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

Bold is mine

Explain what is happenning in this video

 

Old thread. Hope someone's still reading.
I can't tell for sure, but it seems like the people who claim forward motion against the wind is impossible are inventing a law of conservation of force. Of course there is no such law. Force is not energy. You can create large forces from small forces all day long. Force can be created and destroyed. It's not energy. Some examples are in levers and hydraulics, inclined planes, gears... The idea is that a small, high speed force, the wind, is converted to a large, slow speed force, prop thrust.
It is only the product of force acting through distance(energy) that must be conserved. Say you have a wind turbine on top that draws 1000 joules/sec from a 10 meter/sec wind? It would have to have a drag of 100 newtons. 100 newtons * 10 meters/sec = 1000 newton*meters/sec = 1000 joules/sec.
You would then need a prop under water that can push at least 100 newtons of force. The only limit imposed by conservation of energy is that the underwater prop can't propel the boat faster than 10 meters/sec because the power required would be greater than the 1000 joules/sec being generated by the air turbine. Of course friction hasn't been considered at all in this. But to argue that it is not possible seems to be making an argument about how precise mechanisms can be built. It's not something to be dismissed with sweeping generalities, it seems to me. There's no talk of over unity here whatsoever. Let's say the wind turbine took 100 newtons of drag to produce 1000 joules/sec AKA 1000 watts of power. But the turbine was 75 percent efficient. So 250 watts were wasted on turbulence about the blade. Then the drive train took another 200 watts. So 550 watts to the prop. But the prop is 50% efficient. So 275 watts goes into against the wind motion. 275 watts = 275 newton*meters/sec. Since there are 100 newtons of drag from the air turbine then the forward speed could at most be 2.75 meters/sec. 2.75 meters/sec * 100 newtons = 275 newton*meters/sec = 275 watts. But then there is drag from the wind pushing against the hull and water drag slowing it down. There is also mass based resistance to motion during acceleration. But then maybe the water prop is 75% efficient and not 50% like I used. Maybe the drive drain doesn't take 20% of the power like I used. It all seems like a very high school application of physics to prove that at least in theory this can work and that there are no over-unity claims being made.

 

Since it is possible to have a downwind VMG greater than windspeed. It is also possible to create a boat that can travel dead downwind faster than windspeed. The rotating foils only need to have the same relative angle to the local flow as their fixed counterparts on the conventional boat.

It is quite simple in theory and difficult in practice.

 

What does VMG stand for? It would seem in a boat powered solely by the wind, traveling dead downwind, that once the speed of the wind is attained, in effect there is no more wind and thus no more power to be gained from it. Even if there is a current going the same way, I don't think you could possibly go faster than whichever is faster, the current or the wind. No matter how well something is built, there will always be friction or drag and so it would also seem that a boat going dead downwind couldn't even equal the speed of the wind or current, and would always be slower.
Going dead upwind, the same would seem to apply. It doesn't seem possible that no matter what you are using to capture the power of the wind, it could supply more power than what is captured. Upwind travel may be possible, but not at the speed of the wind or even close. That is, if the wind speed is 10 mph ground speed, you would never attain 10 mph ground speed, either dead upwind or down. Sam

 

VMG stands for Velocity Made Good - it means the velocity made towards your destination in spite of not being able to go there directly (for example tacking upwind in a sailing boat).
Now, the flaw in your thinking is revealed in your statement "a boat powered solely by the wind" - strange as it may seem, the boat is not powered solely by the wind - it is powered by the difference in velocity between two mediums, the wind and the water. Normally, sailing downwind, the boat gains its power from the wind over the water. But as it goes faster, this wind, as you quite rightly say, becomes less and when the speed of the wind is reached nothing at all. When this stage is reached, the difference in the velocity between the two mediums still exists, and the boat or land model gains its power from the flow or water (or land beneath). So therefore it must have an air propeller to power itself, using the movement of the water relative to the boat. It depends how you look at it:
Air moving - water stationary.
Water moving - air stationary.
Its obviously difficult to achieve downwind faster than the wind on water because the resistance of the water makes it difficult to get even near windspeed.
However, on land it is easier because the resistance of wheels is much less, and downwind faster than the wind or DWFTTW has been achieved.

