For those of you that know anything about frost prevention, or have even seen aircraft engines like these mounted on poles in an orchard, this paper will make perfect sense to you. It makes perfect sense to me. According to PNAS, this paper was edited by the late Dr. Steven Schneider, making it even more interesting. – Anthony
From a University of Illinois press release:
CHAMPAIGN, Ill. — Wind power is likely to play a large role in the future of sustainable, clean energy, but wide-scale adoption has remained elusive. Now, researchers have found wind farms’ effects on local temperatures and proposed strategies for mediating those effects, increasing the potential to expand wind farms to a utility-scale energy resource.
Led by University of Illinois professor of atmospheric sciences Somnath Baidya Roy, the research team will publish its findings in the Proceedings of the National Academy of Sciences. The paper will appear in the journal’s Online Early Edition this week.
Roy first proposed a model describing the local climate impact of wind farms in a 2004 paper. But that and similar subsequent studies have been based solely on models because of a lack of available data. In fact, no field data on temperature were publicly available for researchers to use, until Roy met Neil Kelley at a 2009 conference. Kelley, a principal scientist at the National Wind Technology Center, part of the National Renewable Energy Laboratory, had collected temperature data at a wind farm in San Gorgonio, Calif., for more than seven weeks in 1989.
Analysis of Kelley’s data corroborated Roy’s modeling studies and provided the first observation-based evidence of wind farms’ effects on local temperature. The study found that the area immediately surrounding turbines was slightly cooler during the day and slightly warmer at night than the rest of the region.
As a small-scale modeling expert, Roy was most interested in determining the processes that drive the daytime cooling and nocturnal warming effects. He identified an enhanced vertical mixing of warm and cool air in the atmosphere in the wake of the turbine rotors. As the rotors turn, they generate turbulence, like the wake of a speedboat motor. Upper-level air is pulled down toward the surface while surface-level air is pushed up, causing warmer and cooler air to mix.
The question for any given wind-farm site then becomes, will warming or cooling be the predominant effect?
“It depends on the location,” Roy said. “For example, in the Great Plains region, the winds are typically stronger at night, so the nocturnal effect may dominate. In a region where daytime winds are stronger – for example a sea breeze – then the cooling effect will dominate. It’s a very location-specific thing.”
Many wind farms, especially in the Midwestern United States, are located on farmland. According to Roy, the nocturnal warming effect could offer farmland some measure of frost protection and may even slightly extend the growing season.
Understanding the temperature effects and the processes that cause them also allows researchers to develop strategies to mitigate wind farms’ impact on local climate. The group identified two possible solutions. First, engineers could develop low-turbulence rotors. Less turbulence would not only lead to less vertical mixing and therefore less climate impact, but also would be more efficient for energy generation. However, research and development for such a device could be a costly, labor-intensive process.
The second mediation strategy is locational. Turbulence from the rotors has much less consequence in an already turbulent atmosphere. The researchers used global data to identify regions where temperature effects of large wind farms are likely to be low because of natural mixing in the atmosphere, providing ideal sites.
“These regions include the Midwest and the Great Plains as well as large parts of Europe and China,” Roy said. “This was a very coarse-scale study, but it would be easy to do a local-scale study to compare possible locations.”
Next, Roy’s group will generate models looking at both temperature and moisture transport using data from and simulations of commercial rotors and turbines. They also plan to study the extent of the thermodynamic effects, both in terms of local magnitude and of how far downwind the effects spread.
“The time is right for this kind of research so that, before we take a leap, we make sure it can be done right,” Roy said. “We want to identify the best way to sustain an explosive growth in wind energy over the long term. Wind energy is likely to be a part of the solution to the atmospheric carbon dioxide and the global warming problem. By indentifying impacts and potential mitigation strategies, this study will contribute to the long-term sustainability of wind power.”
###
Here is the paper on PNAS: http://www.pnas.org/content/early/2010/09/28/1000493107
Impacts of wind farms on surface air temperatures
+ Author Affiliations
Department of Atmospheric Sciences, University of Illinois, 105 South Gregory Street, Urbana, IL 61820
-
Edited* by Stephen H. Schneider, Stanford University, Stanford, CA, and approved August 13, 2010 (received for review January 15, 2010)
Abstract
Utility-scale large wind farms are rapidly growing in size and numbers all over the world. Data from a meteorological field campaign show that such wind farms can significantly affect near-surface air temperatures. These effects result from enhanced vertical mixing due to turbulence generated by wind turbine rotors. The impacts of wind farms on local weather can be minimized by changing rotor design or by siting wind farms in regions with high natural turbulence. Using a 25-y-long climate dataset, we identified such regions in the world. Many of these regions, such as the Midwest and Great Plains in the United States, are also rich in wind resources, making them ideal candidates for low-impact wind farms.
