Mess with your minds: A wind powered craft going faster than a tail wind speed.

[electrodacus]

No one tell this guy about heat pumps.

Heat pumps are not more than 100% efficient (not even close to that). The term used there is coefficient of performance not efficiency.
It is a pump so pumps heat from outside to inside or inside to outside depending on application heating or cooling.

[bdunham7]

Comes from a quick google search and I selected the one that looked to contains the info I wanted to show.
Seems photo is from a Wikipedia article on axial fans  https://en.wikipedia.org/wiki/Axial_fan_design

OK, but I don't see how that refutes the experiment IanB showed.  Pressure in a moving stream of air is anisotropic so the fact that one pressure vector is higher as shown doesn't mean that the orthogonal one won't be lower.  And of course you have to consider how that operates on the propeller, which is another matter.  (hint--it's pointing away!)

You see blackbird and treadmill model exceed wind speed and you immediately think is wind that powers the vehicle (in a way it is but is stored wind energy so you will not stay above wind speed indefinitely).

You keep saying this but a propeller doesn't work by building up a huge reservoir of pressure behind it and then having that pressure push it forward, unless perhaps you are taking off out of a small cave or some ridiculous contrived scenario. Propellers do something entirely different. The idea that you can store enough energy in a pressure field behind the vehicle in the open atmosphere with nothing confining it to keep the vehicle moving above wind speed for 'several minutes' seems absolutely ludicrous to me and you have presented no math, citations or cogent explanation to support that quite wild theory.  If you suggested that energy was stored in the angular momentum of the propeller, perhaps I'd be willing to look at the math before dismissing that, but air pressure seems pretty far out there.

[electrodacus]

OK, but I don't see how that refutes the experiment IanB showed.  Pressure in a moving stream of air is anisotropic so the fact that one pressure vector is higher as shown doesn't mean that the orthogonal one won't be lower.  And of course you have to consider how that operates on the propeller, which is another matter.  (hint--it's pointing away!)

You keep saying this but a propeller doesn't work by building up a huge reservoir of pressure behind it and then having that pressure push it forward, unless perhaps you are taking off out of a small cave or some ridiculous contrived scenario. Propellers do something entirely different. The idea that you can store enough energy in a pressure field behind the vehicle in the open atmosphere with nothing confining it to keep the vehicle moving above wind speed for 'several minutes' seems absolutely ludicrous to me and you have presented no math, citations or cogent explanation to support that quite wild theory.  If you suggested that energy was stored in the angular momentum of the propeller, perhaps I'd be willing to look at the math before dismissing that, but air pressure seems pretty far out there.

I'm sorry but you are have to many misunderstanding for me to be able to explain how vehicle works.
The easier way is to demonstrate that the vehicle is not working as you think then maybe you will spend some significant amount of time to understand pressure differential energy storage and how the vehicle actually works.

I mentioned my math proof many times before is about the power on motor not possible to be higher than on the generator since motor is supplied from the generator. Looks like a simple enough explanation to me and until you are able to understand that there is nothing I can do for you.
There is also the simple experiment I proposed to show exactly that if you prefer to see an experiment rather than an equation.
The wheel only vehicle on a treadmill should be easy enough to setup (exactly as shown in my diagram no flipped vehicle as that will have a very different meaning).
The other experiment may be even more convincing to you but it is harder to setup and that will be a propeller based vehicle pushed to speed in a day with no wind that will show speed above pushed speed due to energy storage as there is no longer any wind.
 
I know I'm bad at explaining things so maybe I can find someone that can do a better job explaining.

[bdunham7]

I mentioned my math proof many times before is about the power on motor not possible to be higher than on the generator since motor is supplied from the generator.

And round and round we go!  I very carefully explained why the motor power does not need to be higher than the generator power and your limited answers demonstrated that you somehow don't believe in simple mechanics.

 
I know I'm bad at explaining things so maybe I can find someone that can do a better job explaining.

