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World's largest electric vehicle (www.empa.ch)
266 points by prostoalex 2 years ago | hide | past | web | 152 comments | favorite

Because the vehicle is electric, there is no need to “heat up” the brakes when descending. This is because the enormous electric engine acts as a generator and recharges the battery pack. That same energy is then used to help the vehicle travel back up the hill. Phys reports, “If all goes as planned, the electric dumper truck will even harvest more electricity while traveling downhill than it needs for the ascent. Instead of consuming fossil fuels, it would then feed surplus electricity into the grid.”

Clever. It can do this because it travels uphill empty and comes downhill full.

That had me pause as well. I'm still a bit dubious. Given potential energy is mass x grav x height, since the vehicle mass cancels top to bottom. You have load mass x grav * height of "extra" energy on the way down, which if you convert at 50% efficiency to charge would be a quantity of energy E which on the way up, if you have a 50% efficient power train would take the mass of the truck to the top of the hill. That suggests that the truck can carry 4x it's mass down hill. But in the phys.org article [1] it says it weighs 45 tons and can carry 65 tons. That is 44% additional mass. And because its linear 44% "additional" potential energy at the top. Which has to be converted twice (mechanical -> electrical, electrical -> mechanical).

I'm not expecting them to meet their goal of producing excess energy.

[1] weighing in at 45 tons when empty plus 65 tons of loading capacity -- https://phys.org/news/2017-09-e-dumper-world-largest-electri...

I think your efficiency numbers are too low.

Large electric motors, 90-95% efficient.

Battery round trip efficiency, 80-85%.

High voltage inverters, likely above 98%.

Roughly seems like regen round trip efficiency would be at least 63.5%.

The weight ratio is (45 tons)/(65tons + 45 tons) = .409

Unfactored are rolling friction loses.

   > The weight ratio is (45 tons)/(65tons + 45 tons) = .409
Sproing! Discussing it here I realize that I kept thinking about it as 'can the energy of bringing 65 tons down equal the energy of 45 tons up' but you are absolutely right that really its 110 tons down, and 45 tons up. That certainly helps.

40 kWh regen per trip on 700 kWh total is very likely to have 98%+ charge/discharge efficiency. If it's doing 20 trips per day and a "day" is 8 hours (I suspect it's actually more), then that's what- a ten minute trip? That would be charging at .34 C. A standard slow charge is between .2-.8 C.

The efficiency of an electric powertrain is much higher than 50%. Tesla claims that the total roundtrip efficiency for regen -> battery -> driving for the Tesla Roadster is around 64%: https://www.tesla.com/blog/magic-tesla-roadster-regenerative...

That would be an excellent comparison. So at least one data point of existing practice.

Although as mentioned previously it needs 69.2% and 100% loading to break even. Could be a challenge.

The Roadster's drivetrain is relatively inefficient for an EV (notably, it uses an AC induction motor rather than a permanent magnet motor) so I wouldn't be surprised if this truck could reach the breakeven point. But I don't have hard numbers to back that up!

Actually the power to weight ratio of all of Tesla's motors far exceeds that of permanent magnet motors. I am sure that the truck would use similar motors, they are both more cost effective and much higher torque (good for trucks).

Compared to fuel wasted on pre-heating and efficiency below 50% for a diesel engine with huge co2 emmissions, this doesn't sound too bad though O:)

It is absolutely a win, no question there. Just being able to recapture any of the energy going down hill and applying it to the return trip is better than the existing practice! I just enjoy the physics of the question, the sort of "How would we compute just what it would take to achieve this?" kind of thing.

Right. This seems like an ideal application for an EV. I'm surprised no one has done it before.

First of all, its 144% additional mass. But the calculation can be done very simply. If the regeneration efficiency would be 50%, then it needs to weight twice down what it weights going up to be a zero sum game. The regneration efficiency should be higher than 50% (Tesla has over 60%) and it is much more than twice the mass going down than going up. So there should be a healthy surplus of energy generated by going down.

