Portable 12V Air Conditioner --Cheap and easy!

Step 1: Background and How it Works

This project is very similar to the ArcticAir Package Unit. In fact, I attached two pictures of it I took at AirVenture this past summer. It looks almost identical to ours, and we built this without ever seeing a picture of the inside! The basic concept is to use a boating bilge pump to circulate iced water through a heater core, then use 12V fans to blow air through that core, which cools the air and pulls out water through condensation.

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?

Comments

[shaggalicious]

Alright, I went out and acquired all the items, put it all together, and I have very very cold air.....but....... no matter what I try, I cannot get enough air flow to even feel any of it coming off of the heater core. I tried having one fan blow down on it and the other blow at me, and that helped a lot. However, it is nowhere near enough to cool off the cab of my truck. I have 2 x 40 mm 3000 RPM 78 CFM fans. I think the exact same pump, and the heater core was off of a camaro I think. The temp directly on the fins of the heater core is 42 degrees, yet, after 1 hour in testing, the cab hadn't changed temperature, and the temp 1.5 ft. from the fan was 93 degrees. I would really love some insight, as maybe I screwed it up (common problem). Thank you.

[CameronSS]

Sounds to me like your fans are too small, if you typed that correctly. The fans I used are 120mm; a 40mm fan blowing at the same speed would only move a ninth the air.

[HippieNation]

Walmart sells dry ice. :)

[leeharrison]

Dry ice is frozen carbon dioxide. Of course, it evaporates into lots of carbon dioxide. Not good in a small room/car/etc. Please don't use CO2.

[lfd81]

Go through and read the hundreds of previous comments regarding dry ice

[Junkyardmaster14]

i already made this one myself and now i knew that someone have the same idea as i have, what the waste of time that i made, i thought i invented a thing but when i always search on the internet after i finished making an invention, i always found someone that has already invented it, :(

[CaptainGroovy]

Where I come from they call these things "Swap Air-conditioner's" a Block of Ice and a Fan and they have been around in some form or another for a long, long time.  In the 1940's and 1950's a number of companies marketed 'Room Coolers' (Squirrel cage fan with a tank that you filled with Ice and Water) their biggest problems (besides using a lot of ice) was spitting due to condensation.

[CameronSS]

As I've stated dozens of times in the comments, this is not a swamp cooler. A swamp cooler blows air over water, which evaporates it into the air, using the principle evaporation is endothermic to absorb heat from the air, so that it outputs cool, moist air. This uses the same principle as your central air conditioner--heat flows from high to low--to transfer heat from the air into the cold water, which outputs cool, dry air. In dry areas the swamp cooler may be helpful, but in a humid Kansas summer, you need something that takes water out of the air, not something that puts more into it.

[jay_in_hsv]

One guy below makes a decent point: Freeze your water in sealable containers (2 liter bottles), place those frozen containers (2 liter bottles) inside your cooler, and just let the air flow directly over them. Condensation collects on the bottles and stays in the cooler thus no increase in humidity. Smaller containers would increase surface area and thus heat transfer rates. Eliminates the need for the heater core and the bilge pump and saves the electricity used to drive the pump.

[jencke]

The heater core is actually a heat exchanger with much greater surface area for heat transfer than plastic bottles not to mention the metal used in the heater core is a better thermal conductor than plastic. In other words the heater core will do a much better job of cooling.

[aqwiz]

 Oh and btw, now it's gonna get even worse, because there are billionaires who have massive superclusters of computers using evolutionary algorithms to find every possible conceivable invention (and they'll likely get the idea to make it recursive right off the bat, I.E. using already successful inventions, and compounding them into more and more complex devices.) 

[aqwiz]

 thus is the problem of true invention in the information age. 

[Junkyardmaster14]

yeahh.... and sometimes they just bought it from the original designer of the invention..

[jkotila]

i had the same thing happen to me, high end car compnaies stole my idea

[Junkyardmaster14]

what type of idea?whats it all about?

[CameronSS]

I feel your pain...once that happened to me and the other guy made millions from what I thought was my brilliant idea...

