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Good idea or never going to work

D

Determined

Well-known Member
One of our sons is looking at buying an older farm house (late 60's)

In the basement or should I say under the basement is an old cistern that has not been used since a good well was put in.

The basement floor is about 6 feet below grade the cistern is below that, guessing 6 foot x 6 foot and say 7 foot deep.

His first thought was he would likely just fill it in and cement the top.

My thought was to keep it and use a small pump to circulate water out of it through a radiator, mount a fan behind it and have a low dollar air conditioner.

Being all concrete and that deep in the ground I would expect 1000-1500 gallons of water to stay in the high 30's to low 40's and provide plenty of cooling.

So let me know, am I dreaming or could this work, around here air conditioning would only get used on and off a week or two each summer.
 
You will heat the water up, I doubt if it would cool off enough with that limited surface area.

You will also need chlorine in it to prevent biological growth.
 
Without the water being able to get "into" the ground, there simply will not be enough heat transfer from the water to the ground.

If anyone there is afraid of storms, might consider turning it into a storm shelter? Would have to provide emergency egress, however -- some way to the outside after an emergency.

Another idea might be to put all of your basement utilities inside, which would free up the rest of the basement for more living space.

Being right on the Canadian border with such long winters, we normally get by just fine with a single 5,000BTU window A/C to cool the house. In winter, we're not so lucky. Heating bills are much more. When you think about it, the temp gradient is also much higher in winter; 65F inside and -30F outside = 95-degree gradient. In Summer, 70F inside to 85F outside is only 15-degree gradient. On a scorching day of 100F, would still only be a 30-degree difference.

I think it would be a waste of time/money/effort to try to cool the house using the cistern full of water. The pump to circulate the water would use nearly as much electricity as the A/C.....at least in [i:fb95cfaa4e]this[/i:fb95cfaa4e] house it would.
 
Do not know where you are but here in Missouri earth mean temp in a cave is 55-60 year round and very likely to be close where you are unless up north and in the winter. I have been in a lot of caves in the area and 55-60 degree water feels cold and can cause a man problem if he stays in it to long. As for cooling yes it would work but how well might depend on the temp of the out side air. Now if it was used with a heat pump it would help a whole lot
 
Old,

The issue is not the initial temperature, but the surface area of the cistern would not be adequate to exchange the BTU's that would be absorbed into the water, it would heat up the water, and not cool back down.
 
What you are trying to do will cool the air but not remove that much humidity.

My air handler is an old gas furnace in basement. I no longer use gas to heat with. I removed the front
of furnace to expose the blower.
I put a fiberglass filter where the furnace door was. I pull the 55 degree air off basement floor before
the air goes through the A coil.

This is a win/win. By pulling air out of basement I no longer need a dehumidifier. Basement has no
smell. Air conditioner doesn't work as hard.

I don't heat basement in winter. Never had a frozen pipe in the past 42 years.
 
Yes no or maybe. It could all depend on how he did it. If working with a heat pump and a radiator system it would most likely work well but if pumping the water in and out yes the water would heat up over time and not stay coll
 
If you use it as a storm shelter, one of my concerns would be the mold and bacteria on the walls. Cisterns can get nasty quick if not used.
 
Sounds as if it would at least be an interesting experiment. A guy local to me had an artesian well on his land. He put a Honda Civic radiator in his ductwork, ran the well through the radiator and had free A/C.






a
 
I agree it would not likely recover temp wise to work well on a full time basis.

If he were to turn it on for 2-3 hours when he gets home from work and only need to use it a time or two a week I figure it may keep up.

Thinking about what junk I have sitting around to try it with; a boat bilge pump to move the water, a Chevy aluminum radiator with shroud for a heat exchanger and a 12 volt fan run off a couple of deep cycle batteries hooked to a few solar panels outside.

If it works then he could make it pretty and permanent.
 
You might do some homework first and see how much water a system like that would take. I bet the cistern wouldn't be enough. I also think the cost to run a pump to circulate the water and fan would cost as much or more than running an air conditioner.
 
I would have a question if the water will do the job being at just 35- 40 degrees if it was being recirculated back to the cistern. I have an old furnace carcus that I took everything out of except the fan. Put a coil in the place where the heating element was located. There is piping from a spring that used to be used as the water supply before a well was dug. Now the water from the spring (which flows at 54 degrees) is fed through the coil and then to an outside drain. Our temp today is at 85 degrees and it is very humid. On days like this the house is kept at 65 to 70 degrees. Electric bill only goes up about $10.00 per month.


