Question. Is extracting wind power causing some climate change problems?

[Mountainmike]

What is pure comedy about your posts in your inability to comprehend how a velocity deficit cannot be maintained even at relatively short distances for high Reynolds numbers so your solution is motivated by denial mode, disguised as word salad and supported by hearsay and supposed papers that never see the light of day in this forum.

Here is a paper for a model wind farm which refutes "velocity deficit can be a substantial multiple of turbulent path (obviously)", the phrase itself being nonsensical as velocity and distance do not have the same dimensional units, but the deficit approaches zero as the wake reaches its fullest extent.

​

Here U is the wind velocity downstream, Uhub is the upstream velocity at hub height, x is the distance from where the wind is upstream and D is the rotor diameter.
As you can see U/Uhub → 1 is a limit in the downstream and the conservation of energy would be violated if the limit was exceeded.
Needless to say the model is also supported by satellite measurements which shows the wake ends when the velocity deficit approaches zero.

How far the wake of a wind farm can persist for?

With the increased penetration of wind energy in our nation’s energy portfolio, wind farms are placed in a way close to each other. Thus, their wakes …

www.sciencedirect.com

You can now retreat into your make believe world where the denials will continue thick and fast along with the pseudoscience .

For goodness sake study, basic, basic science. Energy balance.

Then this won’t be such a surprise to you,
“The velocity deficit of the wind farm wake can be observed up to 100 km behind the wind farm, while the enhanced turbulence intensity can be observed up to 20 km” stieren stevens 2022.

Thats the distance at which it is measurable. Will boundary layers be affected ? Who knows. Nobody can afford the computational cost of long range modelling to find out, and even if they did it would be too coarse and limited to say anything useful.

You are way out of your depth.

 

[Mountainmike]

This thread needs to go somewhere else

The clintel declaration , can a Nobel laureate physicist be an anti intellectual,?



“The popular narrative about climate change reflects a dangerous corruption of science that threatens the world’s economy and the well-being of billions of people. Misguided climate science has metastasized into massive shock-journalistic pseudoscience. In turn, the pseudoscience has become a scapegoat for a wide variety of other unrelated ills. It has been promoted and extended by similarly misguided business marketing agents, politicians, journalists, government agencies, and environmentalists. In my opinion, there is no real climate crisis. There is, however, a very real problem with providing a decent standard of living to the world’s large population and an associated energy crisis. The latter is being unnecessarily exacerbated by what, in my opinion, is incorrect climate science.”

Nobel Prize winner Dr. John F. Clauser signs the Clintel World Climate Declaration - Clintel

John F. Clauser, winner of the 2022 Nobel Prize in Physics for his work on quantum mechanics, has decided to sign the World Climate Declaration of Clintel with its central message “there is no climate emergency”. Clauser is the second Nobel Laureate to sign the declaration, Dr. Ivar Giaever was the

clintel.org

 

[sjastro]

For goodness sake study, basic, basic science. Energy balance.

Then this won’t be such a surprise to you,
“The velocity deficit of the wind farm wake can be observed up to 100 km behind the wind farm, while the enhanced turbulence intensity can be observed up to 20 km” stieren stevens 2022.

Thats the distance at which it is measurable. Will boundary layers be affected ? Who knows. Nobody can afford the computational cost of long range modelling to find out, and even if they did it would be too coarse and limited to say anything useful.

You are way out of your depth.

What doesn’t surprise me is your propensity for straight out dishonesty.
Given you only provided a quote raised suspicions and it didn’t take much effort to find the relevant link and the motive behind it.
This is what the authors actually wrote, “They find that, depending on the atmospheric conditions, the velocity deficit of the wind farm wake can be observed up to 100 km behind the wind farm, while the enhanced turbulence intensity can be observed up to 20 km downstream.”
The embolden parts are what you deliberately omitted in order to misquote the authors to create a completely different context.

First of all, the 100 km distance quoted is the wake from the upstream wind farm received by the downwind wind farm and the resultant enhanced turbulence intensity observed up to 20 km is the downwind wind farm’s downstream.
By conveniently omitting the word downstream suggests both distances are from the wake which reaches the downwind wind farm and therefore validating your idea “Velocity deficit can be a substantial multiple of turbulent wake ( obviously)”.

