Green Fans for air circulation - question

[Carl Johnson]

I know this general subject has been discussed before. (At least: http://golfclubatlas.com/forum/index.php/topic,24106.msg444103/)  Going beyond the issues of poor architecture, wrong grass, second class courses, do they really work, etc.), I have a technical question about how the fans are used.  As explained to me:  “'How do we get greens unable to transpire to perform better?'  The answer is by removing the humid air mass from the leaf canopy.  Fans are agronomic tools whose value is no less than that of an aerator or mower.  They have been installed around bentgrass greens in the humid southeast region of the U. S. ever since most putting surfaces in the southeast were converted to bentgrass over 40 years ago.  Why?  Fans assist bentgrass growth in hot, humid environments in two ways.  First, the fan circulates cooler air over the canopy which helps to cool both the plant and the surface temperature.  Second and more importantly, the fan removes the stagnant, humid air over the turfgrass canopy which allows the natural process of transpiration to take place.  When the plant is able to transpire the entire ecosystem functions properly and thus there are both cooler canopy and soil temperatures."

Here's the question.  When I want to cool my house with a fan, I put the fan in the window or attic blowing out.  That draws air through the entire house (or room), assuming some other opening to the outside through which air may enter.  Fans placed near greens are always, in my experience, blowing toward the green.  One obvious difference is that in the house situation you're dealing with a confined space, while with the green, you're not.  Can someone give me a physics explanation of why aiming the fan away from the green would not work better than blowing air toward the green?

[Ian Larson]

Because how much air movement dies a fan produce behind it? A house is a confined space and can create a vacum affect inside it with air movement. Kinda like when all the windows are open and you leave a door open, the vacum affect slams the door shut. You'll never get that outdoors. The whole point is air movement across the green, you'll never get that by pointing it away. Why are you asking? Is it bothering you to have a fan pointed at the green?

[Carl Johnson]

Because how much air movement dies a fan produce behind it? A house is a confined space and can create a vacum affect inside it with air movement. Kinda like when all the windows are open and you leave a door open, the vacum affect slams the door shut. You'll never get that outdoors. The whole point is air movement across the green, you'll never get that by pointing it away. Why are you asking? Is it bothering you to have a fan pointed at the green?

Thanks for the insight.  Why am I asking?  Mostly intellectual curiosity.  No, it doesn't bother me to have a fan pointed to the green.  Here in N.C. we're having a lot of problems with the greens this summer, a bad one for greens apparently, and our club has just purchased a number of additional fans to put at greens.  That just got me thinking about fans and how they were supposed to help greens.

[John Moore II]

It is a lot like the human body. Even if the air temp is 100 degrees, if you have a brisk breeze, it allows the sweat to move off your body and cool it. The hottest feeling days are the ones where it is both humid and with little breeze. That prevents the sweat from evaporating off your skin. Greens are the same way, when it is humid and the air is not moving, the moisture sits down near the green surface and doesn't allow the green to dry a little bit. The water being on the green can cause fungus, etc., and (likely) can transmit heat through the soil at a higher rate than regular air. So, adding the fan allows the water to perspire/evaporate off the green surface better. (If you're a Super, please correct me, and don't jump down my throat if I got this slightly wrong)

[Matt Wharton]

Mr. Moore you are spot on correct.  It is exactly like the human body.  I am the super at Mr. Johnson's course in N.C. and he is quoting info from my most recent email to the membership.  It has been extremely hot this summer but the bigger culprit is the constant humidity and lack of air circulation.  The equation when dealing with bentgrass is simple (Heat + No Air Movement = No Grass).

[Mark Pritchett]

Welcome Matt!

[Matt Wharton]

Thanks! It is good to be here.

[John Moore II]

Mr. Moore you are spot on correct.  It is exactly like the human body.  I am the super at Mr. Johnson's course in N.C. and he is quoting info from my most recent email to the membership.  It has been extremely hot this summer but the bigger culprit is the constant humidity and lack of air circulation.  The equation when dealing with bentgrass is simple (Heat + No Air Movement = No Grass).