Good luck with the project if you decide to do it.

The volume of water would be the only weak spot. Good luck whatever you decide to do.
 
(quoted from post at 16:56:22 07/15/19) You might do some homework first and see how much water a system like that would take. I bet the cistern wouldn't be enough. I also think the cost to run a pump to circulate the water and fan would cost as much or more than running an air conditioner.
Click to expand...

Just for the fun of it I found a water heating calculator and punched in some numbers to get a rough idea.

Water Heating Power Calculator
This calulator tells you how much minimum heating power is required to heat the water within a specified amount of time.

Amount of water
1500 imp gal

Start temperature
35 f

End temperature
45 f

Time period available to heat the water (minutes)
180 to equal 3 hours run time

Result 14683 watts (equal to 14.68Kw / 50100btuh )

Safe enough to say it will not transfer 150300 btu of heat back into the cistern in 3 hours.

14683 watts would roughly be the equivalent of 12 1200 watt hair dryers to heat the water to 45 degree in 3 hours.

How much the water will cool in 21 hours before it is turned on again I have no idea.

Running the pump and fan off batteries and solar panels would result in no cost for power.
 
Just for the satisfaction of knowing, I would have to give it a try!

Like glen's plan, convert an old AC coil inside a furnace case.

A closed loop water supply could be circulated with a very small pump. The returning water would act as a siphon leaving the pump to only need to overcome the friction of the piping.

If you could incorporate it into the return air duct of the HVAC system it wouldn't need a fan, just draw air through to precool before the AC coil.
 
I don't know. Lot of things sound good in theory. I'm almost willing to bet that after the cost of trying it that it will never pay for itself. Kinda a spend 100 bucks to save a dollar.

Now think about this. Your son right? And he's how old? Got kids? Gonna have kids? That cistern can be a hazard to kids. Sure you can make em safe but the potential of an accident is still there. The bacteria or chemicals to control bacteria. Again with the potential of kids being around it. Is it worth the risk?

Rick
 
A couple of things to consider;

1) Ground water is probably 50 to 60F (agree with Old).

2) The cistern might have flowing water from a spring and probably has a built in drain to control water level, without these
features the water level would be variable and would probably flood the basement at some point and be dry at other times. If
these assumptions are true, I would expel the water to an outside drain away from the cistern.

3) It will take a lot of water to create enough heat transfer to create much cooling in the house. I didn't do the math, but I
would guesstimate, it would take 30 to 40 GPM and a large radiator to make much impact.

4) If the humidity has a dew point temperature higher than the water temperature there would be condensation from the cooling
system.

It would be interesting to try this and see if it works.

Regards
Rich
 
(quoted from post at 15:24:07 07/15/19) Impossible to do the math unless one has all the measurement etc. and you do not have them and I do not have them he does not even have them
Click to expand...

He may not have the measurements etc., but I have the experience.

Our house is over 100 years old, and likely much farther north than the OP. Our well water is so cold that most of the summer, you can barely hold your hands under it. We heat the basement in Winter, but do not cool it in Summer as we have high water table, and are "currently" pumping out between 5,000 and 6,000 gallons of water every 24 hours. That incoming water is quite cold, and yet the mid-80's outside temps still heat the basement air to a point where it stays fairly cool, but certainly not cold.

If we could run all that ground water through a water-to-air exchanger, we could gain benefit. But as I said, the upstairs only uses a 5,000BTU window A/C, and that's rarely ever on the high setting. When the water table is low enough that the basement dries out, the air temp in the basement gets rather warm. I've seen it hit 80F down there.

Our basement also has a cistern. It is solid poured concrete, thicker near the bottom and thinner near tops of the walls. That's the only part of the basement floor that DOESN'T get wet......ever! No air flow in the basement either. No problems with the cistern walls getting mold growth or other unwanted nasties. Not sure why....maybe the normally-cooler temps?