==============================================================
h/t to WUWT readers M. White and Scarlet Pumpernickel
Enginear says:
October 5, 2010 at 6:03 pm
Why not? The wingtips are cutting through the air at a hundred miles per hour or so, that ought to cause enough frictional heating and turbulence (which dissipates as heat) to be worth some concern.
Since I live out here on the Great Plains and have many windmills located nearby I just have to comment on this whole silly discussion.
First of all how do you measure air temp accurately when the air is turbulent? Have suicidal pigeons with thermometers tied to them fly through the windmills?
If you want to mix the air from high to low the blades would have to look like giant soup spoons. Probably not too effective but send me some money for a study and I will build a demo unit.
Bird kills? Ha! We have waaaay too many Canadian geese around here anyway. I think we should surround the windmills with sloughs and put permanent decoys up. Give the meat to the school lunch program or something. That tough greasy bird will need a little tenderizing anyway, so a good smack with a giant blade will probably do the job.
Hadn’t heard about the issue with bats, and I do hate mosquitos, however just how high do bugs fly? Are bats actually flying 300ft off the ground in pursuit of bugs? Heres an idea! Put a couple street lights a few hundred feet away from the big bad windmill and use some of that power to light them up. Problem solved! It will be a virtual bat buffet with all the bugs flying around the light.
Hey, lighten up a little, this is funny stuff!
Matt,
A three-bladed rotor as compared to a two bladed will transmit much less vibration to the mast. The three-bladed rotor has constant moment of inertia with respect to horizontal and vertical axes, a two bladed has a large variation.
The number of blades is a compromise between efficiency and cost, weight, etc.
If there were gains in having more than three blades on a large turbine, we would see such turbines everywhere. Engineers know how to calculate…
I worked for a wind machine company in California for 7 years. These machines were specifically for frost protection and ran on gas, propane, diesel and electricity. The concept has little to do with air movement or heat generated by friction. At night the air is generally warmer as warm air rises and is replaced by cool air at lower levels. This is the inverse of daytime air temperatures, which are warmer near the ground and cooler at higher levels. The wind machine blows the warmer air from 30 to 40 feet above back down toward the ground.
At best, it will heat the ground level by 6 degrees. When temperatures go below 26 degrees there will be crop and bloom damage, even when conditions are right for the wind machine to be most effective. Running the machines at those temps are an attempt to save the trees themselves.
Our company manufactured a very large two bladed fiberglass fan to go on our machines. The fans were light and efficient. but the engines were very large, such as the Ford 450s, which are no longer used in cars. Smudge pots worked better but were stinky and produced oily smoke. Most areas don’t allow them anymore, even though frost conditions occur for a total of a couple of weeks each year.
I don’t see how windmills can help much with frost protection. My understanding is that the blades catch the wind, causing them to turn and generate electricity. If it’s windy, I don’t think there would be the inversion layer needed to blow down warmer air. The air wouldn’t be sucked from behind the fans and blown out the front at a faster speed than the wind itself. Please explain if I’m wrong.
Nothing new here – MIT reported back in March this year – . Authors Prinn and Wang studied both onshore and offshore wind farms, and concluded that onshore farms would reduce heat transport processes that move heat away from the Earth’s surface,and given the projected growth in wind farms, this could have a significant impact globally.
It should be fairly obvious that wind turbines absorb wind energy,and must therefore reduce wind speed, but the effects of this aspect haven’t been fully studied yet. It’s clear that large-scale expansion of wind farms is a form of geo-engineering – we should be sure that ALL the aspects and impacts of any such expansion is studied in detail and understood.
Finally, I can’t think of one thing that’s positive about wind farms. Power stations, factories and mines can (and in some cases are forced to be) hidden from long-distance view. Wind farms by their very nature have to be sited prominently to catch the wind; they despoil the coast and countryside, kill birds,and employ very few. Luckily they’ll all wear out in around 20 years, and perhaps common and commercial sense will have prevailed by then, and they’ll be quietly removed and forgotten as an experiment that went wrong. Unfortunately we’ll have all paid the price for these monstrosities and their ultimate scrapping.
>>A three-bladed rotor as compared to a two bladed will transmit
>>much less vibration to the mast.
But why not have more blades? Prop aircraft have always moved towards multi bladed props, because they are more efficient. Is it hub complexity that restricts windelecs to three blades?
http://media.defenseindustrydaily.com/images/ENG_EuroProp_TP400-D6_Test_lg.jpg
.
>>Ric:
>>The wingtips … ought to cause enough frictional heating
By definition, windelecs are unpowered, passive devices; so they can only take energy out of the atmosphere, not visa versa. The speed of the blade tips is caused by the wind itself.
.