[aqwiz]

 Bahh, it's not really them "Stealing" your ideas, it's called simultaneous thought progression. Essentially because of the nature of our brains, and vastly similar circumstances all across the globe, (localized in some cases) the same thoughts will occur to two or more totally different people. It's happened to me way too many times to count, and thus it can't just be coincidence. The effect is  known and well documented, and has even happened in high profile mainstream science on more than one occasion. 

[nutsandbolts_64]

lol, that happened to me over Yahoo Messenger.

[dserhal]

Back in the late 80's. I was driving an unairconditioned auto parts truck around town delivering auto parts. 1. I wish I had this thing then! 2. Addressing gunsigma and CameronSS: During those times riding in that hot truck, I would stop at a local 7-eleven and all you could seem to buy was a sugary soda....all I wanted was ice cold water. I even laughed that I would actually pay for bottledwater (unheard of then) instead of soda. I thought, hmmm what if I could just bottle water and sell it. The idea seemed asinine! So, I didn't pursue it. A few years later guess what happened? Someone started selling bottled water. I could have been rich beyond my wildest dreams!

[Junkyardmaster14]

so your the one who made it?

[oblitas1980]

what about if instead of regular ice you use dry ice, it will last longer....right?

[Blue_Bird]

Regular dry ice might last longer and be colder, but personally, I'd rather avoid a constant stream of Co2 coming at my face.

[CameronSS]

Read Step 12.

[TotalLED]

What's the melt 2 air time/ Amount. & How much cooling do you get ?

[rcg40]

Always drive in the shade. Put a 5x8 panel on the roof of the truck with a very reflective top. Just an idea I got when I transported some plywood on my roof.

[johnny3h]

Back in the mid to late 1950s, we couldn't afford automotive air conditioning so my Dad "glued" ordinary Aluminum foil to the entire roof of our car. 

I don't recall ever hearing any numbers, but Dad was insistent that the interior temperature was much lower, AND I do recall that the "radiant" heat sensed on my head and skin was reduced to nothing.  It worked great.

However, one serious negative did surface.  When the Aluminum foil began to deteriorate and Dad removed it to apply another fresh layer, we discovered that either the adhesive [I doubt} or the Aluminum had caused TOTAL failure of the white paint on the roof, and the entire area was RUSTED BADLY!!!!!

The point is that "rcg40" is 100% correct about protecting a vehicle's roof from direct sunlight contact.  And the effect increases tremendouly IF there is an "air gap" [allows NO conduction of any heat] between the reflective panel and the vehicle roof. 

[H3xx]

and blind traffic copters. :)

[MrKnowItAll]

Actually, It is not a swamp cooler.

It also does now add moisture to the air.

This is because as the warm air flows over the ice, it will condense water from the air onto the ice.  It will keep doing that until the ice melts.


Pelter:
You could use a pelter to keep the water frozen a bit.  You would need to attach the plate to the floorboard, likely replaceing a section with an aluminum plate.
Fins on the other side(under the car) help extract the heat to the outside air.

Now, this doesnt make it a GOOD Idea.  You have to power your peltier from a battery.  This is the same battery you are using for power.  It also means that
you are in effect using a peltier for air conditioning.  This isn't the best use of your electricity.

This is a fine idea.  Use your already efficient freezer at home.   On a hot day, take along the cooler.      If you have an icebox at work, you can "Fill up" again for the ride home.

So 90% of the time, you are not towing around equipment you do not need.  You are also using an existing cooling agent.  No need to reinvent the wheel.

[johnny3h]

To MrKnowItAll, and all others:

The subject system does NOT add moisture to the air flowing through the evaporator core used as a heat exchanger.  The air to be cooled is NOT allowed to contact the cooling water medium flowing througn the heat exchanger.  Thus no evaporation into the cooled air stream.

IF, and I emphasize IF, the lid  on the ice chest does not fit tightly, then a very TINY amount of air circulation MIGHT occur resulting in a very slight humidity transfer to the interior of the cooled space, but that would be negligable.

Although several later posts have jumped your comment about use of a Peltier device, your post specifically mention heat sinking the hot heat sink of the Peltier device to the exterior sheet metal of the vehicle, and I agree with you, and disgree with your detractors in that such use [insulated by the vehicle's floor insulation and carpeting] would not contribute to heat gain inside the vehicle.

