A Low Cost, Solar-Powered Swamp Cooler

A looming, torturous summer is preparing to bear down on many of us, making this dirt-cheap swamp cooler build an attractive hack to fend off the heat.

Though this is a pretty standard evaporative cooler, the design comes together in a tidy and transportable finished product. The base is a ~$3, 5-gallon bucket from a local hardware store with its accompanying Styrofoam liner. Three 2 1/8″ holes carved into the side of both the bucket and liner will snugly fit some inch-and-a-half PVC pipe with no need for glue.

One last cut into the lid to seat a small desk fan rounds off this build—or you can chop into the styrofoam liner’s lid if you prefer. The video demonstrates using a 15W solar panel to run the fan, and we have to admit that the cooler seems to be an excellent low-cost build. It does, however, require a frozen gallon jug inside to pump out the chilled air for around 5-6 hours per jug. Maybe one of our frugal and mathematically-inclined readers can throw out some guesstimations for the cost of stocking the bucket with a jug of frozen water a couple times a day? Video after the jump.

Thanks [Morgan]

53 thoughts on “A Low Cost, Solar-Powered Swamp Cooler

  1. 1. This is not a swamp cooler. Swamp coolers work on evaporative cooling.
    2. If the fridge freezing the ice is in the same house you’re trying to cool, there’s a net increase in the temperature of the house. (House gets waste heat of running the fridge, plus the heat taken out of the water to make the house.)
    2a. This is mitigated if the water is pre-frozen on a different day, or the part of the house you’re trying to cool is far from the fridge.

    1. Agree, it’s not a swamp box. The original post doesn’t claim that it is. On the other hand, the site is called “the good survivalist”.
      “If you’ve ever had your power go out on one of those hot summer days you know just how important keeping cool can be.”
      If you’ve ever had your power go out, you might have a cordless drill, but then you need a fan. PC case fan and a car battery? Then again, if we’re talking rare or one-off situations, and have ice in the freezer, just get the ice out, and shove it down your shirt.

      What this is, is portable. Some poor kid in a little room with no a/c could make this, and raid the family freezer for some ice.

    2. I have a swamp cooler here in CO. An A/C installation would cause a significant spike in my bank account. Evaporation cooling works well, and this isn’t exactly optimal. I don’t have to use a frozen jug of water – the water from the faucet is cool (because the lines come from the nice, cool ground.) The “frozen jug” is wasted energy.

      The ol’ fan-thru-flowing-water makes a great difference here…especially when the wood in the house warps, and doors stick. ;P

      1. You see here in Florida a swamp cooler is useless. In the summer we see 90% humidity often. I would even bet when we have low humidity it would be considered humid where you live.

        1. Yeah, but, but, if they do it somewhere where anything pretty much works then the project is considered effective..

          It’d probably take an industrial fan to increase CFM and overcome the vapor density and heat in Florida. I’d definitely scap the pre-frozen water jug, it’d be exponentially more obvious how poorly economical it is in such conditions, and go with some electro-thermal , or passive-solid solution with no state change..

          Everyone and their uncle are scientists these days, but good luck finding anyone who factors basic economics and dynamics..

    3. 2. You’re assuming the same time constraints for heating and cooling. If however you are freezing your water in your fridge at a time when things are cool, and then using the frozen block when things are hot while the same energy has been expelled (almost) you’ve made the place more comfortable to live in.

    4. I would have to agree on the exchange of energy. A refrigerator exchanges heat from inside the fridge to the outside, ie your house, this includes the freezer, plus the exchange is NOT 100% efficient leaving a lot of left over heat in the house. An A/C unit exchanges heat inside the house with the air outside, again not 100%, therefore the heat exchanged is less than the energy consumed to exchange the heat. The only way to get something like this to work is to dump the heat exchange exhaust outside, to do so would require a freezer in the garage/outside that is air sealed from the house, but really its probably the same if not less than the efficiency of A/C, since that is almost exactly the same process, and tech being used, ie pressure pumps and refrigerant. Your probably only of setting the cost of the original unit, but since you have to buy the parts for this, you can’t be saving that much. Plus this isn’t solar powered as the freezer requires grid AC, unless you have enough solar cells on the road to power it.

