This water driven power station is relatively simple, but it works for the purpose this couple builds it for. As the 
shows, there is no power wall or anything like it installed, just this small generator with a home-made blade, driven by the whirlpool that the form of the channel produces.
This is in fact quite effective: because the circular shape makes the whirlpool, the vertical rotor basically gets driven on all blades at the same time, thus pushing more energy into its electrical counterpart.