Yup, read the additional comments. Net is:

   E(loaded) -> %eff capture -> E(bottom) -> %eff drive -> E(unloaded)
And as long as you can multiply the two efficiency fractions and stay above 41% you win.

So how far is the trip down, 10 miles? The potential energy of moving 65 tons 10 miles down (think of pulling a rope with a 65 ton weight) is a freaking lot of energy.

That it the beauty of doing as an energy/energy analysis. Energy at the top is total mass x 9.8 x height, energy to get the unit to the top is unloaded mass x 9.8 x height.

The ratio will tell you how much "excess" energy you get, the efficiency of converting that from mechanical energy to stored charge and back to mechanical energy will tell you how much energy you will have 'left'.

And as long as you don't run out of battery capacity to hold energy you're capturing on the way down, the math just works.

The linear/road distance down doesn't matter. It's elevation that provides the potential energy. Pretty sure they are not descending 10 miles in elevation.

It carries 45 tons + 65 tons downhill and then has to carry 45 tons back up. That's the hard part.

With 0 friction and 100% effeciency, the break even would be 45 tons of load? So this has 20 extra tons to make up for the various losses..

Not 20 extra tons. 65 Extra tons.

You should probably edit this comment too- 45 tons up and 110 tons down means the efficiency just has to be >41% (45/110).

I just tried to, and just missed the edit window.

Is 50% a reasonable number? It seems low to me, given that electric motors are ~90% efficient, and battery charge efficiencies seem to be around 80%. To get that to 50% overall, the gears and powertrain would have to be < 70% efficient.

Hard to say, perhaps the most efficient conversion of potential energy to electricity is hydroelectric which can hit 90%, but if you put it into batteries and take it out again that drops some additional points and what ever you lose from heating the batteries. You would want to look at friction losses in the wheels, and coupling losses between the wheels and the brakes. And on the way up, you're going through the power train.

Based on the mass ratio the magic number is 69.2% to hit break even assuming you always load to 65 tons. If you load to 55 tons (15% margin of error) the magic number would be 82% efficiency.

EDIT: See another comment that the ratio is 110 tons to 65 tons, not 65 tons to 45 tons. That improves things. Total system regen efficiency has to be above 41%. That number crosses 60% when the load is down to 30 tons.

In a typical car with gears, you tend to lose about 15% of your power through the drive train on a 2wd vehicle. It approaches 30% with a 4wd vehicle. Since this is based on a diesel vehicle, I imagine it won't be too far off. Maybe worse because of the huge size of everything, but I'm not a mechanical engineer.

Though it is not - I believe - the case of this specific Komatsu model, electric driven dumper trucks are in production, getting rid of the transmission, examples, JFYI:



Basically this kind of trucks have a huge diesel engine and electric generator and four electric motors, one for each wheel.

Power is lost in the generation and powering of the electric motors of course, but there is no transmission overhead (though there is a reduction gearbox on each motor anyway).

Also, the trash has to be compacted. I doubt this will be a net positive. Just a nice side effect.

It's hauling mineral deposits, not trash, so no compacting.

Right you are. There was another thread that was talking about this for garbage trucks. Whoops.

That's the first time in a while my "conservation of energy" mental alarm has false-positived. I could see "mere engineering" getting in the way of the dream but the energy checks out.

I had the same intuition, but if anyone is out there wondering -- there's a hidden source of energy: all the energy that goes into arranging the trash at the top of the hill in the first place.

So the energy that the truck is gaining is really the stored potential energy you got from the kinetic energy of bringing your food home from the store (or other similar things).

I think the idea is really clever, to utilize that kind of latent stored energy to make your trip more efficient.

Dump truck, not garbage truck. This one is transporting rock from a mine to a cement plant. It does not transport garbage. The mine is just on a mountain.

Again, trash is not involved.

Derp, reading comprehension.

