Question about effect of wind power on weather patterns

[HamdenRice]

I was watching the Sunday news talk shows, and the interview with Al Gore, and saw the first commercial of the gigantic publicity campaign being launched by T. Boone Pickens in favor of alternative energy.

Both Gore and Pickens seem to be agreement that the most immediately cost effective renewable energy source would be wind.

My question is, that assuming we launched a massive wind power initiative at the scale that Gore and Pickens are talking about -- basically large enough to replace petroleum -- we would be withdrawing a truly massive amount of energy from current wind patterns.

We have always assumed that geological forces dwarf human forces (you know, one hurricane contains enough energy to power a city for yaddah, yaddah, yaddah). But recently scientists seem to have come to the conclusion that the total of human activity is now at a scale that rivals geological forces.

So the question is: if we withdrew enough energy from wind to power our cities and an all electric car fleet and transport system, could this have an effect on weather patterns?

You know -- law of unintended consequences and all that.

[hobbit709]

1. Weather patters are more determined by high-altitude wnds

than ground level ones.

[HamdenRice]

6. Perhaps I should have specified "micro environment" rather than weather

I used to do a lot of development consulting and was amazed at how third world farmers exploit differences in micro-environments. Weather is affected by high level winds, but micro-environments are affected by various ground level factors.

[Warpy]

2. Windmills are low enough not to affect patterns at all

Consider that skyscrapers in big cities might funnel winds down canyonlike streets but not affect the weather patterns, and they're larger and more solid than wind generators. Consider, too, that wind generators are also supplying only part of the mass and resistance that reforestation might.

The little toys we have on the ground don't affect the planet much, at all.

[HamdenRice]

7. Two considerations

First of all, as a New Yorker, I can tell you that the city certainly affects the local environment. Manhattan is hotter and windier because of the tall buildings.

Funny coincidence, just yesterday I was at a bbq and had a long interesting talk with one of New York City's new "forresters," part of the city's attempt to plant 1 million trees in the next decade in order to affect the climate, asthma and other environmental factors.

Second, don't buildings just channel wind, rather than withdraw energy as windmills do? In other words, the net effect of that many windmills would be to slow down local winds.

[Warpy]

9. Buildings offer more resistance than windmills

because they flex only slightly. They're also much larger.

In addition, don't confuse local temperature and wind speed for planetary weather patterns, which is what I was talking about.

[HamdenRice]

10. Consider three pipes

The pipes are fed from identical sources -- three pools of water that sit above the beginning of each pipe that contain exactly the same amount of water.

The first pipe is one foot in diameter and runs 10 yards.

The second pipe is one foot in diameter for 3 yards, has a step down coupling to 1/2 foot in diamter and 3 yards of 1/2 foot diameter pipe, then a step up coupling, and the remaining length is 1 foot diameter pipe.

The third pipe is one foot in diameter and runs 10 yards (like the first pipe), but in the middle of the pipe, there is a series of turbines that generate mechanical power from the flow of the water.

At the end of the three pipes, the velocity of the water coming out of the first and second pipes will be almost the same. Despite the bottleneck, the second pipe loses only a little energy from friction of the stepped down length of pipe.

But the third pipe transfers a lot of the gravitational energy of the water to the turbines and the water will come out of the third pipe more slowly.

Buildings that don't move are like a bottleneck, like the second pipe, but they don't extract energy from the wind. Wind turbines are like the third pipe.

So I don't think buildings are comparable in energy extraction to wind turbines.

[Kokonoe]

3. Wind power energy when used, turns into heat.

Heat moves air, and turns into wind.;)

[havocmom]

4. from personal experience at the sites of some wind turbines, the wind continues on its way

it just spins all the pretty propellers along the way.

The wind near Livingston, MT just laughed at some huge windmills. It huffed and blew out the turbines, which simply could not keep up with the power the wind shed as it blew through. <--- true story

[Crazy Dave]

5. Answer (1) was a good answer

My main concern was wildlife and migrating birds, etc. They do have environmental impact studies and flight patterns of birds in ares of consideration. It is good to bring up these questions in my opinion because a lot of these people are only in the business for the money and really don't give a shit about the environment. Just cashing in on America's current feel good, flavor of the month, going green trend.

[ladjf]

12. The large turbines turn very slowly. The blades are clearly visible

to the human eye. Birds are too quick to be hit by one of the slow moving blades.

