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dug well air conditioning
By greenkarson, Section Heat Posted on Mon Aug 17, 2009 at 01:50:31 AM MST
gud well air conditioning

just thinking about a new project to cool my house. I guess its simuliar to a heat exchanger heres my plan.
my dug well is ten feet from my house its 24 feet deep water temp about 12 C to 14 C I have a forced air furnass for heat in my basement. so i was thinking i could use a small rad out of a car installed in my duct work and pump well water through it with a small circulation pump so water dumps back out into well again with the furnass fan running it should cool the house. my house is only 1100square feet very tight and well insulated.
any ideas or thoughts on this?

dug well air conditioning | 31 comments (31 topical)

Re: dug well air conditioning (3.00 / 0) (#1)
by joestue on Sun Aug 16, 2009 at 08:11:52 PM MST

It is illegal to dump water back into a well, regardless how clean it is.

otherwise everyone would do it....

Re: dug well air conditioning (3.00 / 0) (#2)
by Basil on Sun Aug 16, 2009 at 08:23:53 PM MST

I plan to do it. I did some testing and on a 90+ deg f air in. I had 72 deg f air comeing out. It works. If you do it run the water to your garden so it can filter back in the ground. If you run it back in the well it will just warm the well up. Plus it's ilegal in most places.

Bad luck or none at all.

Re: dug well air conditioning (3.00 / 0) (#3)
by harrie on Sun Aug 16, 2009 at 08:53:53 PM MST

Yes, this works very well. I have a flowing well that come's out of the ground at 42 degrees year around. I run it thu a heat exchanger that is attached to my cold air return on a gas furnace. After the water goes thu the exhanger, I dump it into a pond. You will however have condensation that will run off the exchanger. the furnace fan is controlled manualy, along with a small pump. If its 80 or 90 outside, my house stays below 70. it also lowers the humidity substanclly. Deffenatly worth doing.

Re: dug well air conditioning (3.00 / 0) (#19)
by framistan on Thu Sep 03, 2009 at 08:03:09 PM MST

Your water is 42 degrees... i will bet you live in the NORTHERN part of the
united states. I live in the "MIDDLE" (st louis) and my temperature readings are about 60 degrees 20 feet underground. I measured also in a deep cavern (meramec caverns) and it was only a few degrees cooler than 60...(about 54). Further south, in louisiana... i would think they may have it at about 70 degrees...it would be interesting if someone would post here to correct my estimate. The further south you live, the less effective the cooling would be.
"There are no IMPOSSIBLE PROBLEMS... only WELL-HIDDEN-SOLUTIONS."
[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#22)
by Airstream on Fri Sep 04, 2009 at 06:54:47 AM MST

Not exactly - If our Northern ground temperature is 50 but the high day-time temps are 85 there is a 35 degree spread; if the ground temp is 65 and daytime highs are 100 its the same spread...

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#4)
by spinningmagnets on Sun Aug 16, 2009 at 09:06:16 PM MST

When you are looking at aluminum heat exchangers (Car radiator) consider an intercooler from a turbocharged car or truck as a possibility. Very popular in diesels.

Since intercoolers are meant to be high-flow for air, they are less restrictive. Car radiators are meant to flow a fluid, but the coolant pump of a car is fairly powerful. They are designed to trade heat with 180F fluid and 100F air.

If the temp difference between your well water and the house air is much smaller, and the restrictive small passageways cause much less flow with a low-pressure fluid pump, you may be disappointed with the HX performance.

Much easier to restrict flow on a good-performing HX, than to try and boost performance of poor HX.

Re: dug well air conditioning (3.00 / 0) (#5)
by bob g on Sun Aug 16, 2009 at 10:02:01 PM MST

don't use a brass radiator whatever you do, as stated its illegal to dump back
into the well, and brass radiators use 50/50 lead tin solder, the lead will leach over time,, last thing i would want to be responcible for is lead in the aquafir.

bob g

Re: dug well air conditioning (3.00 / 0) (#6)
by scottsAI on Sun Aug 16, 2009 at 11:09:42 PM MST

greenkarson,

Yes, STOP.

Do not dump water back into well. For the reasons mentioned and another key reason.
Some locations will allow you to dump water back into another well if nothing contaminates it.

Problem with one shallow well. (yours is shallow)
The return water is warm, with no draw on the well, the same water circulates getting warmer and warmer. May take a while, but it ultimately happens. Normal house demand is not enough to keep fresh cool water coming into the well area.