I also agree with you that the use of a Peltier device would be expensive, unnecessary "over-kill" in the effort to cool the passenger compartment of a vehicle.

[CameronSS]

Have you read Step 12?

[robbied]

If you put an aluminium plate in the bottom of your ice chest, attached to a peltier unit, heatsink and fan, then you can keep the ice water icey as long as you run the peltier unit

[CameronSS]

A peltier creates a heat difference, it doesn't simply become cool. It moves heat from one side of the unit to the other, and adds a bit in the process.

[robbied]

The heatsink and fan disperses the heat from the 'warm' side, the better the sinking, the greater the temperature difference.

[CameronSS]

But where do you think that heat is going? It's being "dispersed" right back into your car.

[tkjtkj]

yes, it will warm water but the major heat exchange is between the air and the ice, where ice has a tremendous 'latent heat of fusion' .. Ie, ice that's warming up gets to be about 32degF, and will stay at that temp for quite a while, til all melted, and only then will the water temp rise.
At this link is an interesting chart showing just how good water is for this purpose, compared to other substances:
http://en.wikipedia.org/wiki/Enthalpy_of_fusion

[tkjtkj]

sorry, but i dont recall replying to any peltier device .. My comment referred to 'ICE' and its qualities.  Forgive me if by error i clicked to reply to you; it was not my intention. What you contributed really had zero to do with the instructable at issue, in any event.

[CameronSS]

The latent heat of fusion of water has nothing to do with the use of a peltier junction to cool the water. There are no electronic components that can simply remove heat energy from the air, only components that can add heat energy, and some that can move the energy from one place to another, which also adds heat. A peltier junction (thermoelectric cooler) moves heat energy from one side of the plate to the other, which creates that temperature difference. If you add a peltier to pull heat out of the water (cooling it), it is only releasing that heat outside the box into the cab, so nothing is accomplished.

When I finish these scholarship essays, I shall add some information to the Instructable, since it appears that no one can be bothered to read the comments.

[tkjtkj]

your 'scholarship essays' are totally misplaced.  There is NO ref in any way/shape/or form to any peltier technology.   Bow out.

[tkjtkj]

I could not care less about your alleged 'scholarship' , whatever the hell that means ...
If you thought my comment was not in your area of concern , why did youi even bother to reply to me and then to inappropriatly belittle my 'on point' and eruditious contribution?  Cool your heels and just walk away ..  That'd be the honorable thing to do.

[CameronSS]

Is there a reason you are being so inordinately argumentative? I have essays to write for a scholarship; once I complete those, I can work on the Instructable. They are unrelated to the conversation except as priorities above the Instructable.

You replied to a comment thread between myself and robbied, which was about the feasibility of using a peltier junction to cool the ice further. Your comment did not seem to relate to anything on this page, so I simply assumed that it was a disjointed response to the comment to which you had replied.

[matbh]

or warming the water...

[jacobevolved]

Peltier floorboards. Problem solved. You could even install a pole switcher for winter months.

[willrandship]

That is starting to sound more like a whole-car thing rather than for a cooler...not bad for that, though. Even-ish car cooling!

[Danish M1Garand]

The fly in the ointment. The heat needs vented outside or it is pointless. A Peltier unit in an icebox in the bed with ducting to the cab would help. I had a peltier icebox and found it to be nearly useless. It seemed to drop the contents only about 20F under ambient. Ice from the C-store worked better.

[Danish M1Garand]

Yes but the drag on an alternator or in his case the loss of juice to the drive train would cause a shorter range.

[robbied]

The small peltier unit I bought for my car fridge would draw less than the circulation pump. It was only 4 amps at 12 V. It wont refreeze the water but will keep it cool.

[robbied]

Just to add, this is the way car fridges work.

[ScubaSteve]

Could you extend the life with dry ice?

[unibomb bk]

no because water n dry ice create carbon dioxide n you cant contain the gas either because of expantion.