And there's a big clue for you.  I saw a quote recently that seems appropriate--"whatever cannot be said clearly is probably not being thought clearly either"  You may be entirely convinced of whatever it is you are convinced of for whatever reason, but your inability to demonstrate this to multiple people, all well capable of understanding the matter should serve as an indicator that perhaps you have made an error somewhere. 

[electrodacus]

And round and round we go!  I very carefully explained why the motor power does not need to be higher than the generator power and your limited answers demonstrated that you somehow don't believe in simple mechanics.

That is exactly where you are wrong so should think more about that statement.

And there's a big clue for you.  I saw a quote recently that seems appropriate--"whatever cannot be said clearly is probably not being thought clearly either"  You may be entirely convinced of whatever it is you are convinced of for whatever reason, but your inability to demonstrate this to multiple people, all well capable of understanding the matter should serve as an indicator that perhaps you have made an error somewhere.

Unfortunately there are enough people that do not understand what conservation of energy really means and so with that there is a bad understanding of how the world works.
It seems the education system is failing in this regards.  I say this seeing university level physics professors getting this wrong.
You will think internet will help in educating people but unfortunately bad ideas spread more than boring correct ones.

[Kleinstein]

No one tell this guy about heat pumps.

Heat pumps are not more than 100% efficient (not even close to that). The term used there is coefficient of performance not efficiency.
It is a pump so pumps heat from outside to inside or inside to outside depending on application heating or cooling.

In some sense the situation with the vehicle with the prop driven by the wheels similar:  At first galne it may look like over unity efficiency, and thus may be mind-blowing to some. Hower it is not: the prob produces more forward force than the wheels need backwrard force to drive the prob. But this is just the force. Over unity gain for the force is nothing new, known from the lever and pully.

For the power / energy side it is not over unity: the wheels see a relatively high speed to the ground and thus generate high power from a given force, while the prop works relative to the wind. So at a speed of the vehicle a little faster than the wind the prop gives out litte power (energy), because the speed (relative to the wind) is low.  So it is a bit like with a pully: high speed and low fore on one side and low speed and high force at the other side.

[electrodacus]

In some sense the situation with the vehicle with the prop driven by the wheels similar:  At first galne it may look like over unity efficiency, and thus may be mind-blowing to some. Hower it is not: the prob produces more forward force than the wheels need backwrard force to drive the prob. But this is just the force. Over unity gain for the force is nothing new, known from the lever and pully.

For the power / energy side it is not over unity: the wheels see a relatively high speed to the ground and thus generate high power from a given force, while the prop works relative to the wind. So at a speed of the vehicle a little faster than the wind the prop gives out litte power (energy), because the speed (relative to the wind) is low.  So it is a bit like with a pully: high speed and low fore on one side and low speed and high force at the other side.

No comparison can be done between a heat pump and what happens here.
Also there is no overunity that is just wrong description of how vehicle works as vehicle will not drive indefinably above wind speed as claimed by others it will just drive for a limited amount of time base on amount of stored energy.

In the case of a pulley same as with vehicle is exactly as you say high speed low force on one side and and low speed high force on the other but that means same power on both sides.
So think about that Power needs to be equal on both sides in order for vehicle to maintain speed (not accelerate just maintain speed in ideal case).
Say you have an ideal pulley and put in 2N at a speed of 6m/s and then at output you get 6N and 2m/s so you have 12W on input and also 12W on output
That means there is no gain in therms of power or energy (power over time).
Same will happen with a vehicle at wind speed power in and power out will need to be equal just to maintain speed if we exclude energy storage.
So vehicle below wind speed there is a gain from the wind at wind speed if ideal vehicle there is no gain and no loss and above wind speed there is a loss as apparent wind has now changed direction so it is counterproductive.

[bdunham7]

wind has now changed direction so it is counterproductive.

I'll leave the rest of your statement alone, but this is another thing you insist on that is simply wrong.  The wind has not changed direction relative to the parts of the propeller that it is interacting with.  That's the whole point of the propeller.

