Earlier this was for a much larger cylinder, say kilometers across, where you could leave the nature at the top intact. They have explanation here.<p><a href="http:&#x2F;&#x2F;www.authorstream.com&#x2F;Presentation&#x2F;heindl-958931-hydraulic-energy-store-system&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.authorstream.com&#x2F;Presentation&#x2F;heindl-958931-hydra...</a><p>(Edited to change info it was the same guy, added url)