Is there a limit to wind power?

[A.T.]

You could get some minor convection as heat energy from radioactive decay in the Earth's core bleeds outward. There would be some disturbance due to the lunar tides.

Volcano eruptions would probably cause the biggest disturbances. But what happens with the atmosphere as it cools down?

 

[Andrew Mason]

Interesting... as one of the reports quoted earlier suggested that hurricanes could be tamed by suitably located windfarms ..

A typical hurricane contains an awful lot of energy - more than any windfarm could use or possibly even survive. Since hurricanes start in the deep ocean regions, I don't think windfarms are going to stop them from forming.

AM

 

[Buckleymanor]

Energy conservation still applies. If there were no energy inputs, the wind would die down. You could get some minor convection as heat energy from radioactive decay in the Earth's core bleeds outward. There would be some disturbance due to the lunar tides. But by and large, yes, there would be no wind.

Does the coriolis effect have a big input. I tried to pick the bones out of these generalisations but can't distinguish if global is more important than local.http://www.coriolis-energy.com/wind_energy/wind.html

 

[Andrew Mason]

Does the coriolis effect have a big input. I tried to pick the bones out of these generalisations but can't distinguish if global is more important than local.http://www.coriolis-energy.com/wind_energy/wind.html

There would be no coriolis effect unless the air was already moving with a n-s component. So without the sun, coriolis effect would be unimportant in affecting winds. Actually wind would be unimportant if there was no sun because if life had survived it would be deep underground.

AM

 

[Wes Tausend]

Wonderful post!

And, I don't mean to catch anyone off guard. I just find some questions very interesting, and don't really have an answer, so I design over-simplified models in my head.

One thing I forgot, was acoustic energy. Trees are very noisy when the wind blows. But, as you said; "Entropy".

But these hypothetical questions are very difficult to model. You have to start out with ideal "text book" initial conditions, and then start adding in your pieces of duct tape and fans.

I've been thinking about my "torque" comment the other day, and decided it might need more research. I may be completely wrong about it.

If the Earth were a solid perfect sphere, with no features, no moon, and no skin effect drag on the atmosphere, then the atmosphere would probably get tidally locked to the sun. If you added a single tree, at the equator, would not some of the energy of the atmosphere get transferred to the Earth, via the non-perfect tree?​

​

OmCheeto,

Thanks for the accolade .

OmCheeto said: ↑"I just find some questions very interesting, and don't really have an answer, so I design over-simplified models in my head."

I like to design "oversimplified models" in my head too. I might get an argument here, but I believe these philosophical thought experiments are at least as useful as mathematics in order to completely understand our universe. One is useless without the other. Actually, math is merely a branch of the tree of philosophy, or rather it is derived from geometry and logic, both the same branch of philosophy. The best rule in my book still is: clever logical thought experiments first and foremost, promptly followed and tested by mathematical models.

OmCheeto said: ↑["I've been thinking about my "torque" comment the other day, and decided it might need more research. I may be completely wrong about it.

If the Earth were a solid perfect sphere, with no features, no moon, and no skin effect drag on the atmosphere, then the atmosphere would probably get tidally locked to the sun. If you added a single tree, at the equator, would not some of the energy of the atmosphere get transferred to the Earth, via the non-perfect tree?"

You may not be completely wrong about such a torque. According to meteorology, the Coriolis effects, (http://en.wikipedia.org/wiki/Coriolis_effect#Meteorology) that are part of the surface wind equations, cause trade winds (http://en.wikipedia.org/wiki/Trade_wind) that are distributed in a seemingly detrimental direction against Earth's rotation. Whereas the continuous replacement air to feed such a movement may come from more polar regions which are close to the slower moving upper latitude surfaces, the easterly trade winds blow counter to day-night rotation very near the equator, giving them apparent lateral leverage advantage to retard Earth's rotation via friction. In other words, this process may be counter-pressurized in areas close to Earth's axis, and then possibly more in sun-driven polar vertical loadings, leading to unbalanced equatorial surface drag.

