Ok I have been reading up on waterwheels and don't know which to build a undershot waterwheel or a VAWT submerged underwater. I want to produce about 3kW to put into a 12V inverter. The VAWT was going under my dock and would be for the most part unseen. Second question how big would the undershot waterwheel have to be to produce 3kW? I have about a 9 knot current and can have a depth of 2 Meters.