The theory seems congruent to what AR wrote. There are some other interesting videos associated with this demonstration, if you check the Youtube sidebar. Don't know how they would work on a larger scale, but if the demonstrations are legit, enough power could be generated by each unit to power a single residence independent of any other source, provided the drain is kept within reason.
http://www.youtube.com/watch?v=h5uiK_Qny...