Then on the other hand, with mixed wind directions, it also depends on how hard the wind is blowing across any given surface and how many windmills, trees or tabs of tape there are in it's path. You are quite correct, the process is very complicated, but it does appear from this knee-jerk vantage that sun power, besides that of gravitational tidal forces on water and soil, is applied to gradually slow the rotation of earth. Coriolis wind energy must come from somewhere, and I still believe it is as I said earlier, primarily the sun. But putting my earlier statement about sun energy only, in question, the wind may also be deriving energy from, and somehow robbing Earth of it's rotation... depending. Maybe we need to tap into the jet streams with Earth anchored kite generators since they are going in the right direction to keep us spinning, probably a good thing.
OmCheeto, is some of this along the lines of what you are thinking?

A tidally locked gaseous body is an interesting concept and worthy of it's own thread. I say this because basically, if there were no skin drag effect from solids, it seems our atmosphere "shell" would act unaffected by the liquids and solids beneath it, just as though it were a thoroughly gaseous heavenly body, and therefore it should logically tidal-lock either way. The tidal "periodical stretch" slowing of a rotating gaseous body might ostensibly be most minimumly caused by the "slipperier" friction of it's fluid gaseous molecules, just as tidal-lock rotational slowing gradually occurs by the supposed greater tidal friction of liquid (and greater yet, semi-solid particles). So the gas friction would seem to be lesser, but so would the rotational angular momentum of a low body mass of gas be less also. This might even be a wash as to whether an atmosphere immune to solid core friction would tidal-lock first before the core.

Wes
...

 

[A.T.]

There would be no coriolis effect unless the air was already moving with a n-s component.

Any component not parallel to the rotation axis would cause a Coriolis effect.

 

[OmCheeto]

Interesting... as one of the reports quoted earlier suggested that hurricanes could be tamed by suitably located windfarms ..

A typical hurricane contains an awful lot of energy - more than any windfarm could use or possibly even survive. Since hurricanes start in the deep ocean regions, I don't think windfarms are going to stop them from forming.

AM

Given the complexity of the problem, I'd say that "taming hurricanes with strategically located wind farms", is about as doable, as herding cats.

 

[jerromyjon]

I like to design "oversimplified models" in my head too. I might get an argument here, but I believe these philosophical thought experiments are at least as useful as mathematics in order to completely understand our universe.

You're my only living idol that I know of. Suskind seems awesome but makes no sense to me at all.

Maybe we need to tap into the jet streams with Earth anchored kite generators since they are going in the right direction to keep us spinning, probably a good thing.

I was thinking about that as well. More along the lines of balloons than kites but both works great, too. Balloon lofted kites with 3-phase generators, anchored to tracks to follow the fringe of the stream, leaving the middle open for traffic. What a wonderful world it would power, barely affecting it, while the billions of people who desire Earth's latest and greatest electrically parasitic empowerment devices trample God's green Earth with fossil-fueled locomotion and microenvironments and the infrastructure which becomes exponentially unmaintainable. Billions of people maintaining food and water is a miracle at this point. Is electricity and these devices which certainly won't last our lives really a priority?

 

[gleem]

I have a wind generator on my sailboat for charging batteries. I find that while the power capabilities of the turbines can be great for me 400 watts of energy output is too low to depend on it solely. Wind speed necessary for good output is too infrequent in the vast majority of places and at certain times of the year non existent. So my issue is consistent output. I find my 270 watt solar panel array much more reliable compared to the 400 watt wind turbine.out producing it about 3 to1 in kwatt-hrs. Along the east coast of the US and the Caribbean anyway. I measure energy in amp-hours at 12 V my consumption is about 130 amp-hrs/day about 85 from solar, 30 from wind and 25 from engine alternator. So place your turbines carefully I realize my turbine is at surface level and that there is a significant wind speed gradient.