Secondly by omitting the dependence of atmospheric conditions on the velocity deficit is another piece of deception.
As the link makes very clear atmospheric conditions affect the recovery rate or how quickly the velocity deficit is reduced which according to you couldn’t be done as it would violate the conservation of energy.

This is the second time you have been caught out lying in this thread.

 

[SelfSim]

First of all, the 100 km distance quoted is the wake from the upstream wind farm received by the downwind wind farm and the resultant enhanced turbulence intensity observed up to 20 km is the downwind wind farm’s downstream.
By conveniently omitting the word downstream suggests both distances are from the wake which reaches the downwind wind farm and therefore validating your idea “Velocity deficit can be a substantial multiple of turbulent wake ( obviously)”.

Secondly by omitting the dependence of atmospheric conditions on the velocity deficit is another piece of deception.
As the link makes very clear atmospheric conditions affect the recovery rate or how quickly the velocity deficit is reduced which according to you couldn’t be done as it would violate the conservation of energy.

I have a slightly off-topic matter I'd like to discuss .. could you please check your CFs inbox so we can take it offline?
Cheers

 

[The Barbarian]

so is wind power extraction - at best unreliable - causing greater temperature swings?

Iowa now gets over 35% of its electric power from wind. Sounds pretty reliable to me. Few weeks ago, I was traveling though the state. A lot more of them out there, now.

his will not work as the reaction force on the sail is equal and opposite in direction to the force exerted on the sail by the air.

Actually, it can work a little if the sail is designed so that the flow is directed rearward at the edges. But basically, you are right; a fan-operated sail vehicle is highly inefficient and impractical.

What is being extracted?

In wind farms, kinetic energy of moving air is being extracted. And the movement of the air is the result of thermal energy (mostly sun) and the rotation of the Earth. I don't have the numbers at hand, but I doubt very much if the amount of kinetic energy transferred to wind farms significantly affects temperatures.

 

[The Barbarian]

You are all missing the point. Is it deliberate?
my point is whether wind extraction is causing greater land temperatures? Ie disturbing climate balance?
literalky a green house effect. A green house is in essence a window free enclosure .

A greenhouse is pretty much all windows...

 

[sjastro]

Actually, it can work a little if the sail is designed so that the flow is directed rearward at the edges. But basically, you are right; a fan-operated sail vehicle is highly inefficient and impractical.

It won’t work.
If you mount the fan to the vehicle with the sail, the mass of the fan becomes the total mass of the vehicle and the force exerted by the fan is an internal force.

If at rest turning on the fan will not set the vehicle in motion as the internal force exerted by both the fan and the moving air on the sails are cancelled out by a reaction force which is equal and opposite in direction by Newton’s third law.
Internal forces cannot set the vehicle in motion without violating the conservation of momentum.

In a nutshell for the vehicle to be set in motion requires a non-zero external force such as wind.

 

[The Barbarian]

It won’t work.

If the sail is curved, the air hits the sail, and then moves of the side. If the angle is such that it deflects the air backwards, there will be a small net force in the forward direction. But not much.

If you mount the fan to the vehicle with the sail, the mass of the fan becomes the total mass of the vehicle and the force exerted by the fan is an internal force.

Yep.

If at rest turning on the fan will not set the vehicle in motion as the internal force exerted by both the fan and the moving air on the sails are cancelled out by a reaction force which is equal and opposite in direction by Newton’s third law.

Assuming that the sail is not set to deflect the air backwards at all. A perfectly flat sail that covered the entire airstream would exactly fit Newton's Third Law, and the cart would not move at all. I've taught physics. And some students submitted models that showed a bit of net force for the reason I mentioned. Think of the thrust reversers on jets.

Nothing even made a single axle rotation, of course.

 

[sjastro]

If the sail is curved, the air hits the sail, and then moves of the side. If the angle is such that it deflects the air backwards, there will be a small net force in the forward direction. But not much.

Yep.

Assuming that the sail is not set to deflect the air backwards at all. A perfectly flat sail that covered the entire airstream would exactly fit Newton's Third Law, and the cart would not move at all. I've taught physics. And some students submitted models that showed a bit of net force for the reason I mentioned. Think of the thrust reversers on jets.

Nothing even made a single axle rotation, of course.

