There's a similar approach that seems promising - dropping a huge weight down disused mine shafts, and winching it back up at times of low demand. It looks to b

There's a similar approach that seems promising - dropping a huge weight down disused mine shafts, and winching it back up at times of low demand. It looks to be a lot simpler than the railway wagon approach. The UK has loads of potential sites, I imagine the US does too. A fairly detailed look: http://euanmearns.com/short-term-energy-storage-with-gravitricity-iron-versus-ion/ http://euanmearns.com/short-term-energy-storage-with-gravitr...