 

[HuskyNamedNala]

The short answer, we are in the atmospheric boundary layer, every turbine does taken energy from this layer and contributes to momentum loss. However, temperature gradients due to the Earth's rotation and the sun lead to a "replenishment" of this energy, permitting wind currents via density gradients.

 

[audire]

Sorry for sounding tangential but wouldn't the next step be linking Physics, Quantum and Meta for a more complete view of the world and also is there any even hypothetical work being done on observing/testing metaphysical properties besides mathematics, which is in a way "not physically testable" except through proofs sometimes that sometimes fall short? That is to say how will science as a whole be able to bridge these gaps since I remember being told that string theory was not testable in high school yet only 4-5 years later do i see actual "hard science" observable tests actually being formulated.

 

[ToBePhysicist]

Greetings,
Answering the thread's question:
If asking about the (wind's power) as in P=w/t----->F.V_ins OR:

What determines how much power a wind turbine can produce?
The power is generated from the energy in the wind, so a turbine’s power is determined by its ability to capture that energy and convert it to rotational torque that can turn the generator and push electrons into the grid. A taller tower provides access to steadier winds, and larger blades capture more wind energy. A larger generator requires larger blades and/or stronger winds.

How much energy do wind turbines produce?
Every wind turbine has a range of wind speeds, typically around 30 to 55 mph, in which it will produce at its rated, or maximum, capacity. At slower wind speeds, the production falls off dramatically. If the wind speed decreases by half, power production decreases by a factor of eight. On average, therefore, wind turbines do not generate near their capacity. Industry estimates project an annual output of 30-40%, but real-world experience shows that annual outputs of 15-30% of capacity are more typical.

With a 25% capacity factor, a 1.5-MW turbine would produce

1.5 MW × 365 days × 24 hours × 25% = 3,285 MWh = 3,285,000 kWh

in a year.

What is “capacity factor”?
The capacity factor is the actual output over a period of time as a proportion of a wind turbine or facility’s maximum capacity. For example, if a 1.5-MW turbine generates power over one year at an average rate of 0.5 MW, its capacity factor is 33% for that year.

 

[Evanish]

Here are some links that might interest you.

This site is great. I use it all the time.
http://physics.ucsd.edu/do-the-math/2011/12/wind-fights-solar/

You should also read through the comments on this one.
http://www.theoildrum.com/node/8322

Also, there is this.
http://www.seas.harvard.edu/news/2013/02/rethinking-wind-power

 

[comen Jorum]

Before we base our argument on the "limit" we ask ourselves what is the maximum amount of power produced by the device being rotated to generate power by wind. So, wind has got nothing to do with limit of power but only its blowing strength & speed.

 

[Evanish]

Before we base our argument on the "limit" we ask ourselves what is the maximum amount of power produced by the device being rotated to generate power by wind. So, wind has got nothing to do with limit of power but only its blowing strength & speed.

Wind is power in the form of kinetic energy over time. How much of that you can transfer into electric power depends on efficiency.

 

[audire]

Before we base our argument on the "limit" we ask ourselves what is the maximum amount of power produced by the device being rotated to generate power by wind. So, wind has got nothing to do with limit of power but only its blowing strength & speed.

There shouldn't really be a limit except on consumption? In observer based setting (scientifically provable results) the limit is arbitrarily based on energy needs per say and less on how efficient an energy system really is.

 

[Evanish]

In regards to the OP Let's think about the atmosphere like a flywheel. A certain amount of energy is stored in the atmosphere. Also a certain amount of energy is continually being added to the atmosphere, and a certain amount of energy is continually leaving it. Let's say the amount of energy being continually added to the atmosphere is roughly 100 - 300 TW. If more energy continually leaves the atmosphere then the amount that enters it the atmosphere will eventually have no stored energy left. From this we can gather that the upward limit on wind power as a renewable energy source is no greater than 100 - 300 TW. Reasoning further we can establish that wind power as a renewable energy source is significantly less than 100 - 300 TW. Not all the energy that leaves the atmosphere will be turned into electricity. Some of it will be lost to ground orography and self friction. Given this reality it could almost be said that wind gathering technologies are in competition with the ground orography and the self friction for that 100 - 300 TW.

