# Windmill or Wind Turbine- powered boats: how many are out there, and are they viable?

Discussion in 'Projects & Proposals' started by Duma Tau, Oct 9, 2006.

1. Joined: Jul 2007
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Location: Wellington, New Zealand

### Richard Atkinatn_atkin@hotmail.com

Wow....windmill powered boats. For industrial purposes maybe. But I bet they would be noisey and not very relaxing to look at. How's that for a very scientific point of view.

Rick...there you are again! You build props aswell!!?? I think you work for the US navy or something.

2. ### Guest625101138Previous Member

Windmaster
If a blade is designed to have the same angle of attack across its radius it will indeed be twisted. Meaning the angle of the blade with respect to the shaft it is mounted on will vary with radius.

A "perfectly pitched" blade will have the same pitch irrespective of the radial location. Meaning you could measure the angle of the blade relative to the shaft at any radial position and get the same answer for pitch in every location. Pitch being the distance the fluid would advance in one rotation of the prop without any slip.

I have found that the most efficient blade does not necessarily operate at the same angle of attack over its entire radius but they never have a constant pitch angle - they always have some twist. It is less noticeable with larger diameter blades but still evident. If you are using flat blades then they will be sub-optimal. I use asymmetric foils with optimised angle of attack across the radius, usually resulting in something between -1 to 2 degrees. So they need to be made with some precision to get the best result.

For other than perfectly pitched blades, I specify the pitch at 75% radius.

You did not like me referring to these things as props so I proposed twisted foil. Now you are saying this is misguide yet you suggest no satisfactory alternative. There is no pleasing some people.

Rick W.

3. Joined: Dec 2007
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Location: Finland/Norway

### TeddyDiverGollywobbler

How about hydraulic transmission with Variable Displacement pump and motor. Anyway if the turbine is a bit bigger, lets say 10kW and up, it would give even better flexibility with gearing ratios. Maybe loosing a bit of coeffincy, but with a lighter weight.
What I've been considering is chancing the main engine also work to hydraulic pump too so there's a hydraulic hybrid. Ofcourse it's not so flexible with batteries like electric system, but with engine it wouldn't need to be..

4. ### Guest625101138Previous Member

Teddy
You get into an age old argument over what drive system is the best. Generally electric with modern electronics will be more efficient than hydraulics but then the hydraulic system is not as fragile. Particularly where salt water is concerned.

Efficiency is a bigger factor than size. If the turbine size goes up to cater for additional losses then the propeller size has to go up and there is more power transfer in the system for the same output. Remember, in the upwind case, you have to push the turbine through the air. In the downwind case you have to push the turbine through the water. The bigger the turbine the more thrust required.

The main reason I am going for electrics is the flexibility afforded with batteries for storage and ease of collecting additional energy from solar. There are already electronics available that optimise energy recovery from both turbines and solar systems so these are off-the-shelf.

I also have a redundant propulsion system as I can thrust from either air or water. I intend to use the same motors/generators and controllers for both twised foils so I have parts duplication as well.

These are the factors that are leading me toward electrics.

Rick W.

5. Joined: Nov 2006
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Location: Norwich UK

### WindmasterSenior Member

I did actually know that!!!

Regarding the naming of the parts, its not a question of what I like or what I don't like. The fact is that if you want people to understand what you are talking about you need to use the correct terminology - making up your own names is not an answer when there is established convention stretching back many years which is perfectly sufficient to describe what you mean.

You should be using "turbine" for the element that takes power from the moving fluid and "propeller" that puts energy back in another fluid.
http://dictionary.die.net/propeller
http://dictionary.die.net/turbine

I have also checked these in the Shorter Oxford Dictionary.

6. Joined: Oct 2002
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Location: netherlands

### yipsterdesigner

probably mentioned here before i just hear power squares up by doubling size so a size 2 gives 4 power but 4 size 16 power
not exactly putting it right but you get ( allready have ) the idea the mills best be big

7. Joined: Nov 2006
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Location: Norwich UK

### WindmasterSenior Member

Hi

From this it looks as it your craft will be able to sail directly into the wind and also downwind faster than the wind - is that what you are hoping to achieve?

Also, a turbine has to be "pushed" through the air? Surely, it is pushing itself. The air acts on the turbine and pushes it round - isn't that right? If it had to be "pushed" - what would do the pushing?

8. ### Guest625101138Previous Member

With my proposed Solar-Wind boat I aim to hold a steady 7 to 7.5kts day or night. I might end up down to about 5 kts in the wee hours on a windless night if I cruise all night. My air propeller is too small to work efficiently in light air downwind to provide sufficient thrust to collect power from the water turbine at the same time.

The blades on both sets of twisted foils are asymmetric. I am designing the foils such that the water blades are most efficient as propeller and the air blades are most efficient as the turbine.

Upwind the air turbine has to be pushed or forced through the air. The force is generated by the water propeller in addition to the force required to move the boat through the water. That is the cost of sailing directly into the wind.

Downwind the air propeller generates thrust in excess of that required to propell the boat through the water and the excess force is used to force the water turbine through the water so it collects power.

