I came across this the other day while randomly reading about energy storage techniques, initially piqued by pico-scale hydro: http://www.aresnorthamerica.com h

I came across this the other day while randomly reading about energy storage techniques, initially piqued by pico-scale hydro: http://www.aresnorthamerica.com http://www.aresnorthamerica.com They use electric locomotives and traincars full of rock, along with a big hill, as energy storage. Drive it up during cheap energy times, and back down when you need to produce electricity.