I was watching "Waterworld" the other night. I'm rather enamored with the Mariner's trimaran (boat). I like the vertical axis wind turbine (VAWT) on the mast. But, just how would you do that?
Here's my thought.
You make something like a cross between a Darrieus turbine and a Gorlov Helical Turbine. In short, one of those twisted, multi-blade, egg-beater-looking turbines. Mount it with the central axis on the mast.
O.k. That leaves you with no way to put sails up. The blades will sweep into the area occupied by the main sail and any jib you may have.
Unless, of course, you build the blades of flexible material. Make the upper hub able to lower down the mast, bowing the blades outward into the wind, or rise up the mast, pulling the blades in flat, against the mast. This would give you a way to completely stow the blades, for those times when you want to use sails. It would also give you a way take the turbine out of the wind in gusty conditions, when the sudden gusts could overstress the mast or capsize the boat.
O.k. So, why would you WANT one of these on your boat? Well, if the bottom hub has a generator in it, it would provide a significant amount electricity when your sails are stowed and you are sitting at anchor/in port, etc. That would be a considerable amount MORE electricity than you'd get with a traditional wind turbine, mounted elsewhere on the hull.
I can imagine a boat with a couple "auxiliary/maneouvering screws" powered by electricity, with some batteries. Charge up the batteries while you're sitting at anchor, and use stored electricity to move in/out of port.
Depending on the efficiency of the whole system, and the swept area of the turbine, you might even be able to run the turbine and have it feed power to the screws for regular propulsion, if you are going to be changing course frequently and don't want to fight with the sails.
I'd be interested in hearing the thoughts of others, on this idea.