DIY A/C when camped (ice box air conditioner)?

[zuren]

The family is making a trip next month to visit some friends and family in New England.  My wife and son are flying out and I will be driving out in the van about a week later.  Then we will drive back together over 2 days with the idea that we will camp in the van for that 1 night.  August in the Great Lakes region tends to be hot and humid so I'm considering what else I can do, other than fans, to keep the interior of the van cool overnight that won't strain the wallet, won't require a generator, doesn't need an electrical hookup, and can be accomplished in the next 2 weeks.

I began poking around and found "ice box air conditioners":

Commercial example - http://www.icybreeze.com/
DIY example -

Has anyone tried or built one of these?  It does not seem like a good solution for an extended period or a large space, but for a night or 2 inside a van, it might be just the ticket!

Items I already have:
- Coleman 48 qt. chest cooler: I rarely use this now that I have a Yeti, I've been considering getting rid of it or finding a new use
- 12v, extra large muffin fans: bought these to move air in the van when camped, very low voltage draw

My house battery has more than enough capacity to run the fans overnight.  I have all of the tools required and I have a gift card to the local home center to buy the PVC elbow and ducting, so this would only cost me the sacrifice of the cooler.  I ran a search and did not find anything discussed, so just wondering if anyone has tried it before I move forward.

Thanks!

 

[Trebor English]

Copied from the internet:  

It takes about 144 Btu/pound to melt ice, and warming the water from 32 F to say, 72, requires another 40 Btu. Say 200 Btu/lb in round numbers. 

So 10 pounds of ice is less than 2000 BTU.  To get the equivalent of about 40% duty cycle from a window unit, 2000 BTU per hour for 8 hours you will need roughly 80 pounds of ice.  Bags of ice cubes are about 10 quarts for 10 pounds.  You'll need 80 quarts.  The 48 quart cooler you have with 40 pounds of ice will help cool but don't be surprised if it disappoints.  To try it you only need to get the ice and fan together for a night.

How many BTU per hour will 3 sleeping people generate? 

For a one time use it might be good.  For regular use you need to find a source of ice.

 

[zuren]

Copied from the internet:  

It takes about 144 Btu/pound to melt ice, and warming the water from 32 F to say, 72, requires another 40 Btu. Say 200 Btu/lb in round numbers. 

So 10 pounds of ice is less than 2000 BTU.  To get the equivalent of about 40% duty cycle from a window unit, 2000 BTU per hour for 8 hours you will need roughly 80 pounds of ice.  Bags of ice cubes are about 10 quarts for 10 pounds.  You'll need 80 quarts.  The 48 quart cooler you have with 40 pounds of ice will help cool but don't be surprised if it disappoints.  To try it you only need to get the ice and fan together for a night.

How many BTU per hour will 3 sleeping people generate? 

For a one time use it might be good.  For regular use you need to find a source of ice.

I found this published article that talks about energy expenditure:

https://www.ncbi.nlm.nih.gov/pubmed/3610667

They claim that over 7 hrs. of sleep, a man produces 90 watts, a woman is 75 watts, and I made an assumption that a 3 year old would be half of a woman, so 35 watts.  That is 200 watts total over 7 hours.  I'm not sure if this is correct, but I divided 200 watts by 7 hrs. to get 28 watts per hour.  I plugged 28 into a watts-to-BTUs converter and got 95.5 Btus/hr. total for all 3 people.  I will need to check this math.

I suppose I can run a test before hacking up a perfectly decent cooler that I could give to someone.  I could build an alternate lid (plywood) and see how it works.  I'm not looking to run it for weeks on end, just 7-8 hours at night for 1-2 nights (with an ice refill if necessary) to take the edge off if it is hot.

 

[zuren]

And I have 2 of these fans to use:

Antec Big Boy 200

http://store.antec.com/enclosure-fans/big-boy-200.html#

Link with more useful specs - https://www.amazon.com/Antec-Big-Boy-200-Computer/dp/B000V6FKGM

 

[SoulRaven]

My un-technical opinion is that what you are building is basically equal to an evaporative cooler which is not very effective unless you are in a dry climate. With high humidity, one barely notices a fan blowing, the humidity seems to put up resistance to the moving air, and in their case, the moving air would be humid. That is my guess on the situation based on living around the country and experiencing evaporative cooling.

 

[lenny flank]

Alas, I have never seen any sort of fan system that actually seemed to work effectively. Unless you are actually cooling the air somehow (and that requires some version of an AC), the BEST you can do is keep the inside temp of the vehicle equal to the outside temp.

 

[Trebor English]

That is 200 watts total over 7 hours.  I'm not sure if this is correct, but I divided 200 watts by 7 hrs. to get 28 watts per hour. 

One watt is one joule per second.  Dividing by 7 is wrong.  200 watts is 682 BTU per hour times 7 hours is over 4000 BTU, 20 more pounds of ice.  So, depending on van insulation, you will need at least 20 pounds of ice (thermos) to maybe 100 pounds.  For a one time event the ice will help.  On a recurring basis practicality depends on finding a supply of ice.

 

[ice_maiden]

here is another version of an evaporator cooler from the burningman website.... it's designed a bit different as it continues to circulate the water.... might combine the two ideals

https://eplaya.burningman.org/viewtopic.php?t=33842

 

[Gideon33w]

If the environment is dry enough you can get a lot of cooling just from the evaporative cooling effects. The ice is just gravy.

I just finished my homemade evap cooler which is setup to take ice when wanted. I was debating doing a write-up in it. It is self contained inside of a standard Coleman water cooler. Check my build thread in the Conversions and Modifications section for a pic.

Even currently in the middle of monsoon season here in Arizona it still pumps cold air despite the higher humidity. Using self wicking material, a high output fan, and a more than high enough output water pump means that it is always running plenty optimally.

There is just a few things to keep in mind with an evap cooler that most people goof. One - You MUST have a constant influx of fresh air. Otherwise, once you saturate the air it will stop cooling. This makes it a bit of a balancing act and takes a while to get good effects. Two - The higher the humidity the poorer it works. Too humid and they become pretty much worthless. Three - Ice is just added for EXTRA cooling. If you rely on ice you will consume it an a phenomenal rate and end up spending a small fortune.