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Homebrew Air Conditioning for Under $25
inkey string writes "Summer has arrived, and I've been busy slowly overheating in my student house without central air.
I decided to put my thermodynamics classes to work however, and produced this ~24$ homebrew air conditioner. It'll cool a room to a comfortable level in 15-20 mins, and will run for a few hours on a garbage pail full of water.
It's cheap, environmentally friendly (just fire the waste water off to your garden), and makes a good one hour project for a quiet evening."
I hope his server isn't in his room, because all the thermodynamics courses in the world wont teach you about slashdotting.
...right next to your webserver.
"Now gluttony and exploitation serves eight!" - TV's Frank
Move to San Francisco.
Today it hit 70F, and the news stations are talking about "the heatwave of 2005".
Just great, assuming you have an infinite supply of free ice water. Add teh cost of the ice machine, and it costs a bit more than $24.
I'm a student, with limited funds and a cheap house without air conditioning. To avoid dying this summer, I've built a primitive air conditioner. It's a basic heat pump, using water as the medium. You'll probably need to fiddle a bit with the dimensions of the supplies based on your resources and preferences.
Materials:
Salvage from around the house a:
* large fan
* garbage can
Grab from Home Depot:
* 25 feet of 1/8 inch outer diameter (OD) copper tubing (~ $14)
* 20 feet of 1/8 inch inner diameter (ID) vinyl tubing (~ $6)
* a package of zipties (~ $3)
* 2 small hose clamps (~ $1)
Here's the basic setup. The garbage can is filled with ice water, which is then fed by gravity (a siphon) through the copper tubing coiled along the back of the fan. The hot air passing through the tubing warms the cold water, cooling the air. Waste warm water is then pumped outside.
The system will cool an average room to a comfortable level in approximately 15-20 minutes. Depending on flow rate, a full bucket of water will last approximately 1-3 hours.
It doesn't rip quite as hard as central air, but for less than $30 CAD I'm not complaining.
The main factor affecting the performance is the temperature of incoming water. Cool water will work, but ice water will result in a cooler room, quicker.
Here's what the fan looks like from the back. The biggest issue in construction was uncoiling 25 feet of copper tubing in a 15 by 20 room. Just be patient and don't attempt to bend the copper too severly, it'll fold over on itself and you've effectively chopped your nice copper tubing in two.
When coiling the copper into a spiral on the back of the fan, I started in the middle and put zipties every 15-30 cm (6-12 inches). Use your discretion, you want to preserve the spiral shape and keep the tubing as close to the metal mesh as you can. If you're a bit crazy, sand the paint off the back to improve heat transfer from the metal mesh.
It doesn't really matter how it looks as long as it's reasonably spaced out and consistent. A hint for construction: prebend your zipties into a J shape. Then you can hook them easily in and back out of the metal mesh on the back of the fan. I'd suggest cutting off any extra plastic once you've got them on.
If you look closely, you can see the condensation from the incoming icewater, but no condensation on the tubing leading out. This is perfect, as it means that heat is being transferred from the room to the water.
Once you've got the copper tubing coiled, the rest is easy. Cut your vinyl tubing into 2 pieces, with one about twice the length of the other (one piece 6-7 feet, other piece 13-14 feet).
Attach the shorter piece to the incoming side of the copper tubing. It should slide relatively easily over the copper, but be snug. Attach the hose clamp and tighten. Following a similar procedure, attach the longer piece to the outgoing side of the copper tubing. (I don't believe it really matters whether you feed cold water from the inside or the outside. It's up to you to run some numbers.)
Submerge the shorter end of the vinyl tubing in the garbage can (washed and clean). I suggest weighing down the end of the tube, to avoid it drawing in air and stopping the system. I used twist-ties to attach a thin rock to the end. If you have fishing weights, I would suggest using those.
Next, hang the longer tubing out your window. For the gravity pump to work, the end of the tubing must be below the water level of your garbage can, plus an allowance for head loss in the pipe. Just to be safe, get it as low as you can. I'd suggest arranging it so the waste water will feed into a garden, but student ghettos don't have gardens so in this picture it's being fed into a drain by the basement.