Geo-Thermal wells are 400 ft or so with a sealed circulation path. At 25 feet your well is not deep enough.

Your ground water has the right temperature to dehumidify and cool. Not sure what your humidity levels are but mine the humidity is as important as the cooling.

Buy a normal AC "A" frame, designed to collect the condensate and remove it.
Will not cost much more than a new automotive radiator, which has no previsions to collect condensate. Tubing is much thicker and can take direct well pump pressure.
When using the well in this way, insure the well pump does NOT cycle, kiss of death to a well pump.

Find uses for the discharged well water, water grass, garden, fill a pond, keep roof cool.

Have fun,
Scot.

Re: dug well air conditioning (3.00 / 0) (#7)
by ETech on Mon Aug 17, 2009 at 12:56:44 PM MST

Just a thought to consider:

If the your well could take the heat load....

You could put a coil of copper tubing in the well with compresion fitting to transfer the heat.

The fitting eliminate the lead from soldering.
Just circulate water through the copper coil, no water is pumped out or into the well. Don't use water adatives just in case there is a leak (unless it is food safe).

Just my three cents, Etech

Re: dug well air conditioning (3.00 / 0) (#8)
by greenkarson on Mon Aug 17, 2009 at 03:14:02 PM MST

how much flow is required through the rad? can the water just be at a minimal flow or goes if have to be pushing through pretty fast? I was thinking of just using a little circulation pump the kind you can screw a garden hose on either end.

thanks

Re: dug well air conditioning (3.00 / 0) (#9)
by electrak on Mon Aug 17, 2009 at 05:54:49 PM MST

How much water do you need to pump, it is dependent on tempature differinal and BTU moved, your well is 55F,

1 BTU is 1lb water changed by 1F,
so to get 5000 BTU( a smallish AC) you need 5000 lb/degree of water/hour,
if your air is 75F there is a 25F dT 25/5000=200lb/H or 24gal/H divide be HX eff
Say you can get 75% heat transfer, 24/.75=32 gal/H, 768 gallons a day

-Slower pumping is better, the more time the air has to change temp the better, use lots of HX coils and run counterflow, You want to pump as little as possible out of your well.

Now if you had a stream next to your house, then you would want to pump as much as you could, because you would want as small of a dT from in to out.

So you will need to know how many BTU you need, then back figure water to meet it.

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#10)
by greenkarson on Mon Aug 17, 2009 at 06:27:11 PM MST

need a hand with the math. Outside air averages at 25C to 30C I would like inside to be around 21C. Well water is at 10.5C. Im thinking I need about 12000 BTU output so just wondering how many gpms of water i need.
i just found this heat exchanger for sale wondering what you guys think of it would it be a good one?

Re: dug well air conditioning (3.00 / 0) (#11)
by bob g on Mon Aug 17, 2009 at 07:47:51 PM MST

also you didn't mention how you plan to pump the water, but it is likely that the
energy required to pump may exceed the cooling value of the water in such a system.

you might be better off useing the water as a heat dump for a heat pump system?

bob g

Re: dug well air conditioning (3.00 / 0) (#12)
by bj on Mon Aug 17, 2009 at 09:19:55 PM MST

All the cautions noted, and one more. If you warm up your well water
enough, and there is any biodegradable material in the water, you will encourage bacteria growth. Most well water has no dissolved oxygen, so
it would be anerobic growth. There are some possible nasty things that
can result.

It would be worth getting a thorough analysis on the water before trying
this.
Just another caution
bj

Re: dug well air conditioning (3.00 / 0) (#13)
by greenkarson on Mon Aug 17, 2009 at 10:55:52 PM MST

i will pump water out onto garden aprox 50 feet from well will be using a little pony pump in line. we don't drink the well water anyways its to close to the road alway worried about contamination. the well is only about 20 feet from furnass through basement wall. what do you think of the HX in the picture?

Re: dug well air conditioning (3.00 / 0) (#14)
by electrak on Tue Aug 18, 2009 at 12:16:12 PM MST

That apeares to be a steam heater, getting 12000 btu out with a low DT may have difficuty, but should do something.
As that you do not drink the water, and is most likely surface water, adjust you pump so as to have very little temp rise from in to out, and make sure you are not pumping the well down.
If you can measure flow and temp of the water going in and out you can figure BTUs,
It is better it have more HXs in line and have a higher DT on the same water flow than to pump more water. So if you don't get enough cold, add more HXs
If your garden is for food, test the water and make sure there is no nasty stuff in any parts you use, or it will be in your food.

