Clint
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Post by Clint on Feb 26, 2008 15:46:42 GMT
I was talking to someone who plans on switching from growing with a freezer, to using an air conditioner to grow highlanders (in South Carolina)
I was wondering, does anyone else use air conditioners to cool their greenhouses or basements/chambers in warm climates, like SC, GA, or FL? Is it even possible to cool a small (let's say 10 ft. x 15 ft. or so) greenhouse to, let's say 60 at worst, (or even 50-55, best!) degrees in a place like Florida? What sized AC unit would you need, if an AC unit can even cool a space that size down so low (can it? Or does the cooling capacity for an AC unit depend on the humidity and temp the unit is is? Can this be overcome by using a unit with more BTU? ) Or would you need a walk-in, room-sized freezer/fridge to grow something like, say N. rajah to full size in Florida, GA, or some other warm place/country? Could you further cool the AC'd air by piping it into a swamp cooler (since it's dry now) or would that not work, since it would be cool already? And last but not least, assuming you could do what's described above, how much would this cost monthly (approximately since electricity rates differ) ?
I know Michal Catalani uses AC in TN to grow his excellent plants. Maybe he'll chime in.
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Post by Brian Barnes on Feb 26, 2008 21:37:27 GMT
Hey Clint! Man, I'm glad you ask that question before i did! ;D Actually, I've been dreaming of growing tuberous Drosera here in Fl. for quite some time. It just doesn't stay cool long enough for them naturally. Species like D. erythroriza and D. loweri go belly up on me the first few times it gets over 78F. I'd love to be able to grow them proper and have them flourish for a change... I do know a gent in S. Fl. that uses old ice cream freezers with some great success... The scary thing is.....the electric bill, plus getting it down to that magical 50 to 55F realm, where all the highland Nep and tuberous magic happens, and keeping it there. At least, that's the case for me here in good ol' Fl. I'm curious to see some answers as well... Happy Growing, Brian.
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Post by rsivertsen on Feb 27, 2008 22:22:10 GMT
I've known some folk in warm climates to use industrial sized refrigerants/freezers for a walk-in cool room, to just modifying a small office refrigerator in order to grow some tuberous Drosera and highlang Nepenthes seedlings. It's only the tubers and roots that require the cooler temps, the rest of the plant can be exposed to 85oF temps in full sun. Insulation may help cut down on the electric bills.
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Post by Michael Catalani on Feb 28, 2008 17:59:17 GMT
When dealing with highlanders, you'll have two cooling issues. Daytime cooling, and night time cooling. If you have a greenhouse, the most ideal setup would be to use a swamp cooler / exhaust fan combo for the day cooling. Day cooling in a greenhouse can be tough because you are battling the power of the sun inside a clear greenhouse. Most AC units will fail to compete with the heat of the sun, or cost you so much to run that you would come out cheaper purchasing part of Mt Kinabalu and growing the plants there. For basements and chambers, AC's work well for daytime cooling. For nighttime cooling, AC's will do a better overall job if you have periods during the summer where nights dont drop below the 70'sF. A swamp cooler/ exhaust fan setup can get you into the upper 60's if your source water is cool enough, but thats about it. The one problem of cooling an area with an AC at night is the high humidity. Most AC's operate in a home environment, where 30% humidity is the norm. AC's are designed to handle cooling temperatures with this type of humidity. In a highland Nepenthes growing area, the temps can be 80F, and 70%-80%humidity. An AC will have to work some serious overtime in order to remove the humidity from the air in order to be able to drop the temperature. This means you need an AC that is seriously oversized for the area it is cooling. Another issue that has to be considered is that of controlling the AC. During the day you want it to come on if temps exceed 80F-85F. During the night, you need it to drop the temps as low as it possibly can. This means that the unit will