      But, if you have some way to cool the water down without you having to produce the energy to cool it, now you’ve got something. My grandparents used to live on a farm, and my great-grandad diverted a local creek to run underground to a cellar he built, make a few loops inside, then back out. They used it for cooling the house and food (no refrigerators or freezers at that time), I thought it was smart.

    1. That’s only true if your freezer is 100% efficient (it’s not) and the fan generates absolutely no heat (it does… but a negligible amount). For efficiency-sake you’d be better off using a window A/C unit for localized cooling, I think.

  2. A friend posted this on Facebook last week and I ran the numbers. The recommended cooling power of an A/C unit for a 300 sq ft room is around 8000 BTU/hr. It takes 144 BTUs to melt a pound of ice, and another 40 to bring it to room temperature, so you’d need to melt about 40 lbs of ice an hour to match the A/C unit.

    1. I don’t think there is any comparison on efficiency, but a comparison of cost would be entertaining.
      A small window AC starts around $300, while the bucket starts at ~$3. Surely a refrigerator unit is more efficient at freezing the ice than the window AC is at cooling a room. Assuming you directed both of the devices at yourself or common area of said room, the window AC would quickly lose in a cost battle while achieving the goal of keeping the person/common area cool. While the window AC will be able to cool the entire room or in our case of a cheap window unit most of the room, the empty space doesn’t matter only the person/people dwelling in it.

      If you are dealing in large number of people spread throughout many common areas, then a Central AC unit should come out ahead. In any other scenario from a stand point of cost this humble bucket wins.

      Now convenience, well I think AC units are going to win that hands down. However, if you are in a situation without such units (Central AC died), a few buckets and some ice could save you until it can be repaired/replaced rather than buying a bunch of window units or worse yet sweat it out.

      1. I’m not so sure a small window unit air conditioner starts at $300. You can pick up a 6000 BTU/hr unit for about $110-$130. 8000 BTU/hr will run about another $50-$75 over that. I’ve seen 25,000 BTU units for only $400.

      2. -“Surely a refrigerator unit is more efficient at freezing the ice than the window AC is at cooling a room.”

        Actually, no. The A/C unit operates over a smaller temperature differential than the freezer, so it achieves a higher coefficient of power, or higher efficacy. On a hot day the difference between the hot and cold reservoirs of the A/C unit is 10-20 degrees, whereas the freezer has to work from room temperature all the way down to freezing, which is 40-60 degrees of difference.

        1. Depends on where you are, but the hot-cold differential in the South is routinely 20 degrees and may reach 30, while Vegas or Phoenix can hit 40 (although they can let the fan run a little longer and tolerate the increase in humidity to gain the last bit of cooled air, while the South can’t).

      3. Pretending that the cost of bulk ice from the grocery store is representative of the energy needed to make it, the internet tells me that the price ranges widely by where you are in the US, but it seems to be somewhere between 7-20¢ per pound of ice. 184 BTU/lb (to melt + raise to desired temperature) means we get a cost rate for melting of somewhere around 900-2600 BTU/USD (or 970-2800 kJ/USD).

        In comparison, a random cheap in-window A/C has a typical efficiency of about 10 joules displaced per joule input (so-called EER), and electricity costs around the US vary (I think?) from 8¢/kW-hr to 25¢/kW-hr. kW-hr = 3.6MJ. Total efficiency: 144-450 MJ/USD or 130000 to 420000 BTU/USD.

        At absolutely most favorable (most expensive electricity, least expensive ice), 144MJ/USD ÷ 2800 kJ/USD = the AC is 51 times more efficient per dollar.

        Sears currently is advertizing a 5000 BTU/hr in-window A/C for $125. Assuming the cost of running the fan and bucket are free, how long would it take to make up the cost of buying the A/C ? Further, assume that we only have to balance the heat generated by a human (100W), and there’s no other losses (hah!). In this case, it’ll take 28000 seconds to melt a dollar of ice. In comparison, it’ll take 17 days to spend a dollar of electricity through the A/C.
        Multiply that by 125+3 (cost of running the AC for 42 days) dollars, and you should have bought the A/C instead after 42 days.

        In practice, it’ll be a lot faster, because you’re losing coolth to a lot more places than just cooling one body.

        Finally, for your other point: heat pump efficiency is proportionate to the temperature difference it’s fighting against. For freezing things, you’re often pushing entropy up ≈40°F (30°F in the freezer to 70°F in the house), while the A/C is often pushing against a 10-30°F difference (70°F in the house to 80-100°F outside). The freezer is necessarily less efficient than the A/C.

