One Free Energy

In the paper Mining Energy In An Expanding Universe a source of free energy is described. In an expanding universe free energy can be produced by connecting widely separated bodies with strings. Another way of producing free energy is the Casimir effect. This works by placing two conducting plates parallel to each other. A net force between the plates is then produced. So, there are two known ways of producing free energy. One approach works at very large scales, and the other approach works at very small scales. I don’t think we would be so lucky as to have two sources of free energy, and therefore it is safe to assume that there is only one source of free energy. The above two phenomenon have a common cause.