have to be connected to some sort of controller or dual timer thermostats that can power the AC circuit on when its needed. You will need an AC that can reset itself and turn on when power is cut and restored to it. (Commonly known as auto-restart) Most newer digital AC models dont have this feature. An example of one that does have the autostart feature is found here: www.sears.com/shc/s/p_10153_12605_04275123000P?keyword=air+conditionerIn my highland chambers (6 of them currently), the day cooling is handled by the above AC. The night cooling is also handled by this AC during hot nights, or by venting in outside air if the air is cold enough. It may seem like a large AC that is designed for cooling multiple rooms in a house can quickly cool down an area 1/4th that size at night, but it will be battling the moist soil in the pots. Even venting the cold outside air in with an exhaust fan has to battle the warm moist soil temperature. If I vent in 40F air into an 80F chamber, the chamber temps can drop to the low 60'sF in a matter of minutes. But it cant get the temps any cooler because the soil in the pots release their heat and moisture, and this battle goes on for about 2 hours. Once the heat in the moist soil is spent, the temps further drop into the low 50'sF. I then stop the venting processs. The temperatures will then rise into the low-mid 60sF and then slowly drop thru the night from there. To show the power of the heat that is built up in the soil, I can vent 40F air into an 80F chamber. In about 2 minutes, the temps will be close to 60F. If I stop venting, the temps will be back to the upper 70'sF in a matter of minutes. Its a quick rubber band effect. This is what the AC will have to battle. For those that would like to see this process, you can click the following link: 75.147.200.33/cgi-bin/liveThis link shows the current status of the sensors and relay circuits for my 12 Nepenthes chambers. Some of the sensors are not fully hooked up yet, and the heating/cooling process is not yet automated. But you can watch the cooling process at night. At 8:00pm central time, the highland lights will shut off. At that time I manually start venting the chambers. You can follow the temp and humidity drops for the next hour or so. You'll know when the venting process is completed as soon as the humidity shoots up and the temps slowly rise from the low-mid50'sF to the low-mid 60sF.
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Clint
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Post by Clint on Mar 1, 2008 15:55:57 GMT
Fantastic overview! The unit you use is much smaller than I had expected, honestly. Does it cope well with your summer temps (what are they at day and night, BTW?)
Would AC'ing your basement be more practical, given the cost of using artificial lighting?
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Post by Michael Catalani on Mar 2, 2008 6:27:40 GMT
Our summer days are between 95F and 105F during the day, and they hang in the lower 80'sF at night.
The AC can easily handle the day time cooling. The night cooling is handled in 3 different combos:
1) Outside venting only
2) AC only
3) Venting first, then AC
When the temps outside at night are below 60F, then I can vent the outside air to cool the chambers without using the AC. If the night temps are between 60F-and 75F, I vent outside air for a while. This removes excess humidity and gets the air down to the outside air temperature. The AC can then more easily handle the cooldown from that point. If the outside temps are above 75F, then I can only use the AC.
Venting or using the venting / AC combo saves a lot on electricity, because the exhaust fans only pull about 1amp of power. The AC unit uses about 10 times that amount.
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Post by Randy Zerr on Apr 29, 2008 3:19:02 GMT
I once built a terrarium about 36' x 18" x 18" plexiglas & glass, sides insulated with 1" styrofoam sheet and rigged up a Peltier Junction (solid state semiconductor cooling device) with heat sinks and muffin fans through the plexiglas side. I set it on a timer to run when the lights were off and it would drop the temp in the terrarium about 18 degrees. Not really cool enough for the highlanders but it worked. I tried to pack and ship it UPS and it was destroyed. It required about 1 amp at 12 volts from a power supply plugged into house electricity.
