Submerged Hydro Generator

[drobertson]

Hello

I am working on a project to capture some of the energy in our local tidal flow.  We have a marina that extends aprox 120 ft out into the local harbor.  Due to the way the harbor is shaped we get considerable water flow by the docks.  It peaks 4 times a day with roughly 2 knot currents.  This is incoming flow at low tide and outgoing flow at high tide.  The water at the docks is roughly 12 ft deep.

My vision is to build impellers attached to low RPM alternators.  A row of these would be placed under the docks.  The electricity would be fed into a standard PV charger/electric management system and then used for lights and dock power.

To be honest, I am a newbie to this so I was hoping to get some ideas, tips and tricks from more experienced people.  I am very good at constructing gadgets and I am pretty solid with electronics.  The tuning of the low RPM alternator looks like magic to me at this point but I am willing to put some time in to learn.  Ideas for the impeller/turbine design would be very helpful.

In exchange I am more than willing to share the experience and any information that comes out of the design and build process.

Oh, I do have a few restrictions/considerations.  These units have to work completely submerged with water that flows in two directions.  They also have to be able to handle the thrust from large boats that dock at the marina.

Thanks for any help you are willing to give.

-Doug

[thirteen]

Last year there was some project that was trying to do the same thing and theirs needed to swivel with the directional flow change. They were going to mount it on a cement base. But they had problems figureing out a 360 turn with power? That probably not help just an old memory. Someone on this sight should have information that will help.

[Ungrounded Lightning Rod]

There is a vertical-axis variant of the Banki-Michell crossflow turbine that might be appropriate.  (I understand that these have been used as tide motors, too.)

I'd be a bit dubious about putting a turbine under a marina pier, though.  Falling off a boat during heavy tidal flow can result in someone being dragged under the pier.  That's troublesome enough if there's nothing under there but cabling, sea life, debris, and such.  But if there's a turbine down there they might get sucked in and chopped up - or stuck to the intake by water pressure and not able to get free and back up to breathing air (as sometimes happens to people who get too close to a single intake in a swimming pool or hot tub).

So I'd recommend that any such turbine be located where moored boats - especially the sides of the boats where people going on, off, or slipping off, would heat the water - aren't upstream of ithem under any part of the tidal cycle.

As an alternative, consider mounting such a turbine on floats (turning it into a barge) and mooring it to the end of the pier or in an unused mooring (with the opposite mooring, if any, also vacant.)

[Ungrounded Lightning Rod]

"... where people going on, off, or slipping off, would heat the water ..."

Make that "HIT the water".

(Just got the pins out of the broken finger and my typo rate is still 'way up there.)

[thirteen]

you may have to mark the area for swimer or baoting people for safty.

[TheCasualTraveler]

I would think being in a tidal marina you should have quite a nice breeze. I wonder if there isn't more power in the wind at your location. Any sailboats there sporting an air-x?