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Creative Cooling Solutions?

TheFury

Oh, the humanity!!
Hey folks -

Being that there are so many people here with a) way more experience than I have in building grow chambers and b) a much better understanding of thermodynamics than me, I thought I would reach out to see anyone had any bright ideas for me.

Basically, I recently re-did my grow rack (see my "Grow Rack Re-Pimping" thread in this forum for details). After messing around with the ductwork, the humidifier placement, and adding heatsinks and cooling fans to the lights, I've managed to get temperatures relatively stable between 72 and 84 degrees. In the winter, due to lower ambient temperatures in the room, the bottom end of the temperature range will likely be in the high 60s with the top end still staying around 84 max. With my humidifier I can maintain humidity of 60% minimum and 95-100% maximum. I just need to get myself a hygrotherm or other humidistat to make sure that minimum RH is maintained. With me not around to turn the humidifier on, minimum humidity drops down to about 49% at the lowest.

NOW - here's the deal. My conditions are great (or at least close enough for government work) for lowland Neps. I would love to be able to grow some highlanders but I would need to do some work to get an adequate temperature drop (and to keep the maximum temperature closer to the high 70s rather than low 80s).

I see people here with crazy rigs like air conditioners dismantled and put inside the grow chamber, or cool air piped in from an outboard AC unit. Unfortunately my lease on my apartment limits me to one 6,000BTU unit due to old, crappy wiring... and that quota is already filled with a unit in my bedroom (crucial during NYC's miserable summers).

I also see folks (swords, I'm thinking of you) pipe cool air in from a nearby window. That would be great if a window were accessible! Unfortunately, as I've explained in other threads, my grow rack is set up in my girlfriend's study. I'm operating on borrowed space; her desk is in the window and I can't in good conscience run a big fat duct across her workspace to get at that precious cool air!




SO


I open the floor to you guys.... What do you think I could do to lower the bottom end of my temperature range? Some sort of evaporative cooling mechanism? A heat exchanger? Some magic black box that takes in pixie dust and puts out pure chilled air? I'd like to hear of some successes (or failures) that folks here may have had in their quest to create the perfect grow rack.

Thanks, and I look forward to hearing your insights! :hail:
 
The most ingenious set-up that I've ever seen that MIGHT suit your needs was used to chill a reef tank. The guy took a refrigerator, drilled a hole in either side, and ran flexible tubing through. Inside the frig it was packed with coils of tubing. He ran this on a slow pump with a thermal switch (to a probe in his sump). He swore by it, but I never actually saw the tank running without it, so I don't know how much, if anything, it actually did. For your purpose, you'd probably forego the coils of tubing since you're not using water. But, how you'd pump the air, I don't know.
 
If you can't use an AC then maybe try a peltier device? You might need quite a few of them to cool a large chamber. I know they sell a peltier device for aquariums, or you could make your own.

you could also try an aquarium chiller if you got the cash, but they use just about the same amout of watts as an AC (depending on the size).

Ive seen this guy take an office water cooler and run a line of tube through the chiller bucket and pump that into his aquarium to chill it. It worked for over a year if I remember correctly, but i dont think the temperature drop would be significant enough for neps. I think he was only able to lower the temperature of the water in the tank a few degrees Fahrenheit.

I dont think fridges last very long when used to cool terrariums as they're not designed to run constantly. Also if you drill holes in it or whatnot, you'll diminish the insulation of the fridge which will cause it to have to work harder. In the end you'll probably end up with a burnt out fridge.

If you can freeze a ton of ice you could use that to cool the tank. If you wanted to could dump the ice into a cooler and then drop a coil into it. HAve the coil connected to a computer cooling kit (tubes to a rad intersected by a water pump). Put the rad in the tank and place a case fan behind it. Pretty much the same idea as that dude on the CPUK forums (least that's what forum i think i saw it on), minus the aquarium chiller.

I personally modified an AC and stuck it in my tank and so far so good.

You're kind of hindered due to the electrical limit of your apartment. I'd say its still doable, you just gotta figure out what works for you :).
 
callmemonkey and I were talking about this last week. He's trying out a peltier device - might want to hit him up or wait for him to chime in if he finds this.