[electrodacus]

I'll leave the rest of your statement alone, but this is another thing you insist on that is simply wrong.  The wind has not changed direction relative to the parts of the propeller that it is interacting with.  That's the whole point of the propeller.

Not quite sure what you are trying to say so maybe you can elaborate.
Propeller is connected to vehicle so they will travel together.
Say wind speed is 12m/s then at say 2m/s wind speed propeller is moving as it is connected to wheel and so wind pushes against the vehicle body including the sweep area of the propeller, force pushing the vehicle in the intended direction of travel. The power acting on vehicle by an equivalent wind of 10m/s (12-2m/s) is what helps vehicle move forward plus some of this energy is stored as pressure differential as propeller starts to create an artificial wind if you want in the opposite direction to wind.
Now when vehicle is at say 7m/s the vehicle will experience an equivalent wind of 5m/s (12-7m/s) so at this point wind power available to vehicle is 8x smaller than what it was when it was travelling at 2m/s
This power available from wind will continue to drop to zero as vehicle gets to wind speed and at this point there is no power from wind available to vehicle but vehicle still have a lot of stored energy (that pressure differential I was always talk about).
Once the vehicle speed is say 17m/s the vehicle will experience the equivalent of a wind from the opposite direction of 5m/s   (you can say 12m/s - 17m/s = -5m/s) and this will acct against the vehicle body by breaking the vehicle instead of accelerating it. But this is just against the vehicle body as the propeller is almost transparent from wind from this other direction (air molecules can pass from front of the propeller to the back with no resistance but they can not pas the other way around) So in electrical analog the propeller will act as a diode.

Maybe I complicated to much my answer and the short version is that wind relative to vehicle will change direction.  Think about  being in a vehicle where your fuel consumption will drop if you have back wind but as soon as vehicle exceeds wind speed in same direction vehicle will start experience drag so fuel consumption will increase.

[IanB]

This power available from wind will continue to drop to zero as vehicle gets to wind speed and at this point there is no power from wind available to vehicle but vehicle still have a lot of stored energy (that pressure differential I was always talk about).

You overlook the fact that when the vehicle is moving at wind speed there may be no direct impulse force available from the wind, but at this point the ground is moving very fast beneath the vehicle's wheels. There may be no force available from the wind, but there is significant power available from the ground as it turns the wheels of the vehicle. By capturing this wheel power and turning it into backward thrust the vehicle is able to continue moving ahead faster than the wind.

[bdunham7]

You overlook the fact that when the vehicle is moving at wind speed there is no direct impulse force available from the wind,

Not to the vehicle perhaps, but there is to a properly configured rotating propeller.

[electrodacus]

You overlook the fact that when the vehicle is moving at wind speed there is no direct impulse force available from the wind, but at this point the ground is moving very fast beneath the vehicle's wheels. There may be no force available from the wind, but there is significant power available from the ground as it turns the wheels of the vehicle. By capturing this wheel power and turning it into backward thrust the vehicle is able to continue moving ahead faster than the wind.

If you take any power from the wheels you are slowing down the vehicle and in order to not slow down you need to put all that energy back in to propeller at 100% efficiency that is only possible in theory.  So there is nothing there.
I heard similar arguments from people in the past when I tried to discourage them to use alternator to charge the caravan battery. They where thinking that since they need to drive anyway that energy they take from alternator is free not realizing that for every kWh they take out of the alternator the vehicle fuel consumption will increase accordingly (typical 1 liter of fuel for each kWh) so cost of that energy not only is not free but at $1/kWh is about 50x more expensive than solar PV energy that is just $0.02/kWh

This is the main reason I asked you to test the simple wheel only vehicle in my diagram the one with generator wheel on a fast moving treadmill and the motor wheel on a fixed box on the ground (box is there so that vehicle is level with the treadmill). Then you can see the vehicle can only move backwards from right to left no matter what sort of gear ration you want to setup between G wheel and M wheel.