Call me a skeptic but has this been done to propel a person on a skateboard using devices such as air blowers as depicted in the video?
This forward force would need to overcome the thrust force from the fan acting in the opposite direction along with surface friction and air resistance.
Then there is inertia to overcome to send the person into motion.

 

[Mountainmike]

A greenhouse is pretty much all windows...

 

[Mountainmike]

What doesn’t surprise me is your propensity for straight out dishonesty.
Given you only provided a quote raised suspicions and it didn’t take much effort to find the relevant link and the motive behind it.
This is what the authors actually wrote, “They find that, depending on the atmospheric conditions, the velocity deficit of the wind farm wake can be observed up to 100 km behind the wind farm, while the enhanced turbulence intensity can be observed up to 20 km downstream.”
The embolden parts are what you deliberately omitted in order to misquote the authors to create a completely different context.

First of all, the 100 km distance quoted is the wake from the upstream wind farm received by the downwind wind farm and the resultant enhanced turbulence intensity observed up to 20 km is the downwind wind farm’s downstream.
By conveniently omitting the word downstream suggests both distances are from the wake which reaches the downwind wind farm and therefore validating your idea “Velocity deficit can be a substantial multiple of turbulent wake ( obviously)”.

Secondly by omitting the dependence of atmospheric conditions on the velocity deficit is another piece of deception.
As the link makes very clear atmospheric conditions affect the recovery rate or how quickly the velocity deficit is reduced which according to you couldn’t be done as it would violate the conservation of energy.

This is the second time you have been caught out lying in this thread.

Somebody teach sastro some basic physics
Energy balance.

If you extract wind power you slow the wind and modify pressure patterns in the system as a whole..

That can potentially have a profound effect on moisture take up wind chill, cloud formation , and modfified cloud patterns can cause more or reflection of sun back into space. At that point there is a change to the total amount of sun falling on earth so a fundamental disturbance and all bets are off on effect it might have on the wider atmosphere. What you can say is something has changed in the system in permanence.

It may only have been measured a few K downstream. It is remarkably hard to define a base state from which meaningful measurement can then be made. So who knows what the impact will be is the only answer. What you can say is The more of them, the worse it gets. And there is plenty of mind experiments that can prove a point. Like the reduced empting of swimming pools on less windy days. So we are diving headlong into something we may yet have cause to regret.

So there is a serious question as yet unanswered of wider enviromental change caused by windmills.

For all Sjastro blather and determination to pretend he understand physics he is yet to get off first base with this
He gets lost in all the detail presumably because it is too complex for him, and ignores the generality. Energy balance means less wind which can have a profound effect on micro climate, water take up - and with that cloud formation and potential serious climate change.

As a PROFESSIONAL physicist, used to finding and exploiting holes in current models of physical things, I say there may be a problem.

I am not just an undergrad like him who once did half a course on fluid dynamics. I had to use it professionally with effects of wind and weather on structures.

Why all the nastiness sjastro? what I said is evidently true. There may yet be nasty surprises.

 

[Warden_of_the_Storm]

If you extract wind power you slow the wind and modify pressure patterns in the system as a whole..

But the wind does not remain slowed down. It then picks back up to its original speed once the diffusion from the windmill's sails cease to affect it. Sjastro has shown many, many, many, MANY videos that show exactly that from groups a lot more educated on the subject than you, and you remain thinking that you have a leg to stand on, when you can't even get the basic analogy of what a greenhouse is!

 

[The Barbarian]

But the wind does not remain slowed down. It then picks back up to its original speed once the diffusion from the windmill's sails cease to affect it.

One can neither create nor destroy energy. One can merely convert it to something else. So kinetic energy (wind) that is converted to electricity is no longer available. But this would be true of forests, as opposed to bare plains. Even in Iowa, where such wind generators are very common, I doubt if you could measure the change in winds over a day. Mike is right in principle. I just don't think it's a significant factor.

 

[Warden_of_the_Storm]

One can neither create nor destroy energy. One can merely convert it to something else. So kinetic energy (wind) that is converted to electricity is no longer available. But this would be true of forests, as opposed to bare plains. Even in Iowa, where such wind generators are very common, I doubt if you could measure the change in winds over a day. Mike is right in principle. I just don't think it's a significant factor.

Yes, but that also does not mean that the wind just stops. It's like the water cycle. There will always be wind generated, and thus there will be no drop-off in wind via wind farms nor a slowing down of wind. It's continuously going.