I had to poke a small hole in my screen for this to work.
To get the system started, make sure the vinyl tubing in the ice water is completely submerged. Then,
You may want to post this on thinkcycle.org as additional information for some of their cooling projects
meh
sorry...
Next up, a $24 watercooling rig for his web server.
c 29e9dd8f982b3da/index.html
http://www.mirrordot.org/stories/5cb66a4a72a5269b
This
http://www.eng.uwaterloo.ca.nyud.net:8090/~gmilbur n/ac/
Will someone edit the submission to replace the URL, please? Sheesh.
But sadly this isnt that revolutionary, nor is it very 'green'. It takes a cold source of water to work, and if you have none in your area (tap water wont cut it unless you happen to get fed from a pipe running through a glacier) you have to get cold media from your local refridgerator/freezer. Why not instead rig a direct cycle through your cooling appliance of choice to offer a small, localized cooling effect? It also wouldn't waste water. Just remember, don't try to cool the room with the freezer in it.
Dude, you're in Canada. Open the window.
Now you just have to figure out how to keep the snow off of the carpet.
Unless you have a solar or wind-powered refrigerator, I suspect that the overall system is not actually all that environmentally friendly. What is the energy efficiency of the system?
The real "Libtards" are the Libertarians!
A swamp cooler pulls the air through the actual water. It uses evaporation for the cooling effect. That's rather different than this, which is just a crude radiator. effect.
I think that his garbage can full of ice water should at least have a few cold beers. I mean really, he's in college!
It didn't seem all that likely that most /.ers would care about evaporative cooling, since even in Arizona they only work part of the year (like now, although today the Phoenix dew point got up to 10C. I woke up just knowing it had gone up because the cooler was blowing full speed and it still wasn't all that cool.) Never mind next month when the monsoons start. AC time then for sure.
Lacking <sarcasm> tags,
Thank you mirrordot.
Wait... this retard thinks that using his fridge, inside his house, to produce ice... then cooling with the ice... is going to make his house cooler? He could accomplish the exact same thing by just opening his freezer door, right? I hope this kid's Thermo professor sees this and kicks him out of school.
#1 you can buy a bag of ice at the gas station/convenience store, not free but then neither is the electricity to run your freezer.
#2 even if you used the house freezer, you shut the door and basically you're pumping heat away from the bedroom into the kitchen, obviously you won't get huge temperature differentials, but 5-6C feels very noticeable when you're trying to fall asleep and it's too hot to do so.
-- the cake is a lie
is just to replace the standard incandescent lightbulbs in your house with compact flourescent bulbs.
this will result in you using about 1/8 the electricity to get the same light, but drop the heat output from lighting - a major contributor to household heat - to virtually nil.
I used to have a problem in my new house with having to get a fan until I realized it was mostly heat from lights that was making it hotter than a normal open window breeze could cool. Then I replaced my incandescent bulbs (well, most of them) with flourescent bulbs and suddenly it was cool enough I didn't even need a fan at all.
Now, if the external temperature is above about 98 degrees Fahrenheit (30 C, I think), you may still need to do the water evaporator you describe, but the energy used by it will still be lowered by switching to compact flourescent bulbs for lighting.
Oh, and get a flat panel LCD monitor - that will save a lot of energy usage and heat output as well.
Save the fan to cool off your computer, not your room.
-- Tigger warning: This post may contain tiggers! --
Isn't this just a swamp cooler? Aren't they rendered useless in humid environments? Wouldn't reading this article be a complete waste of time for the majority of us?
Yes, but it would take a lot longer to occur. For example he could just point his fan at the bucket of cold water, however you have a limited surface area for the air to pass over. Running the water through the coiled tube increases the surface area, lowering the temperature much quicker.
Probably some other factors as well, I had a bit of a dumb thermodynamics teacher (not to mention it was over 10 years ago and haven't used it since!).
