Energy from Saltwater?

Not sure that this process of producing energy is going to be truly useful for me as I sit here in the middle of NC, but it's totally fascinating to me that they can do this! They harness the energy that is created when fresh water becomes saltwater: http://ecoworldly.com/2009/03/08/saltwater-power-could-supply-energy-for-most-dutch-homes/ Crazy stuff!