And the math for that is also simple as when you take energy from the vehicle wheel you are actually take it from the vehicle kinetic energy
So say vehicle speed is 12m/s and you apply a 10N breaking force for one second then that is 120Ws worth of energy that is taken out of the vehicle thus vehicle will now be slower as weight of the vehicle has not changed.
To get the vehicle back to original kinetic energy and same speed you need to put back 120Ws and so you will need a 100% efficient propeller just to be able to do that and even then vehicle will not accelerate just be back to same speed it started with.
So since wind can not help when vehicle is above wind speed vehicle will just slow down it it was not for the pressure differential energy storage that provides the vehicle with the delta it needs to cover the friction losses and a bit extra to continue to accelerate at least until this stored energy is all used up and then vehicle slows down.

[Alex Eisenhut]

No comparison can be done between a heat pump and what happens here.

There can if I chose to.

[IanB]

This is the main reason I asked you to test the simple wheel only vehicle in my diagram the one with generator wheel on a fast moving treadmill and the motor wheel on a fixed box on the ground (box is there so that vehicle is level with the treadmill). Then you can see the vehicle can only move backwards from right to left no matter what sort of gear ration you want to setup between G wheel and M wheel.

I think we have all looked at that diagram, and I think we can all see that the vehicle can easily be made to move forwards from left to right.

The reason for this is, as has already been explained to you, power does not have a direction. It is a scalar quantity. Therefore, if the vehicle can be made to move at all by picking up power from the treadmill wheel, it can be made to move in whatever direction we like.

[electrodacus]

No comparison can be done between a heat pump and what happens here.

There can if I chose to.

There is a reason they used the word pump to describe a heat pump. Instead of converting any form of energy to heat like say electricity they use that energy to pump heat from one place to another like pump out of a refrigerator (inside of fridge now cooler but your room hooter) or getting heat from outside to heat your room. Outside may be +5C and inside you want say +20C the heat-pump will cool the outside to heat your room since it will pump heat from out side to inside.
While you get more heat from a unit of energy by pumping than you will get directly converting that energy in to heat (say electric restive heating that is already 100% efficient) that will not mean heat pump is anywhere near 100% efficient is just that it moves heat from one side to another.
This vehicle discussed here can not do anything similar to a pump.
The Wind energy is all that powers this vehicle and that is not available to vehicle when vehicle speed is higher than wind speed. 

I think we have all looked at that diagram, and I think we can all see that the vehicle can easily be made to move forwards from left to right.

The reason for this is, as has already been explained to you, power does not have a direction. It is a scalar quantity. Therefore, if the vehicle can be made to move at all by picking up power from the treadmill wheel, it can be made to move in whatever direction we like.

You (all) should prove that to me either with a test or with math.  You will not be able to do that since it is not possible.
When you try to get any power from the treadmill the vehicle will be pushed backwards right to left proportional with the amount of energy you try to extract.
The motor even if it was an ideal vehicle could at best just move the vehicle back to the starting point.

So if you do not extract any energy from G wheel in ideal vehicle then wheel G will free spin with no friction so vehicle will stay in the same place is started.
If you try to get any power from the wheel that power will be seen as a breaking force at the wheel and that will make the vehicle move backwards (right to left)
Maybe this part is unclear to you and you think you can extract energy from the treadmill while vehicle remains in the same place.
Keep in mind that up to this point the the M wheel was not powered so it is free to spin with no friction as it is an ideal vehicle disused here. And I discus an ideal vehicle to just show the best case and that best case is vehicle staying in the same place.  Real world vehicle will always move backwards (right to left).

[IanB]

You (all) should prove that to me either with a test or with math.  You will not be able to do that since it is not possible.

We do not need to prove anything to you, since we already understand it. It is you who need to to the work, to learn how it is possible. A good start might be to gain a better understanding of science and engineering, so you can stop relying so much on faulty intuition.

[IanB]

Let me ask you a question:

Can I make a wheeled vehicle that when facing head on into the breeze from a fan, will use the wind energy to drive directly towards the fan?

