What I like about the train system is that it should be cost effective and can be built without water. Cost effective because steel and concrete seem to be the bulk of the cost. The lack of water makes it more useful in places like the desert where water tends to evaporate over time and is hard to come by. It would interesting to understand the maintenance burden relative to the renewable energy source it is paired with.

Another, less talked about, issue is replacing peaker plants. Here is an article from 2015 on why that is a good idea (http://www.aiche.org/chenected/2015/04/battery-storage-takes...) using batteries. Even a "small" ARES system it would seem could address some of this need. The challenge being its hard to build something like that in an urban area.