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so, i have a fun little project on my hands and thought I might prey upon the gracious brain power here for ideas, not having not enough time to build and test prototypes.
I need to build a rather large cooler for a food booth at the oregon country fair. I call it a cooler rather than a refrigerator because it needs to be somewhat low-budget and electricity isn't a practical option. What we used last year was about 50cf, which was sufficient in terms of size, but the design really didn't keep things cold enough, having doors on the side and too many gaps on the open bottom.
So, what I'm thinking is this:
-2 chest-type enclosures (one to be used for frequent access and the other for longer term storage)
-plywood shell with rigid foam insulation
-pockets built into the underside of the lid for dry ice
-sealed well but with a small drainage hole built into the bottom
-locate in as shady a spot as possible
i can't decide between stacked milk crates or creating a sliding shelf system, and I almost wonder if i could get away with nixing the rigid foam and substituting it with straw stuffed into the gap between two large nested boxes (maybe a 3-4 inch gap?) ...much greener, but effective enough?
so, ideas? experiences?
thanks!
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Oregon
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Re: uber cooler
Thu, April 23, 2009 - 2:04 PMfew things insulate so well as Styrofoam. It glues up well with plain old Elmer's or a yellow glue like Titebond
You can build a Styrofoam dewar about 2" thick and fill it with Liquid Nitrogen. Put a styrofoam cap on it and it'll keep the LN2, in a liquid state for a very long time.
I'd make my cooler from styrofoam and put some Dry ice in it.
If I wanted it sturdy I'd build a plywood box and line it with styrofoam and use low foaming Great Stuff to seal the cracks
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Re: uber cooler
Thu, April 23, 2009 - 3:10 PMNeed more info on duration of event, target cost, capacity (are you still looking at about 50 cu.ft between the two units?).
In any case here are my semi-radical ideas thus far:
1) Don't build, buy -- look for large (or appropriate) capacity chest freezer(s) on craigslist. It would be nice if they worked, but not essential
as you really just want insulated boxes. One reasonably large working freezer would be helpful for step 2 tho' (I found at least a half
dozen offers around Eugene ranging from $50-$300)
2) You can cool with dry ice, or you can use a working freezer to create consumable cooling modules aka 1.5 liter bottles of frozen water.
Simply plug in the freezer(s) a couple of days earlier stock with appropriate quantity of water bottles, then when ready transport the rig(s)
to the fair.
3) Recycle - when the event is done simply resell the chest freezer(s) or even the bottled water if you wish. -
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Re: uber cooler
Thu, April 23, 2009 - 4:57 PM
hmmmm, I like those ideas ...gonna need to do some noodling around transportation, unloading and set-up, though
but to answer your questions, the booth is operational for roughly days and yeah, 50 cf between the two ...maybe even more to allow easier access to things on the bottom without having to remove items on the top (just slide to the side).
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Re: uber cooler
Thu, April 23, 2009 - 4:54 PM
yeah, i looked up the r-values and straw doesn't seem to be worth the effort ...faced rigid insulation looks like the ticket -
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Re: uber cooler
Thu, April 23, 2009 - 6:11 PMThat pink rigid insulation is pretty good stuff. I don't know what will glue it or seal it but I'd bet money on low foaming Great Stuff. -
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Re: uber cooler
Thu, April 23, 2009 - 9:31 PM2 ideas:
- people looking to replace old refrigerators having little or no resale value will let you have them for the hauling. Choose your optimum size, shape color. Now you already have an insulated sturdy icebox. Remove the motor, condensor, and coils on back to reduce unnecessary weight & ease of transport. Beef up insulation with R-19 slabs cut and glued in place. Partition off an insulated enclosed sealed section of the interior to hold coolant, maybe in a sperate insulated metal box. Coolant pack consists of a hybrid of dry ice with prefrozen water pouches packed in around it. The dry ice can last about 4 days if chest is opened sparingly. Coolant pack replenishable when required without moving/disturbing icebox contents..
- Dealers of used RVs and used auto parts places will have older RVs being junked or parted out. And these will contain cheapo old LP -powered refrigerators. There is virtually very little market for old used appliances from RVs. Most Buyers want the whole rig new, or late-model, purchased all at one time. Get the size of choice and a large flask of LP gas and some connector tubing. A pair of 4' LP refrigerators are comparatively easy to move around and to set up. This solution may work out even more cost-effective than the icebox, when you think about it.