 

Fiona Sinclair's presentation...

...on wind turbine and "autogiro" boats can be found here: http://uk.geocities.com/fnsnclr@btinternet.com/yachts/auto/index.htm

--scot

 

But surely no more energy can be converted from the water moving relative to the boat/air than can be converted from the air moving relative to the water. This would certainly explain how a boat maintains its speed when traveling close to the speed of the wind relative to the water but does not explain how it could travel faster

Or is this just because the relative friction provided by air and the ground/air interface are different there is less friction in the air so the extra energy when it is converted to thrust by the prop can accelertate the vehicle.
If the density of water and air were the same then it would nor be possible to go faster than the speed of the wind relative to the water. But since this is not the case then it is possible. Of course you couldnt do this kind of thing with a sail could you as there would be no way of transfering power generated by the relative speed difference of water and boat to power the sail.
Surely this then means this is a very efficient way of powering a boat?

 

Source of sailing power...

The source of power for a sailboat is not the movement of the wind or the water relative to the boat, but rather the difference in the movement of the wind and water. If the boat is stationary and dropped into a 10 knot S current and a 10 knot S wind, then it will quickly come to rest relative to those, and be stuck, with no differential to extract energy from. IF the wind and current are going different directions, then energy may be extracted by playing the differing forces against each other, by sticking foils up and down, and diverting the flow appropriately.

As a simple thought experiment, assume for a moment an electric boat, with a have a generator with the shaft hooked to a wind turbine and the body hooked to a propellor, and the whole assembly mounted on gimbals to let it spin and turn as needed on any axis. As long as there is a differential between wind and water, then it will produce electricity; the amount of electricity is FIXED to the quantity of differential, the motion of the hull has no impact--if it moves with the current, then the propellor is still and the wind turbine provides all the power, if it moves with the wind, the turbine is still and the propellor provides all the current. In reality there's some slippage there, but that slippage will be there irrespective of the velocities; consider a vehicle mounted between two plates, with wheels top and bottom to act as propellor and turbine, and you get the same thing with no slippage (just rolling friction).

Now, with this fixed amount of energy (assume we propel the hull with an electric motor and propellor), the only limit to the boat speed is friction. Given that our frame of reference is going to be most closely tied to the water (water velocity relative to the "fixed" land being generally slower than the wind) the greatest friction will be on the upwind tack, so it should be slowest, and the lowest frction is on teh downwind tack, so it should be fastest. The amount of energy we can extract is limited only by the size of the propellor and turbine; the more mass of water and air we can deflect, the greater the amount of energy we can extract from a given differential speed.

Traditional sailing rigs do basically the same thing, sucking energy from the differntial speed by deflecting wind and water, and they can certainly exceed windspeed under the right conditions. The only problem with all this is that once we reach windspeed going downwind, traditional rigs loose "traction" with the air, and thus can't exceed windspeed on a dead run, because the sail is fixed to the hull and can't deflect the wind when the speeds are equal. A wind turbine rig at least has the potential to overcome this limitation because the turbine sail (and propellor, which acts like a moving centerboard) are not fixed to the hull. Practically implementing this, however, is the tricky bit. The electric generator/motor case is going to result in lots of losses as we convert energy back and forth; you should be able to do the same thing with a variable pitch wind turbine, but the complexity of the interactions involved makes my head hurt...

--scot

 

Here is a drawing of a Wind Drive system.
KJELL

 

Vertical Windmills?

Hey all... I'm not a boater... nor am I an engineer. Don't know much about the math involved in computing conservation of energy calculations either. I found this site when looking up sustainable wind energy... which led to an image of a windmill on a catamaran etc.
I have since read a bunch of threads about this and that and the ability to travel against the wind... with the wind etc.
Has anyone considered the idea of vertical windmills? They operate with wind from any direction, are quiet and work both as the wind enters and exits the turbine. These are usually used for power generation, but I don't see why you couldn't keep the power recharge capabilities for life on boat, and drive a prop for movement.

