(Update from 4-22-08: I'd forgotten that I mentioned the gas heater on here. Last fall the gas tank and heater were removed, and a ceramic heater was built in. It works great, although not quite as fast, and doesn't use gas.)
However, air conditioning is trickier because the shaft of an electric motor doesn't always spin. Some have used a compressor driven by the motor shaft anyway, while others have turned a compressor using a separate motor. Finally, my dad came up with part of the concept for this system. It pumps ice water through an evaporator core, which has fans that blow air through it. It is very simple, but we found what we were looking for at Sporty's Pilot Shop. They sell air conditioners built into ice chests for prices ranging from $475 for a basic model to $625 for a 24V, dual fan model.There is also an ArcticAir unit for $4750 with a full compressor unit. However, we like our $10 version better. I saw the ArcticAir display at EAA AirVenture Oshkosh this summer, and our unit is more compact and puts out cooler air. All you need is materials, basic construction/assembly and wiring skills, and a bag of ice. Let's go!
Update, 5-12-08: 100,003 views! Yay! I'm no Kipkay, but I'm still proud.
Step 1: Background and How It Works
Advantages: Very compact and portable, lightweight without the ice, no environmentally not-so-friendly chlorofluorocarbons, hydrogenated chlorofluorocarbons, or hydrofluorocarbons, very quiet, and operates off 12VDC, AKA a cigarette lighter. The only disadvantage is that it the ice will melt after 30-60 minutes of operation, depending on the size of your cooler. However, it was built for an EV, so we are only ever out for an hour or two maximum, and the ice lasts longer when it's not running. The third image on this step shows the operation. Have I convinced you to build one yet?
Step 2: Materials
Ice Chest-free, had it on hand If at all possible, get one with a hinged lid. Free from a storage shed or a dumpster. Or, the Igloo Ice Cube 14 looks like it would work,well, as do the Cool 16 and the MaxCold 24. We used an old 12 quart cooler, and it fit a 7 pound bag of ice.
Heater Core-free, salvaged from a '77 VW Rabbit we're parting out You can find these on eBay for 99 cents to $20, or from an auto store for around 20 bucks, or at an auto salvage yard.
Box Fans and Blade Guards-free, from stock in basement They're sold out of $5 120mm 12VDC fans at All Electronics, but Jameco carries these for $12.95 each. Newegg has a nice assortment, too. Under $10 on eBay.
Bilge Pump-$10.44 for a 500GPH unit at Wal-Mart The Attwood V500 was at our Wal-Mart for $10.44-you can get a similar pump for under $10 on eBay.
Hose-free, had it in stock Ours came from an auto-parts store, but it can be found at hardware and auto-parts stores for a dollar or so for a few feet.
12V plug-free, chopped off a car accessory Cut one off an old phone charger or other device, or $5 at Radio Shack, or $3.75 at All Electronics.
Caulking-free, from the stock in the shop Can be found near the bilge pump, or from a hardware store. A couple bucks.
Piano hinge (depending on cooler)-free, in stock Only necessary if your cooler isn't hinged. A couple bucks at the hardware store.
Inner tube piece (optional)-free, blown tube You may or may not need this-see step 7. If you do, use a blown one, or another piece of rubber, or come up with a substitute. You did save the last blown tube for future projects, didn't you? A couple bucks, tops.
Assorted wire, wire nuts, and screws-free, in stock Depends on what you have in stock and where you get it. It's all at the hardware store, too.
Ice-free, freezer's ice maker If you need me to tell you where to get ice, you shouldn't be doing this project.
Obligatory safety spiel: Cutting devices cut. Don't cut yourself on them. Drills drill. Don't drill a hole in yourself, my dad says it hurt when he did it once. Screwdrivers don't really do anything, but don't throw them into running jet turbine engines. 12V doesn't do much, but watch out. Oh, and wear safety glasses while you're at it.
Step 3: Mark and Cut Holes
On the underside of the lid, mark the outline of the heater core, then go in about a quarter inch and cut out a rectangular hole through ONLY the first layer. This will allow airflow through the core, but still make it easy to attach.
Next, you will need to mark the inside of the fans and cut out two circular holes. We originally planned to use a hole saw to cut the holes, but found that we didn't have a bit that big, so we chucked a saw blade into the Dremel Rotary tool and zipped it out, of course wearing safety glasses (hint hint).
