The inventor envisaged turbines with 20 m long blades with a controllable pitch mechanism so they would also provide a degree of thrust as well. The other factor was they'd have to be capable of being lowered so as to enable the vessel to pass beneath bridges and go alongside berths. The base structures would have had to be massive to withstand racking stresses in a seaway and the hydraulics required to operate them would have required a power source probably greater than their output. Then there was the maintenance issue, the potential failure etc. etc. ad nauseum. Rotary wing sails okay but turbines - nope.