The Phoenix area is once again under an Excessive Heat Advisory with temperatures expected to be over 115 degrees through the weekend. It’s already 110° here this morning and it isn’t even noon yet. Earlier this week I wrote about how my swamp cooler was successfully taming the intense desert heat. It just occurred to me that some of you may not be familiar with evaporative coolers, and some of you who might know something about them may have some misconceptions. Here’s what my cooler looks like:
It’s not much to look at, is it? This particular cooler was purchased brand new about five years ago, yet it differs very little from the early twentieth century design upon which it is based.
Behind the louvers are excelsior pads which are kept wet with water. A blower inside the cabinet draws fresh air through the wet pads, and as the air passes through the pads, the water evaporates, causing the air to be cooled. The heat is literally being removed from the air as it vaporizes the water.
That’s probably technical enough for this description. If you want to learn more about how it works, this Wikipedia entry is a good start.
Swamp cooler? I thought you lived in the desert!
Well, yes. At least right now. And that’s where it works the best. Properly called an evaporative cooler, there are a few possible origins of its colloquial name. Perhaps it is because the extra humidity it adds to the air, especially during monsoon season or in an improperly vented room, can make it feel like a swamp. It could be because the air being pulled through the wet excelsior pads cools just like a breeze blowing through wet swamp vegetation. I’ve even heard it suggested that they are called swamp coolers because algae growing in a neglected or improperly maintained cooler can make it smell like a swamp, but that isn’t a problem I’ve ever had in the 30+ years I’ve lived in the desert and used evaporative coolers.
Why use a swamp cooler?
- Energy Efficiency – It uses 1/4 the electricity of mechanically refrigerated air conditioning.
- Fresh Air – An evaporative cooler is constantly adding fresh air, replacing the air as frequently as once per minute.
- Simplicity – An evaporative cooler is a very simple machine, making it economical to purchase, repair, and maintain.
Why aren’t they more common?
For one thing, they only work well in very dry climates, so you are not likely to find them outside of desert areas. Once the dew point gets into the 50’s (relative humidity over about 30%) their cooling performance is severely impaired. Here in North America you’ll find evaporative coolers in the western and southwestern United States as well as in the northern part of Mexico. They are also used in the southern part of Australia.
Even some people who live desert cities have not seen one, or at least wouldn’t recognize one if they did. And others wouldn’t be caught dead using one. I think that’s mostly due to the stigma carried by evaporative coolers as a cooling means of last resort only for the poor who can’t afford “real” air conditioning. While they certainly are inexpensive to buy and install as well as being economical to operate, I don’t understand why that should make them undesirable. I have actually seen ads for RV and mobile home space rentals that state “No evaporative coolers allowed.” So apparently the humble swamp cooler is shunned even within communities that are already considered “downscale” by much of society. It’s a shame so many people are more concerned with appearances and perceived social status than they are about economy, comfort, and environmental impact.
Freshly Pressed
I had an unexpected but pleasant surprise this past Tuesday when one of my posts was selected to be “Freshly Pressed” — featured on the WordPress.com home page. That was quite an honor, and the exposure drove quite a bit of fresh traffic to the site resulting in some new subscribers, too. I’d like to welcome my new readers and remind all of my readers that comments are always open on all my posts, so feel free to surf the archives and share your thoughts.
Homeless On Wheels 
We had swamp coolers growing up here in Texas, although I didn’t realize until years later that they are completely wrong for our climate. We have lots of humidity (sometimes), and “water coolers” as we called them make that worse, but they do feel good blowing on you. I remember my dad would spray them with a water hose when it was really hot because our water corroded them and they never circulated as much water as they should.
Interestingly, the main room of our house had a regular dehumidifying compressor air conditioner, so they worked in opposition to each other.
Stay cool. It’s only about 99 here today, if that makes you feel any better!
Gip
I also have refrigerated air conditioning – having both is best because during our monsoon season (July and August) the humidity gets high enough that the swamp cooler doesn’t work as well as it does in, say, June when we have single-digit relative humidity. But you’re right, Gip, you can’t use both at the same time or they fight each other; the added humidity just makes more work for the air conditioner. Folks who have the option to use either tend to use evap through about the 4th of July, then switch over to a/c until it dries out again in September.
