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

[SamSam]

Originally Posted by Windmaster

More recently the argument is whether a boat or land vehicle can sail downwind faster than the wind.
A researcher in Florida has recently achieved this with model which demonstrates clearly that this is possible. A video exists on the net to confirm it. This model uses an air propeller to drive itself along.
.

Where would the site be for this? This seems to me to be in the perpetual motion category. Sam

[rayk]

Firstly Sam you have to understsand New Science.

Normal people like you and I are mired in the illusion that
output is 'equal' to or less than input.

[ruud]

Hi Windmaster
A boat or land vehicle can certainly sail up or downwind faster then the wind. The fast 18 footers and skate sailing wings have already been sailing faster then the wind at a 40 - 140 degrees angle to wind direction.
The wind turbine propelled vihicle or boat can do that theoretically also directly up and down wind , but not at a 50 - 130 degrees angle to the wind direction.
Then the wind turbine also has to change tack to convert wind energy coming from the opposite side when sailing faster then the wind.

[rayk]

I am curious...

If the wind direction is from north and wind speed is 10 knots.
Can I travel faster than 15 knots on a course of 50 degrees from north?

What is the limit for making ground faster than the wind speed?

It would seem unusual to claim that physics allows infinite extraction of energy from a finite source.

What is the natural limit that cant be broken?

please explain to me wind master, ruud, or globaldude.
(piss off trouty )

[ruud]

The ground or surface speed depends on the efficiency of the conversion of the initional wind energy (which is also course depending) and the frictional loss or drag of the device. The limit of the speed is set by the technology.
For example a fast solar powered car runs much faster with the same energy then a large SUV.

[rayk]

Originally Posted by ruud

The limit of the speed is set by the technology.

The limit of technology is physics perhaps.


What is the maximum conversion ratio that can be achieved?

wind speed : speed in/toward true wind direction

[Windmaster]

To backtrack a little, I have found where you can see the video of a model moving on land downwind faster than the wind - powered by the wind. It is at:
http://www.youtube.com/watch?v=aJpdWHFqHm0
It's not magic!
Here is my attempt at an explanation.
Power is obtained from the moving interface between two mediums, the water and the air or the ground and the air.
As far as the model is concerned, it does not "know" if the ground is stationary and the air is moving, or the air is stationary and the ground is moving.
It can obtain power from the moving air to move over the ground (this is what happens in normal sailing) or, it can obtain power from the moving ground to drive itself through the stationary air. This second case is what happens that allows it to travel downwind faster than the wind. As far as the model "knows", it is existing in a stationary medium (the air) and getting power to drive itself through this medium from the moving ground underneath.

[rayk]

Good video. What do you think about inertia? Can you use that as well to maintain forward motion? They could harness inertia in the next test and go even faster.
If the wind slackens that big prop could probably use a bit of inertia...

I am curious about why the model cant extract more power from the ground rushing under its wheels? How much more energy can be tapped?

The bushes were waving around in the background a bit, quite a windy day.
Good for a test run. On a gusty day, what keeps the model moving when the wind drops away for 3-5 seconds?
Is any part of the model under the influence of inertia yet?

Anyway, why did it stop?

What is the natural limit for wind driven speed dead down wind?
Is it twice, thrice or four times the wind speed?

[rayk]

Watch the propellor carefully. Stroboscopic effect of the camera is helpful.

When the wind accelerates the prop it spins faster, anti clockwise from the rear.

When the wind slackens, the blade decelerates, and spins clockwise, as viewed from the rear. (If we could only figure out how to harness inertia...)

My wife pointed that out to me.....

[jehardiman]

rayk;

The strobe effect of the video frame freeze has nothing to do with the direction of rotation, but rather the relative interference between rotational speed and frame speed. Go look at an old western movie with a wagon rolling quickly, while the wagon always moves forward, the spokes will appear "rotate" either forward, backward, or stand still depending on the frequency interaction.

Also, most of your objections as to the possibility of wind driven vessels have been brought up and adjuciated before. As I have pointed out, energy and forces are vector quantities and it is by manipulation of the vector directions that we produce forces useful to what we want to accomplish, i.e. there is no such thing as "lift"; there are only drag forces in the direction we want. See this thread which points to other proofs of concepts including a videos of several working vessels. http://boatdesign.net/forums/showthread.php?t=1289

[rayk]

I stated that the prop accelerated and decelerated.
It does not spin at a constant rpm.
It may 'appear to rotate backwards and forwards' in your words, not mine.

As for my objections, the easiest way to uncover the science of this phenomona would be to get the dead upwind guys to reconcile their physics and mechanics with the dead down wind guys.
Are they both right, only one, which one?
The outcome is predictably an oil baron conspiracy.