Another idea is what I use to do before I got an AC unit:

photodpe.jpg


The ice chest held a few gallons of water along with a few frozen 2-liter bottles. A pump pushed the ice water through the copper tubing on the fan. Big and ugly, but effective. With it, I was getting a good 10 degree drop in the room. Technically speaking, it does have a dehumidifying effect (condensation on the copper tubing), but it was negligible enough to be unnoticeable. You might try something on a smaller scale so that you can easily duct the cool air into the rack. A rack is going to be much easier to cool than an entire room, so you wouldn't need nearly as big and intrusive a setup (though the bigger the reservoir, the better - more water to pull heat from the room and more space to pack your frozen bottles, which means a longer period of effective cooling time).

Could be worth toying with the idea, at least. Hope it helps any.
 
:0o: That is a great idea! I wonder if I could accomplish something similar on the duct fans that feed my rack. Are you just using a standard aquarium pump?

And peltier devices... fascinating! I'm going to have to look into that some more. Thanks!! Any recommendations on brands?
 
Peltier cooling is very inefficient relative to mechanical compressors. For something as big as a your rack, I don't think you'll like the impact on your electric bill. If you're curious though, I'm know other folks have done it before, and I'm pretty sure there's been at least one thread on it.
The fridge method is good - I'd look into that. But I disagree strongly with drilling holes into the case. A better approach, I believe, is to build a shim to go in between the case and the door - a wedge-shaped block to keep air from escaping the fridge when the door is slightly ajar. Drill the holes in the shim rather than the fridge case. Circulate a loop of water through the fridge and into the enclosure. The water never leaves the loop, and just acts as a coolant to move heat from the enclosure to the fridge.
A simpler, but more expensive, option would be to get an aquarium chiller, which is basically a fridge compressor and water pump put together. The retail price is prohibitive, but if you hunt around eBay and Craigslist you should be able to find one used with some patience.
~Joe
 
peltier is a dead end for anyting larger then a 5 gallon aquarium, way too inefficient for the uninsulated application
(see previous threads on the subject on any number of cp forums)

The closest thing to plug and play is the aquarium chiller plumbed to a heat exchanger (automotive heater core or evaporator coil) in the rack (IMHO)
 
There he is! XD
~Joe
 
Thanks for your input! Would I "get what I pay for" if I sprung for one of these?

Also... what if I picked up a liquid CPU cooling system and somehow rigged that to a fan to chill the air it blows? Thinking about something like this.
 
  • #10
Hey joe, yeah Im alive.... I have neighbors with trees down and a barn is setting on a house down the road, but no damage at my place...

no electric yesterday... but all is well mate, what an April

---------- Post added at 10:25 PM ---------- Previous post was at 10:20 PM ----------

that is not the type of chiller we are refering too...

something more like this:
http://www.marinedepot.com/AquaEuroUSA_Max_Chill_Aquarium_Chiller_1_4_HP_Less_with_a_Built_In_Controller-AquaEuroUSA-ED1151-FICHINQCBC-vi.html


1hp = 746watts and 1 watt is a little over 3.4 BTU's/hr IIRC
 
  • #11
I'm not sure what that is in the eBay link, but it's a lot smaller than what I had in mind. The one I've seen up close was about the size of a big toaster and could hold a 100g saltwater tank with very hot lights over it at 55F on a hot summer day. Most have built-in digital thermostats that let you target a very particular temperature range.
Glad to hear you're OK Butch. I've been sans TV for a long time now so I didn't know about the storms until someone mentioned it today at the NASC meeting. Hope there aren't any repeats.
~Joe
 
  • #12
I used a fountain pump from Home Depot, like $20.
 
  • #13
Ah, thanks for clearing that up Av and seedjar. Prohibitively expensive indeed.

Has anyone looked at something like this? It's a USB-powered mini "air conditioner." Basically it has this removable tank that you fill with water and freeze, and it uses that to cool the air. Thoughts?
 
  • #14
I don't have experience with anything like it, but my first impression is skepticism. o.o;;

EDIT: Perhaps I should elaborate. It just seems to me that, for long-term, effective cooling, you're going to need to be running that thing constantly, which means quick melting, which, in turn, means frequent refills+freezes. But then there's downtime while it re-freezes, but if you're depending on it being available, you might be SOL.
 
