Portable Evaporative Cooler (swamp Cooler)





Introduction: Portable Evaporative Cooler (swamp Cooler)

In areas with low humidity, regular air conditioners don't work very well. A simpler solution uses water evaporation to cool and humidify air. These are called evaporative coolers or swamp coolers and are used in homes all over the Southwest U.S. Air is pulled by a fan across a wet pad, which lowers the air temperature by 20-30 degrees, and provides much needed humidity as well.

We attend a week-long festival in the remote Nevada desert, where daytime temperatures climb well over 100 degrees F.In this situation, it is necessary to be completely 'off the grid', self contained, and self reliant. In order to remain comfortable, we made portable swamp coolers out of common materials, powered by solar panels, to cool our enclosed living spaces. They have also been used at home in more permanent installations to cool greenhouses. Additionally, they could provide temperature regulation to desert homes where electrical power is not available.

Step 1: Materials

36-44 gallon heavy duty trash can with lid
Evaporative cooler pad x 12 feet x 29 inches
Hardware cloth or chicken wire x 6 feet x 24 inches
Submersible 12 volt bilge pump x 1
1/2 inch irrigation tubing x 10 feet
1/2 inch T-connector for irrigation x 1
Automobile radiator fan or solar fan x 1
16 inch diameter HVAC tubing
Large drain pan
U-bolts x 3
Solar panel and deep cycle battery

Step 2: Examples of Materials

With the exception of the fan (and solar panel if you use one), most everything can be found at a Big Box Hardware-type store (Lowes, Home Depot, etc). Much of it can be scrounged for free, as well, if you are patient and resourceful.

Step 3: Assembly

First you need to make a way for the air to pass thru wet padding:
Cut 2.5 inch diameter holes in sides of garbage can. A drill bit made for cutting doorknob holes works perfectly.  Leave the lower 10 inches of the garbage can intact, without holes. Line the inside of garbage can with blue evaporative cooler padding x two layers. Keep it in place with hardware cloth or chicken wire on the inside. Keep that in place with the U-bolts drilled thru the garbage can sides. Now you have a garbage can with ventilation holes, lined with evaporative cooler pads which are kept in place with hardware cloth wire.

Now you make a dripper to keep the padding moist:
Make a circle with the 1/2 inch diameter irrigation pipe; join with a 1/2 inch T-piece. Drill very small holes about every 2 inches in bottom side of circle for water to drip from. (If you want to get really fancy, you can insert drip irrigation emitters in the holes, which will give you a known gal/hour drip rate. )

Now we need to get the water up to the top of the pads:
Place 12 volt submersible pump in bottom of garbage can. Connect the pump to the drip ring with 1/2 inch tubing. Feed wiring thru one of the holes so you can connect to battery power later

Next, we need a fan at the top, which will suck air in, thru the holes in the sides of the garbage can, thru the evaporative cooler padding, and out the top into the HVAC tubing which will deliver cool, humidified air to the location of your choice:
Cut out a circle in top of garbage can lid and mount fan.Make sure it blows upwards! Used auto radiator fans are cheap, blow lots of air, but use a LOT of amps. So we eventually bought a solar-type fan for about $200 that runs forever on a 45 watt solar panel hooked to a deep cycle 12 volt battery. An auto radiator fan  will use more juice than this system puts out, and only runs about 20 hours before draining the battery faster than the solar panel can charge it. However, if you have enough solar panels, the auto fans REALLY put out lots of cool air, compared to just a breeze from the solar-type fan.

Wire it up! Soldering connections is a good idea, but you may want to make the wires to the top lid/fan/HVAC tubing component unpluggable so they can be removed for easier packing for transport. I also installed a switch to cut off the pump in the cool morning hours and just have a fan. It gets too cold, otherwise!

The entire unit will need to sit in a catchment basin, to collect water that drips out from the sides (this dripping is inevitable). Big black tubs from a garden center work well. you may need to drill holes in the bottom of the garbage can to allow this water to percolate back inside to the pump.

Step 4: Where Stuff Goes

First photo shows completed body without top.The next three views are looking down into the cooler, showing the pump and drip tubing. Next is a view of the top with fan installed. Then, a view of the whole thing put together, and one of it in use. Solar panel is not in view.

Step 5: Running It

You'll need about 6 gallons to fill it and wet the pads. Afterwards, uses about 2 gallons/hour, depending on the humidity and temperature. More holes in the drip ring may lead to more water usage. And that's why the emitters might help decrease water use. For home/permanent use, install a toilet float valve hooked up to a permanent pressurized water source.

Step 6: Swamp Cooler in Action in the Nevada Desert

The camper is called a Flip-pac, the sleeping area is over the cab of the truck. The swamp cooler HVAC tubing is directed to our sleeping area. The solar panel (it is pretty dusty, here) keeps the deep cycle 12 volt battery charged. The battery provides a consistent flow of electricity to the swamp cooler pump and fan. By the way, the green structure behind the truck is our fancy shower.



