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Old 05/08/2006, 09:24 AM   #1
pnosko
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Geothermal Cooling from Another Angle

A search revealed many threads where cold water is passed through a coil placed in a sump. I'm going to be doing some excavating for a home remodel, and got the idea of using geothermal cooling by passing my tank water through a closed loop buried in the ground and possibly encased in concrete.

I don't know what material is used for the hoses that provide thermal heating in the floors of homes. But if they are not toxic, wouldn't a loop using this hose be a good way to pull heat out of the tank water?

Thoughts? Risks? Other comments? Thanks.


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Old 05/08/2006, 10:10 AM   #2
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If you were to circulate regular water through the loop, you would only have to worry about the coil in the tank or sump being toxic. If you circulate tank water, you have the whole loop for considering toxic parts. Also, circulating regular water, you dont have to worry about things clogging up the lines because its always the same water. Just some things to think about...

I think the most important thing to consider over what you circulate, is what type of material to use for the loop. Not only does it have to be non toxic, but it has to conduct heat well. If you were to use pvc, I would think the gph would have to be very low to cool it down enough to make a difference.


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Old 05/08/2006, 10:17 AM   #3
Steve C.S.
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I just met with a guy about putting geothermal units at the park I work at. He said they use a very heavy water hose type material. PVC expands and contracts too much to be safe (his words, not mine). I asked him about the geothermal principle and fish tanks. He said use very small diam. tube and slow water movement. He also recomended a very large sump that could hold several hundred feet of coil to get the most out of the heating and cooling. We have about 400gal of tanks in our nature center and thats what got us talking. The man said if done right it would save a great deal in electric costs.


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Old 05/08/2006, 11:22 AM   #4
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I was reading a while back about a house that was built using thermal cooling/heating and incorporating flow through house air ventilation etc etc.
One of the main features was how the water was heated and cooled for everything from heat in winter to bathing water.
A large part of the plumbing was placed underground, below the frost/freeze line just for the purpose of cooling.
If I remember right they used the grey type pvc not the plain or regular type because the grey type can expand and comtract (semiflexible).
In the end they were able to maitain a year round temputure of 76-78 degrees F with no mechanical heating/cooling at all.
I see no reason the same methods couldnt work on large aquarium systems.
Now this home was bulit into a hillside with a large part of it underground so that went a long way toward keeping temps stable. But the potential savings on chillers would be worth it on large systems.


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Old 05/08/2006, 11:39 AM   #5
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I recall someone either thinking about doing this, or actually did it several years ago on this board. I'll have to go searching....


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Old 05/08/2006, 12:13 PM   #6
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I can now foresee one drawback to pumping tank water though a cooling medium like the ground in that the use would not be constant, lest most of the time I'd be reheating water that didn't need to be cooled in the first place.

But if I didn't use it constantly, the water in that closed loop would go "stale" while it is turned off. If the water contains living matter (for sure it will), it would die, and I'd end up introducing a volume of polluted water every time I turned it on. Right?


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Old 05/08/2006, 12:19 PM   #7
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I wonder though, if you just shut of the pump, and left the line "open" wouldn't there still be enough water movement so that it wouldn't go "stale". The water in the pipe would still be cooled, and therefore it was seek equilibrium with the warmer water. Wouldn't that create enough movement to prevent the water from going "stale" ?

(I am really just thinking out loud here)


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Old 05/08/2006, 12:32 PM   #8
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I used a geothermal loop using tank water. It worked extremely well for the time i used it. Here is a thread about it. It is long but it discusses alot of indepth talk about different methods. I have some details of my system in it.

http://reefcentral.com/forums/showth...hreadid=817756

Hope you find it helpful.


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Old 05/08/2006, 12:34 PM   #9
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In one of the other posts where someone was using system water in the loop, they had two pumps. One low volume for continuous circulation (so wouldn't go stale) and a second high volume on a thermostat.


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Old 05/08/2006, 12:50 PM   #10
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Hmmm...if you ran tank water underground like you suggest and used a long enough hose for the loop and a low enough flow rate it might even be able to double as a denitration coil.

Sorry if this is a dumb idea, but it was just the first thing that came to mind...


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Old 05/08/2006, 12:50 PM   #11
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That was me.


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Old 05/08/2006, 01:21 PM   #12
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I think the fine line between denitrification and anerobic is to small to control with that type of system and still have enough flow to lower the tank temp.


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Old 05/08/2006, 04:42 PM   #13
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Quote:
Originally posted by das75
In one of the other posts where someone was using system water in the loop, they had two pumps. One low volume for continuous circulation (so wouldn't go stale) and a second high volume on a thermostat.
I would think the low volume is what would be needed to provide cooling anyway, not high volume (which requires a bigger, hotter pump).

I will be using a DSB, so extra denitrification is not a useful benefit.

Thinking out loud is highly encouraged and appreciated! Thanks to everyone so far for a great start to this thread.


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Old 05/08/2006, 05:03 PM   #14
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The small pump pushed just enough water through to keep it from going stagnet. The larger pump would come on when cooling is needed. I imagine the small pump does have some cooling effect but you don't want it to be very much otherwise you fighting your heating all the time to maintain a constant temp. The large pump has to push enough volume to lower the tank temp and keep it down when neccesary. The larger pump does cause alittle more heat but it is offset by the extra cooling capacity of the extra water. BTW the small PH was about 75gph i think and the large one was about 300gph.


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Old 05/08/2006, 05:10 PM   #15
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When you are reducing the temperture of anything, you are not actually cooling it. You are removing the heat. This requires some kind of heat exchanger. One of the problems with any DIY chillers is an efficient heat exchange material. Plastic does not work well and almost all metals corrode in salt water. This is why titanium coils are used. If you've priced any titanium coils you quickly see that its almost as cheap to buy a chiller.

My questions about the geothermal approach are how many degrees could you effectively reduce the temperature and when chilling is not necessary, what is the effect of water sitting stagnant in the lines?

Mike


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