[HamdenRice]

13. That's good to hear nt

[Crazy Dave]

14. I see birds fly into glass buildings all the time

And they've got to see their own reflections right? They'd see themselves about to fly into another bird.

[ladjf]

17. To see themselves heading into a glass building, (1) they must

be angled directly 90 degrees to the plane of the glass, (2) the lighting would have to be correct, including the position of the sun and (3) the glass would have to be coated with a clean, mirror like film. This is a completely different scenario than flying within the radius of a large,long and slowly turning turbine blade.

[kristopher]

22. In fact radar tracking data shows they deliberately avoid the entire wind farm.

See study:

Remote techniques for counting and estimating the
number of bird–wind turbine collisions at sea: a review
M. DESHOLM,1* A. D. FOX,1 P. D. L. BEASLEY2 & J. KAHLERT1

1 Department of Wildlife Ecology and Biodiversity, National Environmental Research Institute,
Grenåvej 12, DK-8410 Rønde, Denmark.

2 QinetiQ Airport Radar, Malvern Technology Centre, St Andrews Road, Malvern, Worcestershire, WR14 3PS, UK

2006 British Ornithologists’ Union, Ibis, 148, 76–89
Blackwell Publishing Ltd

[newfie11]

31. Agreed

We have wind generators around here and the birds have no problem.

[hedgehog]

8. Here's my take on this:

1. The global climate change is a result of the shift in the balance of atmospheric gases. A marginal amount of carbon dioxide is sufficient to increase heat retention. A trivial amount of fluorocarbons added to the atmosphere was sufficient to deplete ozone at high altitudes and increase UV transmission to ground level. Thus, a small change in one component of a complex system can have a major effect.

2. On the other hand, the use of turbines doesn't add or subtract any energy from the system. All the energy extracted is eventually returned as waste heat somewhere along the line. Also, the use of wind turbines replaces other activities such as coal burning or nuclear power generation which do add energy to the system. I'd say that at worst, the wind turbine is a wash when it comes to changing weather patterns.

3. There has been a lot of R&D on wind turbines in the last 35 years. The original units had short, fast moving blades that were hell on the birds. The more recent units have large, slow moving blades that the birds can see and avoid.

[HamdenRice]

11. "the wind turbine is a wash" -- that's system wide

I was thinking about this because I think one of the proposals is to put most of the turbines in some wind corridor in the mid west. The turbines would not add energy to the system, but if we were talking about enough wind turbines to extract enough energy to power the entire country in a concentrated area, we would extract a huge amount of energy from one part of the system and distribute it nation wide (in cars, homes, and other power users). I would think it would have a local effect.

As for high altitude winds, wouldn't a significant slowdown of ground level winds create drag on higher altitude winds?

Of course, none of this to defend carbon burning. I just musing about unintended consquences of a nation powered almost entirely on wind, which is what Gore and Pickens are talking about.

[hedgehog]

15. I see where you're coming from , but what is the size of the corridor?

Even if you take a 10 mile swath, what percentage of the wind is passing through a dense line of wind turbines? Now compare that to a hundred mile or 500 mile swath.

[kristopher]

21. That isn't what they are proposing.

The idea is to move to "renewables", not "wind". Wind is but one part of a mix that would ultimately consist also of solar thermal, solar photo-voltaic, geothermal, and wave/current/tidal.

[kristopher]

16. Turbines are no different than trees, building, hills, grass and other objects that

Turbines are no different than trees, building, hills, grass and other objects that exert drag on the wind. Your distinction based on extracted energy is, I believe, false. See the wiki entry http://en.wikipedia.org/wiki/Planetary_boundary_layer

I understand the logic of the question, but I'm not sure your visualization of the aggregate surface area of the rotors is in proper proportion to the total mass of the atmosphere. Why do you think a million wind turbines (just to pick a nice round number) scattered over the surface of the planet would have appreciably more effect on wind patterns than planting a million equally distributed (turbines are spaced about 1/2 mile apart) large trees?

[HamdenRice]

18. See post 10 nt

[kristopher]

20. That doesn't address the point of the initial question at all.

We aren't dealing with a system of pipes. If you want to use a water analogy imagine the effect on the Mississippi River of scattering one dump truck full of pebbles along its entire length. Each individual pebble has a demonstrable and measurable effect, but in relation to the flow of the river, the effect of that quantity of new obstructions (wind turbines) added to existing obstructions (trees, mountains, hills, buildings, grass, waves etc) is totally drowned out.