My point is, right now we're having outside temps in low to mid-80's, high humidity (I'd swear I saw fish swimming through the air! :shock: ), and thousands of gallons per day of cold ground water coming in. Basement temp is just comfortable. Not cool, just comfortable. If he fills his cistern with water that has no means of passing the heat gain into the earth, then that water will simply warm to a point that it will no longer provide any cooling effect. Then, that much water would 'hold' the heat during the night, when your house is trying to cool down naturally. Look into solar greenhouses that use 55-gal. plastic drums filled with water that absorb heat during the day, then give it off at night. They don't use the barrels in the Summer, as no need to heat the greenhouse at night. There simply wouldn't be enough heat exchange between the cistern water and the cistern's concrete floor -- no economical way to put the heat gained from the rest of the house into the earth. In effect, your heatsink wouldn't be the earth, but just the cistern.
 
If the cistern originally collected rain water, it might have a solid concrete floor.

1885 gallons of water in a 6 x 6 x 7 foot cistern would be a nice size for an energy reservoir, but its surface area would be way too small to transfer enough energy from the ground to cool or heat an average size home. A geothermal well would work better.
 
OK, some math.

If mine is correct, 50,000 BTU will raise 1885 gallons of water 3.3 degrees per hour, each hour.
 
Ground temp is around 54F, not 30s-40s. Older cellars are always cool. Just put a fan in the cellar and blow
the cool air up the stairway. Simple and effective. I have a 3x12" floor vent in our kitchen with a small 6"
cage fan in the cellar connected to it. I just plug it in during hot weather and it does quit well at
cooling the front of the house. Some times cellars are pretty stinky, so this may not work in your
situation. Our cellar is partially finished off so no stink problems.
Loren
 
David, thanks for the math, how did you decide on 3 degrees temperature rise?

A decent reverse flow heat exchanger the outlet temperature of the water should approach the inlet temperature of the air, but lets say you only get half way there and the air going in is 80F and the water in is 60F, the temperature rise of the water would be 10F.

Not nitpicking, but it is an interesting first year engineering question.

FYI the farm house my parents had in central Pa, had a cooling trough in the basement, water came through the wall from a spring and went out through a drain pipe on the other side of the basement.

Thanks
Rich
 
I don't see how it will work for cooling the house. I was filling crop sprayer today from the well. I am sure that water coming out is less than 40 degrees . you cannot wash your hands too long as they soon gets the numb. but once that water is stored there it will warm up some too. then once you start pumping it around it will warm even more. bit it all depends on the outside temperature if like 90 degrees outside and if house is 90 degrees inside don't think you will be cooling it too much. I do think you would have a slight decrease though plus with a fan moving the air would make it feel more tolerable.
 
BTU's are BTU's, they have to go somewhere.

The cooling water for the geothermal "must" warm something, that is how it works, you have to count on the surface area of the cistern to reject the heat. I really doubt that amount of surface are will reject anywhere near the BTU's required to cool the house. The water will warm up as it cools the house and not cool back down. You also have to stir the coolant as it needs to change from the inside to the outside of the pipe, this is like stirring a pan of soup.

Energy is neither created nor destroyed, it is a mass energy balance problem.
 
quess I should have check the temperature today. I know its a lot colder than 54 degrees. also years ago we used the well as a fridge before we got power. things were lowered in a pail on a rope and pulley. even kept the cow cream down there till had enough to fill the cream can before taking it to town to sell.
 
I just found a US map showing ground water temps across the entire country on Google. I don't have that copy, paste and post thing down so I couldn't transfer it here. The map showed temp to be a bit cooler than 54F where I am, but in some of the GT classes that I took the instructor said 54F was a good rule of thumb around here, and of course it will vary some depending on depth, from the dead of winter to late summer----Loren
 

My math says that it could provide water at 20 degrees below room temp for 8 hours. The BIG question is how many days will it take the water in the cistern to cool back down. Determined, everybody seems to miss that you said that you would probably use it 2-3 hours a week, I say that it is obvious that the water would cool down again. I think that you could probably use it for 2-3 hours a day for 2-3 days a week. It would certainly remove humidity whenever it is on, so a drip pan would have to be kept under it. probably with a drain. The investment would be very little so I say DO IT!
 
I agree with David G, that as a closed-loop heat sink it is insufficient. However, if, as some suggest, it is spring fed and includes a drain to maintain level, then it might drain off sufficient warm water to be replaced by cooler spring water. In addition to any heat removed from the air, it must overcome the heat added by a pump and piping system.