Same reasoning applies though, albeit other processes doing the lifting.

But that was going to happen anyways. Today, a dump truck spends energy going downhill by burning fuel and brakes that it doesn't need to if it's electric.

tectonic drift, specifically.

I thought the same, but then it made me wonder how many mines are built such that you are hauling ore down instead of up?

I don't know enough about mines, and googling "most common mine design" isn't cutting it. Could anyone weigh in with more insight? The only big mines I've seen look to be pits, like the Bingham Copper Mine near SLC.

I do remember reading something about ore trains in some Scandinavian country using regenerative braking to power nearby towns and its own trip back up.

Here is a coal mine in Alberta [0]. If you turn on the 3D google maps, you'll see that it's at the top of a mountain. They transport the coal down into the valley and then onto rail cars.

0- https://www.google.ca/maps/@49.6515022,-114.8604751,14053a,3...

It's fairly common in West Virginia, google 'mountain top removal' for plenty of examples. EX: http://appvoices.org/end-mountaintop-removal/before-after/

The two most common types of surface mining are strip mines (where there isn't much up/down climbing) and open pit mines (where the loaded portion is going up). It's possible the mine in question is an open pit mine where your loaded descent to the dump site distance > the loaded climb distance out the open pit.

I came across this the other day while randomly reading about energy storage techniques, initially piqued by pico-scale hydro: http://www.aresnorthamerica.com

They use electric locomotives and traincars full of rock, along with a big hill, as energy storage. Drive it up during cheap energy times, and back down when you need to produce electricity.

Unless they are using this dump truck to fill in an old pit it doesn't seem like that should happen very often.

The logistics of feeding the power back to the grid are also a bit wonky. Is it going to be dragging a cable behind it? Is there an inductive charge/discharge pad that it drives over? The article has no useful details on this, and the whole idea seems rather half baked.

Think about it like this: mountains are places where deep mineral layers are pushed up into the surface, exposing them. It's where you find many of the dense, valuable ores without layers of dirt and non-valuable rock overtop. Mountains are actually great places to mine.

I think that's a little unfair. I'm sure they've done the maths since they're building a massive electric truck. Maybe the article was overstating it a little but it certainly not technically impossible for it to store electricity and then release some of it once it's back up the top.

Why would feeding power back to the grid be any different from charging? When the battery gets full you'd plug in and mostly discharge it.

Doesn't an electric train have overhead power cables?

Depends on the system.

> An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or on-board energy storage such as a battery or fuel cell.


It depends what you're mining, is the obvious answer.

The example in the article was a cement factory - cement is basically made from limestone, and you can find mountains of the stuff. In general, you're probably looking at sedimentary deposits that have been uplifted - coal was another example someone else gave, you can probably also find mountaintop salt mines.

In either case you are probably expending way more energy digging and mining the coal such that the hauling is negligible.

Moving away from coal would have a much greater positive environmental impact than engineering the hell out of the hauling efficiency. Like wind power, solar power, hydro power, for instance, all of which don't need any hauling once built.

The Bingham actually has a conveyor works lower in the pit that goes through the side of the mountain to the processing plant.

At least it did when I was there, this was before the big collapse there a few years ago...

I have the same speculation as you -- the only use of dump trucks I've ever seen is to haul stuff uphill. Maybe it's different in some parts of the world, if anyone can weigh in.

They could almost certainly build a conveyor since anywhere they have a road they pretty much have a suitable slope. However depending on how the mine is used the top end might be moving around a lot and need to be rebuilt frequently where a truck can simply go to where it is needed as that changes. It may also make more sense to run the truck all the way down and back then to run the truck over to the head end of a conveyor.

Edit: autocorrect

Any mine that is at a high altitude relative to where the ore is taken. Even if you have to move the ore up a bit to get it out of the mine, then there is a long trip down.