[Kaljakaaleppi]

Dry ice is nice, but it is CO2, which is a poisonous, odourless gas. The molar mass of CO2 is around 44 grams per mole. As one mole of gas equals approx 24 litres (at 25 degrees C), half a kilo of CO2 in your car, slowly evaporating is not a good idea. Otherwise, it is an exellent idea, if you figure out the ventilation. But be sure, poisonous odourless gases is not too cool to have in your car.

[todreich]

Carbon Monoxide is the poisonous gas, Carbon Dioxide not so much.

[Kaljakaaleppi]

Quite true, CO sticks to haemoglobin 250 times better than O2, so it is truly poisonous. I have to stand corrected here, the biggest risk is that CO2 is an asphyxiant, and therefore should not be used in a closed container (like a car). In several labs it is forbiden to transport gases like N2 or CO2 in elevators with people in the elevators at the same time. In a case of leakage and elevator malfunction, death is quite likely.

International Chemical Safety Sheet:
http://www.inchem.org/documents/icsc/icsc/eics0021.htm

At our own lab we get tons of reagents, stored on dry ice. I have always wanted to take this stuff with me to our countryhouse for cooling food, but have not figures out how to transport it in our car safely :D. Maybe in the trunk, with the trunk lid open a ittybitty...

[johnny3h]

To Kaljakaaleppi and ALL:
For years, I have transported "dry ice" inside my vehicle routinely by placing it inside a cheap Styrofoam cooler, with a vent tube to the outside of the vehicle.

I drilled a small hole in the lid, inserted a piece of aquarium air pump tubing which was long enough to reach outside via a window, and then sealed the tubing to the lid using a small amount of adhesive from a Hot Glue Gun.

I then used duct tape [but any tape would work] to temporarily seal the crack between the lid and the cooler.  As the dry ice sublimed to CO2 gas, the slight pressure would force the gas outside the vehicle via the vent tube.

[todreich]

 Thank you for the data!  : ) I had dismissed the suffocation aspect of the gas out of hand as I did not think that a reasonable amount of dry ice would present a suffocation danger. Reading the MSDS sheet brings me cause to re-think my previous casual dismissal.
  Again, thank you for the clarification and data.   

[koriko88]

Do you think "blue ice" or some other sort of non-water ice might provide more longevity?

[Danish M1Garand]

Blue Ice is just gelled water frozen. East of the Mississippi we have excess water. Hell I even have a pump that runs weekly to get rid of fresh water from below the grade of the basement. Neighbor across the street who sits 3 ft lower than me has a sump that runs daily. If the water waste bothers you just water your garden with it. I would loved to have known about this before I got my new company truck. The old one didn't have AC. The new one has the HAPPY MAGIC BUTTON with the snowflake totem on it. I worship at the alter of the snowflake totem.

[dserhal]

And you could ditch the bilge pump. What about dry-ice? Most ice cream places will sell dry ice.

[johnny3h]

To dserhal and ALL: 
The ICEWATER serves two purposes.  Naturally, the ice first acts as a coolent by taking heat from the water, BUT...
More importantly, the cooled water acts as a medium to tranfer the heat from the heater core heat exchanger to the ice water reservoir, and the cooled water back to the exchanger. 

The subliming CO2 gas would not be as efficient a transfer medium as the ice water.

[Danish M1Garand]

Dry ice sublimates into CO2. If the car were just tight enough it might suffocate you.

[dserhal]

True DanishM1Grand, I didn't even think of that. So, with dry ice you need to have ventilation which would be hot air and probably counter productive.

[n0ukf]

The main advantage of those blue ice packs is that when they thaw, they don't get everything wet like ice cubes do, they're contained in the non-leaking bag/jug. I don't think they have much (if any) more thermal mass than water.

[sloperdude]

Your cooler doesn't entirely do away with fluorocarbons, unless you're getting that ice from a frozen lake. It's just using the refrigerant from the icemaker that made the ice in the first place.

[dserhal]

sloperdude, my fridge and freezer run ANYWAY. Making my own ice for this is actually a more efficient way to use my already existing freezer.

[CameronSS]

I'm trying to be patient and adhere to the "Be Nice" policy, but I'm starting to get annoyed with people who are restating what has already been said. I'm not going to clutter this page up with another long-winded debate, so feel free to read my previous response.