The piston idea seems like a appealing design requiring minimal new technology. The plant is the same as existing pumped hydro plant, the weight can come from t

The piston idea seems like a appealing design requiring minimal new technology. The plant is the same as existing pumped hydro plant, the weight can come from the native rock. Using a rolling membrane for the seal is discussed at https://heindl-energy.com/technical-concept/engineering-challenges/ https://heindl-energy.com/technical-concept/engineering-chal... Naively that does seem plausible but it's a very large sheet of material to manufacture. What are your thoughts on that approach?