I’ve never heard of a swamp cooler — thanks for the little lesson on what they’re all about.
I can’t believe how hot it’s been in Phoenix. Wow.
It was 87 degrees in Ohio yesterday and I thought is was unbearable. We have really humid summers here, which creates a thickness that just hangs in the air some days.
I feel for you with that humidity, Jenny. I originally came from back east – New Jersey and New York, and also spent time in Florida. With enough humidity the 80’s are uncomfortable and the 90’s miserable. What helps out here in addition to the dryness is the fact that pretty much everything is air conditioned (including most cars), so people spend as little time as possible outdoors in the actual heat.
like gip… i grew up hearing them called a water cooler. my uncle had one and my grandmother. when we’d come here to visit from new york, it seemed very exotic to me! i liked the smell. like walking thru the woods on a rainy day. 🙂 hahaha. must have needed a cleaning?
we’re having a cool front… only 99 all week!
maybe i should move back to new york. i swear the heat hurts, literally. i cannot even image 115. it’s 9:00 pm as i write this and only 99.
i think it’s a neat little unit. tellem’ to go green and look the other way if they think it’s such an eye sore. (it isn’t.)
congrats on freshly pressed!!!
I love the smell too, Tammy. Especially the first time the cooler is run each year, with fresh pads. And that nice woodsy smell is normal; not a sign that it needs cleaning. The pads are excelsior – aspen wood shavings – so the smell is indeed that of wet wood.
I remember sitting in front of the swamp cooler on my aunt’s farm (this was in Kansas, it would work on the hottest days – it was usually dry) and feeling the little escaped water droplets hit my face.
I’ve always wondered why nobody has combined a swamp cooler with a heat exchanger so you can cool some dry air and blow it in without raising the humidity inside.
Hi Bill. If the cooler was spitting water droplets, then it was probably out of adjustment… most likely the water flow was too fast. As for your idea of a heat exchanger, iIndirect evaporative cooling alone would not be efficient enough. They do, however, have two-stage coolers, that use a combination of indirect and direct evaporative cooling that can deliver air that is both cooler and drier than a conventional direct evaporative cooler. They are also more complex and more expensive, but depending on the application, the improved performance can help offset the additional cost.
115 degrees is a lot like hot! I’ve never used a swamp cooler before, but the name rings bells for me (for some reason). It seems similar (at least in class and status) as my basic little wall unit air conditioner. Are they more efficient than a wall unit? I know it wouldn’t work in Florida anyways. We’re already living in a swamp down here… especially in July and August. 🙂
Evaporative coolers come in all sizes and several styles, Tanja. They make big whole-house coolers that go up on the roof and connect to the ductwork as well as smaller wall/window mounted coolers. A swamp cooler is much more efficient than an air conditioner. As a comparison, a small window or wall unit like yours probably draws 10-15 amps, while a small swamp cooler draws only about 2 or 3 amps. But like you said, it would never work where you live. It relies on evaporation of water to achieve cooling but your air is already saturated.
Thanks for the info! Had not considered this type of cooling for in an RV before. Checking online, I find there are portable units available, which might be perfect for my needs. Am currently using one overhead AC to attempt to cool the entire space. The unit sits in the main area, so the bedroom, in the back, stays quite uncomfortable during the day. With a portable unit for the bedroom space, I could shut down the large AC when resting. Would appreciate spending less dollars and still be able to stay inside. With the temps here in Okiehoma reaching into the 100’s by noon each day for the past month, the RV has to be cooled, or the temps reach unlivable highs.
Wondering… what other types of “insulation” are you using for your unit?
Thanks again!
I dunno if a swamp cooler would work for you there; how’s the humidity?
We’re once again under heat warning for the past few days; I saw 120 on my thermometer yesterday, and 118 today. The humidity is also too high right now, as it is monsoon season, so I’m having to use air conditioning. It just manages to keep it under 85 in here.
Not much insulation; Like most RVs it really wasn’t designed for temperature extremes. It helps to keep all the shades closed though to eliminate radiant heat ingress through the windows.
Three years late comment…..
Also, you could drive two hours north to Flagstaff and have temps that are 20-25 degrees cooler and lots of tree shade to park underneath. But maybe your work is here in Phoenix.