Wind Power - Is it truly green?

Question

The whole world seems to think that wind power is environmentally friendly.

How can this be so when we are now extracting many thousands of GigaWatts of power from the wind by means of wind generators. This must in turn have a braking effect on the earth´s air currents. Look what happens when El Nino occurs causing the water currents to reverse off South America? It causes droughts + fires in the USA and floods in Australia.

I will be very relieved if someone can convince me that wind power will not have an adverse effect the worlds weather patterns.

At the moment it is my opinion that the whole world seems to be burying it`s head in the sand on this issue! I´m all for green, renewable energy, but is wind power truly green?

Martyn Pridham

Answer 1

I think with any system if energy is removed then the 'natural' state of the system must be disrupted somehow. With wind we must consider how much we are taking out of the overall system. The first thing to note is that the winds are largely driven by solar heating - causing high and low pressures to form through air density differences which act to even out by transporting air between them. The sheer scale of the energy and the vertical distribution of the wind means that even with our best efforts we can currently only harvest a small amount of the wind energy at surface level, let alone for the whole 10km of the troposphere. The effect that this will have is for the wind farm to be 'seen' by the lower winds as an area of increased surface friction, in a similar way to a large tree might be seen. This might lead to local effects close to the turbines but I don't think it would be noticeable without high-tech equipment. As for global effects like El Nino then we would have to be seriously affecting the upper controlling winds (like the jet stream) and global circulation cells.
I would say that if the entire globe was covered in wind turbines then I would expect some dampening of the atmospheric circulation system, but since this is unlikely and we currently (key word!) extract a tiny percentage of the available energy then it is not of concern.

According to Greenpeace, we currently extract 6.0xE4 MW per year in the world. The total energy in the global wind is estimated at 3.6xE9 MW. With five orders of magnitude difference we have a long way to go before we impact on the wind in the atmosphere. Also there is a limit of 59% (called Betz limit) on how much we could extract.

To be green I think we should reduce our energy consumption, be efficient, and use the whole set of renewable available to "play with a full set of clubs". In addition, I think we should return to this issue if wind power begins to extract a more significant amount of energy from the atmosphere.

Answer 2

Hi Martyn,

It's a very good point you make and it's reasonable to think that wind turbines would have a braking effect.

If you look at the structure of a turbine it's mounted atop a slender (usually circular) column which is aerodynamically shaped - the wind can easily pass the structure with only minimal resistance. Similarly, the blades are designed so the wind easily passes by them.

Wind in motion is fluid, it gets diverted when it hits the turbine but reforms in the lee of the turbine and continues on it's way. The effect that turbines have is microscopic. Trees and buildings on the other hand are anything but aerodynamic and these can impede windflow. You've perhaps noticed that if you're in a forest it can be very calm but outside the forest there can be strong winds blowing.

To maximise windflow turbines are spaced apart (also to prevent the blades touching), the last one I visited they're 110 metres away from each other which in comparison to some is quite close.

An average modern wind turbine provides enough energy for about 1000 people, 6.5 million of them could supply the world's energy needs - it might sound like a lot of turbines but it's only one per 78 sqaure kilometres, not nearly enough to have any noticeable effect.

Answer 3

Fear not! Wind is powered by uneven solar heating of the atmosphere. As to any drag effects, trees and mountains create far more drag than a few wind farms, which only take a TINY percentage of the available power. There's no way that could ever change. Wind is one of the best possible means of generating power. The only problem I've heard of at all is that sometimes birds get caught in the turbines. But that is rare, and easily remedied using sonic or visual deterrents.

Some solutions really ARE solutions.

Answer 4

Martyn, i dont think it will have any effect on wind currents at all.
Trees, buildings etc all catch the wind in a similar way but instead of wasting this energy, wind turbines harness it.
Secondly, a little turbulence at ground level caused by static objects will not affect air currents as they are higher up in the atmosphere.

Answer 5

I doubt we can build enough of them, and wind is a renewable resource, rather than a current like the gulf stream for example.

My concerns with wind power are two fold. Firstly, just what is the pay back time (energy used to manufacture v energy obtained), and second - they make a hell of a racket.

Answer 6

It might have a very small effect. But the CO2 from burning fossil fuels that is not emitted because of wind power has a far far greater (bad) effect on the weather.

Nothing is perfect. But wind power is pretty good. Actually the main problem is keeping them from killing birds. They're designing systems to minimize that:

http://www.wisconsinbirds.org/WindPowerandBirds.htm

Answer 7

Yes I think so at least it doesn't make CO2,which of course GOD tuck care of when he put plants on the earth that need CO2 to live.The amount of wind generators could be increased 10 folds and still not affect the wind speed where u could honestly measure it.

Answer 8

No they are not:

1. Not efficient (only work when the wind blows0
2. Huge carbon footprint to manufacture and build.
3. Environmentally noisy (in the papers: one couples home near some turbines is now worthless and their lives are lighted by the noise).
4. Bad for birds (swans etc which the blades can kill)
5. Look terrible and spoil the landscape

Answer 9

i think it is great. period.