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#15)
by cruzan on Tue Aug 25, 2009 at 08:41:34 AM MST

You can find a nice heat exchanger tailored for this type of application here:

http://www.ctwoodfurnace.com/parts_water_to_air.htm

Comes in different sizes even.

I was thinking about a similar application using water in my large (>10,000 gal) backyard pond to keep the house hospitable during heat waves (> 95 F), which happen maybe for a week or so per year here in Oregon. The deterrents I ran into are:

The pond temp during the hot part of the summer is up around 65F, so cooling ability is severely compromised. Cool water is routinely used for AC in buildings, and some cases they even use natural sources (Cornell University has such a setup using lake water). But I think in those cases the source water is in the range of 45 - 50F. How cold does the water have to be to effectively cool the air?
Using the 1 BTU per gallon of water calcs and a delta T between 65 and 95 I would need to run the pump fast enough to deliver maybe 10,000 BTUs to keep the house in the mid 70's (I'm guessing). I could put the exchanger in the plenum of the existing furnace and run the fan (2000 cfm) to deliver cool air throughout the house, but....

- The cost of running the fan is 1 kw/h. A high efficiency AC maybe uses 3 or so kw/h. If the refrigerant based AC delivers 36,000 BTUs, then I'm not really saving any energy by running my pond-conditioner compared to a high SEER AC.
- On a hot day (95 F) running the AC for 10 hours could raise the pond temperature by one degree F (based on 10 hours at 10,000 BTUs), so on consecutive hot days the effectiveness of my pond conditioner erodes. But.....we do have evaporation off the pond that is facilitated by some splashy water falls. I could also run the outflow from the heat exchanger back into the pond through a mini cooling tower (no 'real' towers allowed in this suburban neighborhood). What I do not know is how effective such an arrangement would be in the Portland climate - humidity is probably around 50-60% in the summer. Any thoughts?

Great forum! Thanks for any feedback!

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#16)
by Airstream on Tue Aug 25, 2009 at 08:53:55 AM MST

Don't omit 'Radiant cooling' factor from pond heat shedding calculations.

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#17)
by cruzan on Tue Aug 25, 2009 at 05:24:05 PM MST

Do you mean heat transfer to the ground? (the pond is 4 ft deep) Or heat absorption from the air? Don't know how to factor those in. All this is pretty rough anyway and I am on the fence about giving it a try. It's $250 for the heat exchanger and probably a day's work to install it (I already have a pump that will work). If I were more sure this whole hair-brained idea would work I would do it!

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#18)
by framistan on Thu Sep 03, 2009 at 07:34:34 PM MST

I have been planning MANY years to build such a system... but may never get around to it due to money shortage.So I wish you to succeed very much. Here are a few thoughts for you to ponder ....

HEAT RISES... UP in water... so the water at the TOP of your well will be warmer, and the water at the BOTTOM will be the coldest. So you would want to withdraw water from the deepest part... and dump back at the top surface. And place insulation-wrap around the UP-pipe so it doesn't RE-WARM on it way back up!

EASY PUMPING.... if you circulate the water up and back down, you will NOT need a big pump... because the water traveling down will counterbalance the water going UP... If you dump the water on the SURFACE of the ground, then you are not circulating, you are PUMPING, and that requires more amperes and a bigger motor.

DUMPING WELL... if you had a 2nd well you could dump in that one a few yards away
to keep the temperature from rising... which i am not convinced is a problem yet.

LARGE RADIATOR... I believe you will need a large-ish radiator to accomplish the heat-exchange. The fellow who suggested the made-for-the-purpose heat exchangers was well intentioned... but the $80 dollar one was only 12 inches by 12 inches. and it is made for HEAT exchange (delta-t) of very hot water from a woodstove. not COOLNESS exchange of water only 25 degrees cooler that ambient air.... so unless you can afford the BIG BIG one at several hundred bucks... i suggest you get a car or truck radiator or other options that would be cheaper.

PUMP--AND---DUMP... some say is ILLEGAL... I say so what! You could place a
closed loop pipes into the well, and you are not really "pumping." you are just
circulating water up and back down through the same pipe adding a few degrees
warmth to the ground. The earth contains GIGANTIC amounts of tonage of rocks and water down there... I dont believe your "puny" radiator will warm the EARTH enough to worry about germs and mold contamination of the aquefer. I have a few other suggestions,(easy well drilling, other pumping methods,etc) but dont want to make this too long.. email me at framistan@sbcglobal.net (If you would like to discuss further).. the picture is me drilling a 20ft hole using a post hole twist drill.

