Huh. That's some pretty impressive efficiency. I don't know why, but the thought of a train carrying a brick uphill only to bring it back down again strikes me as a little bit comical :)

Very interesting though. I wonder how far those trains travel, and if there's some way to use them simultaneously as energy storage and transmission infrastructure. I guess it depends on how the energy is recaptured. I'm just wondering because that could solve some of the cost issues associated with putting big solar arrays out in the middle of the desert...

Something like a linear alternator maybe?

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