Welcome Matt. It pains me to know that Carl posted that here and didn't ask you directly. Whether me meant to do this or not, it makes it seem like he doesn't trust you to do your job. I hope that is not the case. The part of my post that I was worried about was my comment about the water in the green causing it to heat up more than the dry air. Is that the case where the water can cause additional heating in the green and cause more stress on the turf?

[Matt Wharton]

Considering I am a newbie I will give Carl the benefit of the doubt.  He doesn't know I am here (at least not yet).  You are very knowledgeable about what you speak.  Water is a conductor, therefore wet soils are hotter than dry soils.  The most difficult part of summer bentgrass management here in the transition zone of the U.S. is trying to keep the rootzone from getting too wet.  When too wet, the soil temperature rises to levels detrimental to root survivability.  This is why summer thunderstorms can be problematic (too much water when the temps are too high).  The fan blowing across the green not only keeps the turf a little more dry near the surface but allows for the transpiration process to function properly.  If the green were to get a little too dry we would irrigate by hand with a hose on the area in need.  It is much easier to add water when needed than to remove it when there is too much.

[John Moore II]

Matt- When I worked at Mid South (professional staff, not green staff) we had problems with over watering on hot days and ended up with a very shallow root base. We wound up having to vent the greens two or three times mid summer. My course is currently having these problems on a few greens. I haven't yet, but I have seriously considered asking them to let me get a hose and spray some water on these greens, or even operate the aerating machine with the vent tines. A couple of our greens are in bad shape.

We have a course in Virginia Beach that has bentgrass greens AND FAIRWAYS. I want to go play there right soon here, see how that experiment is holding up this time of year.

[Carl Johnson]

Mr. Moore you are spot on correct.  It is exactly like the human body.  I am the super at Mr. Johnson's course in N.C. and he is quoting info from my most recent email to the membership.  It has been extremely hot this summer but the bigger culprit is the constant humidity and lack of air circulation.  The equation when dealing with bentgrass is simple (Heat + No Air Movement = No Grass).

Welcome Matt. It pains me to know that Carl posted that here and didn't ask you directly. Whether me meant to do this or not, it makes it seem like he doesn't trust you to do your job. I hope that is not the case. The part of my post that I was worried about was my comment about the water in the green causing it to heat up more than the dry air. Is that the case where the water can cause additional heating in the green and cause more stress on the turf?

John, it should not pain you and I am sorry that it apparently did.  Note that in my initial post I quoted from Matt.  I respect and trust Matt and, of course, that's why I quoted his explanation about why air circulation helps the greens.  I have absolutely no doubt on the circulation issue.  If you'll look at my question, it had to do with mechanics of the air circulation promoted by the fans.  Sure, I could have asked Matt.  I ask him questions from time to time and always get a pleasant, straight, helpful answer.  I just thought it would be an interesting topic for the GCA.  Ian Larson did address my question.  Thanks, Ian.  From a common sense standpoint, my thinking was the house example was likely not a good analogy.  I had not thought of it in terms of a vacuum, but that makes sense to me.  My conclusion was that if you were taking air away from the green, then you'd be drawing from somewhat of an infinite space, unlike a house, and impact on the green would be negligible.  Another question, which I know Matt could answer, but might be of interest to others here, so I'll ask it now, has to do with how much air is moved and how quickly, sort of a breeze equivalent, by a fan (of which I am sure there are many sizes)?

When my interest in fans was piqued, I took a look on this board to see what I could find.  In my initial post I put in a link to an earlier discussion, which seemed to "dump" on fans, or the need for them.  Rather than get that thread going again, I decided to start a new one.  I don't necessarily want to revisit the issues raised there, but I will say that I strongly disagree with those who believe that the presence of fans necessarily indicates the wrong grass on the greens, bad architecture, and second rate courses, but right now I don't want to get into those arguments.

And, of course, welcome Matt to the GCA.

[John Moore II]

Carl, sorry for the mix-up, however, it did seem to me that it was possible that you might have been going around your super, but that only ran through my mind when he posted and said he had emailed that to you. If you did not mean your statement as I felt it could possibly have been taken, then I'm sorry.

I will say that I don't really like fans around greens, but I understand that it is necessary at times due to site constraints. Looking at Sahalee on TV today actually made me wonder how they do without them on any of their holes.