Q.
Kenmore 5150 BTU Single Room Air Conditioner $89.00 new http://www.sears.com/sr/javasr/product.do?BV_UseBV Cookie=Yes&vertical=APPL&pid=04274054000&subcat=Si ngle+Room+Units
I know students are poor, but really. You can probably pick up something like this at a garage sale for $20.
You call that innovative? This is how people cooled their buildings before in the invention of the room air conditioner. And, to be redundant, where is the cost of amking that ice water? You want innovative? THIS is innovative! And even it is old. And it will probably be cheap when it really catches on. More info, in case you're interested.
What?
Other than the obvious ingenuity involved in the creation of this device, the reason things like this don't exist in the real world is that they're hardly efficient. And comparing the purchase price instead of the operating costs of such a device is a sure sign you're missing something.
Air conditioners are unbelievably cheap and unbelievably efficient nowadays.
As others have said, this setup has all sorts of problems, from a reliance upon a source of ice that may very well be dumping more heat into the local environment than it saves, to wasting water.
Though this system doesn't use a pump, a recirculating system with a small electric pump could end up creating more heat than it saves.
If you're really bent upon saving energy in a cost-effective fashion, adding insulation is almost always efficient. Good blinds on the windows are also a great investment.
"I assumed blithely that there were no elves out there in the darkness"
number one, yes i realise that in a closed system freezing ice to cool yourself off is foolish. this is why i make ice in the kitchen, and cool my room off at night.
which addresses the why no recirculation/you need an infinite supply of ice criticisms. this was designed to cool me off before bed, so i could fall asleep without wanting to kill myself. once the bucket runs out of water/ice, it just becomes a regular fan which is fine once the house cools off in the wee hours. plus i dont have to worry about knocking anything over in a morning daze.
ive rigged it up to a slowly flowing garden hose which will keep things cool indefinitely, but i find it easier and a bit cooler to just pick up a big bag of ice and dump it in when it gets really hot.
anyways, take it or leave it. and to the graduating chemmie that said he was ashamed to call me a student - come visit me at my office by the weef lab (e2-1311), im sure i can address any of your concerns to my satisfaction.
Put the bucket outside, in the wind, with a pump to cycle the water through the fan coil in the house, then back to the same bucket outside. Instant swamp cooler with the swamp outside and the cool inside.
It should be quite a bit more efficient than this guy's system.
If he's getting ice from the freezer in his apartment/room, it is negating his attempt to cool his apartment/room. Heat removed from water in the freezer to make the water freeze is put right back into the house by the thermal coils on the back of freezer/refridgerator.
Have you ever been to a turkish prison?
Around here you can get them from Home Depot and the installation kit runs about $650; labor is up to you but if you're replacing an old one it shouldn't be too tough to do yourself.
Lacking <sarcasm> tags,
Mirror: www.138productions.com/ACMIRROR/
The store needs to make a profit on top of the cost of the electricity to maintain the machine, and the ice...
...supplied by the ice company which bought the machine, maintains it, and freezes the ice, and trucks it to the store from their "plant"...and make a profit.
You do realize that 1kW/hr costs about 22 cents, whereas a 20lb bag of ice costs about $5, right?
You have to move 330J of energy to freeze one gram of water, basically. We'll assume a 50% efficiency here (pretty poor, I believe). A bag of ice, say, 20lb- would need about 3 million joules (watt-seconds), or 6 million watt-seconds of electricity. That's 1662 Watt-hours, roughly.
Or about 36 cents.
#2 even if you used the house freezer, you shut the door and basically you're pumping heat away from the bedroom into the kitchen, obviously you won't get huge temperature differentials
Most refrigerators are virtually incapable of pumping that much heat (there's a reason they're insulated), and furthermore, are designed to work at a temperature range 60-90 degrees cooler than what you're asking of it. Ever noticed that a fridge takes forever to get from room temperature down to operating temperature?
This idea is so stupid, I can't believe I just wasted 5 minutes on this post. I want that 5 minutes of my life back.