 

[sjastro]

Somebody teach sastro some basic physics
Energy balance.

If you extract wind power you slow the wind and modify pressure patterns in the system as a whole..

That can potentially have a profound effect on moisture take up wind chill, cloud formation , and modfified cloud patterns can cause more or reflection of sun back into space. At that point there is a change to the total amount of sun falling on earth so a fundamental disturbance and all bets are off on effect it might have on the wider atmosphere. What you can say is something has changed in the system in permanence.

It may only have been measured a few K downstream. It is remarkably hard to define a base state from which meaningful measurement can then be made. So who knows what the impact will be is the only answer. What you can say is The more of them, the worse it gets. And there is plenty of mind experiments that can prove a point. Like the reduced empting of swimming pools on less windy days. So we are diving headlong into something we may yet have cause to regret.

So there is a serious question as yet unanswered of wider enviromental change caused by windmills.

For all Sjastro blather and determination to pretend he understand physics he is yet to get off first base with this
He gets lost in all the detail presumably because it is too complex for him, and ignores the generality. Energy balance means less wind which can have a profound effect on micro climate, water take up - and with that cloud formation and potential serious climate change.

As a PROFESSIONAL physicist, used to finding and exploiting holes in current models of physical things, I say there may be a problem.

I am not just an undergrad like him who once did half a course on fluid dynamics. I had to use it professionally with effects of wind and weather on structures.

Why all the nastiness sjastro? what I said is evidently true. There may yet be nasty surprises.

Why didn’t you address my post which caught you out for being dishonest by cherry picking quotes from a paper that purportedly supported your nonsense?

You could have done the honourable thing by growing a backbone and apologizing, not making any comments, or if I am being motivated by nastiness provide a vigorous defence as to why there was no cherry picking involved.
You did none of the above which is further confirmation of your guilt and is indicative of your true intellectual level which includes one of the most ridiculous arguments I have ever encountered by making an issue of my knowledge of fluid mechanics which ‘only goes’ to third year applied maths undergraduate level.
This at the very least gives me the ability of spotting BS such as the downwind stream tube being a permanent effect which belongs in the realm of La La land.
Even a high school science student should understand without the benefit of fluid mechanics there are no permanent effects due to turbulence mixing.

The other point is your ongoing strawman attacks that I don’t understand basic physics which you could have addressed by answering my ongoing question of how windmill effects are permanent within the optics of fluid mechanics.
Your failure to do so is indicative of dishonesty as the reality is you are profoundly ignorant and unable to recognize the debunking of your nonsense is based on textbook fluid mechanics.

Maybe I should also consider the possibility you are deluded into thinking a paradigm shift in the field in which case, I’m sure Messrs. Dunning and Kruger will be very interested in taking you up as a test case.
In the meantime if you can’t post anything constructive stop posting.

 

[sjastro]

One can neither create nor destroy energy. One can merely convert it to something else. So kinetic energy (wind) that is converted to electricity is no longer available. But this would be true of forests, as opposed to bare plains. Even in Iowa, where such wind generators are very common, I doubt if you could measure the change in winds over a day. Mike is right in principle. I just don't think it's a significant factor.

If you inject a dye into water, the dye as it comes out of the needle forms a stream which eventually dissipates further downstream due to turbulence.
Now consider the case of the downwind stream tube where the wind velocity is less than its surroundings.
Air generally has a lower Reynolds number than water but in a stream tube it is considerably higher which means turbulent flow is more prevalent and the velocity difference is eventually lost through turbulence mixing.
Then there is the pressure differential to consider between the downwind stream tube and its environment which will also equalize further downstream.

By comparison water which has a kinetic viscosity of 1 x 10⁻³ Pa.s, a density of 1000 kg/m³and a velocity of 10 m/s over the length
L = 100 m, the Reynolds number is:
Re = 1 x 10⁷.

The idea the downwind stream effects are permanent is pseudoscience and as the evidence shows the velocity deficit or difference eventually drops to zero.

 

[timewerx]

But the wind does not remain slowed down. It then picks back up to its original speed once the diffusion from the windmill's sails cease to affect it. Sjastro has shown many, many, many, MANY videos that show exactly that from groups a lot more educated on the subject than you, and you remain thinking that you have a leg to stand on, when you can't even get the basic analogy of what a greenhouse is!