"There are no IMPOSSIBLE PROBLEMS... only WELL-HIDDEN-SOLUTIONS."

Re: dug well air conditioning (3.00 / 0) (#20)
by ghurd on Thu Sep 03, 2009 at 08:42:59 PM MST

I have a couple issues with that.

IIRC, some region in AZ(?) (Phoenix? Flagstaff?) raised the ground temp a few degrees in a short time from geothermal cooling.
And I doubt the water table is exactly shallow in that area.
Anyway, it is a fact.

The idea of a radiator being larger is fine.
Not sure how much I like the idea of a car radiator cycling who knows what into the aquifer.
I don't want my kids to drink anything that could have gone through a radiator.
"Erin Brockovich" kind of thing.

Not sure why many people are so against a closed loop system in the first place.
Making a SS underground exchanger would not be very expensive in the big picture.

Here is where I think I get creative:
AZ for example. It gets cold at night.
Why not have a second exchanger out where it is cold?
Thermostat control switches from the inside radiator to an out side radiator and the pump turns on.
The pump uses a minuscule amount of power. A 20W pump would do a lot for a 20 cent / KWH, 8 hours a day, $4 a month. That is cheap for a thermal battery.
Seems a no brainer to cool the rock the system sends heat to when the surface ambient temps are high. With the right pump(s) the system's overall efficiency may even improve.

G-
Ghurd.info
[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#23)
by GaryGary on Fri Sep 04, 2009 at 03:21:06 PM MST

Hi,
Speaking of other simple solutions, I always thought that this setup showed some promise:
http://www.builditsolar.com/Experimental/RadiationCool/EvaproRad.htm

Its a very simple way of using a combination of radiation to the sky coupled with some water evaporation to cool a large tank of water over the night. The stored coolth would then be used the next day for cooling the house.
Its very simple and cheap to build, and the performance (at least in my dry climate) is quite good

In the small 14 sqft test setup I did, it achieved 470 BTU per sqft of "radiator" -- so, a couple hundred sqft "radiator" would cool the tank water overnight by an amount that would be equivalent to running a 1 ton AC for 8 hours. When you figure the pumping power, it works out to a 41 SEER AC -- it could be even better with a more efficient pump. The "radiator" is easily built, and costs a bit over $1 per sqft.

This will work best in climates where it cools off at night, and where there are often clear skies at night for good radiation to the sky. I am in SW Montana.

A side benefit is that you can use same "radiator" to heat your swimming pool in the summer :)

Gary

Gary gary@BuildItSolar.com www.BuildItSolar.com
[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#26)
by framistan on Sun Oct 11, 2009 at 06:19:13 AM MST

OK... mr Ghurd... I have thought it over and i agree with you that PUMP AND DUMP is not a good idea. Because many people DRINK that well water. a fact i overlook living in the city, near an airport that has nuclear waste buried nearby that has been leeching into our groundwater for 40 years. Nobody drinks well water here anyway. But even so, it is wrong to contaminate it further i agree. But the idea of just CIRCULATING the water through pipes will not hurt anything. I have found a
webpage where a man has made a system and he is using it to cool his house! His system is a little different than some discussed here He has an interesting RADIATOR solution everyone should see. ... have a look http://www.instructables.com/id/Free-Air-Conditioning/
"There are no IMPOSSIBLE PROBLEMS... only WELL-HIDDEN-SOLUTIONS."
[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#25)
by cruzan on Fri Sep 11, 2009 at 06:54:43 PM MST

Of course the heat exchanger should be as large as possible. I don't see why somebody would not be willing to pay a few hundred for a heat exchanger if the alternative - traditional AC - would run $4k - $6k.

You should also consider running the water back into the same will through a mini cooling tower like this one:
http://www.davidwilbur.com/node/6
Even with relatively high humidity (say 60-70%) you can get a 5-8 F decrease in water temperature.