These kind of "free energy" deals are intriguing. I knew a guy who got free natural gas from the storage caverns located below his home.
 
Determined, my first father-in-law lived in Ballinger, TX.
When I went out there to visit, he had a similar setup.
He called it a "swamp cooler". It was a car radiator mounted in
a window with a fan on the outside. He ran it off his garden hose
when it got "hot out". LOL It was well over 90 outside and VERY
comfortable in the house.
If you have all the stuff laying around, what are you out to try it?
I do believe you may need more volume than a bilge pump though.
What would really be nice is if the cistern refills itself with fresh
cold water and you could just exhaust the warm water outdoors.
 
What you speak of here is an Evaporative Cooler. They've been around a long time, and they work well, especially in drier climates. They're not as effective in humid conditions.

Evaporative Coolers are starting to make a comeback in certain circles. Some folks are beginning to prefer the limited capabilities of an EC to those of an A/C, with its fan and condenser and refrigerant.
 
We had one when I lived in Albuquerque, would freeze you out at night, the air temperature will "approach" the dew point, but cannot get below.
 
Assuming a 20 degree delta T on the water, in / out, you would need 50,000 degree pounds per hour / 20 degrees = 2500 pounds per hour or 5 gallon per minute of water moving in and out of cistern to maintain the cooling.
 
(quoted from post at 20:32:11 07/15/19) Assuming a 20 degree delta T on the water, in / out, you would need 50,000 degree pounds per hour / 20 degrees = 2500 pounds per hour or 5 gallon per minute of water moving in and out of cistern to maintain the cooling.
Click to expand...

I was not making that assumption David. I wouldn't think that Determined could come up with anything that would remove that much heat given his general design scope. My assumption was that if the water is 20 degrees below room temp that it would remove a worthwhile amount of heat. Determined mentioned a small pump.
 
I would use a heat pump, or maybe an AC unit with the water from the cistern cooling the condenser.

On heat transfer there is good heat, which has a large difference in temperature, and poor heat with low differential, 54 degree water would not provide any good differential, thus the need for a heat pump. You would need a good source of 40 degree water with just a radiator to provide any cooling in a 80 degree room.
 
If you were to make a closed loop system, put coils in the cistern, pipe with pumps to radiators with fans to cool the air in the house, it would likely help. I would try it, even if just on a small scale
to test it. would not cost much to try, and it may just work better than expected.
 
Alright. Let's instead apply Occam's razor- the theory that the most obvious answer is probably right. IF a water-filled cistern in your basement could provide enough cooling water to cool the rest of your house, don't ya think most of us would have one already?
 
(quoted from post at 19:19:30 07/16/19) You have the right idea, Rick. Seal that thing up before
someone?s toddler finds it.
Click to expand...


710ltd2002, how would you like it if someone were accusing you of having a kid trap in your house? It is foolish to assume that it is not secure.
 
(quoted from post at 20:38:20 07/16/19) Alright. Let's instead apply Occam's razor- the theory that the most obvious answer is probably right. IF a water-filled cistern in your basement could provide enough cooling water to cool the rest of your house, don't ya think most of us would have one already?
Click to expand...

Of course not. This is an old house built way before drilling rigs, when dug wells were the norm. Many houses had cisterns for catching rain water, as well. The building that served as my town's town hall for two hundred years has a cistern, though it is for fire suppression.
 
(quoted from post at 22:38:20 07/16/19) Alright. Let's instead apply Occam's razor- the theory that the most obvious answer is probably right. IF a water-filled cistern in your basement could provide enough cooling water to cool the rest of your house, don't ya think most of us would have one already?
Click to expand...

No they wouldn't.
It's much simpler to turn the ac on and pay the monthly bill, today everyone wants convenience that they can pay for at a monthly rate.
No many homes built with cisterns in them in the past 30 years or longer so not much thought put into a system like that due to it being such a small market.

Since the cistern is already there I'd use it, even if it only cools the air 5-10 degrees that's less work for the ac system, aka lower utility cost.

Don't know how that cistern is covered but around here must cisterns have a large heavy concrete lid covering the opening or have a steel bolted down lid like the one for the cistern under my front porch.
I don't consider a cistern with a proper lid to be a child killing danger as some have indicated, if it doesn't have a proper lid, SHAME on the adults for endangering their children.
 
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