I agree. Wind is created when warm mass of air over land rises up and cooler air moves in to replace it. Warm air will rise, no matter what. Nothing will ever stop it. Wind will simply find its way around to maintain average speeds.

However, I used to experiment with miniature wind turbines, they deflect some (not all but some) of the wind around them even more when they're bunched up together.

Given their close proximity to the ground, they will deflect some of the wind away from the ground. I wonder if this makes the wind pick up less moisture from the ground. But it will definitely pick up less heat from the ground in the vicinity and downwind of the wind farm and may lead to hotter and more humid conditions in these areas due to reduced cooling.

Eventually that wind or air current will rise up over warm spots over land if there is less moisture in the air mass, it will create less clouds. If the air current is also cooler because it picked up less heat from the ground, it may not rise high enough or in less volume to create clouds and keep more humidity in water vapor form. Clouds help reflect solar heat back into space and helps cool the air and the ground if they fall back as rain. Water vapor is a greenhouse gas and it would be better if water exists in the atmosphere in condensed form as clouds.

See here a CFD (Computational Fluid Dynamics) of wind farm / wind turbine installation showing air current being slowed down at the ground level. Higher wind speed towards the red colors.

The effect some distance downwind is still significant:

The wake still takes quite some distance (50 km) to recover and that's a lot of ground area

Wind farm blockage and wake effects | UBC Okanagan CFD Laboratory

Wind farm wake recovery: Space constraints and electrical tie-in costs force many wind farms to be constructed within close proximity of other wind farms. The low-momentum/high-turbulence wake downwind of large wind farms may require 50 km or more to recover, undermining the energy generation...

cfdlab.ok.ubc.ca

Anyway, I'm not criticizing wind energy as a problematic source of energy, in fact, it may be the cleanest, most ecologically-friendly source of energy. The main problem stems from the fact, our society have massive energy demand and possibly greatly exceeding what is necessary to operate our advanced technologies.

 

[The Barbarian]

Yes, but that also does not mean that the wind just stops. It's like the water cycle. There will always be wind generated, and thus there will be no drop-off in wind via wind farms nor a slowing down of wind. It's continuously going.

Since wind ultimately depends on differential solar heating. Since solar inputs continue, there will be wind. Topography, like forests, hills and mountains and wind farms will absorb some of that kinetic energy, which will be replaced by more solar heating. My observation is that wind generators are a rather minor factor in this energy transfer.

 

[Mountainmike]

But the wind does not remain slowed down. It then picks back up to its original speed once the diffusion from the windmill's sails cease to affect it. Sjastro has shown many, many, many, MANY videos that show exactly that from groups a lot more educated on the subject than you, and you remain thinking that you have a leg to stand on, when you can't even get the basic analogy of what a greenhouse is!

Another one who doesnt get energy balance.
do none of you understand basic physics here?

if you take energy out, the kinetic energy sum has decreased in a closed system.

it doesn’t cone back to original speed unless you put more energy in so something changed permanently.
you describe a perpetual motion machine. Try patent it, see what happens:

it seems sastros inappropriate use of big words has confused our other non scientists here.

meanwhile in the real world beyond sastros grade 8 math, if you change convected moisture by slowing the wind all bets are off on cloud formation, and if cloud formation changes , then sun energy incident changes , and so climate will change . The question is how not whether.

My message is there could be a problem created by windmills, and nobody knows enough to deny it.
least of all sastro with tramlined thinking, trying to use big words to impress, or insult, but forgetting the basics, along the way.

As aPROFESSIONAL physicist used to modelling such things, and finding the holes in other peoples assumptions , I think there could be a problem. It is all I have said,

There are too many political agendas and commercial interest to seek the truth. So studies will downplay the problems for now. Until it is so obvious even Sjastro can see it, and so it becomes a fashionable bandwagon.

 

[Warden_of_the_Storm]

Another one who doesnt get energy balance.
do none of you understand basic physics here?

if you take energy out, the kinetic energy sum has decreased in a closed system.

it doesn’t cone back to original speed unless you put more energy in so something changed permanently.

it seems sastros inappropriate use of big words has confused our other non scientists here.

But Earth ISN'T a closed system! It's open! Energy comes in as readily as it goes away.