[electrodacus]

Let me ask you a question:

Can I make a wheeled vehicle that when facing head on into the breeze from a fan, will use the wind energy to drive directly towards the fan?

Yes a vehicle can drive against wind as it has access to wind power but that vehicle can not exceed wind speed.
So a vehicle that has a propeller based wind turbine generator driving against the wind can do so and accelerate only up to wind speed if no energy storage is involved.

We are mostly discussing the vehicle that has a propeller based fan driving in same direction as the wind and that one can also not exceed wind speed without energy storage.

You need to get that the two vehicles are setup very differently one has a fan the other a wind turbine so not the same vehicle is used and also in both case the vehicle can not exceed the wind speed without energy storage.   

[IanB]

Yes a vehicle can drive against wind as it has access to wind power

In that case your treadmill cart can drive against the treadmill as it has access to the treadmill power.

[electrodacus]

Yes a vehicle can drive against wind as it has access to wind power

In that case your treadmill cart can drive against the treadmill as it has access to the treadmill power.

No it can not as that will be a different arrangement with the flipped vehicle (motor wheels in from of the generator wheels while generator wheels are still on the treadmill) That will represent a vehicle driving against wind at lower than wind speed.
You are just confusing the two and think they are the same thing.
The vehicle as shown in my diagram can not move from left to right.

[PlainName]

(motor wheels in from of the generator wheels while generator wheels are still on the treadmill)

Just to be clear, and remind me of what this is about...

In your diagram the treadmill is pushing the G wheel, yes? Absent the drive belt the G wheel will thus rotate and the vehicle will remain static (more or less - we are ignoring friction effects for the moment). With the treadmill turning the G wheel, and still absent the drive belt, we should be able to place a hand or other attachment on the vehicle and move it left or right without apparent bias or effort, right?

At this point I think you need to either agree with the above or state explicitly where it is wrong.

Now, the M wheel has been free to turn, the vehicle has been free to move and the G wheel is rotating clockwise. If we add the drive belt, the difference is that now the M wheel is rotating clockwise. Since it has a grip on the platform - just like the treadmill has a grip on the G wheel - the vehicle will move right. There is nothing to stop it moving right since we agreed above that the G wheel being rotated by the treadmill is not imparting motion, merely causing the wheel to turn. So the vehicle moves right and the G wheel rotates faster, which imparts faster rotation of the M wheel which causes the vehicle to move faster to the right.

Of course, it won't be quite like that in practice because there will be friction resisting the turning of the G wheel, which will impart a small movement of the vehicle to the left. However, I think that should be ignored since otherwise you could add X amount of friction sufficient to stop the wheel turning at all and prove nothing except the experiment is testing the wrong thing.

Which bit did I get wrong?

[electrodacus]

(motor wheels in from of the generator wheels while generator wheels are still on the treadmill)

Just to be clear, and remind me of what this is about...

In your diagram the treadmill is pushing the G wheel, yes? Absent the drive belt the G wheel will thus rotate and the vehicle will remain static (more or less - we are ignoring friction effects for the moment). With the treadmill turning the G wheel, and still absent the drive belt, we should be able to place a hand or other attachment on the vehicle and move it left or right without apparent bias or effort, right?

At this point I think you need to either agree with the above or state explicitly where it is wrong.

Now, the M wheel has been free to turn, the vehicle has been free to move and the G wheel is rotating clockwise. If we add the drive belt, the difference is that now the M wheel is rotating clockwise. Since it has a grip on the platform - just like the treadmill has a grip on the G wheel - the vehicle will move right. There is nothing to stop it moving right since we agreed above that the G wheel being rotated by the treadmill is not imparting motion, merely causing the wheel to turn. So the vehicle moves right and the G wheel rotates faster, which imparts faster rotation of the M wheel which causes the vehicle to move faster to the right.