Please help metamoderate.
I had never heard of a swamp (evaporative) cooler until I moved to AZ. At first, I didn't like the idea of adding a ton of humidity to the air in order to cool some space, but when I bought my first house, I learned that I LOVE swamp coolers.
Newer homes never have them, but the older house that I bought (built in 1979) had a monster one installed on it. During the early parts of summer (when the humidity is low) I can keep my house at 72 degrees when the outside temp is about 100 and my electricity bill is $65/mo.
If I ran my AC unit and kept the house equally as cool with it, I would be looking at no less then a $150 in early summer and $200+ as the temp gets into the range of 110+.
At this point, what I would love is a thermostat that runs both my swamp cooler and AC unit and can determine when to use one versus the other and switch automatically between them. Anybody know of such a device?
cheers.
"Perhaps most amazingly, votaries of 'diversity' insist on absolute conformity." -- Tony Snow
Spend another $26, and buy a real airconditioner for $50 at CostCo.
It's $99.99 with an instant $50 off rebate at the register.
Less work too.....
I don't know if this guy ever took shop class, but the simple old trick of filling the part of the copper tubing to be bent with sand will help prevent it from collapsing from a too-tight bend.
...to cool a room, as has been noted repeatedly, a few refinements that can be done easily and cheaply:
:)
1) Get a second trash can. Drain to trash can number 2. This will allow you to save water, plus:
2) Put salt in the water. The ice and chilled water mixture gets colder with salt.
You probably don't want to drain salt water to the yard.
You can run from one trash can to the other, then when it's done draining, swap one can for the other and ice down the other can. If you've got some freezer space to dedicate to the project, the bottles of ice are probably an excellent idea-- have a set in the freezer and one in the heat pump.
Yeah, but does it run Lennox?
If you live somewhere that it gets significantly colder at night than in the daytime, that works.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
still gotta pay for the water bill.
Nah... at most rental properties water is included.
Reminds me of me el-cheapo humidifier I once made... put a bucket of water on the ground. Drape a slightly damp towel over the back of a fan down to the bucket and let a process similar to evapotranspiration in trees turn liquid water into humidity. Drops temperature a tiny bit, which is unfortunate as I'd use this in the winter when it's dry indoors. But it is a quick way to dump a couple gallons of water in the air overnight.
Just make sure that you have something like a towel of plastic sheet on the ground in front of the fan, as a small amount of water is atomized in the process rather than evaporated. This factor really makes sure that this is a short term solution rather than long term. That and you eventually have to wash the towel, as salts from the water build up and leave it kinda nasty.
I'll never make that mistake again, reading the experts' opinions. - Feynman
Not only is ice not free, but the refrigerator (being a non-ideal, non-reversible thermodynamic entity) is putting off MORE HEAT than what it is cooling (the same is true of an A/C unit... that's why they are located outside). Since he is in a dorm room, the freezer is located in his room, the constant cooling of additional water in addition to his normal "load" will actually cause his room to head up more. If he gets the ice from a common machine down the hall then yes, the bucket itself is pretty efficient, but the machine as a whole (which must include the production of ice) sucks it bigtime compared to a commercial air conditioner.
Moral of the story: "The laws of science be a harsh mistress" -Bender, Futurama
-philski-
Years ago, during a heatwave in Oakland, I built a homebrew swamp cooler with some muffin fans and a mist nozzle from McMaster (like 32215K11).
From thermodynamics, the say you have 1kg of water to work with:
Changing it from ice to water: 334kJ
Raising it from 0C to 25C: 104kJ
Converting from liquid to vapor: 2,260kJ
Compared with vaporizing water, melting ice is trivial.
For swamp coolers to work, the humidity has to be low--if it's high the ice bucket trick is a good one. But for those in dry hot climates, a swamp cooler works well.
I connected mine to a hose spigot with 1/8" tubing, which supplied a continuous flow of water to the mist nozzle, which was mixed with a good flow of hot dry air from the fans, and resulted in a good flow of cool slightly damp air.