 

[OmCheeto]

...
OmCheeto, is some of this along the lines of what you are thinking?
...

After 6 hours of research yesterday, I have no idea what I was originally thinking.
About the only thing I've said, that I'll defend saying was;

Given the complexity of the problem...

Have you seen the following simulator?: "earth, a visualization of global weather conditions, forecast by supercomputers"
If you click on the "earth" link in the bottom left of the screen, the following will pop up:

The Overlay "WPD", wind power density, blew my mind, at different altitudes:

1000 hPa |    ~100 m, near sea level conditions
 850 hPa |  ~1,500 m, planetary boundary, low
 700 hPa |  ~3,500 m, planetary boundary, high
 500 hPa |  ~5,000 m, vorticity
 250 hPa | ~10,500 m, jet stream
  70 hPa | ~17,500 m, stratosphere
  10 hPa | ~26,500 m, even more stratosphere

Wind directions, and power densities, are all over the place, at varying altitudes.
I think we could cover the entire windy landmass, with windmills, at the 100 meter level, and notice very little difference.

wind power density at 100 meters above the Earth's surface​

wind power density at 10 km above the Earth's surface​

Interesting that even at 10 km, the wind is diverted around the northern part of South America.

The green circle on the images is over my house.
Wind energy density above Om's house (45°N 124°W)
100 m: 0
1500 m: 8 kW/m²
3500 m: 11 kW/m² (our highest local mountain peak)
5000 m: 34 kW/m²
10 km: 62 kW/m²
18 km: 0.7 kW/m²
27 km: 0

I was somewhat fascinated by the winds at 10 km along our local coast, so I did some calculations:
250 hPa (10 km)

coordinates         wind speed  power density
50.14°N 124.36°W    266 km/h    78.8 kW/m^2 (northern edge)
45.78°N 124.00°W    260 km/h    72.8 kW/m^2 (southern edge)

distance between 50°N 124°W & 45°N 124°W = 440 km
output at 20% extractable from just 1 meter: 6.6 gigawatts
*
Grand Coulee Dam nameplate: 6.8 gigawatts

Grand Coulee is America's most productive hydroelectric dam.

Though, a 10km tall, 440 km long scaffolding, strikes me as a bit of an economic/engineering problem. Not to mention, the wind is constantly shifting.
But, as I've said before, there's nothing like some good mental aerobics, on a rainy Sunday morning.

ps. New Zealand is about to get hammered by a hurricane. If anyone is up to it, click on the "earth" link above, and check out the "WID" for different elevations.
pps. @StevieTNZ , HOLD ON!

 

[Don harwood]

The true power of wind... bombuli.com ...

 

[Don harwood]

Betz is DOA bombuli.com 3/8 Roe Area Velocity:cubed

 

[anorlunda]

I think A.T. gave the correct answer in post #4.

On a global scale, that energy is extracted from the wind anyway by interaction with the ground / natural obstacles. On a local scale though, you change where it is extracted, and where and it gets dissipated as heat.

If there was no windmill, 100% of the wind energy must eventually dissapate in the form of heat.

When there is a windmill, we produce electricity, but 100% of that energy also eventually dissapates as heat.

Unless the locations and timing of the two kinds of dissipation are widely different on a global/historic scale, the net effect on climate must be zero regardless of how much wind power is used.

 

[Evanish]

I think A.T. gave the correct answer in post #4.
If there was no windmill, 100% of the wind energy must eventually dissapate in the form of heat.

When there is a windmill, we produce electricity, but 100% of that energy also eventually dissapates as heat.

