I started reading this with cynicism because lololol magic electricity from nothing, but no, if it goes down while full and up while empty it could work. And of course they can hook up a diesel engine if it doesn't properly work.
I am too lazy to find a source, but I saw a similar thing a few years ago with an electric mining truck (recover enough energy going downhill loaded to go back uphill unloaded).
They use to do this with mining carts. "One" goes down the hill full while pulling the empty "one" back up.
There are a couple of good undergraduate physics final problems buried in here.
There's that one train line carrying ore from Northern Sweden down to the Norwegian coast that is net-positive in energy-generation.
Fyi, virtually all diesel locamotives already employ regenerative braking. They just send the electricity to resistors, turning it into heat. The amount of energy is simply staggering. No battery tech can absorb the power fast enough. Its funny that this train is in australia. Only on a very flat run will braking be so slow that power can be stored efficiently.
The things people will do to avoid putting up catenaries truly are wild.
Article is the announcement from 2022, now they unveiled the prototype: https://electrek.co/2025/06/21/fortescue-infinity-train-elec...
Posted 3 days ago (12 points, 1 comment): https://news.ycombinator.com/item?id=44339903
Usually mines end up deep underground and require a lot of energy to get the materials to the surface and loaded on to the train. However once you’ve achieved that it is possible to just let gravity carry you back to sea level.
What if the train need to go uphill loaded and downhill empty?
As a strict matter, this is non-renewable energy.
An elevator with more steps. Still cool.
This is old news in Scandinavia.
A clearer title for this would be:
Battery-electric "Infinity Train" will charge itself using potential energy.
(Potential energy being stored in the position of the mined ore)