10 ms·
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
by philipkglass 9y ago
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.
- TheSoftwareGuy 9y agoHah. Never thought about harvesting the gravitational potential energy of garbage before.
- sushisource 9y agoWow. Thank you for pointing this out. The article does a terrible job and makes it seem like "Oh hey free perpetual motion"
- Z1nfandel 9y agoI 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.
- jandrese 9y agoUnless 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.
- Fjolsvith 9y agoDoesn't an electric train have overhead power cables?
- grzm 9y agoDepends 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. https://en.wikipedia.org/wiki/Electric_locomotive https://en.wikipedia.org/wiki/Electric_locomotive
- razorunreal 9y agoWhy 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.
- aidos 9y agoI 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.
- hwillis 9y agoThink 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.
- ramy_d 9y agoexactly what I came here to find out. Thanks.
- jerf 9y agoThat'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.
- SomeStupidPoint 9y agoI 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.
- hwillis 9y agoDump 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.
- SomeStupidPoint 9y agoDerp, reading comprehension. Same reasoning applies though, albeit other processes doing the lifting.
- hwillis 9y agotectonic drift, specifically.
- woodandsteel 9y agoI wonder if someone could come up with a more direct way of converting tectonic drift into electricity. The total amount of energy available would be stupendous, but there seems to be a problem with it being low-density from being spread over such a large area.
- schraitle 9y agoI 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.
- kazinator 9y agoRight, 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.
- azernik 9y agoYup! Just less infrastructure investment and land use than the usual mining expedient of a giant conveyer belt.
- ChuckMcM 9y agoThat 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-electric-vehicle.html https://phys.org/news/2017-09-e-dumper-world-largest-electri...
- deleted 9y ago[deleted]
- brianwawok 9y agoSo 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.
- sp332 9y agoIt carries 45 tons + 65 tons downhill and then has to carry 45 tons back up. That's the hard part.
- brianwawok 9y agoWith 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..
- hexane360 9y ago
- FussyZeus 9y ago> 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?
- hwillis 9y agoYes, 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.
- FussyZeus 9y agoAh 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.
- rubenbe 9y agoIn 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.
- dwighttk 9y agoWill it produce enough electricity to offset the projects that move dirt uphill? What is the uphill/downhill ratio of dirt moved in the world?
- mmaunder 9y agoFinally. A perpetual motion machine. Never knew it would be a dump truck.
- bitmapbrother 9y agoA similar technology is used in Formula 1 to harvest energy during braking.
- randyrand 9y agoMost mining is the reverse. Travel downhill empty and uphill fill.
- woodandsteel 9y agoOk, 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.
- robotresearcher 9y ago>> 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.
- hydrogen18 9y agoProbably for "emphasis".
- robotresearcher 9y agoYeah, that seems to be a thing. But it has a "different effect" on me when I read it.
- hydrogen18 9y agoI "agree".
- kumarvvr 9y agoYeah 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.
- Baeocystin 9y agoNot if you add mass at the top of the hill.
- TwoBit 9y agoOK but what if it's hauling out of a pit?
- hwillis 9y agodepends 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).
- matthew349hall 9y agoThis gave me pause as well but eventually made sense and I was like, "heck yeah that's awesome"