DIY swamp coolers for emergency use?

Jonnie PekelnyContributor - August 22, 2020

For those of you lucky enough not to be in California just now, we’re having record heat and also record levels of wildfires, caused by a series of mostly dry thunderstorms that came through last week (NoCal doesn’t GET thunderstomrs usually, and certainly not in August.) The air is bad and I’m trying to figure out how to keep the place cool and filter air. So far I haven’t been able to convinece myself to sleep with closed windows.

As part of my solution I started looking at swamp coolers. The ones that particularly interest me are homemade ones, like this one: https://www.ebay.com/itm/Mini-Coleman-Red-5qt-Portable-Swamp-Cooler-Air-Conditioner-4-USB-Fan-Adapter/153685876714?hash=item23c8645fea:g:W8EAAOSwsQ5e9Aec. They also come in larger sizes. I’d probably buy one rather than build it myself because I don’t really have the right tools or level of handiness to make one out of the plastic coolers, and styrofoam seems too breakable.

Since I’m mostly interested in using these when I sleep I’d probably try to fill the cooler with a few frozen 2 liter bottles and maybe some extra ice so the cool air production lasts.

I’m just wondering if anyone has used similar contraptions.

Do they work to cool a medium sized bedroom? I know they’re not like air conditioning but if they can drop the temp some that would help a lot. Do they work if the window is open?

I live in coastal Northern California with a relatively mild and relatively humid climate (although getting dryer and hotter by the year!) Do swamp coolers still cool down a room in that kind of climate if you fill them with ice?

How much ice or what configuration of ice would I have to put in and what size cooler would I be looking for to keep it going for say 6-8 hours while I sleep?

What size of fan would I need to be able to feel the air some feet away? I would ideally like a USB fan so I can rechage it from a power pack if the power goes out.

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Hmm. I see two potential problems here. The first is that if you theoretically make ice using the refrigerator in your home then the net effect will be to heat the building. Refrigeration systems work by transferring heat from one place to another. Your refrigerator transfer heat from inside the ice box to the air surrounding the refrigerator. Due to system losses, the net effect of refrigeration systems is to generate heat. So if you make ice in your home, then transfer that ice to somewhere else in your home, use a fan to blow across that ice (the fan generates a little more heat), the net effect will be to make the entire home a bit warmer. 

The second problem is that even if you source ice elsewhere, or think of it as sort of local to the room, it’s likely to be a very small amount of cooling. Conventional cooling systems are measured in tons, with each ton being 12,000 btus of cooling capacity per hour. This is the amount of heat that it takes to melt 2000 lbs of ice over the course of 24 hours. This is just a massive amount of cooling capacity. Most residential systems start at 1.5 tons of cooling, and are often in the 3-5 ton range. Each pound of ice in the cooler will probably be worth ~ 200 btus of cooling (assuming you start at 10F, it takes .5 btus to raise the ice temp 1F, 144 btus to melt the ice, and 1 btu per degree temp increase of liquid water). Divide this by an 8 hour night, and you’ve got 25 btus/hour per pound of ice. At 10 lbs of ice per night you’ll end up with 250 btus/hr. The smallest window ac units are in the 5000 btu/hr range.

 

The problem with swamp cooler is humidity. They sorta work in dry climates but in a place that is humid already, condensation will run down your walls and mold will be everywhere. Been there done that!!! 

I have some usb fans that I bought at Walmart and they work well. Here is a link. 

https://www.walmart.com/ip/Mainstays-4-inch-Metal-Mini-360-degree-Pivot-USB-Personal-Desktop-Fan-Black/172867863

 

Looking through old forum posts and found this one that I wanted to comment and follow up on. Jonnie, I see that you are still active on the forum, so hopefully you will see this and can give us an update. 

Did you ever end up going with one of these DIY options? If so, how did it work?

I haven’t made one of these, but I don’t see them being able to cool down an entire room like an air conditioner unit. The best I can see is it just blowing cooler air directly in front of the vent there. Which would be fine for your case of setting it next to your bed and having it blow cool air on you. 

 

Swamp coolers are best for airflow in the entire house. But, They are not maintaining the cooling. Portable Air conditioners are best for cooling the room where you sleep. When Climate change and Heat increase day by day then a central air conditioner with airflow is best for you.