        1. If you’re buying ice at the grocery store, you’re burning fuel or making a lot of trips walking there … or you have to keep it frozen until it gets used in your room heater — err, freezer. But maybe the assumption is that the freezer is out on the front porch.

          1. Yeah, I was assuming that the cost to deliver the ice to the store is included in the customer’s price, and the cost of carrying it home should be ignored in comparison to making the ice yourself.

            Even if the true cost of ice is 1/5th what the grocery store charges you (although I doubt there’s that much markup), it’d still be 10× more cost efficient to use an in-window A/C.

    2. Don’t forget to pay atention the details, what your friend posted is for a 300 sq ft area, here they are talking about something like 10 sq ft, so it is 30 times small, so it would only need 40/30 lbs of ice… this is clearly for small areas to have a desired efect..

      And you should ask your friend to complete his post because it is vague, that 8000BTU/hr is to decrease temperature by 1º or by 10 or 15º ?

      Because melting ice will have always same BTU, so with more ice, you get cool more time, the change here is in cooling duration..

    1. That would work save for the fact that the whole point of cooling off is to avoid being sweaty and wet. The wetness is part of what we’re trying to avoid. I can handle being hot and dry, and cold and dry, but either one wet and I’m just plain uncomfortable.

      1. Yeah it works great in dry places. Humid areas it wouldn’t work. I did this 2 summers ago when we had a week of really high heat until I got my AC into my window. Swamper was broke and i wanted to do stuff on my computer but it was getting up to 110 in my room. I would ring out the shirt so it wasn’t sopping wet just damp.

  3. if you think a frozen jug of water will cool a room… well that is just funny. soak your t-shirt and have the fan blow directly on you for a better cooling effect. Note: this does not work in Lousiana or other places that have 120% humidity during the summer.

  4. On the subject of DIY air cooling, I’ve had this idea:

    Heatsink+fan on the cold side of a peltier blowing cool air at you, whilst the hot side of the peltier has a CPU watercooling block with water being pumped through it from a big bucket of cold water.

    Is it worth spending a bit of money+time getting the PC watercooling parts and rigging it up ? (I think I’ve asked this before, can’t remember)

    1. It might work; how well is anybody’s guess – I don’t know if I would spend a lot of money on trying it, though.

      I’ve had the idea of cooling via indirect evaporation – stack a few transmission (or larger) radiators together, plumbed in series. Put them outside. Run your water loop through that. The water loop runs inside the house/room to a smaller radiator and fan blowing through. Then, pump water in such a manner to run over the outside radiators, perhaps with another fan/blower to help with evaporation (these two water loops are completely separate).

      Basically, an evaporative cooler without putting the extra humidity in the room air. Not quite as good as air conditioning, but maybe you could achieve the same temperature drop as an evap (depending on the outside humidity and temperature, which is always a limiter), without the indoor mugginess that can be an issue. You may need to add some kind of antifreeze or such to the indoor/outdoor transfer loop to keep corrosion down, too.

      1. You’re limited by wet-bulb temperature, unless I’m mistaken. So you’ll rapidly approach dew point unless you live somewhere that you only need this to cool during peak daylight heat hours and can flush out household air for fresh dry air every night.

        1. I live in Phoenix, AZ – and I know I am limited by “wet-bulb temperature”; but during the driest part of the year (that is still hot – basically, right now) – it would be almost perfect I think. At night, it’s cool enough to open the windows and flush out for fresh air. For me, it’s more an idea than anything – just something I’ve idly thought about from time to time…

    2. The parts wouldn’t be an issue, but a peltier plate would probably use the same electricity as an ac. Actually, thinking about it based on looking into peltier plates for other purposes, it would probably be cheaper parts wise to just buy an ac.

      1. I’ve just ordered a small 12v pump, a CPU cooling block and 5 meters of PVC tubing, the total came to a bank breaking £11.34!

        I already have a peltier, several old CPU heatsinks and fans, and an old 203watt Xbox PSU for powering everything. Hopefully the parts from China will arrive before summer ends. Not looking to cool a whole room with it, just give me some air that’s cooler than what a fan on it’s own can deliver, if not then oh well I tried and it didn’t cost a fortune :)

        1. The CoP of a peltier is typically less than 1 at full power so you’re just melting the ice faster for the same rate of cooling.