By what factor can these machines travel against the wind?
Is it unlimited speed from the wind?
What is the limit?

[jehardiman]

Originally Posted by rayk

As for my objections, the easiest way to uncover the science of this phenomona would be to get the dead upwind guys to reconcile their physics and mechanics with the dead down wind guys.
Are they both right, only one, which one?
.....<snip usless inflamatory comment>
By what factor can these machines travel against the wind?
Is it unlimited speed from the wind?
What is the limit?

You don't know a thing about the aero/hydrodynamics of rotating lifting surfaces and the dynamics of free-free systems, do you? Otherwise you wouldn't ask a question about a system that is limit seeking, and that the limit is structurally and situationaly dependent. Get a good texts on turbines, propellers, and aero/hydro drag first, read them, understand them, and draw up the FBD's and do the energy balances, and then come back to your questions and I'll try to help you. But I cannot teach you aero/hydrodynamics over the net if you can't get past your limited understanding of first principles.

BTW, the reason the whole concept works is that water is 826 times denser than air which means that the energy advantage for propulsion is 5.3 to 1. That means that you only need to extract 18% of the energy from the air plus losses...say 20% of the required... so 22% overall. This means that speed to windward is limited to ~13% of windspeed *Cdi/Cdt.

[SamSam]

Originally Posted by Windmaster

It can obtain power from the moving air to move over the ground (this is what happens in normal sailing) or, it can obtain power from the moving ground to drive itself through the stationary air. This second case is what happens that allows it to travel downwind faster than the wind.

Nope, sorry. I can't buy into that. It could do it in gusty winds by storing energy in the form of inertia generated by gusts that it would use up in calms but thats not what I think of as going faster than the wind. If the wind was a steady X mph (in relation to the ground), the thing shown on the video, or any other arrangement (sails, etc) getting it's power from the wind, could never go any faster than X mph (in relation to the ground) minus whatever drag was created by the mechanical parts with friction etc. The fact that it stopped by itself at the beginning and end of the video with the wind blowing from 'behind' seems to me proof that it can't go faster than the wind. If it could go faster than the wind, it seems to me it would go until it broke and was unable to keep going. Not only that, it seems it would keep going faster and faster until it disapeared, and not just into the distance.
I'm referring to straight downwind.
I also don't think anything powered by the wind could propel itself faster than the wind (in relation to the ground) straight upwind. If the wind was 10 mph, and some contraption was geared to travel 5 mph against the wind, it might be in an apparent wind of 15 mph which might seem to be 'faster than the wind', but in relation to the ground, it's only half the speed of the wind.
Of course, I've been wrong numerous times before. Someone once posted that if you encircled the earth with a piece of string, and then encircled the earth with a piece of string that was held 1/2" off the surface, the second string would only be 3.14" longer. I mentioned BS. I was wrong. Sam

[rayk]

Originally Posted by jehardiman

You don't know a thing about the aero/hydrodynamics of rotating lifting surfaces and the dynamics of free-free systems, do you? Your principles dont describe anything else except your fruity devices. Your principles are not universally applicable. Conservation of energy is universally applicable, except to your stuff.
Otherwise you wouldn't ask a question about a system that is limit seeking, and that the limit is structurally and situationaly dependent. Get a good texts on turbines, propellers, and aero/hydro drag first, read them, understand them, and draw up the FBD's and do the energy balances, and then come back to your questions and I'll try to help you. That implies that I should learn what every one else accepts and then ask you for to impart the final secrets of over unity, free energy, and the location of King Solomons mine.
But I cannot teach you aero/hydrodynamics over the net if you can't get past your limited understanding of first principles. You can teach any one aero/hydrodynamics, so long as you dont veer off into jibberish. That seems to be the natural limit of New Science.

BTW, the reason the whole concept works is that water is 826 times denser than air (Something missing here.) which means that the energy advantage for propulsion is 5.3 to 1. (Something missing here.) That means that you only need to extract 18% of the energy from the air plus losses...say 20% of the required... so 22% overall. (Something missing here.) This means that speed to windward is limited to ~13% of windspeed *Cdi/Cdt.

Please continue....

[jehardiman]

rayk;

I must admit I'm missing some of the subtler points of your argument about why such a system defies the law of conservation of energy (I get the “you’re a fruit” part).

Could you please explain WHY you think this system defies the law of conservation of energy? Please use standard the thermo equations (U, Q, W, m, V, g, etc) starting from the total energy equation and diagrammatically show where you draw your energy boundaries so there can be no misunderstandings due to language. Don’t worry, I’m pretty sure I can follow the math.