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Underwater turbine thing, It's an idea...

frickinfrack

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Feb 10, 2021
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Thoughts and comments requested and appreciated.
At some point in the near future my wife and I will be moving to a river-front property that has a pretty consistent 4-5 MPH flow (like a gazillion GPH every day). It seems like a waste to not try to harness a little of it to charge some batteries and compliment a some panels down the line. I don't want to be noticed and want to have zero impact on the ecosystem there. it will have a dock so I'm thinking something under the dock. Is the underwater generator (non turbine type) a thing? I'm guessing a waterproof 3 phase motor with a prop on it in a tube would work. Thoughts?
 
A turbine thing is on the market as a worthless $200 toy.

Yachts, sail boats use towable turbines.
 
A turbine thing is on the market as a worthless $200 toy.

Yachts, sail boats use towable turbines.
Aha! Thank you kind sir. I have a new search term. Edit: They look like trolling motors This is gonna be simple!
 
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Google Wattandsea
4-5 MPH might be on the low end for it to work, but I'm sure that could be fixed with a larger propeller. They make about 10A at 12V. It's nice because it works at night and on cloudy days, when solar doesn't.
 
Google Wattandsea
4-5 MPH might be on the low end for it to work, but I'm sure that could be fixed with a larger propeller. They make about 10A at 12V. It's nice because it works at night and on cloudy days, when solar doesn't.
Yeah a 300 watt unit is like $3500 nice.
5 knots make 120 watts nice.
Anything for yachts is gonna be pricey.
 
Wonder how a pipe, carrying water from higher point in stream to lower, would work to boost what you get from a prop/generator setup?
Laid on the bottom, I mean, to not be noticed. There's probably no noticeable drop in elevation. But the pipe would at least keep water from going around the prop.
Next thought, what if a larger pipe at first, narrowing just before the prop? This would obviously increase flow an velocity if it followed a drop in elevation. Just not sure if it would help here. But maybe. Like a 12" pipe funneled down to 6" for the prop/generator.
Maybe a larger prop of ideal shape would be better.
 
Wonder how a pipe, carrying water from higher point in stream to lower, would work to boost what you get from a prop/generator setup?
Laid on the bottom, I mean, to not be noticed. There's probably no noticeable drop in elevation. But the pipe would at least keep water from going around the prop.
Next thought, what if a larger pipe at first, narrowing just before the prop? This would obviously increase flow an velocity if it followed a drop in elevation. Just not sure if it would help here. But maybe. Like a 12" pipe funneled down to 6" for the prop/generator.
Maybe a larger prop of ideal shape would be better.
If I was to go through all that, I would just put in a turbine. Might have to change my mind on this and not try to reinvent the wheel. 6" pipe to 1 inch hose to nozzles in a turbine may be the ticket.
 
"Turbine" as in Pelton wheel needs velocity. Optimum speed of wheel perimeter is 0.5x velocity of water stream, because it changes direction about 180 degrees after interacting with wheel. Want velocity of water from nozzle to drop to zero, giving up all its energy.

Takes head for that to work. If water taken from a point 10' higher goes through a pipe, then a nozzle aimed straight up, the stream rises to a height of 10' (ignoring friction). Calculate velocity of a weight dropped 10', and you have the velocity of water coming out of a nozzle.

A Pelton wheel only works with relatively high head.

Otherwise, a "turbine" or propeller in the water flow would be a design that cuts through the water at much higher velocity than the flow rate, to turn a small generator. High speed low force is cheap. To build something low speed high force is expensive and large, e.g. water wheel.
 
"Turbine" as in Pelton wheel needs velocity. Optimum speed of wheel perimeter is 0.5x velocity of water stream, because it changes direction about 180 degrees after interacting with wheel. Want velocity of water from nozzle to drop to zero, giving up all its energy.

Takes head for that to work. If water taken from a point 10' higher goes through a pipe, then a nozzle aimed straight up, the stream rises to a height of 10' (ignoring friction). Calculate velocity of a weight dropped 10', and you have the velocity of water coming out of a nozzle.

A Pelton wheel only works with relatively high head.

Otherwise, a "turbine" or propeller in the water flow would be a design that cuts through the water at much higher velocity than the flow rate, to turn a small generator. High speed low force is cheap. To build something low speed high force is expensive and large, e.g. water wheel.
This is exactly why I posted here. Thank you. Now I have a picture of something like a squirrel cage semi-submerged under a dock. Hmm...
 
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