For the most part, turf grass is very similar to humans. If it is surrounded by water, it heats up muh faster; think climbing in a bath tub with either really cold or hot water, it feels much hotter or colder than air of equal temperature. Same with fans, think a fan blowing across your skin (or a green) on a hot day; they each cause the water to evaporate off the surface and that cools. I can't think of a proper analogy for aerification; perhaps Matt can give me some help on that one.

[Ed Oden]

First of all, welcome Matt!  Like Carl, I am a member at the club where Matt is the Super.  And I've had the pleasure of serving with him on our Green Committee for the last couple of years.  I have complete confidence and trust in Matt and I am sure Carl does as well.  The fact that Carl can directly quote Matt is a testament to the lines of communication that Matt maintains with the membership through his regular emails and newsletters and his availability to answer questions.  One of Matt's many strengths is his ability to explain things in a way that anyone can understand.  Much of what I know about our course is a reflection of what I have learned from Matt.  I am sure he will be a great addition to the board, although I have no idea when he will find the time to post.  The guy works ALL THE TIME...that is, except when the Hokies are playing.

[Matt Wharton]

Carl, John and Ed,

Thanks for welcoming me into the group.  Carl, I know you did not mean any "slight" which is why I gave you the benefit of the doubt.  I am new to GCA and you were not aware.  As for your question, the fans we currently use on 1, 12 and 16 and the fans we are in the process of acquiring are rated at about 40,000 cfm and will move air up to 3 mph at a distance of 125 ft.  It is not a coincidence that number 16 is the best green on the course right now and it happens to sit closest to its fan compared to the other two greens.  Ed, thanks for the shout out to my beloved Hokies!  Today is the last day of July and that means only one more month of "hell on earth" to endure before football season.  Gentlemen, the only good thing to ever come out of August is September!  John, in reference to your comment about Sahalee, I do not know anything about their facility but I can tell you from experience that when it comes to televised golf championships things are not always what they appear.  Many times facilities with fans will take them down and bring in numerous "temporaries" or "portables" to use exclusively for the week so as to not "litter" up the viewing with the fans.  Don't know if that is the case up in Washington but it happens all across the country.  Also, there are many courses which utilize fans but the tour is in town at a time of year when they would not be in use therefore they are not out on the course at that time.   

[Mike Hamilton]

I will say that I don't really like fans around greens, but I understand that it is necessary at times due to site constraints. Looking at Sahalee on TV today actually made me wonder how they do without them on any of their holes.

For the most part, turf grass is very similar to humans. If it is surrounded by water, it heats up muh faster; think climbing in a bath tub with either really cold or hot water, it feels much hotter or colder than air of equal temperature. Same with fans, think a fan blowing across your skin (or a green) on a hot day; they each cause the water to evaporate off the surface and that cools. I can't think of a proper analogy for aerification; perhaps Matt can give me some help on that one.

John,

I don't know if they use fans there, but the climate in the Seattle area is vastly different in the summer than Charlotte.  I believe on average they actually get less total rain in the summer, although from my trips there it tends to be overcast and misty more often, and daytime highs average about 15-20 degrees lower.

I would assume that the fans serve the dual purpose of cooling and drying.  The evaporative cooling occurs (this is the nerdy explanation) because of the latent heat of evaporation.  It takes an enormous amount of energy to cause water to undergo the transition from liquid to vapor...in fact if my memory is correct, it takes about 7 times more energy to turn already boiling water into steam that it takes to heat the same water from the freezing point to the boiing point.  This is the real reason why this cools (with a green, a sweating body, or in an industrial cooling tower)...when the water evaporates it absorbs that energy from your body or the green and disperses.  Moving the air with a fan speeds up the evaporation and improves the cooling by constantly moving less saturated air closer to the water.

I would think that in cooler (and in Seattle, more humid) climates the cooling would not be needed, and the evaporation will occur more slowly so the fans would not effective for drying either.

Growing up as a poor redneck in the 70s in Charlotte (in an unairconditioned house with an attic fan!), the first time I played a course that had enough money to use fans my first thought was that they were there to cool the members after putting out. 

