Given the mass of the cars they&#x27;re talking about, they&#x27;d need substantial engineering to get a good solid level grade that&#x27;s not going to subside or slip, which isn&#x27;t always going to be straightforward.<p>As you say, however, it&#x27;s very geo&#x2F;topo specific - so in places like North Wales, pumped hydro is still clearly the way to go, but in the Mojave, this rail based system could work well.<p>It reminds me of the defunct system we had in a house I used to live in - 8&quot; or so diameter shaft in the basement floor with a weight, a cable, a winding, and a dynamo - you&#x27;d have the servants crank it up during the day so you could have electric light at night. Quite popular in the late nineteenth century among early adopters of electricity.