Wow. Thank you for pointing this out. The article does a terrible job and makes it seem like "Oh hey free perpetual motion"

I wonder how much of a charge it needs to have at the beginning of the day in order to sustain itself via just the surplus from regen braking. The article mentions charging by 40kWh on a descent, which I take to mean that it's less than that to ascend.

In a company created electricity metering, I heard a similar story of a train fetching logs in the mountains in Scandinavia.

The train left the station in the valley empty and returned fully loaded with logs from the mountain. At first they didn't believe their own measurements, but it was effectively generating electricity.

> Clever. It can do this because it travels uphill empty and comes downhill full.

Admitting up front I know very little about mining: Aren't most mines operating today of the strip variety? I.e. a big damn hole? My mental picture of the places most of these trucks operate is where they drive into the hole empty and come back out full, uphill. Am I wrong?

Yes, according to wikipedia 85% of minerals and 98% of metal ore is produced by surface mining. Surface mining is above 300 m deep, and usually above 100 m. This includes mountaintop removal and highwall mining, which are still basically underground. Strip and pit mining are the other main types of surface mining.

Even so this type of mining tends to happen in mountainous areas. Mountains are places where minerals are pushing up from deeper areas, and they're subject to more erosion, so you find a lot of valuable minerals. They are also colocated with seams, which are chock-full of minerals. Valleys and low spots are places where sediment accumulates and covers minerals, and are rarely worth mining. The altitude of a mine is usually much, much greater than the relatively negligible depth of the mine itself.

Ah so it wouldn't be the mine itself that would be the uphill/downhill discussed, it's moreso the route from the mine to where the ore is processed. I got it now, thanks.

Hah. Never thought about harvesting the gravitational potential energy of garbage before.

Dump(er) truck, not garbage truck. This one is transporting rock from a mine to a cement plant. It does not transport garbage. The mine is just on a mountain.

Again, trash is not involved.

These are probably more commonly used in mining than in landfills.

Right, so it is basically a "middle man" which modifies the manner in which the cargo comes down the hill under gravity.

An escalator that moves people down could conceivably work without any external power source other than the people.

Yup! Just less infrastructure investment and land use than the usual mining expedient of a giant conveyer belt.

>> there is no need to “heat up” the brakes when descending

I wonder why the journalist chose to use the scare quotes, as if the heating up was metaphorical.

Probably for "emphasis".

Yeah, that seems to be a thing. But it has a "different effect" on me when I read it.

I "agree".

Will it produce enough electricity to offset the projects that move dirt uphill?

What is the uphill/downhill ratio of dirt moved in the world?

A similar technology is used in Formula 1 to harvest energy during braking.

Most mining is the reverse. Travel downhill empty and uphill fill.

Ok, but you are still sending the same weight of the truck up and down, so maybe this truck would save some money in that sort of case, too.

OK but what if it's hauling out of a pit?

depends if the pit is at the top of a hill or not. The hill is usually higher than the pit is deep (<100-300 m).

Yeah no, since there is always some amount of loss, the energy gained back from moving downhill is always lesser than the energy spent going uphill.

Not if you add mass at the top of the hill.

exactly what I came here to find out. Thanks.

Finally. A perpetual motion machine. Never knew it would be a dump truck.

I've heard people say that one reason why we shouldn't bother with electric cars is that they still generate a lot of carbon from their production supply chain. All the minerals and metals mined, the parts being shipped around, the energy in manufacturing, etc.

But things like this demonstrate why that is the wrong way to look at it. We can, and absolutely should, electrify everything. The whole supply chain.

The truck in the mine, the smelting factory, the assembly line, the warehouse, and the big rig that delivers it to you. There's no reason why every one of these couldn't run on renewable electricity. The only reason they don't is because until recently it was more expensive, but that is no longer true. The total lifecycle carbon impact of everything we make can go to nearly zero as all these points electrify and as our grid migrates over to renewables.

That it can't happen all at once is no reason not to start.