He would be much better off just aiming the fan over the top of the barrel of ice water and getting the evaporative cooling going along with the cooling from the ice. In fact I can't remember but its something like 5 or 10 degree temp drop by just putting ice water in front of your fan as opposed to the fan alone. But his rig is rather a waste in comparison. He should look into evaporative cooling if his climate isn't too humid to start out with.
"You can now flame me, I am full of love,"
I think my way is much more efficient and more environmentally friendly. I just hooked my freezer up to my perpetual motion machine and leave the door open. Infinite cold air, and no puddle of wasted ice water outside my window.
This is all very well and good, but he's missing one thing - capacity.
Air-conditioning systems are sometimes rated in "tons". That's "how many tons of ice required to melt in a 24hr period to get the same cooling effect."
Surprisingly, in AC terms, a ton is not a very large unit. A typical car air-conditioner is about 2-2.5 tons. This size AC is capable of cooling about half a house. So, a 5kg bag of ice? Forget it. Go buy a real air-conditioner. Scrounge around - 30 bucks can buy a decent old second-hand unit.
You are in a twisty maze of processor lines, all alike.
There is a lot of hype here.
Your roof is only one part of the issue, probably a minor one if your have an attic.
During the daytime the sun warms the roof and walls of a house. The surfaces most perpendicular to the Suns rays will get hotter, faster.
In the morning the sun is low in the sky and the light rays are mostly perpendicular to the house walls. Since the air is still relatively cool from the night period, the heat imparted to the walls is mostly released back to the atmosphere.
For the mid-day the walls are washed in light mostly parallel to the walls, but the roof is heated quite a bit. With an attic and proper insulation and ventilation, most of this heat will be released back to the atmosphere.
In the afternoon/evening the sun is again low in the sky an the rays are again perpendicular to the house wall, causing them to heat up. Now, though, the atmosphere around the walls is also warm so less of this heat is released back to the atmosphere outside the house and instead finds it in to the home . Heat is conducted to the interior walls and then to the air in the house. Additionally heat is radiated from the interior wall surfaces to the occupants causing people to feel warmer than the thermostat reading would imply.
The radiation portion of that scenario is why opening the windows does not alleviate your warm feeling and cooling the roof does not help much.
If you were to run water down the west walls instead of the roof during the afternoon you could remove the accumulating heat. Better yet shade those walls, you would go a long way to keeping cooler. Another option is to more heavily insulate the western walls, building up their thickness if necessary.
Shade is the most efficient way of keeping cool, you remove the heat before it gets to the home and either release the heat to the atmosphere, or let plants convert it to food.
Article X: The powers not delegated... by the Constitution...are reserved...to the people
>>Put salt in the water. The ice and chilled water mixture gets colder with salt.
:}
>Errggh.... no it doesn't
Errgh.. yes it does.
Salt in the water just allows it to be a liquid at a lower temp.
Which means what? It means that you've shifted the equillibrium between ice and water to a lower temperature. Which will lead to the ice melting faster until the depressed freezing-point is reached. (after which the melting will actually proceed slower than before since the whole solution is colder)
The reason you use ice in an icecream maker is to allow better thermal conduction to the container with the ice cream.
I assume you mean 'salt in an icecream maker'. And that is wrong too.
But if you don't take my word for it (although you should; I've got a degree in physical chemistry), then perhaps you should go look at this entry in the General Chemistry Online FAQ, which adresses exactly this.
Perhaps you should read the whole thing before you start correcting people on basic chemistry.
If you have a fan only setting on your thermostat then go down into the basement and bypass the air return ducks so that it's sucking in cold air from the basement. think of your concrete foundation has a big ass heat sink.
Where he of course met Guinan and Data and was almost killed by time shifting aliens that were attempting to steal our souls. Wouldn't that be anyones worst season?
"Genius may shine aloof and alone, like a star, but goodness is social, and it takes two men and God to make a Brother."