deployable parachute behind the truck and for super emergencies the front backwards facing rocket engages, duhh

There is no way that aerodynamics account for 50% of energy use when doing long haul trucking and moving tens of tons of stuff.

Assuming your truck does 60 mph, it appears it does[1]. 80Hp for rolling resistance, electrical and all other losses, 120Hp for aerodynamic drag.

Of that, cars modified to be super efficient (eg. [2]) can get the Cd down to about half (from about 0.31 to 0.17). Trucks could probably achieve an even greater improvement, because production cars already have a slanted windscreen and rear trunk.

So, overall, I stand by my claim that energy use of trucking could be reduced by about half with aerodynamic techniques.

[1]: https://theicct.org/sites/default/files/publications/AERO_RR... (figure 2)

[2]: https://www.aerocivic.com/

If you cut half the air resistance and air resistance is 120 out of 200 hp, that's only a 30% total reduction.

halving aero drag != halving fuel consumption at the speed EU trucks are limited (55mph): https://www.researchgate.net/figure/Figure-11-Fuel-Economy-w...

Trucks in Europe are not allowed to travel 60mph.

True, they have to do kilometers per hour over there.

You're right because internal combustion engines are so inefficient that more than 50% of energy is wasted before it can even contribute anything. But in terms of useful energy leaving the engine it's a different question.

Once you get to long-haul speeds, the energy cost is almost entirely split between air resistance and rolling resistance, but air resistance has the edge, (about 50%), rolling (30%), drivetrain (5%), and everything else (10%).

After you've accelerated the truck to highway speed, the weight only matters due to friction. The friction and aero costs are large enough that the acceleration cost doesn't dominate.

All these assume flat terrain. As soon as you start adding hills things look completely different. That's the one reason why I think e-trucks make sense, the ease of regeneration rather than burning off the momentum as heat.

> Make it more aerodynamic. EU trucks today have flat fronts and flat back. They're super aero-inefficient

Since you obviously haven't driven on the roads these trucks need to navigate, I'll just say it: they're flat because they have to navigate lots of tight roads and turns...

Edit - obviously missed part of the comment but still, long-distance trucking is less significant in the EU. Rail networks take goods much closer to the final destination than in the US... That's why it actually makes sense, now.

Didn't the person you're replying to say:

> which are to allow them to navigate small streets

> The flat front and back are primarily to meet maximum length regulations, which are to allow them to navigate small streets.

Please continue reading the comment, the sentence right after says the exact same thing you do, without your unnecessary snark.

Still silly considering their solution is a large amount of complexity for limited benefit. Most roads have lower speed limits (thus aerodynamic drag is not nearly as significant) and long-haul trucking isn't really a thing in the American or Aussie sense... Far more rail networks, less distances to drive.

Like, they're being rolled out now... Electric vehicles actually make sense in Europe (distances between most places are short).

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