>I've heard people say that one reason why we shouldn't bother with electric cars is that they still generate a lot of carbon from their production supply chain. All the minerals and metals mined, the parts being shipped around, the energy in manufacturing, etc.

"A lot" = 15% more.[1] Approximately 1 ton of extra emissions, which it takes a daunting 4,900 miles to pay back- less than 5 months of the average American's driving. A great deal of this pollution comes from energy use- that report[1] says that if the grid was powered by 80% green energy then manufacturing a BEV would produce 25% less pollution than a normal car.

[1]: http://www.ucsusa.org/sites/default/files/attach/2015/11/Cle...

Right, all things considered they're still less carbon intensive than and ICE car, especially with a few hundred thousand miles on the odometer. People seem to conveniently forget that an ICE car requires a lot of carbon to manufacture, and then creates even more with every mile driven. So even at the start the EV is ahead (or as your source says, within 5 months it's ahead).

I'm a little triggered when people bring up BEVs being more intensive to manufacture. That report I linked was used as the posterchild for why BEVs are garbage, like Wired's "Tesla's electric cars aren't as green as you might think"[1]. But the report is amazing! It put to bed fears that electric cars needed 50% or more as much to make, that they needed to be driven 150,000 miles to break even, etc etc. On top of that it says that BEVs will be cleaner than conventional cars to build. It was an incredibly great result to that investigation, but people still turned around and portrayed it was a bad thing. That really annoyed me, since it was more optimistic than even most proponents of electric cars had expected. I personally thought electric cars would always produce more waste just by virtue of weighing more, but they are so much simpler to create that that isn't true.

[1]: https://www.wired.com/2016/03/teslas-electric-cars-might-not...

Even if 100% of electric generation was coal power and regenerative braking wasn't a thing it still makes sense.

Once you get the consumers all using one fuel it's an order of multiple magnitudes easier to then switch out the energy supply with something cleaner.

Until the majority of the world's energy usage is electrified, it's a completely pointless thing to bring up how that electricity is actually generated.

Electrifying everything is a good goal, but you need to be a bit careful how quickly you do it if you don't want to increase your overall CO2 production. For example building solar panels too quickly can increase total CO2: http://www.lowtechmagazine.com/2015/04/how-sustainable-is-pv...

There are ore train cars that use regenerative braking on the way down the mountain, generating as much as 5x the power needed for the empty trip back up. Reportedly, they power the mining town at the top of the mountain.


> “Nickel manganese cobalt cells are also the choice of the German automobile industry when it comes to the next generation of electric cars,” Held said.

Interesting claim. I'm not familiar with NMC batteries.

Here's what wikipedia says:

> Handheld electronics mostly use LIBs based on lithium cobalt oxide (LiCoO2), which offers high energy density, but presents safety risks, especially when damaged. Lithium iron phosphate (LiFePO4), lithium ion manganese oxide battery (LiMn2O4, Li2MnO3, or LMO) and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC) offer lower energy density, but longer lives and less likelihood of unfortunate events in real world use, (eg, fire, explosion, ...). Such batteries are widely used for electric tools, medical equipment, and other roles. NMC in particular is a leading contender for automotive applications. Lithium nickel cobalt aluminum oxide (LiNiCoAlO2 or NCA) and lithium titanate (Li4Ti 5O12 or LTO) are specialty designs aimed at particular niche roles. The newer lithium–sulfur batteries promise the highest performance-to-weight ratio.


So, it's another kind of lithium-ion battery.

Yeah. It's a subset of Li-ion. Tesla vehicles use NCA and their stationary storage products use NMC [1]. They are pretty similar but NCA is lighter and cheaper and NMC has better cycle life (and hence long-term value). It makes sense to use NMC for this application since weight is a non-issue.

They're both significantly cheaper than LCO (the most common) and because of that NMC has become a lot more common than it was. They're also much better behaved (ie happy to put out high-power bursts, temperature-stable, and less likely to ignite), but last longer than other chemistries like FePO4 (which not well behaved but quite hard to ignite).