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kby
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Post by kby on May 7, 2008 6:53:24 GMT
I once built a terrarium about 36' x 18" x 18" plexiglas & glass, sides insulated with 1" styrofoam sheet and rigged up a Peltier Junction (solid state semiconductor cooling device) with heat sinks and muffin fans through the plexiglas side. I set it on a timer to run when the lights were off and it would drop the temp in the terrarium about 18 degrees. Not really cool enough for the highlanders but it worked. I tried to pack and ship it UPS and it was destroyed. It required about 1 amp at 12 volts from a power supply plugged into house electricity. Actually, I'm pretty impressed; that's a much bigger drop than I'd expect with the typical Peltier that's currently available in the numerous coolers (from experience as well as what I've read about Peltier devices). What was the ambient temperature of the room the tank was in and what temp did the tank actually get down to (I assume with lights on it was higher than ambient so turning off the lights causes some drop)? I guess the styrofoam should insulate you form ambient, but was there styro on top where the lights were or above the lights?-kby
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Post by Randy Zerr on May 8, 2008 2:50:35 GMT
Styrofoam was just on the sides. I left the top bare so to see in The usual temperature indoors during the summer in Louisiana was about 78F The Peltier would cool the terrarium down to 60F at best by the early morning. It wasn't all too effective.
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Post by Randy Zerr on May 9, 2008 0:21:37 GMT
Peltier junctions are a neat invention. A special semiconductor matrix that causes heat transfer from one side to the other when 12v DC current is applied. The one I had was about 2" x 2" and about 3/8" thick with an aluminum heat sink on each side. If anyone wanted to try the same, Peltier junctions such as used in the Coleman thermoelectric coolers are easy to work with. No pumps, no tubing, no leaking Freon, and few parts. Just some quiet running small muffin fans such as used to cool computers (can probably be had by the dozens for free now) , and a 12 volt DC power supply. Multiple Peltier junctions can be set up in parallel for more cooling effect and easily controlled with an adjustable wall timer on the power supply. For the size terrarium I built (36" x 18" x 18") 2 junctions would have been perfect. Also a section of plastic flex ducting with holes along it's length to better circulate the cooled air inside the terrarium. I bought my junction from the spare parts supply from Coleman. I see they are online now. www.coleman.com/coleman/ColemanCom/subcategory.asp?CategoryID=8570Each junction was $20 back in the early 90's. Probably more now. Ebay might be a great place to find them including entire thermoelectric coolers.
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kby
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Post by kby on May 9, 2008 7:01:09 GMT
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Post by Randy Zerr on May 9, 2008 12:31:56 GMT
Ah ok, so it was indeed given up on. I knew they were inefficient but not that bad! Probably not worth bothering with. I wasn't al lthat impressed with the one I built, but it worked. Sort of. Oh well. thanks
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kby
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Post by kby on May 9, 2008 18:03:08 GMT
I didn't mean to be too discouraging. I actually have had some second thoughts after reading how much of a drop you got. I'm not sure my experimental results are all that conclusive; I was trying to effectively use water as a thermal transport medium and it does have a lot of heat capacity plus there would be more transmission losses having the water cool the air & soil. On the other head, reading the theoretical efficiency comparisons is pretty depressing. The other thing that kind of depressed me was that I think in the best of worlds (like using those Coleman coolers or things like them) where someone has worked out most of the bugs, they only really say you can keep things at about 45F at best, and that is in the small pretty well-insulated container. The typical terrarium setup his a lot more thermally leaky. As far as temperature readings I am not so sure on mine. Using the fridge unit & even with a muffin fan it looks like it's only maybe upper 50s, lower 60s depending on the location within the tank (about the same size as yours, maybe even smaller), but I know there's ice/frost on the evaporator so at least very locally it's 32F.
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Post by Not a Number on May 9, 2008 20:22:35 GMT
A drop of 18 degrees F is by no means insignificant. I think the derailed enthusiasm earlier was from the expectation that cooling without moving parts would be more efficient than mechanical cooling.
Darlingtonia seem to be basically highland in nature as far as temperature requirements go. Daytime temperatures in the Sierra Nevada's can go well above 95F (35C) in the summer with night time temperatures maybe in the mid 50's F (12C).
I'd guess that many of the problems of growing Darlingtonia in the southern states (basically sub or semi-tropical climates) are the summer night time temperatures.
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