Battery-electric “Infinity Train” will charge itself using gravity (2022) | Hacker News Reader

Battery-electric “Infinity Train” will charge itself using gravity (2022)

newatlas.com

72 pointsjermaustin152 comments

https://en.wikipedia.org/wiki/Regenerative_braking#History

Regenerative braking has been in extensive use on railways for many decades. The Baku-Tbilisi-Batumi railway (Transcaucasus Railway or Georgian railway) started utilizing regenerative braking in the early 1930s. This was especially effective on the steep and dangerous Surami Pass. In Scandinavia the Kiruna to Narvik electrified railway, known as Malmbanan on the Swedish side and Ofoten Line on the Norwegian, carries iron ore on the steeply-graded route from the mines in Kiruna, in the north of Sweden, down to the port of Narvik in Norway to this day. The rail cars are full of thousands of tons of iron ore on the way down to Narvik, and these trains generate large amounts of electricity by regenerative braking, with a maximum recuperative braking force of 750 kN. From Riksgränsen on the national border to the Port of Narvik, the trains use only a fifth of the power they regenerate. The regenerated energy is sufficient to power the empty trains back up to the national border. Any excess energy from the railway is pumped into the power grid to supply homes and businesses in the region, and the railway is a net generator of electricity.

What's particularly interesting here is that the Pilbara, where the mines and trains in the article are located, is only 500–1000 metres elevation, and the train tracks are hundreds of kilometres long. So we are talking of an average grade of one in several hundred. i.e. very much not steep!

Topographic map of the Pilbara: https://en.wikipedia.org/wiki/Pilbara#General

Map of the rail network: https://en.wikipedia.org/wiki/Railways_in_the_Pilbara

Also worth mentioning that Pilbara ore trains are consistently almost the longest trains in the world, (although just for fun BHP railways holds a record of operating the longest train in the word at 7.3km 99k tonnes in 2001).

But they are likely the heaviest at around 42,000-43,000 tonnes per train with an average length at just under 3000 metres (1.85 miles) each.

That's a lot of mass to drive recharging, and the laden to unladen ratio easily exceeds that of a European swallow.

https://www.youtube.com/watch?v=vBXZbn7q7jQ

Yeah, there's probably a nice formula with peak and average grades, ratio of laden to unladen weight, rolling friction, and drive and recharge efficiencies, to determine whether it's possible or not.

Oddly enough I made such tables ~ 1985 as a side project to some mine event recording for optimising operation software I wrote as a side project to doing a degree.

Tom Scott made a video about a lower-tech version of this [0], an aerial ropeway that transports loads of shale over a mile and a half using the power of gravity. There's no need for regenerative batteries here, as the empty cars going back uphill are directly connected (via the rope) to the laden carts traveling downhill. Simple, elegant, and efficient.

0: https://www.youtube.com/watch?v=6RiYXI1Tfu4

It's also done for downhill mining conveyor belts.[1]

[1] https://library.e.abb.com/public/e2feea97fac59fccc12576c4005...

The “lower tech” version is probably more efficient as well lol since regen braking isn’t very energy efficient

Like the SFO cable carts?

See also - many mines around the world using enormous electric trucks that never need to be re-charged. They go uphill empty, and re-gen their entire battery on the way down when fully loaded.

https://www.greencarreports.com/news/1124478_world-s-largest...

I wonder what they are doing with the excess power. I'm sure it wouldn't be worth it to pump back to the grid, but maybe to off load into mining equipment, especially since the truck would need to start at around 60% battery charge each day to avoid over charging.

Running other equipment within the mine and lessening the load on the generators, generally.

I am embarrassed to say how little sense that made to me - the mines with which I am passingly familiar are all open-pit copper mines, where the extraction takes place below the processing, and I could not get my head around the idea that this one truck was taking some material down to the mine.

Of course the answer is that this mine is at the top of a mountain, and the processing facility is lower. The material the truck hauls is lime and marl.

It really is breathtaking - in a heartbreaking way - that we have 'developed' to the point as a society where we regularly destroy entire mountains.

Removing them is not without consequence - a mountain alters the weather around it.

So incredibly foolish.

wait until you find about about Kardashev Type II civilizations

Seems like a circular problem, how did you get all the cargo at the top of the hill in the first place?

they're extracting the cargo from the earth at the top of the hill.

It's a mine. The hill is the cargo.

Mountain forming is how all that cargo got to the top.

Crazy, basically using the stored potential energy to their advantage.

Never occurred to me to use the energy to create electricity. Makes me wonder if you could build a power plant at the bottom of a mountain that slowly levels the mountain to power the local grid.

I wonder just how much potential energy could be extracted from a mountain?

I've got an idea.. we build a wall at the edge of a huge mountain area. Water collects behind the wall during the winter, and then in the spring and summer we let the water out through a hole in the wall, which spins generators while the water flows out the hole.

Interestingly, there's a lot of current work around grid energy storage. Storing excess wind/solar power for use overnight, etc.

Everybody assumes batteries (lithium etc.) as the way to go. However the greenest / most efficient way to store the energy is actually just pumping water uphill to a reservoir, and extracting the energy by letting it flow back down.

Of course this storage system only works wherever there is someplace "higher" to pump the water. My understanding is that it's not worth the trouble to build a hill/mountain to pump the water up.