          Use multiple peltiers at lower power, around 1/4 of the wattage, and you could maybe double or triple the cooling.

          Remember that you have to dump the heat out, not just put it in a bucket of water. Otherwise your contraption just keeps heating your room more.

          1. If I have to use more peltiers then that means buying more of those and more (or a larger) water blocks for them.

            My intention is to keep the bucket of water outside of the room as the reply below suggests, hence ordering 5 meters of tubing.

            Not expecting miracles from a single peltier setup, I just want to experiement with the idea and this seems to be a good starting point.

    3. I tried something like this a while ago.
      Where I live we are lucky enough to have cold tap water.
      I got hold of an automotive heater core, and the blower motor for free.
      A couple pieces of garden hose, and used my 12V battery charger.
      Bought a submersible 12V pump.

      Filled the bath tub.
      Used the pump powered by the battery charger, to flow the cold bathtub water through the heater core.
      Used the same charger to run the blower motor.
      Second piece of the garden hose as a return to the bath tub.

      Worked pretty well. Kept my bedroom at a temperature that would let me sleep.
      Every few days drain the tub, and refill with cold water.

    4. I thought about using a peltier for making a cooling vest that circulated water like a space suit liner, on earth you only have to have a vest instead of a full body cause you only need to target your core. Turns out some one recently developed a similar product but they use a bucket of ice water. One use they were demonstrating was surgeons during long surgeries. I was thinking military applications. My cousin had the same Idea and asked me about it I told him my solution, he just wanted to use air instead of water. :S

  5. if you are in an area where you get ice in the winter you could build an ice house and stock up on essentialy free ice by freezing it in the winter and storing it.

  6. I can see this working, but I wouldn’t expect it to cool like an ac. I once built a poor mans ac with some copper tubing shaped in a spiral in front of a box fan. I used an aquarium pump to run ice water through the copper tubing from a Styrofoam cooler. It actually lowered the temp in my living room by 10-15° on a 100° day after we blacked out the windows with mylar blankets. I still have the pics somewhere….

    1. Tubing itself is not that great by its lonesome for heat exchange of gases due to vortex shedding, you’ll get nice mixing but shitty contact time. Need greater surface area, try aluminium foil streamers on the coil or a metal colander in contact with the coil to laminarize the flow/while creating backpressure->slowing down volumetric flow -> increased contact time. And put some salt on it

  7. I brainstormed on this a bit and came up with this:
    Ever since ancient times humans have kept cool by minimizing the direct Infrared (IR) energy from the sun. The ancient Bedouins of Arabia (even today) use loose fitting white linen with a headdress drape over the back of their necks. This allows then to reflect sunlight away from their bodies and have a air flow under the garment. Also, I spent some time in the California desert known as Anza-Borrego. Not a very hospitable place to be in mid-August. Simply stepping under a lone tall pine tree totally minimized my direct sunlight exposure and I felt cool.

    Automobile manufacturers know that by placing dark window tint on the car’s windows they minimize the IR energy getting in the car hence causing a cooling effect by not heating up the car in the first place. And you can still look out the window. I would imagine the house’s that have a southerly exposure in North America experience LESS heat in summer if they are let’s say a white house and have window tint on all south facing windows (just reverse that for the Southern Hemisphere). Skyscraper architects know that using some sort of gold or silver anodized glass allows for easier building cooling. Astronauts use it for their face masks.

    So I guess I’m saying that IR is your enemy in all summer exposure scenarios. So any way you can block out the sun can only help you cool down by not having the energy in your house in the first place. Look at underground facilities. The lack of sunlight doesn’t allow the ground below to heat up helping your home to stay cool.

    So just short of making a personal water cooling plumbing system built into a body vest or around your neck (Sharper Image neck cooler?), think about insulating your house or vehicle well. Then invest into some cheap Walmart window tinting (~$20 per a few feet – in automotive dept) for all of your sun-facing windows. Also think about getting light colored vinyl siding for your house too. Or have Earl Scheib-like cheap auto painter (he’s gone now as of 2010) paint your car white (or a very light-color).

    If you don’t like the idea of making your house into a Dark Palace like No Such Agency in Ft Meade MD (their cooling bill is low), think about making temporary window tint shields out of Plexiglas (Home Depot or Lowes) cut to the shape of your windows and covering them with window tint (tint dealers will do it for around $99).