Both ideas are green in that landfill-ready items are being remodeled reused and recycled. -
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Re: uber cooler
Fri, April 24, 2009 - 7:25 AMUntrue about the used RV parts. Used propane fridges are in high demand, due to the cost of new units. A working used unit will go for 1/2 of retail.
I've used the old house fridges for everything from rodent/bug proof storage containers ( lay it on it's back), to warm boxes to protect sensitive chems. and paint from freezing in cold clim's. Bypass the door switch so that the light stays on when closed ( insert old joke here). You do need to change out the standard light socket to accept the small base 7 watt bulbs. the 25 watt bulbs are to much, for anything but extreme cold. I don't see any reason it wouldn't work as a cooler, with some added insulation. -
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Re: uber cooler
Fri, April 24, 2009 - 9:51 AMEven at 1/2 it's a value. They last virtually forever. I'm currently running a 1947 Servel that I swapped a chainsaw for (went to axe & maul instead) back in 1985. & they work F$%+~ing good!
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Re: uber cooler
Fri, April 24, 2009 - 11:13 PMI'm not sure why you want to avoid electricity, but I'm going to make an assumption and go with being green. Unfortunatly, being green isn't as simple as the energy consumption of the end product. It takes quite a bit of energy to produce liquid nitrogen or dry ice. Much more so than to run a standard refrigeration device. Probably the greenest thing to do would be to simply run used refrigerators on a generator.
I get amused at the people who trade in their perfectly functioning cars for hybrids that burn 1/3 less gasoline, but consume over 1000 barrels of oil to manufacture. -
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Re: uber cooler
Sat, April 25, 2009 - 9:06 AM
well, mostly i'm looking for simplicity. Plus, I don't think generators are even allowed in the central part of the Fair (lots of rules for this shindig).
Propane could very well be an option next year if I can't pull off the dry ice idea this year. We get a large tank to run our stove and oven, so it's completely conceivable to run another line to a fridge. However, it sounds like with my space requirements (50cf) and with the usual size of propane fridges, I would need to rip some guts out of several and retrofit them into some larger insulated boxes ...more time or money than I want to spend, but at least if I don't strike success this year I'll have plenty of time to bring that project to fruition.
Some questions come to mind though ...how much fuel do those things generally use? ...and how loud are they? ...would suck to drain a tank during a peak rush of hungry Fair folk, and even though it's a pretty loud affair, I would rather not add more noise to the mix ...at least not mechanical noise (joyful or musical is just fine)
thanks again for all the replies and ideas -
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Re: uber cooler
Sat, April 25, 2009 - 8:41 PMLP refrigerator works on liquid ammonia heat exchange evaporation system, In Paul Theroux's book, Mosquito Coast, the hero builds one in the jungle. A small flame burning under the ammonia reservoir basically burns all the time to keep liquid gasifying and then coling in continuous cycle. t's pretty economical. Think a large pilot light on the whole time. No sound when your exhaust uptube is clear, but if obstructed with animal debris or dirt then a sort of throaty whisper is produced. Used indoors you absolutely need to vent off carbonmonoxide to outside.
The business parts of a pair could be combined installed into a larger icebox made of a larger refrigerator-freezer chest. -
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Re: uber cooler
Sat, April 25, 2009 - 10:12 PMhmmm ...now it's starting to sound kinda like a fun little project!
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Re: uber cooler
Mon, July 13, 2009 - 11:56 PM
follow up:
so the oregon country fair is over and the 2 coolers i built worked quite well. I was down to the wire in putting the things together, so I didn't get to optimize my design as well as I would have liked, but I'm pretty happy with the results. The first cooler was built with as much scrap material as I could gather: 2" rigid foam inner box with 1/4" tile backer in the bottom, a middle layer of packing peanuts (roughly 2") and then an outer layer of the foil-faced bubble wrap stuff. The lid was a single sheet of 2" rigid foam attached to a hinged cedar frame. The framing was a bit excessive to support the different layers and subsequently it was quite a heavy box. I simplified the second box: 3" of rigid foam with the hardi-backer bottom and a cedar 2x4 frame. The lid was similar with the exception of a built in box for small slabs of dry ice and a lower plastic sheet to act as a drip shield. There are other design details, but this covers the overall basic design.
in over five days we used about 140# of dry ice and was able to maintain the temperature around 40 degrees, despite being consistently opened, closed and reloaded ...the health inspector was impressed, as was I.