@Matt
“it seems to me that having 6 or even 12 blades would allow you to capture more energy from the passing wind that you miss only having three. Just look at any old pump windmill used by ranchers and farmers and they have 20 blades.”
It’s a complicated issue with respect to all the details.
1) Slowing down air to a standstill at the turbine’s rotor plane is completely counter-productive. Which is rather easy to understand because if the wind passing the rotor plane would come to a standstill the rotor would not ‘see’ any wind at all. Thus the wind’s kinetic energy can be harvested only partially:
http://en.wikipedia.org/wiki/Betz%27_law
2) Turbine blades do not work like kites ‘deflecting’ the wind but like glider airfoils. You will probably never see a biplaned glider because the most efficient glider airfoils are slender, high-speed, low-friction/turbulence designs (turbine blades are big and their tips are indeed moving fast).
Now imagine a parcel of air passing the rotor plane. Adding more blades to the rotor would mean cutting through this parcel more often, slowing it down each time (depending on the velocity of the parcel as well, og course). But slowing it down too much willl result in lower efficiency (see 1.) thus adding more blades might actually reduce efficiency while still adding costs. Under favourite wind conditions, two or even a single high-speed blade can perform even better than three (at least in theory – in practice unbalances, resonance and material stress become very serious issues). Therefore the danish three-blade design is a very good general-purpose compromise.
HTH. I’m well aware this just sort of scatches the surface a bit and so should you.
Wolfgang
So if the wind is blowing it keeps the frost down and the wind turbines turning, and as the wind turbine turns it creates wind to keep the potential of frost down?
Why don’t I see any difference between having and not having wind turbines?
Paul Bahlin says:
October 5, 2010 at 4:39 pm
There’s never a free lunch, right? Since the entire planet is basically a solar powered biosphere, it would seem that extracting significant amounts of energy from it to create electricity, has to have an impact in the energy budget. If you get enough of these things spinning there will be an impact that nobody has thought of yet.
One effect I have considered is that much like turning on the AC in your car will create a load on the engine, how much of a load are we putting on the earth? since these are anchored in at some point we would likely add enough resistance to affect Earths rotation. Now as to how much wind resisance that would be (could be a number of windmills that we cant even generate) I have not calculated as I dont even know where to begin the math.
stevengoddard says:
October 5, 2010 at 4:08 pm
Wind farms are causing dangerous climate change. My model says that wind farms in Texas cause more floods in Pakistan.
A definite aplication of the Butterfly Effect.
Standby for the unintended consequences from massive wind farms.
I can see negative effects from the turbine wind turbulence increasing surface evaporation of water from the soil and being detrimental to plant growth.
The frosts in spring also serve to kill early weeds and control insect pests.
“The impacts of wind farms on local weather can be minimized by changing rotor design or by siting wind farms in regions with high natural turbulence. ”
What are these guys proposing then? Adding another counter-clockwise turning rotor for the benefit of a little rime beneath now and then?
And why would s/o prefer turbulent sites? Here in Germany manufacturers are contemplating hub heights of 120… 140m just to escape unfavourable turbulent conditions. Makes no sense to me at all.
Wind Farms will be next to Solar Power which can support mankind. With better designs and good understanding, we can make the best out of this resource
Hey, Ralph, can you add a distinguishing moniker to ‘Ralph’?
Barry is wrong in suggesting that wind turbines will cause cooling by taking energy from the air. They are converting the kinetic energy in the flowing air into a rotational movement. They are less than 50% efficient in this regard and much of the energy is wasted in frictional loss in the hub and gear train and in creating turbulence. The turbulence dissipates in noise which can travel a very long distance and in heating of the local air through friction. I’m sure it’s true though that the major effect on local temperatures is due to downstream mixing of ground level air with higher level air. This would seem self-evident from first principles.
As for their harm, forget bats and birds and give some thoughts for the poor humans forced to live within 2km of these things. They seriously disrupt sleep and ruin health.
Wind turbines are about as useful as garden gnomes in reducing CO2 emissions and Swamykant is either deluded or works for the wind industry. Their sole purpose is the harvesting of subsidies. Apart from green idolatry, why are these ugly monstrosities foisted upon us? As someone is bound to say: “Follow the money”
Stupid me!
Here I thought planetary rotation generated wind and the shape of the planet regulated where the directions of the wind were dominate.
Swamykant says:
October 6, 2010 at 4:09 am
Wind Farms will be next to Solar Power which can support mankind. With better designs and good understanding, we can make the best out of this resource
How does the usable energy produced by wind farms compare to the energy required to smelt the steel for the towers that support the turbines?
Never mind the amount of energy needed to extract the ore used in steel production.
