Sounds like this one: https://www.youtube.com/watch?v=CMR9z9Xr8GM https://www.youtube.com/watch?v=CMR9z9Xr8GM They do say it is about equivalent to a single AA

Sounds like this one: https://www.youtube.com/watch?v=CMR9z9Xr8GM https://www.youtube.com/watch?v=CMR9z9Xr8GM They do say it is about equivalent to a single AA alkaline. It is not exactly an optimized efficient setup, but still, it gets the point across. Pumped hydro is a grid scale option, in places that have the ability to store a lot of water.