Rick W.

9. Joined: Jul 2007
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Location: Wellington, New Zealand

### Richard Atkinatn_atkin@hotmail.com

Rick, I had no idea you were going this far with the windmill. I thought it was for your microwave or something. This is very iinteresting.

10. ### Guest625101138Previous Member

Richard
I always intended to build or buy a sailing boat for my retirement. To this end I started playing with 3-4ft models after I sold my last yacht 16 years ago now. The models were fun but it did not get me on the water so I started with pedal boats in a nearby lake that prohibits power boats. I have learnt some things about efficiency trying to go as far and as fast as I can with my 120W engine.

The design progression goes:
I learnt that slender hulls are efficient.
I do not like the idea of a moderate size cat being mast down going nowhere in the ocean.
A slender monohull does not have much ability to carry sail unless it has a canting keel. I did not give the idea a lot of consideration though.
I would like a boat that is seaworthy yet trailerable.
I would like a boat that can sustain 7kts under most conditions.
I am an electrical engineer and am impressed with value for money of current technology like motors, controllers and solar cells. (I built my first battery/electronic/electric vehicle in 1976)
I have learnt a lot about efficient foils and propeller/turbine design from my pedal boats.
I saw the DDFTTW videos and this made me think a bit harder about the potential for props/turbines.
There was a post somewhere on these archives that covered the merits of electrics and battery storage in combination with turbines.
batteries can serve the dual purpose of energy storage and ballast. The VRLA gel type have fair life and do not leak - price is going up though.

These were the lines of reasoning that has got me developing a Solar-Wind coastal cruiser for effective point-to-point coastal passages. Time will tell if it is a good idea or better, a good example based on a good idea.

One thing I have learnt throughout my working life is that not many people have a good grasp of physical concepts. It does not surprise me how readily people dismiss ideas that are later seen as obvious. It takes about 30 years of development to get a good technology concept to every day use. There are many examples like telephone, TV, computer, solar cells, motor vehicle and so on.

Rick W.

11. Joined: Jul 2007
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Location: Wellington, New Zealand

### Richard Atkinatn_atkin@hotmail.com

Rick, are you at the stage now, where you can actually build a solar/wind boat that will perform to about 70% of your goal? In other words, is it looking promising, or is it still a huge challenge with the goal looking some way off in the distance?

just curious, that's all

12. ### Guest625101138Previous Member

Richard
All the numbers are adding up OK. I am confident about hull shape, motor, controller, batteries and water prop. These are things I have tested thouroughly and have reliable data on.

I have tested the air turbine to the point of blades and primitive performance testing. Even a 2.2m blade needs to be mounted well for serious testing so I have not got around to scientific results. However I have looked at a wide variety of wind turbines and my blade performance is similar - I have slightly less energy recovery from the air stream but lower thrust force in given wind conditions.

I have not played around with modern large solar panels. Just tried little ones a few years ago. (My watch and calculator are light powered though - so my tiny contribution to sustainable development - actually I got fed up with changine batteries)

NA believes the hull sections can be built under my target weight. Stability is very good - as you would expect with a keel full of lead batteries.

I am expect to get inside 10% of my target performance. I can do better than that now with pedal boats and the small electric catamaran so there should not be a lot of difficulty scaling it up.

Rick W.

13. Joined: Jul 2007
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Location: Wellington, New Zealand

### Richard Atkinatn_atkin@hotmail.com

Cool. So mostly it's just the wind turbine that needs to be optimised...the solar panels are just a case of choosing the right ones. Sounds like your design is nearly complete. All you have to do then is retire and have fun!

I must admit I like the robustness of the solar/wind turbine concept. There are no huge forces that will cause something to break. You are not likely to be in need of a rescue squad.

14. ### Guest625101138Previous Member

Richard
I have attached the latest iteration of the design. It still has the wind prop/turbine missing but it has some of the internals outlined.

Aim will be to have the entire hull developable so it can be cut out in flat panels from foam sandwich composite.

The only real concentration of forces is in the long keel to carry the batteries. These weigh 268kg. There is also a concentration of forces around the attachement points for the three hull components. My aim is to get any connecting holes above the waterline so I can float the sections separately if I choose to assemble it this way.

I have not yet sorted out the assembly process but I do know the front section will be easily carried by one person and the stern section, without the prop/turbine, will be manageable by one person. Both the water prop/turbine leg and wind prop/turbine will be removed for transport.

With a desalinator and fishing line I should be close to autonomous and able to move about at a respectable pace.

Rick W.

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15. Joined: Nov 2006
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Location: Norwich UK

### WindmasterSenior Member

This is all very interesting (but a little off topic)

The solar/wind boat is an interesting concept, but this thread was really about "wind turbine boats" by which I think it relates to boats powered directly by a wind turbine, as opposed to storing up energy using a wind turbine.

Here is something for Rick:
A picture of a "seriously" big two-bladed wind turbine on a boat - used to power the boat directly - but I would think it would charge up the batteries fast also !

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