Wind turbines dont have to be so ugly – I know it is a subjective thing but I think this is quite attractive:
There are a number of designs for vertical axis wind turbines but I have no idea how they compare with conventional designs for efficiency, but they do not need a wind vane design as they are omni-directional.
Not only do they affect local weather but they also affect local Doppler Radar. There are a couple of wind farms in neighboring counties and they are picked up on radar. I believe that the image that doesn’t show the interference may be due to the radar not seeing close enough to the ground, it is afterall coming from about 75 miles. Those blips are there 24/7 rain or shine and they do slightly shift around a bit.
Interference
No Interference
*mods, can you fix the links if they aren’t correct?
[Reply: No info contained in 2nd link. ~dbs]
More stuff on wind farms since I nearly live in a 4000 wind mill farm.
1. There are no crops immediately near the wind farm, because during the summer months the wind is too fierce to grow, plow, or to spray plants. So using windmills to help crops is goofy unless we are discussing little tiny home windmills and not the big industrial type.
2. Wind farms are beautiful, many people stop their cars and take pictures of these beautiful machines. Cyclist like to ride the roads near them, very beautiful.
3. I still haven’t been able to figure out why there can be 100 windmills not spinning, during no wind, and yet there will be one wind mill in the lot going like crazy — weirdest thing.
4. Wind is EXTREMELY inconsistent seasonally – there are no economically viable battery back up systems that will outlast a 4-6 month period of no significant wind, there must be an entire energy production system built to compensate for off season demand, which by definition in my way of thinking means, Wind is only a partial answer and will not save money as it’s cost will be additive to a year around system that must be built at 100% capacity anyways.
5. So far I have not seen any windmills self destruct, but it is obvious a few of them have as scraps of windmill metal litter the landscape on some hills around here. So I think it is probably a bad idea to co-locate big industrial windmills and homes and businesses.
6. Birds do not like 50 and 60 mph hour winds especially when they can fly 5 miles away and live at a more reasonable air speeds. The Altamont wind farm is a located in a sort of wind funnel between the San Francisco Bay and the San Joaquin Valley. In my opinion, Bird killing is way over stated by researchers with an incentive to overstate it. Birds do like the windmills during periods of no wind as they make great perches.
7. Ironically, the next county over is working on approving a big fossil fuel power plant just North of the wind farm. They like the placement there because they only consider the environmental impact in their county. Well the wind during 6 months of the year blows hard and directly into my county less than 1 mile away – thus no environmental impact. 🙂 ah politics. While, as I stated before, the wind farm is losing turbines every year due to maintenance issues and they are not being replaced – partly due to environmentalist freaking out about the bird kills and threatening lawsuits and getting settlements and research studies.
So get this, we have environmentalist pushing wind, wind farm is built, wind farm probably kills a few kill birds, other environmentalist sue raising the cost of the wind farm, wind farm is slowing dying, new fossil fuel plant is built. Think how much money, effort, lawsuits, papers, etc. was wasted in a process that just resulting in us doing what we always do.
Dr. John M. Ware says:
October 5, 2010 at 3:45 pm
“Is it still true that wind farms kill many birds?”
Yes, the rotating blades do but the fish are safe from the same fate for now because wind farms keep sea-levels down.
😉
The way bats die due to wind turbines is a completely different mechanism from that of birds. Their lungs explode due to a pressure drop, similarly to the way a divers’ lungs would if he returned to the surface too quickly. Their echo location allows them to avoid actual collision with the blades, but to no avail.
For a lot more information go here…
http://ontariowindperformance.wordpress.com/2010/09/14/table-of-contents/
In Ontario night time performance on average (or on the median) is no better — or worse than day time. Over a year the performance is pretty much level. This may be different in other areas I realize.
Production goes up on the front, and during a large “weather/storm” system and drops for a day or two after.
Read “Powering Ontario” to start if you want an overview of the production — then you can go through the detail data to your hearts content. Ontario has over 625 turbines and about 1,200MW on tap. However, the production is spotty at best. On occasion there is zero production. On many occasions they produce less than 5% of nameplate power.
All of the articles use the original production source data. That makes it difficult for anyone to dispute the data. So far we have had no successful challenges of the findings. As far as I know there is no similar assessment of any other wind power system.
For Medical Issues — just google Wind Concerns Ontario. They are holding a conference on Medical issues this October.
Cheers!
To read how the Ontario government is shoving these industrialized wind facilities down the throats of rural residents, please visit:
http://windconcernsontario.org
Indeed!, local people get angry hot with them.
Current so called wind turbines are useless for a multitude of well researched and published reasons.
Basically they are very inefficient at capturing wind energy, have expensive and heavy gearboxes and really ordenary generators. Engineers are asked to design them to a capacity/price demand, so thats what they do
Some of the discussion here ignores well known differences between prop planes and jets. Ask yourself which is the more efficient.