    People who spend a lot of time in their cars (i.e. Private Eyes and spooks) have done just that (temporary or permanent). They put these things up in the summer (even the front windshield while parked) and take them down in the winter (or when you leave the target area). That way you stay cool while still being able to see your target. Later remove them so your vehicle doesn’t look like a druggie-car and get pulled over by the Local Yokels who hate temporary window tint with a passion (LOL). Because they can’t see what you’re doing in there I guess.

    I do like the OP’s use of a Walmart interior car fan ($8 – $10), I see he dismantled the oscillating base and attached it to a Harbor Freight solar cell (~$145). That alone would add to your cooling effect even without the gallon of ice water. Someone already makes the cheap smaller window attached solar car exhaust fan and they work great too. You could duplicate that with a 12 volt DC junk muffin-fan from that old PC you threw out (or are about to),

    The solar cell could come from Radio Shack or Edmund Scientific. Or try and get some NanoSolar from that inventor in California who only sells to the federal govt. It paints on top of your power wires and is flexible and has more output than conventional cells. Good luck with that…

    1. Derail: Bonus points for mentioning Anza-Borrega in a post. Loved the area, and loved those Ricardo Breceda sculptures dotting the landscape. Saddened to learn, upon googling to make sure got the artists name correct, that the man with the vision to make that happen, David Avery passed away in the last couple years. But thanks, sonofthunderboanerges for bringing back memories of a great road trip!

      1. Yeah Borrego Springs is awesome if you like being in a dry hot oven. I was dumbfounded by the Salton Sea. Its so much like an inland sea that the USN uses it for sonar testing, And if you go up to the Chocolate Mountains at the US Marine training center, you can find GOLD just about anywhere “on top” of the soil. Of course, you will be shot so I guess all you’ll get is just Lead (LOL).

        I can’t believe people actually live out there all year round. El Centro is an amazing little desert town. It is so modern too. I pulled in there to the 711 buy a Styrofoam bucket and ice to really cool off. The frickin’ asphalt roads are so frickin’ hot! And those locals just love their crazy pontoon boats out on that smelly Salton Sea! You know it is just agricultural fertilizer water irrigation run-off?

        No I can’t remember ever seeing any Breceda mythical monsters out there. That would have been way cool. However, they do have their own ever-present UFO called “Goldie”. It’s obviously some classified thing-a-ma-bob out of Edwards AFB (Nellis Range Nevada – just around the corner?).

        BTW – Nanosolar got run out of business by the king-oil-cabal (drat not again!). You can buy their stuff on EBAY now. Not selling the solar cell paint though. I guess that’s reserved for the feds? Also you can get CLEAR infrared filters for your windows. Doesn’t have to be tinted.

    1. Not a bad idea. However, you have to find a way to deal with the heat on the other side of it. Heat sinks are good idea. In 1834 Jean Peltier (a French Watchmaker) passed DC voltage through a bismuth-antimony (metals) junction and noticed this effect named after him. Emil Lenz, a Russian college professor, went so far as to freeze water into ice with it. The USAF used them to control friction heat in supersonic jet nose cones.

      You can buy some for around $2 – $5 on AMAZON but you could just dig some out of one of those portable electric coolers for soda cans, found at thrift stores like Goodwill, Salvation Army, or Savers. You might even have one yourself in the attic or basement in the junk you meant to throw out last spring. Like maybe that old portable college fridge?

  8. You know what all this jibber-jabber proves ? That, collectively, people have become waaaay too spoiled and incapable of surviving the way our ancestors did. I speak strictly of folks here in the USA (not third-world impoverished nations).

    Thinking back to “frontier” days of when the first settlers and pioneers set out to make a homestead for themselves, they had no creature comforts like running water or conditioned climate controls. Yet, they survived and conquered the land.

    If we have a complete collapse of the national power grid (EMP – Carrington class CME event perhaps), many people are going to perish because they lost the ancestral knowledge of how to survive without technology.

    1. What the jibber jabber proves is that people can no longer live in wide open dwellings that take advantage of natural cooling methods. Because of over crowding, people can no longer trust the people around them, so they build first for security, then for creature comforts. A closed up building, although somewhat secure, needs some type of auxiliary cooling, or the closed secure nature of the building will overheat the inhabitants during the summer months. It sucks to be us.

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