It's like storing energy in electric cars by parking them at the top of big hills. Charge the cars during the day, and park them at the top at dusk. Then drive

It's like storing energy in electric cars by parking them at the top of big hills. Charge the cars during the day, and park them at the top at dusk. Then drive one downhill every hour at night, using regenerative braking to pull some of the potential-turned-kinetic energy into the battery as electricity. Then discharge the car into the grid. Descending the hills in east Auburn and Kent in WA State usually regenerate 400-500 Wh into my hybrid. Gravitational potential batteries have less vampiric effects than chemical batteries, but still some possibility to suddenly discharge, in a landslide or similar event. And they are less efficient than hydroelectric, as another poster has pointed out.