Energy grids running on renewable energy sources need storage. The most common way to store energy on a grid scale is through “pumped” hydropower, where the excess energy available during off-peak is used to pump and store water at a higher elevation, which can then be released to produce electricity as gravity pulls it down to a lower elevation again. The Taum Sauk Hydroelectric Power Station in Missouri works exclusively on pumped-storage. Pumped hydro is effective, but needs lot of water and a suitable site for storage. Can the same principles be applied without using water as the prime mover?

A California-based company called Advanced Rail Energy Storage (ARES) has come up with a unique land-based alternative that could provide grid scale energy storage using electric locomotives.