[TZ]

19. If this was at all true

They'd be using wind farms to destroy hurricanes (shearing the tops off with wind force). Wind patterns are effected by upper level atmoshperics, not by anything on the ground.

[HamdenRice]

26. huh?

No, I don't think they would. Moreover, I don't think you can build an entire wind farm large enough to slow a hurrican between the time you know where the hurricane is going to hit land and the time it lands (ie a day or two).

[TZ]

27. They have actually floated this theory before

To put a bunch of windmills in the gulf to "blow away" or lesson hurricanes.
However the formation and strength of hurricanes actually has to do with upper atmoshpheric wind patterns..Thats why seasons like last year have lower than expected hurricanes..The formation was inhibited but the strong upper air wind shear..It kept blowing the tops off of storms.
This is why the idea that something land based could possibly affect the atmoshperics of the planet is a bit far fetched..Like people who believe that earthquakes can actually be controlled or effected by man made things..Not likely. Geology and meterology are much too powerful and complex to be effected to any large effect by things we do.

[HamdenRice]

28. I understand your specific point about wind farms and weather, but

but this statement, "meterology are much too powerful and complex to be effected to any large effect by things we do" would seem to be contradicted by global warming, dessertification, and mountain top removal mining.

[Howzit]

23. The problem with your question is that it may be understood as "what is wrong with wind power?"

Windmills reasonably damp air flow because they take energy out of the stream. Your question about if there are enough windmills, can they affect "natural flow" and cause an imbalance of sorts is not an unreasonable one.

Some say man is too insignificant to affect anything nature does. Other say, man's actions invariably interfere with nature, and the greater the interference, the greater the potential harm.

For instance, solar panels may yield a useful cooling effect greater than would result from a reduction in CO2 only, due to solar energy that would have been converted directly to heat being converted to electrical power. This solar electric power would replace electric power generated by burning fuels so the net energy flux would be reduced. Such an effect may be very localized and measurable only in cities or near concentrations of solar panels and wind farms; but what do I know.

[kristopher]

24. There is no problem with the question at all.

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, D19101, doi:10.1029/2004JD004763, 2004

Can large wind farms affect local meteorology?

S. Baidya Roy
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA

S. W. Pacala
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, USA

R. L. Walko
Department of Civil Engineering, Duke University, Durham, North Carolina, USA

Abstract

The RAMS model was used to explore the possible impacts of a large wind farm in the Great Plains region on the local meteorology over synoptic timescales under typical summertime conditions. A wind turbine was approximated as a sink of energy and source of turbulence. The wind farm was created by assuming an array of such turbines. Results show that the wind farm significantly slows down the wind at the turbine hub-height level. Additionally, turbulence generated by rotors create eddies that can enhance vertical mixing of momentum, heat, and scalars, usually leading to a warming and drying of the surface air and reduced surface sensible heat flux. This effect is most intense in the early morning hours when the boundary layer is stably stratified and the hub-height level wind speed is the strongest due to the nocturnal low-level jet. The impact on evapotranspiration is small.

snip

4. Summary and Discussions

<29> This study used a new parameterization to numerically simulate the impacts of a hypothetical wind farm in the Great Plains region on the local meteorology. Results show that wind farms significantly slow down the wind at the turbine hub-height level. Additionally, turbulence generated in the wake of the rotors can enhance vertical mixing that significantly affects the vertical distribution of temperature and humidity as well as surface sensible and latent heat fluxes. The impact is strongest in the early hours of the day primarily due to the strong hub-height level winds associated with the nocturnal low-level jet. Also, the nocturnal boundary layer is stable with large vertical gradients of momentum, humidity and temperature. Under this situation the effect of enhanced vertical mixing is likely to be larger than that in a well-mixed diurnal boundary layer.

<30> A wide range of typical summertime synoptic atmospheric boundary conditions are used in this study and hence, our conclusions regarding the interactions between wind farms and atmospheric flow are generally robust. However, the surface flux signals are probably valid only for relatively wet and cool soil conditions. More work with other types of land surface boundary conditions is required to test the robustness of the surface flux signals.