[1]: http://fortune.com/2015/05/18/tesla-grid-batteries-chemistry...

Mods, can you change the link in the OP? For those who aren't familiar, Inhabitat is an extremely click-baity source and almost all their content is entirely credulous restatements of press releases or articles from other publications. As someone who follows sustainable architecture issues I categorically ignore anything they publish.

I'm surprised they didn't use one of the existing diesel-electric hybrid dump trucks as a base model. That seems like an easier conversion than converting a truck with a mechanical transmission.

Here's an example diesel-electric hybrid dump truck: https://en.wikipedia.org/wiki/Liebherr_T_282B

That truck is an order of magnitude larger than the one in the article. I imagine that at some point hybrid electric power trains become a necessity but before that they are excessively complicated.

Are there existing hybrid trucks of a similar size to the one in the article?

I'm not sure the new/changed title is very good. Those giant earth movers, on tracks, that you see in mines are electric vehicles. They are just plugged in with giant cables.

Well, some are. I presume some run on other power but I've not seen one.

well, it is not the biggest electric truck even.

I'm not surprised, but I'm unfamiliar with larger trucks that are solely electric powered.

This is not close to being the world's largest electric vehicle. Early submarines were electrically powered and more than twice the size (60ft vs ~30ft), eg. the Nautilus of 1886.

And I thought of the humble metro trainset


50-odd tonnes and I've witnessed zero to 80km/h in about 6 to 10 seconds or so.

But, yes a nice big yellow machine running on batteries is an impressive milestone.

1.3 m/s² is quite something, quite a bit more than a typical tram or S-Bahn (both ~1 m/s², which is still quite a pull...).

The drivers only do the high acceleration when the tram is mostly empty and no standing passengers I've noticed.

For those in Birmingham UK: St Paul's to Jewellery Quarter is a longish bit of track just outside the city centre.

There was a copper mine in Arizona I went and toured about 5-7 years ago. The trucks were `diesel-over-electric` hybrids, but not fully electric. The shovel at the bottom of the pit was fully electric, with 4160volt 3-phase power lines delivering hundreds of amps. I believe the electricity was running a massive hydraulic pump on the shovel, making it also an interesting hybrid.

Such vehicles with Diesel-electric drive trains have existed since 1973.

Like Terex_33-19_"Titan" https://en.wikipedia.org/wiki/Terex_33-19_%22Titan%22

Only 8x? Doesn't seem like that much? Maybe more aligned to the patterns in which the trucks are used.

Ya, this dump truck: 148 gal, compared to honda fit's 11 gal tank. That's like 13x. Tho the amount of energy on board only affects the range of the vehicle, so it's not that interesting.


You need enough charge to drive a short distance and do some maneuvering with a full truck, unload, get uphill with an empty truck, and get it loaded and drive a short distance fully loaded to the slope. From that point on you're back to charging the batteries from regenerative breaking while you're rolling downhill.

That sounds very doable in the battery charge that allows a Tesla Model S to travel from LA to NY.

Which makes me think: wouldn't it be nice if a Tesla or aforementioned dump truck could serve as a battery?

An addition or alternative to a powerwall or whatever the tesla home battery's called?

It's good that they used existing truck base and focussed only on the fuel. But I couldn't see any data on actual efficiency/mileage, the whole article was focussed on how big the battery was on the big truck. "Its size and strength ensure it can transport materials from a mountain ridge to a valley 20 times per day." Is the only data on it's efficiency ?

121 tons max loaded weight in original spec http://www.ritchiespecs.com/specification?type=con&category=...

Be interested to know what range they anticipate from the 4.5 tons of batteries

~infty / until the mechanical brakes are worn down after the battery is fully charged from driving.

it seems to be a perpetual motion machine then? Just needs consumables such as brake pads repaired?

The old UK milk floats had a range of 60-80 miles http://www.milkfloats.org.uk/faq.html

No, perpetual motion means more energy from less. This moves mined rock downhill, so the work of moving it uphill was done by geological formation.