Of course, it won't be quite like that in practice because there will be friction resisting the turning of the G wheel, which will impart a small movement of the vehicle to the left. However, I think that should be ignored since otherwise you could add X amount of friction sufficient to stop the wheel turning at all and prove nothing except the experiment is testing the wrong thing.

Which bit did I get wrong?

Yes in ideal vehicle the G wheel will just free spin and stay in the same place.  If you want to push the vehicle effort will be required assuming vehicle has some weight other than zero. If you assume vehicle has no weight then yes there will be no effort.

So the statement is wrong if your vehicle has weight as to accelerate the vehicle from left to right even with zero wheel friction you need to put kinetic energy in to vehicle.

Now if you connect the wheel G and M with an ideal belt and gear ratio is 1:1 then vehicle will still be standing in the same place (no movement in any direction). In a real world transferring power from G to M trough a belt is not 100% efficient and so those losses due to friction will make the vehicle slowly move from right to left.
Any other gear ratio and you make things way worse meaning vehicle will move much faster from right to left and there is no way to move the vehicle from left to right.

[IanB]

Now if you connect the wheel G and M with an ideal belt and gear ratio is 1:1 then vehicle will still be standing in the same place (no movement in any direction).

Let's observe that if nothing slips, then this situation is impossible.

If wheel G is in contact with the belt and the belt is moving, then wheel G is turning clockwise. If there is a 1:1 belt between wheel G and wheel M, then M is turning clockwise at the same speed as wheel G. If wheel M is turning clockwise, and wheel M is in contact with a fixed platform, then wheel M is moving from left to right. If wheel M is moving from left to right, then the whole cart is moving from left to right.

[bdunham7]

Propeller is connected to vehicle so they will travel together.

Please read a Wikipedia article or something on how propellers work.  You are completely overlooking the fact that each element of the propeller is moving in a circle orthogonal to the direction of the wind and travel here.  Each element then maps out a helix in the air as it travels, unless it is in still air or travelling at exactly wind speed, in which case it tracks a circle.  Each element reacts with the air in way determined by its configuration.  In the common case where the propeller is essentially a symmetric airfoil, it's reaction will be determined by the angle of attack, or the angle between the chord of the element and the angle of the vector describing its motion.  Thus if the propeller has any pitch at all and is spinning at all, it can still push on the wind even if the vehicle is travelling at exactly wind speed.  And of course, then the wind pushes back.

Now the energy part should be obvious and easy after all this discussion.  Power is force x speed.  The power needed to exert a given force on the air by the propeller is (whatever the force is) x (airspeed--which is the difference between vehicle speed and wind speed) whereas the power generated by the wheels can be (whatever the force is) x (the vehicle speed).  Not including losses and parasitic drag and yada yada.  Note that this means that at if the vehicle speed the same as or only just a bit over wind speed, the ideal amount of power needed for the prop is zero or infinitesimally small, which may offend your intuition.  This is actually correct if you don't consider losses, but a typical propeller would have quite high losses at very slow speeds.  So if you actually want to design a vehicle like this, unlike your treadmill car, you would have to really start thinking about parasitics and propeller efficiency. 

[electrodacus]

Now if you connect the wheel G and M with an ideal belt and gear ratio is 1:1 then vehicle will still be standing in the same place (no movement in any direction).

Let's observe that if nothing slips, then this situation is impossible.

If wheel G is in contact with the belt and the belt is moving, then wheel G is turning clockwise. If there is a 1:1 belt between wheel G and wheel M, then M is turning clockwise at the same speed as wheel G. If wheel M is turning clockwise, and wheel M is in contact with a fixed platform, then wheel M is moving from left to right. If wheel M is moving from left to right, then the whole cart is moving from left to right.

With 1:1 gear ratio and no slip is allowed the treadmill will be locked so there will be no movement.
The treadmill will try to push the vehicle back while the back wheel will try to move the vehicle forward so there will be equal but opposite power acting on the belt. In real world the M wheel will slip unless friction between wheel and red box is higher than treadmill power so assuming treadmill is not overpowered the vehicle will move backwards (right to left).