This idea is nuts, just watch https://www.youtube.com/watch?v=NIhCuzxNvv0 https://www.youtube.com/watch?v=NIhCuzxNvv0 if you don't understand why. Does no one

This idea is nuts, just watch https://www.youtube.com/watch?v=NIhCuzxNvv0 https://www.youtube.com/watch?v=NIhCuzxNvv0 if you don't understand why. Does no one do fundamentals at school anymore, water is around the same density as concrete (~2.4 times smaller) except you can just use a simple pump. The reason they use concrete in these designs is because if they used water people would say it's stupid. That's literally the reason. It's the same for mineshafts. These concepts are introduced to confuse you. "But pumped hydro requires some very specific geography—two big reservoirs of water" So does concrete. Expect you are building the geography and it'll be around the same size if it stores around the same energy.