# Use existing pond for cooling cabin?



## volleypc (Jul 25, 2010)

We have a small pond near the cabin that is about 12 foot deep (verified). I am wondering if I can install an intake near the bottom and have some type of open surface tank (cooler size) in the cabin with a fan blowing over it to cool the cabin. My goal would to be a small pump hooked up to a thermostat so that when temp gets over 78 degrees it comes on and runs continously. Any ideas?


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## TnAndy (Sep 15, 2005)

Not worth the effort is my guess. 

Relatively small surface area of the open tank inside AND the fairly small temperature differential between air and water temp, and I suspect unless you're sitting ON the tank, you won't notice anything.

IF you were to greatly increase the surface area by using a large radiator ( like out of a truck ), that might help, but I'm not sure even that would do the trick.

Unless you live in a high humidity area, the best route to go is a "swamp cooler" based on evaporation of water.....but they don't work well in a area where your relative humidity gets up above 40-50%.


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## volleypc (Jul 25, 2010)

Unfortunately I am in an area of high humidity.. Mississippi. I guess I need to get out my old thermodynamics text book and make a few calculations. I expect the water at 10 foot would stay pretty cool and the cabin isn't very large. Thanks for the insight.


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## SolarGary (Sep 8, 2005)

Hi,
I think something like a car radiator or the HVAC coil equivalent would be much more effective. 
See the first story here by Nathan:
http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm#Storage

But, you would probably need something more to control humidity. I guess that if the pond water was cool enough, the radiator might condense some water that could be drained away. 

Gary


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## ace admirer (Oct 5, 2005)

i would think you are going to need more surface area than just a tank....a heat exchanger like others have mentioned.....with the heat exchanger, you would not have the humidity problem that would probbly exist with an in house open toped tank.

(like everything else, heat exchangers have an efficiency....basically if you put 78 degree water in you will not be able to cool air below 88 degrees, a delta temp of 10 degrees for each exchange media. )

the best of all worlds would probably be a new concrete poured floor with cooling pipe installed in the pour.


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## Harry Chickpea (Dec 19, 2008)

I'm reminded of a story by Alexander Graham Bell from before the days of air conditioning. He was living in Washington D.C. and it was unbearably hot one summer. He had, within his home, a standard concrete flat bottomed swimming pool that had been drained. He remembered that cold air sinks and hot air rises, so he instructed his staff to place ice around the rim of the pool. He then entered the empty pool and found it was about twenty degrees or more cooler. The experiment was so successful he added a carpet, desk, chair and sofa.

So... you don't have ice and you don't have an indoor pool you can drain. What might work to some extent would be to make a false ceiling with chicken wire holding up some polyethylene sheeting at a very slight angle. A drip hose on the high side and drain on the low side would allow a thin sheet of cool water to flow over the poly. Since cold air sinks, it might lower the temp in the cabin a few degrees. By having it near the ceiling it would also block some heat radiation coming from the roof, which would be another important factor.

Be aware that as the summer goes on, the water will be warmer and the system will likely stop being effective by the end of July.


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## Cyngbaeld (May 20, 2004)

You might want to get a temperature reading on the pond in midsummer.


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## roachhill (Jul 8, 2009)

there is a 12 volt cooler doodad for semis where you put ice and water in a cooler and the cold water is circulated though a radiator with fan to cool the air. If a large supply of cold water were available I don't see why it wouldn't work without the ice. I wouldldn't expect miracles from such a setup but it might do to keep a small room comfortable. Not that I've tried it but I was looking at the cooler for cooling my sleeping loft down on hot summer nights.


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## ace admirer (Oct 5, 2005)

ok for those of you looking at evaporative cooling, need to study the psychometric chart for your temperature vs humidity,,,,,it just does not work in high humidity areas like the south east. works great in area of low humidity.


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## fishhead (Jul 19, 2006)

The first thing I would do would be to check the level of insulation in the house. Once that is taken care of a pond should provide cool water all summer if you use a closed loop lying on the bottom of the pond.

You can also keep a house cool with shade from vines.


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## volleypc (Jul 25, 2010)

I am using passive cooling so it is designed with reflective roofing, plenty of shade, etc. I am not trying to use evaporative cooling because it will not work in this area. I think I am going to do a test with thermometers and chilled water soon to see how well it works. The pond is farily shaded so I do not expect the summertime temperatures for the lower level of the pond will be above 70 degrees. I am worried about it being anerobic so I need to do some test for odor as well.


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## fishhead (Jul 19, 2006)

You can avoid that problem by using a closed loop system. Then it doesn't matter what is growing in the pond.


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## Parttimefarmer (May 5, 2011)

You sound like you are describing a homemade water furnace system. I am looking into that at the moment. It's closed system geothermal that can use a well or pond (we have a spring that's always cold). Maybe look at that and see how they do it, check their methods against your ideas and create a viable homemade version that's more what you need.


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## sirquack (Feb 18, 2009)

I am glad I am not the only one who thought of closed loop geothermal. It would be most effective to cool in the summer due to the relative shallowness of the pond. 
We are looking into the same options for our country home,but we are looking at a closed field loop since it can be used for both cooling and heating. The cost is quite a bit more, but over time, more than makes up for itself, especially if you also include passive solar, active solar and wind turbines into the system.


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## RW kansas hogs (Nov 19, 2010)

I like the geothermal idea, But is your cabin insulated? You can spend all the $ you got on things cooling your cabin but if it isnt insulated, All that cool air will leak out the windows and roof. 
How old is the cabin for starter's?


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## volleypc (Jul 25, 2010)

RW kansas hogs said:


> I like the geothermal idea, But is your cabin insulated? You can spend all the $ you got on things cooling your cabin but if it isnt insulated, All that cool air will leak out the windows and roof.
> How old is the cabin for starter's?


New Construction. I will be starting it this spring. 2x6 walls insulated plus 1 in rigid foam board. Light colored metal roof with with high reflectivity and metal faced foam board. The walls or shaded as well. I am still working on window size/brand/style but it will be a good product. I want casing windows but not sure I can afford them. Roughly 600 sf plus loft,


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## RW kansas hogs (Nov 19, 2010)

Sweet deal Volley, Just remember the more $ you spend on insulation the more $ you save on your cooling bill, I would put in a few celling fans & and a a/c window unit untill you can aford to do what ever kinda system you want to install. 
Another way to keep your place a lil bit cooler is to build a wrap around pourch roof, It keeps the sun off your exterior walls and helps with the coolong bill somewhat


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## fishhead (Jul 19, 2006)

The water at the bottom stays quite a bit cooler than the water in the water column. Even in my fish ponds that were hitting 85 degrees the bottom stayed cool.


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## Zoomyn (Apr 12, 2019)

A general rule of heat flow is needing a 40*f temperature differential across a solid-to-air heat exchanger... when the difference drops below that the energy transferred decreases rapidly even if a comparatively huge amount of energy is used blowing air & pumping a rivers worth of water through the exchanger.

Now using that source of coolth (opposite of warmth) to condense ‘ground source’ air conditioner freon would be extra efficient as no electric needed to power condenser coil fans...


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