<31> This study takes into account only localized processes with timescales of the order of days. Processes with longer timescales are important for land-atmosphere interactions. Since high-resolution mesoscale models are computationally expensive, a coarse resolution general circulation model (GCM) can be used to investigate this issue. This will also let us explore the seasonality of the impacts of wind farms on local meteorology.

<32> Observations show that turbine Cp and rotor-generated turbulence are weak functions of the background wind speed. For simplicity, we assume them to be constants. The sensitivity of our model to these assumptions needs to be tested. Parallel to these modeling exercises, it is imperative that field observations be collected at different wind farms to improve the calibration of our rotor parameterization. Another issue of importance is the relevance of the size of the wind farm. It needs to be seen if the environmental impacts are constant or scale up or down, as the wind farms get larger or smaller.

<33> This is a preliminary study meant to highlight this issue as an interesting problem that requires detailed investigation. The results however can have significant implications for wind power engineering. The findings suggest that reducing rotor-generated turbulence will not only reduce the meteorological impacts of wind farms but also increase the efficiency. This work also demonstrates that mesoscale modeling can be a source of valuable information with many potential applications including environmental impact assessment, site selection and array design for wind farms.

http://www.agu.org/journals/jd/jd0419/2004JD004763/

The discussion really focuses on the area directly under the turbines.

[HamdenRice]

25. Thanks! That seems to point to a definitive answer

although the paper suggests, rightly, I think, that this is problem that needs to be investigated, not so much with respect to whether we should move to wind power, but where to locate wind farms, how concentrated they should be and what the environmental impacts will be.

[kristopher]

29. It is about the same effect trees have.

I wasn't minimizing the impact earlier when I wrote that turbines are just like other objects that exert drag on the wind. One use for trees in landscaping and farming is to act as a wind break. But turbines are deliberately spaced a minimum of about 1/2 mile apart to reduce that effect.

I also wanted to point out one other thing about your pipe example: if we scale the radius of your 12" pipe to the bottom 1/5 of the atmosphere, a wind turbine on the side of the pipe would only extend about 1/20th of an inch towards the center of the pipe and would be a small fraction of the thickness of a hair.
Also the pipe would be an old one, well corroded and pitted in many places with buildups of minerals clinging to the sides of 25% of it.

Thought experiments like that can be important to understanding something properly. I know you were trying to illustrate a narrow point, but when you referred me to it as a response to my first post, it was clear you were taking much more away from it than your original point.

Once you scale it properly, you can see the answer to your original question better I believe.

[HamdenRice]

30. Interesting point about trees versus buildings

Whether we are talking about trees, turbines or buildings, I think the interesting question is whether more energy is taken out of the wind when the object it confronts converts the wind to kinetic energy.

Trees sway with the wind converting wind into kinetic energy (as do wind turbines). Buildings do not.

I would think that both trees and turbines create more drag and turbulence and therefore change wind patterns more.

As for wind turbines of a scale being considered to replace petroleum being comparable to a forest, on that scale it might mean changing the wind patterns of a prairie or desert to the wind patterns of a deciduous forest -- and that's a pretty big change.

[trotsky]

32. Buildings most certainly do sway.

Larger buildings are *designed* to do just that, and dissipate energy from the wind rather than brace against it.

[HamdenRice]

33. Marginally

The question of the OP and the preliminary answer provided by Kristopher has to do with how much wind energy is converted to kinetic energy.

Trees, like, wind turbines, convert a large amount of the energy of the wind that passes through them to kinetic energy (and the turbines in turn convert the kinetic energy to electricity).

Buildings not convert a very large portion of the energy of the wind that passes them into kinetic energy, and therefore do not absorb much of the wind's energy, so much as channel it in different directions.

That's why on a windy day, in the skyscraper canyons of NYC, it feels very windy, indeed, while below a deciduous forest canopy on a windy day, it may not feel very windy at all.

[trotsky]

34. But that's not what you said.

You said:

Trees sway with the wind converting wind into kinetic energy (as do wind turbines). Buildings do not.

And I just pointed out that buildings do indeed sway, skyscrapers especially. Comparing many standalone buildings with gaps between them and a dense tree canopy is kind of silly anyway. A better comparison would be walking down a row in an apple orchard. I guarantee you'll still feel the wind there.

[Name removed]

35. Deleted sub-thread

Sub-thread removed by moderator. Click here to review the message board rules.

[.... callchet ....]

36. Windmills

In the interest of efficiency and the windmill proliferation , why do all the windmills have only three blades?