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#21)
by thirteen on Thu Sep 03, 2009 at 09:57:46 PM MST

could you use solar power to run a pump for your cooling water system with a backup grid power source also? Just an idea to play with

Re: dug well air conditioning (3.00 / 0) (#24)
by Perry1 on Fri Sep 04, 2009 at 04:47:48 PM MST

Hello,
Aren't you just talking about a ground source heat pump? These systems are well understood and there is lots of info on the net that describe their operation as well as vendors and applicable regulations and codes and standards. Forgive me if I am just stating the obvious.
One thing that I haven't seen touched on in this thread is their ability to move heat from one reservoir to another in a bidirectional manner. In other words, it supplies cooling in the summer and heating in the winter. If your ground sink is a constant 50 degrees and it is 5 degrees outside you have warm water (relative) coming up instead of cold.
Perry

Some links to help.

http://www.igshpa.okstate.edu/geothermal/geothermal.htm

http://en.wikipedia.org/wiki/Geothermal_heat_pump

http://www.geokiss.com/

that last link has a downloadable calculator for system design.

Perry

Re: dug well air conditioning (3.00 / 0) (#27)
by cb92 on Sun Oct 18, 2009 at 11:47:59 AM MST

I'll post my idea here, seems as good as any. When I was building a new house, and the backhoe was digging the drain field, I thought, why not have him dig a root cellar for me at the same time? The house had a cinder block foundation on concrete footings. Same for the root cellar, with a concrete floor. While the contractors are there, you know.
The idea was to have a connecting tube or tunnel from the crawl space to the root cellar. I was going to make ice all winter in simple forms and store it in the cellar. Ice houses go way back. Modern insulation would make one work good. The winter cold would give me free freezing.
All summer long, I would use that cold, either directly with air flow thru the tunnel(damp)or a fancy heat exchanger.
At summers end, the root cellar would hold this years harvest from the garden, 'till it was canned. Some could stay right there if it could tolerate the icy temps.
The melt water gets pumped out from the sump, to the garden.

Re: dug well air conditioning (5.00 / 1) (#28)
by ghurd on Sun Oct 18, 2009 at 12:44:48 PM MST

Welcome to the board.

Ice houses work well, and I cut more than my 21th century share of ice for an ice house.
Problem is there is not a whole lot of total BTUs in an ice house, and the BTUs are very well planned out or very labor intensive or both.

It takes a LOT of sparingly-used super-insulated ice to keep up with a half dozen household-sized refrigerators in the 44062 area.
It takes a lot less in the Reservoir Gouin area, but the beer is still cold.
I am sure it would be easy to make an impact, but don't expect a whole lot.
I don't care how you built it, but double the insulation. ;)

There is the Legionaries(sp?) thing too. Condensation.
G-
Ghurd.info
[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#29)
by cb92 on Mon Oct 19, 2009 at 02:25:54 PM MST

You're right about the labor thing. As I get older, doing work just to keep warm in the winter is less appealing. I still want to store that free cold. How about having a big tub of water in the ice house and circulate antifreeze from a big radiator above to a coil of copper in the tub? In the dog days, circulate the water from the frozen tub to another radiator in the house. Like one poster said, use one from a central ac unit that has drain pans.
Talking about Legionnaire's disease, what is that gunk I have to wet-vac out of my window unit? It clogs up the whole works.
P.S. I am interested in using exhaust heat from my truck to drive my alternator, ac, etc. Is anyone working on that, can't find it in the site. Thanx for the reply. Mike.

[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#30)
by ghurd on Mon Oct 19, 2009 at 03:37:33 PM MST

Materials do some unusual things regarding their heat capacity during their change of physical state. 'Ice' is usually good.
And H2O ice gets bigger than the fluid volume.

Just guessing. The crap in the AC is mostly common particulates (dust), with a high concentration of mold-type yucky stuff.

Exhaust heat, as related to a truck.
Heat is directly convertible to watts mathematically. Removable heat is (arguable) a small portion, conversion to electrical power is low efficiency, the cost is high, and it probably won't make as much power as it takes to drag it around with the truck.
'Peltier' would be worth a Google, if for no other reason than to forget about it on the truck.
Co generation or co gen would be worth a Google search of the board for something more relative.
Basically, there is no chance of efficiently running the stereo and tail lights, let alone the A/C clutch (the A/C is not electrically powered except for the clutch).
G-
Ghurd.info
[ Parent ]

Re: dug well air conditioning (3.00 / 0) (#31)
by southpaw on Tue Oct 20, 2009 at 06:13:03 AM MST

hi
just a comment regarding exhaust heat and power production.
I am sure some of the highway tractors use thermopiles in the exhaust stack
instead of belt driven alternators.
try googling thermopile and exhaust.

dug well air conditioning | 31 comments (31 topical)

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