[Carl Johnson]

" . . . Growing up as a poor redneck in the 70s in Charlotte (in an unairconditioned house with an attic fan!), the first time I played a course that had enough money to use fans my first thought was that they were there to cool the members after putting out.  "

No doubt about it . . . an important secondary function.  Carl

[Bill_McBride]

I'm looking forward to playing Carolina Golf Club in October in the Dixie Cup.

Will the fans be gone?? 

[John Moore II]

Mike-You make a good point about courses in Seattle, or a place like that. The air might blow some of the water off the green, and that would work fairly well. But the lower temperatures would put far less stress on the greens than higher temps. So, given the lower temperatures, fans are probably not needed. You really only run into problems when you have fairly heavy rain mixed with higher humidity the next day (and depending on how the rain moved through, you might not actually have really high humidity the next day) and high temperatures. Remove one of those from the equation and you have much better growing conditions for cool season turf.

[Tim Nugent]

It can be very instructive to members to take surface tempature readings without fans (soil temp, at surface and above surface, then with fans and chart how quickly the temps change.  Most golfers would be surprised at how hot (over 100 degrees) a putting surface can get.  Also, the fact that roots begin to die at high temps.  The shallower the roots, the more die.  A major reason Poa, with it's shallow root system will checkout before bent and why stressed bent will have a better chance to recover.

The study of Thermodynamics ishows the relationship between heat and humidity.  Look at how an air-conditioner works, it lowers the humidity of the air which, as was mentioned earlier, is a conductor of heat.  Air itself has little heat "holding capacity". Look at how fast the desert temps drop once the Sun goes down.  Without the Raditant energy of the Sun, the low humidity of the air lacks  the ability to retain any heat.  Most of the heat you experience is being radiated up from the soils.

[Mike Hamilton]

It can be very instructive to members to take surface tempature readings without fans (soil temp, at surface and above surface, then with fans and chart how quickly the temps change.  Most golfers would be surprised at how hot (over 100 degrees) a putting surface can get.  Also, the fact that roots begin to die at high temps.  The shallower the roots, the more die.  A major reason Poa, with it's shallow root system will checkout before bent and why stressed bent will have a better chance to recover.

The study of Thermodynamics ishows the relationship between heat and humidity.  Look at how an air-conditioner works, it lowers the humidity of the air which, as was mentioned earlier, is a conductor of heat.  Air itself has little heat "holding capacity". Look at how fast the desert temps drop once the Sun goes down.  Without the Raditant energy of the Sun, the low humidity of the air lacks  the ability to retain any heat.  Most of the heat you experience is being radiated up from the soils.

This is of course way OT, and has nothing to do with golf, but since we have now mentioned thermodynamics...

Tim, you are on the right track, but your examples are a little misleading.  Air conditioners ARE based on the thermodynamic stuff mentioned earlier, BUT do not cool by lowering the humidity of air.  They cool by cycling a chemical substance (now some form of CFCs) which easily transitions from liquid to vapor and back at appropriate temperatures.  The coolant exits your home as a cool gas and is compressed and heated.  In a condensor it gives off heat to outside air and is condensed to a cool liquid.  This is all under higher pressure (due to the compressor).  The liquid is passed through an expansion valve, and on the other side, in your home, can now quickly evaporate.  This evaporation occurs in coils and the heat is supplied from air in your home which is then cooled.  Coincidental to this cooling, moisture in the air will often condense which is why air conditioners need drains, but the cooling is accomplished by the coolant evaporation, not moisture removal.

And on to deserts.  Desert night time cooling is related to the dry air, but primarily not because of the lower heat capacity.  Cooling at night occurs by radiation heat transfer back to space...this occurs much more rapidly with ultra clear skies.

Hopefully this is of some use to superintendants

[John Moore II]

Mike-The radiational cooling that takes place in the desert is also a product of the sand and its heating/cooling properties. (given your explanation, I am sure you know this, but others here might not) The sand heats up and cools much faster than something like a standard 'black' soil that is in your backyard. This works as something of a double ended sword for golf course Supers since they need to add sand to the greens in order to promote proper air and water movement through the soil, but it also can cause the soil to heat up more because of the heating properties of the sand. These heating/cooling properties are what make the greens slightly hotter on the hot days and also slightly more prone to frosting.