If I understand it correctly, ~20MWh is for the full size model at 700m depth and with a radius of 15m (prototype radius is 1.5m and it is located at a depth of 100m).
And building concrete spheres that can withstand the pressure of a 700m water column is probably an interesting design challenge on its own.
And building concrete spheres that can withstand the pressure of a 700m water column is probably an interesting design challenge on its own.