Unless the locations and timing of the two kinds of dissipation are widely different on a global/historic scale, the net effect on climate must be zero regardless of how much wind power is used.

I worry a little about those large powerful winds higher up. Can anything we do down here influences them in some way? those things have a large effect on weather right? What if someone tries to harness them with Airborne wind turbine could that maybe effect them? How exactly does energy get fed into those winds, does any of it come from down here?

 

[RaulTheUCSCSlug]

I think it would be interesting to see the molecular interaction between the wind and as it collides through the trees and measure it. (Possibly by measuring the average ambient temperature of the wind before it hits the tree, and then measuring the temperature after) Then comparing that to other windmills.
Also I am aware of more efficient windmills that have whale like blades that "slice" through the air better, but I thought you would want windmills that take the most collision, since they will have more kinetic energy to work with?

I don't know, but living in California, the windmills do provide a nice view going down the Altamont.

http://ak7.picdn.net/shutterstock/videos/4614053/preview/stock-footage-wind-turbines-in-altamont-pass-wind-farm-california.jpg

 

[RaulTheUCSCSlug]

I worry a little about those large powerful winds higher up. Can anything we do down here influences them in some way? those things have a large effect on weather right? What if someone tries to harness them with Airborne wind turbine could that maybe effect them? How exactly does energy get fed into those winds, does any of it come from down here?

I believe the air circulates due to changes in temperature right? So I would imagine that the wind near the surface does affect it, but I think our hot pavements making the ambient temperature hotter have changed these gusts more then a windmill farm ever has. Especially since pavement and building have tended to increase the ambient temperature of cities.

 

[Evanish]

I believe the air circulates due to changes in temperature right? So I would imagine that the wind near the surface does affect it, but I think our hot pavements making the ambient temperature hotter have changed these gusts more then a windmill farm ever has. Especially since pavement and building have tended to increase the ambient temperature of cities.

I don't imagine one wind farm would matter much, but if people are getting Terawatts from wind it's a bit worrisome. I hope someone has done studies on this.

 

[jim mcnamara]

From a totally different perspective: One of the problems in power generation/distribution is control - determine where power is required and generate it to meet increasing or decreasing demand.

Wind is really variable, so in one area too much wind may require wind turbine shutdown and 20 miles away it may be nearly dead calm. What this means is that keeping the power grid in a known state solely with wind generated power is very difficult. It also may entail huge cost with today's implementation. Based on this model, the likelihood of getting to very high percentages of all power being wind generated in our lifetimes is small, without some gigantic strides in energy storage and transmission technology.

Current example of good implementation: Samso Island http://en.wikipedia.org/wiki/Wind_power_in_Denmark#Sams.C3.B8_Island

 

[Andrew Mason]

From a totally different perspective: One of the problems in power generation/distribution is control - determine where power is required and generate it to meet increasing or decreasing demand.

Wind is really variable, so in one area too much wind may require wind turbine shutdown and 20 miles away it may be nearly dead calm. What this means is that keeping the power grid in a known state solely with wind generated power is very difficult. It also may entail huge cost with today's implementation. Based on this model, the likelihood of getting to very high percentages of all power being wind generated in our lifetimes is small, without some gigantic strides in energy storage and transmission technology.

Current example of good implementation: Samso Island http://en.wikipedia.org/wiki/Wind_power_in_Denmark#Sams.C3.B8_Island

These are all valid points. But we have not yet begun to reach the optimum level of input to the grid from wind. Germany uses wind to provide about 10% of its electricity generation. Canada uses wind for about 3% of its electricity and the U.S. about 5%. Since the grid balances supply and demand, when there is demand and wind is available it displaces fossil fuel generated power.

No one is suggesting yet that all power can be generated from a single source such as wind or solar. But it is conceivable that all of our power could be renewable (i.e. directly or indirectly from the sun).