  • #15
Look on craigslist under for sale commercial/business - refrigerator. Plenty of glass door two/three door units for sale. You might even find a walk-in glass door as used by flower shops. You'd need to add a timer for the cooling circuit and beef up the lighting but there are already openings for the wiring for existing lighting.
 
  • #16
Aaaaaand...BUMP!

I've been thinking more and more about Reaper's setup mentioned on page 1 and ways that I can finagle the system so I don't have to constantly re-freeze the ice packs. I've also been reading up on Av's experiments with Peltier devices and thinking of ways I can take advantage of those nifty gadgets.

Then I stumbled on this guy:
http://www.target.com/p/Koolatron-Fun-45-Kool-Cooler-45-P-45-25/-/A-10590839

It's an electric cooler that uses a Peltier device to bring the temperatures inside the container down to about 40 degrees below ambient, which for all but the hottest months of summer means it'd stay within 10 degrees of freezing in the ice box. It uses less power than a 40-watt light bulb, and it's quiet. Hmm, the gears in my head are just whirring around right now. If I filled that thing with water and ice packs, it would probably hold the cool temperature for a good couple of days before I needed to re-freeze the ice packs, eh?

Now the question becomes: once I draw the cool water out of that reservoir, how do I transfer the chill to the air inside my rack? 1/4" copper tubing looks awesome, but if I'm trying to chill the breeze from a 4" PC fan, I'll have to contend with the bend radius of that copper tubing... I likely wouldn't be able to get a complete loop around the fan without crimping the tubes.

Does anyone have any thoughts on this cooler? How about small-scale heat exchange devices? Anyone ever tried something like that?

Thanks for all your advice!
Edit: seedjar, sorry to dismiss the idea of an aquarium chiller... but seeing that it draws about as much power as an AC and costs $400, it's not a realistic option for me. Maybe some day I'll have the wiring (and the bank account balance) to run one of those things!
 
  • #18
Yeah, it's the same kinda cooler. I had one in college and thought it was a piece of garbage because it didn't keep my beer cold enough. But maybe my expectations were too high. As long as this thing can maintain temperatures that are a good deal colder than a non-mechanical cooler would be able to achieve, then that's a win considering the intended application.

Do you think the rate of cooling on this thing would be too low? With a small fountain pump, I'd only be moving a small trickle of water through the cooler. Hmm, food for thought. But if coolers are pretty expensive to start with, why not throw down an extra $25 and get something a little less... passive?

As for the heat exchanger - this thing is pricy, but would something like this work?
http://www.amazon.com/Thermaltake-C...?s=electronics&ie=UTF8&qid=1315754046&sr=1-16
I know these are supposed to radiate heat and not absorb it, but would the exhaust from this thing be cold if I pumped icy water through it?
 
  • #19
After reading this thread I had an Idea. How about using a radiator/heater coil/heat exchanger of some sort. Even the little small one from amazon. Get an in line pump to make a closed system like in the computer water cooled cooling. Pump water into a holding reservoir inside a small cheap dorm room fridge. It would circulate the cold water from inside the fridge through the heat exchanger coils and back into fridge. No need to replace the ice packs and the fridge already has a thermostat to keep it cold. All you would need to do is drill two holes in the side or top for the tubing to go through. I personally would add copper coils inside the fridge with a holding tank too. The coils would allow the water to cool faster and the tank would house already cold water. I would use some sort of antifreeze in the water to aid in the heat exchange. If you had a tank and coils inside the fridge the water should stay cold enough even if you are circulating the water and warming it up witht he heat exchanger.

When i am able to build my cool vivarium I do believe this wil be the route I first take for cooling. When that happens best believe I will have pictures.

This setup is a little more involved than Butches Idea but I do believe it might be a little cheaper.

Then if you want to get even more involved reserach phase changing refrigeration. Some people can get stuff extremely cold.
 
  • #20
Mm, yeah that idea does sound veeery enticing. Thanks for the input! I'm just afraid of the power that a fridge, even a small one, would draw. They're also a little pricey, but then again, after all parts and components are tallied up, my little idea costs a pretty penny as well.

EDIT - hmm, looks like I mistakenly assumed that mini fridges draw more power than they do. They run at about 10% the power of a decent-size window AC unit (~70W vs ~700). It costs less to operate 24/7 than a 100W light bulb!. Maybe this isn't such an unrealistic option after all. To Craigslist I go!
 
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