you where faster than me :) The seal is great: http://www.heindl-energy.com/gravity-storage/idea-function/sealing-the-rock-piston.html http://www.heindl-energy

you where faster than me :) The seal is great: http://www.heindl-energy.com/gravity-storage/idea-function/sealing-the-rock-piston.html http://www.heindl-energy.com/gravity-storage/idea-function/s...