Tada! You now have a rectangle on the inside and two circles on the outside. Now that you cut out these lovely holes, lets fill them in.
Step 4: Attach Heater Core and Fans
To attach the heater core, we used silicone caulk. A bead all the way around seals the lid and provides plenty of bonding force to hold the heater core in place. Make sure to get the core centered, straight, and with the nozzles pointing in. If your lid is hinged, you will want to do a test fit before attaching the core to ensure that the nozzles clear the edges. If your lid is not hinged, it may be easier to attach it first. We ended up cutting the output off to make it fit better.
Step 5: Attach the Bilge Pump
Step 6: Attach the Lid (Optional)
By hinging the lid, it makes it easier to open for loading ice and letting air flow in during operation. It also prevents the lid from sliding off and dribbling water out of the heater core while driving. You can use whatever you want for a hinge-a rubber strip glued on, a couple of cabinet hinges, whatever. We used a piano-type hinge that we found in our stockpile of random stuff. It goes all the way across the back, and allows the lid to flip all the way back, but still close completely.
Step 7: Plumbing and Fan Guards
We also attached a piece of bicycle inner tube rubber to catch water that drips from the output and that condensates on the core. It was cut to fit around the back edge and a couple inches up he sides, and secured with a mega-rubber band we found. This may be unnecessary if you attach a hose to the output, or if your heater core is configured differently.
This would also be a good time to attach wire fan guards to the fans. Just put some screws through the guards into the top holes.
Step 8: Wiring
Step 9: Operation
If everything is hooked up right, the pump should be humming away, and the fans should be blowing. The water is chilled enough to cool the air within a few seconds. You can put this in your car with the dead A/C (note: this will cool pickups and small cars. Don't bother on your Ford Excursion), you can hook it up to a wall outlet through a 12V battery charger, or you can clip it onto a small 12V gel cell.
Step 10: Test Results
I attached a PDF of JPEG of a scan of a notecard that my dad took notes on. What it basically says is the following: When the unit was started, the air in the cab was 95 degrees, parked in the shade after a morning of sun,and the outside heat index was 108 degrees. Within five minutes the cab had cooled to 75 degrees, and the air output was 65 degrees. With two quarts of water that had been refrigerated and 8 pounds of ice cubes, the ice had melted after 40 minutes, leaving 50 degree water, with an output of 65 degree air.
In other words, it works! And it works great! On Sunday, August 12 we brought it to Kansas City for a monthly meeting of our electric auto group. WE met in a small meeting room of a library, and ran the air conditioner off a small 12V battery on a table. Many of the members were impressed that they could feel the room getting cooler, and many tried to buy it from us on the spot. We are also in correspondence with an EV owner from Alabama who is eagerly awaiting the publication of this Instructable (I hope). If you're reading this, you know who you are, and I hope you like it.
Step 11: Possible Modification and Other Notes
This being a Go Green contest, I should put in a spiel about why you would bother with this. The main purpose is to make it more comfortable to drive a zero-emissions electric truck in Kansas in August. This runs off any 12V power source that can shove out 3 amps, so it can be used in other areas that need cooled, such as a hot workshop. Also, the ice lasts for hours when it's not running, and you can leave it on while you run into the store. The only disadvantage is that you could say it wastes water in the form of ice, but you can empty it out on your garden or lawn. It uses only ice water for cooling, which is about as non-toxic and environmentally friendly as you can get, and it kept a hose, a cooler, and a heater core out of a landfill. In other words, it uses environmentally friendly power to run environmentally friendly coolant through recycled parts in a zero-emissions vehicle. Can you get greener than that? I mean, this is #008000 at its best! Just make sure to recycle batteries.
Thank you for reading!
Step 12: Tales From the Comments
Dry ice instead of water iceFirst, a clarification: water ice isn't 32°F, it's whatever the temperature of the freezer is, anything below 32degF...just like how the steel on your car can be 10°F on a cold day, or 100°F on a hot day. Dry ice can be any temperature below -109°F. Since it is much colder, id would theoretically put out colder air. The two main problems with this idea are:
1) Dry ice has a lower specific heat capacity than water ice, so while it is colder, it won't last as long.
2) Dry ice sublimates to CO2, which, in a confined space, will at best impair judgment, and at worst cause loss of consciousness. Driving a car requires being alert. I highly discourage using dry ice.