And when you have the space and the ability to build such pumped-storage hydroelectricity facilities, they require much cheaper and much more environment friendly materials.

And most already build hydroelectricity facilities can be retrofitted (although at high cost) to become pumped-storage hydroelectricity facilities.

> And most already build hydroelectricity facilities can be retrofitted (although at high cost) to become pumped-storage hydroelectricity facilities.

Really? You need a huge downstream reservoir to hold the water that you are going to pump to the upstream reservoir.

What prevents you from digging a very deep downstream hole to store such water besides cost?

I think you need a bigger word than digging, it wouldn't be a gang of navvies with shovels. The cost would be enormous, there are better ways to spend the money: solar, wind, better electricity networks, DC interconnects.

An excellent blog post on this idea: https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/

> greenest

What does green mean here? Most of the developed world's easily used hydro sites are already in use. Expanding them in most countries means relocating lots of people, building huge dams, drowning towns, villages, and historical artefacts, losing agricultural land, disturbing river flows and irrigation systems.

Not always very 'green'.

I don't think "everybody assumes batteries". Pumped hydro has been around for a long time, and anyone with any interest in the subject knows it's cheap and effective.

500m is plenty 'high'...

https://en.wikipedia.org/wiki/Dinorwig_Power_Station

What about all of those open pit mines? Surely some of them have access to a lower elevation location where the water could be piped. Or, two adjacent pit mines.

I think cutting up the mountain into managable pieces might consume a lot of produced energy.

In Sitzerland they developed a such truck (2017). He drives down fully loaded with stones and does load the batterys. Then the truck drives up again empty.

https://www.empa.ch/web/s604/e-dumper

With the advent of recuperative braking, Sisyphus found a new purpose in afterlife after Hades had modified his punishment a little bit.

Not gonna lie, I checked their price and it didn't jump 200% in one day. so...?

As the article questions - "Is this a super-specific single use case, or something that will be able to roll out to a wider market?"

Reading the other comments, and understanding that the technology (brake-to-charge) exists already in the market, I wonder what is the 'patentable' thing that would propel their stock. Would they manufacture engines & components (i.e. to install to every wagon's braking system?) Doesn't that IP/patent already exist?

Now if only we could produce all resources on top of Mount Everest and consume them all in Death Valley.

Didn’t think perpetual machines would still make HN front page

I mean it is clickbait but it is also a thing that can easily work and there are already mining trucks that do this.

They work because they transport matter from a higher place to a lower place and therefore are much heavier downhill then uphill.

Electric trains and trams in Europe already have regen braking. And no need for batteries!

How does that work without batteries? Where does the energy go?

Back into the power grid.

Quote: When regenerative braking is employed, the current in the electric motors is reversed, slowing down the train. At the same time, the electro motors generate electricity to be returned to the power distribution system

https://www.ctc-n.org/technologies/regenerative-braking-trai...

I assume it goes into the grid. Possibly to other trains that need the power right then.

The light rail MAX trains in Portland use regen braking without batteries, as one train is slowing it's generating power for other trains that are in motion[1].

1: https://www.wired.com/2013/06/portland-light-rail/

Yeah, but that does require a fair bit of additional infrastructure, running overhead wires and having it connected to the power grid. Makes sense in populated areas, but for mining trains in Australia, potentially 1000s of kms from the nearest city? This seems like a reasonable alternative

This could be such a cool detail for post-apocalyptic SF story where someone drives old electric mining truck up the mountain to load up useless rocks to charge the truck on the way down and provide a little bit of electricity for their little community of survivalists.

You should write it! :)

It’s not perpetual motion, it’s just moving things downhill with extra steps.

The extra steps are useful for sure. Storing the generated energy in batteries works on a route where the net cargo movement is downhill even if there are some uphill sections along the way.

They're gaining energy by taking bits of the hill down the hill.

Of course it's not really a perpetual machine. It only works as long as there is enough material to transport downhill.

That's not what is happening here. It uses gravity to generate energy as the mass going downhill is significantly greater than the mass going back up. The mass of the load is used for "powering" the regenerative braking system (resistance is converted to electricity, stored in the batteries) when going downhill. The batteries are now charged when at the bottom. The heavy load is removed from the train. The generated power is used to take the train with significantly less mass back up to be refilled. There is no "perpetual" energy here. Basically the fuel is the load. It still takes energy to load and unload the payload. No magic here. It's just a function of how much mass can the train take downhill, how much regeneration occurs during that operation, and how much energy it takes to take the empty train back up to the top.

Just as you can take a tiny regenerative toy car, give it a few little revving pushes on the floor (let's say 4 feet of regeneration), you can let it go and have it go 100 feet, as all that mass you used from your arm to charge the battery was transferred (obviously not 100%) to the battery. It's not perpetual motion. It's just converting mass into energy. Pure physics here.

This is the same concept when using water, rocks, sand etc. and gravity for batteries. It's just a simple transfer of potential energy.

Understand, I was thinking it will only work in narrow applications like removing mountain of rocks. Plus saying infinity implies some sort of unity

A normal truck uses it's brakes constantly when going down hill, turning all that potential energy of the cargo into heat. This truck charges batteries to slow itself down via a generator. At the bottom, it weighs much less, thus even accounting for loses, there's enough energy to get the "lightweight" truck back to the top.

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