What is needed, perhaps, is a world-grid for electrical power. Solar panels in the Sahara desert connected to a similar arrays in the Gobi desert, Western Australia and Death Valley all connected to wind turbines in Europe, South America, North Africa, China, the Middle East and North America, and all joined together with hydro-electric production might be able to provide a renewable emissions-free reliable power supply for the entire world.

The real advantage of solar and wind, it seems to me, is the speed at which it can be constructed and implemented and the fact that it needs minimal operating resources. I am not opposed to nuclear and I think it is foolish to shut down existing nuclear facilities such as Germany and Sweden have elected to do. I think the concept of the Integral Fast Reactor bears looking at. But nuclear carries large construction and operating costs, and very long planning and construction time required. In the long-run, renewable energy will prevail. It is just a matter of getting the technology to do it.

AM

 

[mheslep]

But we have not yet begun to reach the optimum level of input to the grid from wind. Germany ...

Until some magically cheap and massive storage mechanism is developed, it may be that wind is already over developed in the like of Germany, given the rapid rise of its electric rates to the neighborhood of 35 cents/kWh (residential). While it is no doubt technically possible to recover much more wind energy from the atmosphere, it remains intermittent in nature, falling for moments to zero on more days than not, and occasionally falling to zero over vast areas for days. So, while intermittent power like wind can reduce the use of the existing conventional power fleet, almost none of the existing fleet can actually be closed down and replaced with wind and solar, as it would need to be to reduce cost. The result is two full capacity systems sitting side by side but running at different times, an enormously expensive scenario.

Germany for instance, has built some 73 GW nameplate (peak) of combined solar and wind in last decade or so, equal to the average load of the entire nation. Yet the size of the thermal and hydro fleet remains almost unchanged. Germany even continues to build new coal plants, with coal still providing 46% of electric generation, a larger share than in the US. The closed German nuclear plants are replaced with a tripled in size biomass combustion generation (10% of all German generation), so that Germany amazingly burns up half its timber harvest every year.

 

[Andrew Mason]

Until some magically cheap and massive storage mechanism is developed, it may be that wind is already over developed in the like of Germany, given the rapid rise of its electric rates to the neighborhood of 35 cents/kWh (residential). While it is no doubt technically possible to recover much more wind energy from the atmosphere, it remains intermittent in nature, falling for moments to zero on more days than not, and occasionally falling to zero over vast areas for days. So, while intermittent power like wind can reduce the use of the existing conventional power fleet, almost none of the existing fleet can actually be closed down and replaced with wind and solar, as it would need to be to reduce cost. The result is two full capacity systems sitting side by side but running at different times, an enormously expensive scenario.

Germany for instance, has built some 73 GW nameplate (peak) of combined solar and wind in last decade or so, equal to the average load of the entire nation. Yet the size of the thermal and hydro fleet remains almost unchanged. Germany even continues to build new coal plants, with coal still providing 46% of electric generation, a larger share than in the US. The closed German nuclear plants are replaced with a tripled in size biomass combustion generation (10% of all German generation), so that Germany amazingly burns up half its timber harvest every year.

This is all true. And these are all very good arguments for expanding the grid. The wind is always blowing somewhere in the world and the sun is always shining somewhere.

AM

 

[mheslep]

What is needed, perhaps, is a world-grid for electrical power.

If nuclear costs raise concern, see transmission costs for intermittent power. The most recent advanced transmission line completed in N. America was the West Alberta Transmission line: 500 kv, HDVC, 1 GW, 350 km, $1.7B, or $7 million per GW-mile. Imagine then, replacing a US east coast nuclear plant, perhaps the 4 GW nuclear plant completing construction in Georgia, where there's little wind resource, with transmission to ample (but intermittent) US mid-west wind. Average US wind capacity factor is 33%, so that the line must support 12 GW of wind power while it blows to replace the average of the nuclear plant. Distance is some 850 miles, so total cost based on the most recent installed technology is $23 billion, requiring right of way for perhaps six different lines across five states.