Wind turbines create fog and coulds - what?

My guess is the air is compressed, and as you compress air, it tends to "squeeze" the water out of it, as the same volume of water has to fit in a smaller volume of air. So I would speculate that the air somewhat compressed as it comes off the blades.

 

I was just reading that water vapor in the atmosphere is a much greater cause of global warming than carbon.

 

When the humidity is very close to 100%, and the air near the surface is layered with significant temperature differences across a short vertical distance, it takes very little disturbance to turn clear air into fog/clouds, or vice versa.

 

Huh?

Citation please,,

 

There is almost no elemental carbon in the atmosphere, most of it has oxidized into CO2.

So, Wind turbines lower global warming by condensing water vapor into fog and clouds? (Water vapor is the gas form, clouds lower atmospheric tempuratures due to reflectivity)

 

When I was a kid I believed that the steam coming out of power station cooling towers was where clouds came from.

 

The article in question refers to wind turbines near water. The air in these areas is often stratified, with a thin layer of moist surface air. The wind turbines act like giant mixers, mixing the moist surface air with cooler upper air. The resulting drop in temperature causes the moisture in the air to condense, producing fog.

You see something similar with advection fog, where a layer of warm, moist sea air moves in over colder ground.

Tom

 

Interesting - we should install a bunch of wind farms off the coast of northern California where fog has decreased 30% over the past century and is threatening redwoods who rely on that moisture. Don't know if there is enough wind off the coast up there to make it worth-while, though.

 

Fog and clouds are usually brighter then what is under them and therefore reflect light and heat back up and out causing cooling not heating!

 

I think it's because turbine blades are airfoils.

Haven't you guys ever looked out the window when you're flying. If you're in humid air, you'll see fog form at the back of the top surface of the wing, and you'll see condensation on the top surface of the wing.

Here's a couple of sites with pictures and explanation.

[ame="http://en.wikipedia.org/wiki/Wingtip_vortices"]Wingtip vortices - Wikipedia, the free encyclopedia[/ame]

Wing Condensation On Fighter Jets — Tech Ops Forum | Airliners.net


The bernoulli effect means that the air pressure drops as air passes over the curved part of the airfoil (aka, lift occurs). If you take a gas and reduce the pressure, the temperature drops (same principle as the expansion coils on a 'fridge.) Take nearly-saturated air, drop the temperature while making it turbulent, and you get fog.

My guess is that the effect is pretty small for a typical turbine, so you only see it when the air is right at the dewpoint -- hence you might see a persistent fog trailing downwind of the turbine, because the air is so close to saturated -- it doesn't immediately evaporate back to water vapor.

Neither of the pictures in the articles looks to be fog generated by the turbines, through -- it looks like a bunch of turbines in an existing fog bank. In both cases, the fog extends well beyond the turbines. (One of the commenters there said the same thing.)

Ah: Here's a much better picture, which, disturbingly, does not appear to support what I just said above. Ah, well.

 

Wind turbines can generate "angel mist" from the low pressure, but the amounts are small and localized. The fog effect comes from stirring up the air.

Tom

 

I stand corrected.

 

Getting off-topic, but I wonder why they didn't offset the turbines to the prevailing wind direction instead of having them all line up in columns and rows.

I would think that the turbines in the back would get higher wind speeds that way, but maybe they're far enough apart that it doesn't make a difference and it makes installation a bit simpler/easier.

 

Damned interesting question. I stumbled across several discussions of exactly that, and it boiled down to, no matter what you do, sometimes the wind is going to blow from the wrong direction.

That said, yeah, seems like straight rows might minimize some materials use or something, but certainly creates more highly variable output -- when the wind is just right, your power drops 30% on N-1 rows of turbines.

Surely with that much money invested, they've thought it through. Possibly, the fraction of time when the wind is in perfectly the wrong direction is fairly small (looks like even small change in direction would have given the downstream turbines clean air.) That, coupled with the natural variability of the power source anyway, and maybe they just rationally don't much care.

All this is armchair speculation and probably worth as much as my last answer was.

Cool picture nevertheless.

 

I disagree intuitively. Air with enough velocity to have useful power isn't going to be stratified enough. Also, enough wind to generate significant power isn't going to have enough effect to mix up that air. Perhaps better said, if there is enough wind to give some real power, then the air is going to be mixed up way more by the wind than by the blades of a wind turbine.

The compression of the air (from the air foil!) is changing the relative humidity and therefor the dew point.

 

Water vapour caused one-third of global warming in 1990s, study reveals | Environment | The Guardian
"The research, led by one of the world's top climate scientists, suggests that almost one-third of the global warming recorded during the 1990s was due to an increase in water vapour in the high atmosphere, not human emissions of greenhouse gases. A subsequent decline in water vapour after 2000 could explain a recent slowdown in global temperature rise, the scientists add."

 

I'm going to butt in here. I was with you, originally, but after looking at that picture, I'm pretty sure I was wrong.

Two details matter.

One, the fog streams start well behind the turbines.
Two, there's a well-defined low-lying foggy stratum coming in upwind.

My interpretation of that picture:

The turbines set up a vortex of disturbed air, it expands as it moves downstream from the turbines, it finally contacts the low-lying fog layer. At that point, either it just kicks the existing foggy stratum up into the air (no new fog, just redistributed fog), or, maybe, by mixing air layers, in addition, it creates new fog. Sure looks like additional fog creation, but I'd like to see several such photos before I'd be completely convinced.

Also, note that it's a pretty featureless plane upwind -- nothing to mix the air before it hits the turbines. Plausible that you might get rapid-but-laminar flow upwind.

 

And again, water vapor is not fog or clouds. (perhaps it is coulds?)
Water vapor is the gaseous form, it raises temps. Fog and clouds are water droplets, they reduce temps by reflecting sunlight.

 

It is a kind of torque effect that spins things to the left and sucks the life out of businesses, retirement accounts, and the stock market. Combined with the vacuum produced by the loss of jobs and empty promises, the atmospheric low draws foul weather and storm clouds into the region. In a kind of Newtonian reciprocity, the void is quickly filled by a growing trade deficit and national debt, reaching a new equilibrium in which everyone, particularly the next generation, gets less. Thank you for the opportunity to cut through the fog.