I found an image on google of a catamaran and of a vertical windmill called a "Turby". I quickly put the two images together in Photoshop.
Any boat designers/engineers here think that this could be a viable option?

Image attached.
Cheers,
Chris

 

Viable, yes. Havilah Hawkins (from Camden, Maine) sailed his own boat directly into the wind as a demonstration of its viability back in the eighties I think it was.
His had three blades on a horizontal rotor.
The theoretical maximum for wind engines is about 59% I think. The issue is getting the rotors to the right angle of attack at various different wind speeds. While a normal sail need only adjust draft and reef, the mechanisms to achieve variable pitch of rotors are expensive and complicated.
Windmills are expensive enough, but imagine them made to withstand salt corrosion and to work well in any available breeze. Then too, speed limits will not be exceeded, so there is no more effective power to be had.
Sailing direct to windward is the one advantage in favor of rotors.
My feeling is that electricity generation and storage capacity will become cheaper in the future, so that a boat could use its propeller in reverse as long as it was at hull speed anyway. Then, that energy could propel the boat to windward later. Lithium ion rechargable batteries, like my camera uses, would already make this possible, though very expensive to purchase.
Both windmill boats and normal boats would do better as batteries became cheaper. That is another advantage of a windmill boat. One that may favor a smaller windmill as part of a hybrid system in the future. The windmill (as a mizzen, for example) would make electricity whenever there was wind, and the mainsail and an electric drive to the prop would actually power the boat

Alan

 

Windmill Boat Model Videos

I have just completed posting my radio controlled model videos on Youtube.
They show two of my models. A trimaran which can sail in ANY direction relative to the wind, (its driven by a wind-turbine with an underwater prop). Also shown is a very basic wind-turbine landsailer model on the beach.
Check out this url at: http://www.youtube.com/watch?v=GzNq3aEyP2w Many in this discussion seem to think that sailing directly into the wind is a bit marginal and rather difficult. I think this will show it's very easy and no big deal! I'm looking for comments and criticism so don't hold back. Honesty is always appreciated!

 

Windmill boats have been around at least since 1931-
If you think being hit on the head with a boom hurts - stick your hand in a propellor

 

Withdrawal of videos

I must apologise to all. I had to withdrew my videos from Youtube due to patent issues.
In reply to the last post.
I assume the term "propeller" refers to the wind turbine. "propeller" is a misnomer because it implies something that propels. Personally, I always stick to the strict rule that a "propeller" is usually used underwater to propel a boat, whilst a turbine is something that collects energy from an outside source.
Anyway, that aside, the assumption that the turbine blades rotate at enormous speeds is erroneous, in fact the blades on my design do not rotate (and never can), rotate faster than the windspeed. So a blow from one of these could easily be less that that of a swinging boom. On a fullsize design of mine, a person actually walked into the turning blades without injury! Yes, they have been around, maybe even before 1931 but I don't that means there can't be an improved version.

 

Interesting concept - but I dont believe that the blades won't do any injury.
For a start "do not rotate (and never can), rotate faster than the windspeed" is a bit hard to define - because the arms of the turbine all operate at different speeds depending on how far from the axis you do the calculations.
Assuming the Outer tip is the bit that "never goes faster than windspeed " - that still leaves a 20kmh piece of, say, foam and fibreglass to contend with. The fact that your crew got hit by one and survived can only mean the wind was slow that day. I have tried to stop a small surfboard doing say 4 kmh in a wave and got a nasty bing.

As regards "I had to withdrew my videos from Youtube due to patent issues.". Of Course !! - because they have been around since 1931 !!!! How many hours of development and millions of man hours and development have been expended since then - and still not become a common form of transportation ?

Not to discourage your enthusiasm and creativity, the amount of time others have tried without success rings warning bells to innovators everywhere.