Do Windmills 'take' the energy out of wind?

My sibling and I were arguing over the Thanksgiving holiday about wind generators.

He is older, and may have a bit of different understanding about things, but he is under the impression that windmills 'remove' the energy out of wind. That if one builds too many windmill generators, that there will not be enough wind for any of them.

Is this true? I mean, my position was that yes if you put them two closely together, that you might not get the efficiency one would like, but it would not stop all winds downwind.

I thought wind was created by the sun heating the earth, and the earth cooling in areas.

Neither of us are scientists, if you couldn't tell already.

Any help on this would be appreciated.
DocMoreau

There is only a finite amount of energy in the system (ie the universe). So yes of course windmills remove energy from the wind - they don't magically make energy, they transform it firstly into a rotary movement that is then transformed once more into electricity.

Energy is NEVER created or destroyed... All it does is change form

But the amount of possible energy that can be taken from the wind is huge - and the amount that is really taken is tiny.

Did you realise that when they sling shot satellites around planets like they did with the voyager probes they also 'steal' energy from the planet.

All's fair in love and thermodynamics

First law: "Energy can neither be created nor destroyed. It can only change forms."

Second law: The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

Third law: As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

Really the first law most relates to your question



[edit on 1/12/2008 by Now_Then]

Yes, any time you remove energy from a system, it will leave that system with less energy. If a windmill didn't slow down the windsm, you could put an infinite number of them back to back and each one would put out as much energy as if it were all alone.

The windmill actually works by transferring some of the energy in the form of pressure differential (which is what you are referring to when you mention the sun heating the earth) into rotational kinetic energy in the windmill blades. That energy drives generators and is transformed into electrical energy.

Now, as to the real question, will removing that energy from the winds harm the environment... I honestly don't know. I feel certain there is a level of windmill existence that would be no problem, but so far no one (that I have heard of anyway) has investigated whether the windmill farms springing up across the country (and around the world) have made an impact on climate, and what that impact might be.

It's a great question, and one I have been musing over for some time. It can be shown that there is a correlation between the two (windmill farms and climate changes), but without study, we simply do not know if that correlation is actual or coincidental, nor the extent of the impact if any.

TheRedneck

Thanks.

So what we are saying is that yes, with enough windmill generators, there is the potential to remove all the energy from the wind (and convert it to electricity), but that it is the wind that would die, and not the energy itself.

To a degree, I am correct in saying that the wind itself may be 'replenished' by the heat and cooling from the sun's rays, but that the energy is 'taken out' of the wind.

Very interesting. I wonder if this thread could be a launching point into researching whether or not wind farms are effecting climate change or causing environmental concern.

I remember a few years ago that the Kennedy Clan was involved in something to do with the wind farms off Martha's Vineyard being considered 'eyesores' to the natural beauty of the environment.

Man, my brother will love knowing that he was 'right' even if it is not all the way correct what he was saying.
DocMoreau

There is never any more or less energy in the universe than there is at any given point in its history. However, windmills do work on the principle of transfer and conversion of energy. The wind has kinetic energy because it is in motion. That kinetic energy is transfered to the blades of the windmill and makes them turn. That turning motion is used to power a generator, where the kinetic energy is converted to electrical energy.

So yes, wind turbines do 'remove' the energy from wind, but the total energy in the system stays the same.

No, they take the free electrons from the air by the physical manipulation of an electro-magnetic field within an electric generator. The kinetic energy from the wind is converted into mechanical (turning), heat, and sound.

Originally posted by DocMoreau
So what we are saying is that yes, with enough windmill generators, there is the potential to remove all the energy from the wind (and convert it to electricity), but that it is the wind that would die, and not the energy itself.

Errrmm, look at it like this - if all the energy in the closed system (I've just declared the world a closed system!!... no energy will enter OR leave - what we have now is it, %100, no more no less) is shared out equally - then no energy - or matter (matter requires energy to move) would change form / move. So yep, eventually no wind, but in my closed world I think wind would take a long time to stop - you got to wait for the oceans to stop first, then the geological activity - and finally the last little breath of the last little dodo.

Then yes eventually the wind would stop, the sea's would stop, the fires would stop, the animals and the plants would stop.

The mud slides and the glaciers would stop, after the building have fallen down the mountins will begin to fall down... One day the entire surface of the Earth (my closed system) will be level - nothing can fall any lower, nothing can roll down hill.

All the chemical reactions and physical interactions that will EVER take place have now happened - the Earth is a very boring place by this time. No temperature change at all - that would mean energy being moved, every thing is uniform heat, no sound of course, that is energy.

All the metaphorical ripples from the pond have gone - the pond is still.

All energy has reached equilibrium.

Second law: The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

This is the most depressing law in Physics..