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    52 Discussions

    I attend more n likely the same hot dry dusty gathering. Many years we have lucked out and had some 110 to run AC's or wall plug swamp coolers. Not so this year at Chilleville. Your unit is mondo and your awesome flip pac camper with the requisite silver bubble insulation probably has similar cooling needs to my Alaskan pop up camper. How many Gallons of agua are you going through on a typical blistering playa day nap? Or lets just keep it per 24 hours average. I was thinking a 5 gallon bucket or ice chest style within my camper might do the trick. I wonder if there is a cooling advantage or disadvantage to having your evap cooler inside rather than outside. Better brush up on thermodynamics. I guess at some point the humidity inside a structure would make it so the cooling effect of evaporation was diminished. didn't notice this when using a plug in one inside a van one year. Is Bill Nye a burner? Very interested to know how much H20 your mega swamp consumes, gracias.

    1 reply

    It needs to draw in outside dry air to have continued cooling effect. Otherwise like you said, the humidity will just continue to build and eventually prevent evaporation.

    What type of fan is pictured here? To me it looks like a HVAC condenser fan but those use a ton of energy.

    if you're asking if a swamp cooler works for a house, then yes, my brother lived in NM and used a swamp cooler to cool his house. His used a fan. If you want to be off grid with your swamp cooler you need a way to blow the cooled air throughout the structure such as this person used with solar panels.

    Well, my question is if the air getting cooler (and will therefore sink) would be enough to make the air circulate: Inside air getting warmer, entering upper vent, entering swamp cooler, sink and finally enter the house again.

    You'll probably need a fan to get enough air circulation through the matting to make a difference. I doubt convection flow by itself will move enough air.

    No, you never want to recirculate inside air through a swamp cooler. All this will do is make the inside air progressively more humid and gain heat as the multiple passes reduce the efficiency of the cooler.

    What you need to do is draw hot, dry outside air into the cooler, expell the cool, moist air into the house and then let it exit through an open window before it has a chance to heat up again. As it's expelled more cool, moist air from the cooler takes its place.

    I'd think that question would depend on how large your space is, and how broken up (with walls or furniture) it is. FWIW, Kitty

    Air is led from a vent near the roof in a insulated pipe into the swamp cooler, where the pipe (but not the house air) is in contact with the moist media. Evaporation make the air cooler and presses it down, trough insulated pipe and into an vent near the floor. Water is release into swamp cooler from mains or rain barrel as shown.

    Swamp coolers are indeed "one pass" devices. Draw dry, outside air into the cooler, exhaust the more humid, cooler air into the house. Then open a window at the far end to exhaust the air so more cool air can take it's place.

    If you set up the swamp cooler to recirculate interior air, all you will do is load up the interior with humidity. Letting the humid air out and replacing it with fresh cooled air is the key to making a swamp cooler work.

    very kool (see what i did there ;) am thinking to build one for my camper @ the burn this year... really 2 gals/hr? just run for the hotest part of the day i guess. cheers mate, and good job. a thought, if you had the mesh on both sides and made a cylinder inside the barrel, you wouldn't need the outer catchment? As the builder, you think that would work???

    @ Twoyellowdogs.  The output of any swamp cooler depends on two things:

    1.  The Relative Humidity of the air it has to cool by evaporation, and
    2.  The size of the unit [amount of SURFACE AREA through which the air is drawn].

    I notice that your trash can hole pattern  leaves LOTS of un-cutout area.  I would guess you have about a 40 to 45% open area. 

    Without changing ANYTHING else, IF you would either drill the holes larger so they ALMOST TOUCHED each other, OR drilled a lot more smaller holes in between, you would INCREASE the surface area of the matting for airflow, and thus INCREASE volume of cooled air created.

    Ideally, like the commercial swamp coolers mounted on the Tucson rooftops, the wet mat area would be massive, with ONLY a thin metal framing to support the matting, hoses, and fan.

    You could accomplish this by either drilling more holes, OR replacing the trash can with two layers of "hardware cloth" with the matting sandwiched between, and then just the bottom of the trash can at the bottom as a reservoir.  The double layer of say 1/2 inch hardware cloth would be more than strong enough to support the system, AND provide almost 100% exposure of the wetted padding to the air flow.

    NO offense is intended as you have created a great cooler AND a great 'ible.

    1 reply

    Aloha!!! EXCELLENT points, johnny3h! The original idea is basically pure genius, but with some of the modifications you mention, this system would be pretty stellar. But, seeing as how tooyellowdogs built this to be used in an area where the dust is almost as fine as baby powder (so I've heard from 'Burners'), not to mention, 'windy', the unprotected moisture matting may be subject to clogging from the random/fugitive dust flying around and collecting turning (possibly) into 'mud'. Just a thought ~ ~ ~ I plan on building one of these for a greenhouse/grow space in a high desert location where humidity is almost totally lacking ~ ~ ~ Aloha ~ ~ ~

    You have made a great swamp cooler, really nice design! But, I think it's not worth it spending so much money and time on this product as it would be not effective in extreme humid conditions. You should have purchased portable air conditioning instead which is great for humid for humid climates. Visit the following website for more useful information: http://www.amtekair.com/

    You probably need about 3-5 gallons to prime the system and get all the pads wet then about 3 gallons per day. We used cooler melt water (ours and as many neighbors as we could get water from) to supplement the amount of water we brought onto the playa.

    I'm building one of these for the upcoming burn. How many gallows of water does it use per day/hour. As you know, it's not like we can go to the faucet if we didn't bring enough water.

    would it help significantly to rig a tarp to provide shade over the cooler and the duct work?

    I did not notice any problem with the dust. Much of it is washed off with the water drip. There will be mud in the bottom pan, but not enough to bother the pump. I replaced the blue pads every 2 years.