Well yeah. It doesn't really make sense to count it if it has to be plugged in.

This is a classic example of stupid science reporting. For decades now the classic diesel engine locomotive used in trains and the electric trains themselves are the largest electric vehicles of any kind. The Komatsu heavy truck is anything but accurate example of "World's largest electric vehicle".



And by the way all Diesel Submarines and Ships are also electric drive trains.


It depends on how you define "electric vehicle". It is pretty clear that they mean "batttery driven, no engine attached". And in that context, their statement is correct.

A vehicle (from Latin: vehiculum[1]) is a mobile machine that transports people or cargo. Typical vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses), railed vehicles (trains, trams), watercraft (ships, boats), aircraft and spacecraft.[2]


Based on that definition the nuclear powered aircraft carriers would the biggest electric vehicle.

All the nuclear carriers I know of use steam turbines for drive. Nimitz use four turbines, one for each propeller, driven via gears.

You guys are talking without references, please post some reference without that its all lame talk.

this is a classic example of pointless pedantry in the face of actually interesting reporting

This isnt the first truck of this kind even such trucks have been in existence for more than four decades now.

Terex_33-19_"Titan" for instance was released in 1973.

https://en.wikipedia.org/wiki/Terex_33-19_%22Titan%22 had 2,461 kW gross power.

Or this one released in 2004 https://en.wikipedia.org/wiki/Liebherr_T_282B When it was released it had 2,000 kW of electric drive haul.

So your comment is a classic example of lame talk without reference, talking out of a hat isnt worth anything.

At no point in history have electric motors been less powerful than ICEs. That's not the interesting part. The interesting part is the battery. Comparing battery electric vehicles to series hybrid vehicles is asinine.

For vehicle of that size to have a controlled descent using only the magnetic field (from the generator) as the braking force, it has to be one massive magnet, no? In which case, it is also adding to the overall weight of the vehicle.

It needs the same size motor as the one used to drive it to the top. The forces are the same, just in the opposite direction.

Apologies if it sounds too dumb, but on the descent you have additional mass of your cargo that needs to be opposed by equal amount of braking force (magnetic or otherwise), on the ascent you have an unladen truck which needs lesser energy to move. So essentially the magnet has to be sized for the descent not for the ascent. Or am I completely missing something?

It's not dumb at all.

But this truck would need to be able to back up, make u-turns, etc, while fully loaded.

So the motors must be strong enough to drive it uphill even when fully loaded, if only simply for the sake of positioning and maneuvers.

It weighs a lot more coming down, since it's full.

See my reply to the sister comment.

Ah, I see what you mean.

Since size isn't much of a constraint it probably uses electromagnets instead of rare earth magnets as fitted on cars.

Also trains have been doing it for decades.

Look into self-exciting generators as a way to (mostly) avoid big permanent magnets. Tldr:

> Modern generators with field coils are self-excited, where some of the power output from the rotor is used to power the field coils.

Electric motors, like just about everything else, can get mechanical advantage through gearing. I.e. you can use a smaller magnet if it's geared to spin, say, 10 times versus 2 times per meter traveled.

Ever tried to open a magnetic lock?

Thank you to all those contributing insightful comments to this and other HN posts!, it’s why I visit daily.

Isn't the ISS bigger?

The line can be blurred with space craft, but I'd argue that not having a destination makes the ISS more of a habitat than a vehicle, even though it's in constant motion.

High tech green energy used to more efficiently strip mine/mountain top removal. Yay?

In developed nations the use of raw materials is pretty much level- meaning that if it got cheaper there still wouldn't be that much of an increase in consumption. So the primary effect of something like this is to clean up mining that would happen anyway.

In the grand scheme of things it's not that big a deal since the primary energy used to extract materials is an order of magnitude or two less than the energy used to process them. But still, the less oil we burn the better!

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