So on that note I lift my decree that the Earth is a closed system ~ one onto it's self and I allow the glorious influence of the universe to 'mix it up some' - a reprieve, of sorts, for the planet - for we have now still in a closed system (the Universe) - that, according to the 2nd law one day also reach equilibrium it's self.... And then we would want another closed system to inject some energy to mix this one up.

Of course none of this takes into account dark energy / matter.

Phew




[edit on 1/12/2008 by Now_Then]

Originally posted by DocMoreau
Thanks.

So what we are saying is that yes, with enough windmill generators, there is the potential to remove all the energy from the wind (and convert it to electricity), but that it is the wind that would die, and not the energy itself.

just the same as trees block the wind, and buildings block the wind....so will windmills.

we have a TON of windmills out this way. some of the old timers think it will make it more windy. Goobers.

it is a HUGE waste of time/money. When we need the wind the most (hot dog days), the wind blows the least. And they can't store the energy. So all those generators are left in an idle state (running) constantly to meet demand spikes.

it is a sham. we are wasting time and money on a sham. but lots of broke old farmers are making a killing on windmill leases.

[edit on 1-12-2008 by bigfatfurrytexan]

The earth is not a closed loop energy system. Energy is given to the earth from every celestial body that eminates light or radiation. It would be impossible to take all of the wind energy. You would have to have generators in every layer of the troposhere to the point of blacking out the sun in order to take all of the wind energy. Which coincedentally by blocking out the sun you would kill the majority of wind/wind energy. As far as the comment about generators taking electrons from the wind you are incorrect. Study some more physics specifically electromagnetic physics and thermodynamics.

Yep, wind generators slow down the wind as they generate power from it. Put too many too close and they'll all generate less power. People who work in the wind power industries are very much aware of this, so the spacing and placements of the windmills you see in wind farms represents the optimal economic balance of cost to power generation, based on the amount of land used, the number of generators built, and the amount of power per generator.

As energy is removed from the wind, the wind slows down. Energy from the wind is transformed into electrical energy and waste heat by the windmills. The wind gets it's energy from the sun, so it's not like you can run out of wind. All the energy in wind would otherwise eventually become heat and the kinetic energy of whatever it moves.

I honestly don't think that windmills harm the environment by slowing the wind. They might chop up a few rare birds from time to time, but that's a different issue. Windmills are pretty insignificant compared to nature.

I've been wrong before, though.

reply to post by DocMoreau

So what we are saying is that yes, with enough windmill generators, there is the potential to remove all the energy from the wind (and convert it to electricity), but that it is the wind that would die, and not the energy itself.

Purely theoretically, all usable energy is simply a matter of energy differential. Solar radiation (energy from the sun) is received by the planet. Some of it is converted through chemical means into plant growth and thereby chemical energy in the form of sugars and complex organic molecules. Some is converted into heat by striking an absorbent surface. This heat then is transferred to the surrounding air and creates density differentials that create wind, steered by the viscosity differences between earth, water, and air and the rotational influence of the spin of the planet.

A frequently misunderstood concept is that energy cannot be created nor destroyed. That concept is true; In fact, energy exists all throughout space. It is simply not detectable unless there is a potential difference between the ambient energy levels and the energy levels we are attempting to locate. If you light a match in a closed room, the heat does not disappear, but it will dissipate throughout the room in a given time so that no more energy can be detected from it. The air inside the room will all be at the exact same temperature, and to the eye it will contain no usable or detectable energy. In fact, the room is a bit warmer than before, so the energy is still there, simply dissipated so no more work can be performed by it inside the room. Similarly, when a battery is exhausted, the energy it released during its lifetime is not gone, only transferred into more ambient forms and is therefore unusable.

I doubt we will ever stop the wind, since the initial energy potential (the warming of the sun's radiation) is constantly being replenished. We could, however, slow the wind enough, theoretically, to make drastic changes in the earth's prevailing weather systems. As I mentioned before, the real question is, how much energy can we safely pull out of the wind before we start creating havoc on our weather stability?

TheRedneck

I just seen something interesting on a Horizon program about time - the length of a day on Earth 'wobbles' each day, the last measurement they took said 2 days before it was like 1.9 milliseconds longer.

He said this was because of the wind! - pushing on mountains and what not - either sppeding up the rotation or slowing it down!!!

Do windmills cause electromagnetic radiation that possibly surge out into the atmosphere when the blades are in motion. I understand that windmills too close to a home can possibly cause television and radio reception problems from time to time.

I sell and install Wind Farms.

Think of it like an eddy in water.
The blades on a turbine are not going to stop the air.

The amount of power is directly related to:
A. The amount of air displaced
B. The density of the Air

Spinning blades are a by-product, and not the cause.

Air to 'die'...that is quite amusing.