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Underground Air Cooling


By framistan, Section Diaries
Posted on Thu Nov 1st, 2007 at 05:27:06 AM MST
A prototype system of  cooling presented for your ideas and input  for improvements



My plan to use UNDERGROUND coolness to cool a building started
when I insulated my garage workshop.  When I started, I had a
building that i wanted to make easier to HEAT in the winter. But
I found an UNEXPECTED bonus.  After adding an attic to the garage
and insulating all the walls with styrofoam, and the attic also
insulated, I noticed in the SUMMER the temperature of the building
had gone down from about 110 degrees before i started.... to about
85 degrees... without any airconditioning!   I realized that the
coolness of the earth from the concrete floor was cooling the small
garage. I didn't expect this to happen.  I had accidentally ALMOST
airconditioned the building in summer without using anything but
the coolness of the earth!   And the coolness was only the SURFACE
coolness, not the REAL coolness located ten feet down of 60 degrees F.

I started getting curious about what the ACTUAL TEMPERATURES are
if you dig 3 feet down... or 6 feet or 10ft or 20 ft.  I couldn't
find any graphs or data ANYWHERE.  But EVERYONE always says, "yah, it
sure is COOL underground."  Nobody could tell me EXACTLY what the
temperatures are though. So I decided to dig a big hole and measure
it for myself.  Here are the RESULTS:

DEPTH    Summer     Winter

  1. Ft.     78 F.       28 F.
  2. Ft.     74 F.       32 F.
  3. Ft.     70 F.       34 F.
  4. Ft.     68 F.       38 F.
  5. Ft.     66 F.       40 F.
  6. Ft.     64 F.       42 F.
  7. Ft.     62 F.       44 F.
  8. Ft.     60 F.       46 F.
  9. Ft.     60 F.       48 F.
  10. F.     60 F.       52 F.
  11. F.     60 F.       54 F.
  12. F.     60 F.       58 F.
  13. Ft.    60 F.       60 F.
CAVE      56 F.       56 F.

The data might be off a little because temperatures were measured
different times of the year, using different thermometers... etc.
but it gives us a ballpark idea of how far down you have to go to
get real cool temperatures.  The 56 degree reading I took when in
a cave called Meremec caverns in Missouri.  



Here is a Dual Thermometer showing temperatures at the TEN foot level
and at the 20 foot depth.  Readings taken at the beginning of summer.
So I was convinced UNDERGROUND COOLING could work. But HOW to get the
coolness up above-ground and IN the HOUSE??   One of the FIRST problems
to overcome, is HOW TO DIG the hole without spending LOTS of money to pay
well-drillers, or LOTS of work HAND-DIGGING with a shovel.  One method I tried
was a WATER-INJECTOR drill made out of GASPIPE and attached to an electric
drill.......as pictured here :



This drill took me WEEKS to design and build.... and it drilled a 2 inch wide
hole about ONE FOOT down when the electric drill BOGGED DOWN and stopped !  
Another method had to be found.  So I tried something an OLD MAN had told me
about...  HE said, "use a TEE-handled hand-powered drill. They are easy to
use and just ADD lengths of half-inch-gaspipe to get down as far as you want."

So I tried it and IT WORKED!  



As you can see, I was able to use this drill method to drill down about
20 feet in about 6 hours of drilling.  I was sure to check for OVERHEAD POWER
LINES first before doing this though.  And I kept my small dog AWAY from the
hole untill it was done.  Keep in mind the dangers of working on such a project
as this because If you decide to undertake this project, YOU are the only one
responsible for accidents not me.

 During my many YEARS of working on this
system, I discovered an interesting thing about HOT WATER that i don't believe
most people are aware of.  Everyone knows that HOT AIR RISES, and COLD AIR
FALLS DOWN, RIGHT?   But did you know that HOT WATER RISES ALSO?   I did
an experiment using a 5 foot long pvc pipe with a cap on the bottom.  I filled
up the pipe with hot water  and placed my temperature probe down the pipe.  
here are my results:

       60 inch level........(top)  temperature is 120 deg F.
       40 inch level........       temperature is 114 deg F.
       20 inch level........       temperature is 104 deg F.
       00 inch level........ (bottom) temperature 95 degrees F. !!

I did ANOTHER experiment where i placed some cold water in an OLD glass
coffeepot. then using a little squirt bottle, i squirted some COLORED water
into the BOTTOM INSIDE of the coffeepot.  When I held a candle under the
coffeepot, I could SEE the colorwater RISING up.... proving again that
HOT WATER RISES.  Some of you may say "SO WHAT." but think about it!  
If you drill a pipe STRAIGHT DOWN into the ground to use as a radiator
of heat I believe the heat will RISE UP alongside the pipe that you are
trying to COOL!!!  Therefore, I believe the best method of drilling a
heat exchanger into the ground is at an ANGLE... NOT straight down!
Horizontal pipes would work too... if you can get them DEEP ENOUGH where
the real coolness is.  



Another discovery I have made is that CIRCULATING WATER is easy to do.  
you don't need a giant 200 watt waterpump.  A little 4-watt 66 gallon
per hour $10.00 pump will do it!  this is because water circulated does
not have to be LIFTED out of the ground like in a WELL.  In a WELL, the
water must be LIFTED a couple hundred feet. That takes a HEFTY PUMP that
uses a lot of electricity.  Here is a picture of my UNDERGROUND radiator
going into the 20ft. hole.  




Like I said at the beginning, this system is a PROTOTYPE.  I don't claim
it is working yet.  Here is my radiator i built, but didn't get much
cooling from it.  I do believe this system will eventually work, but
may need some input and suggestions from everyone interested.  


My wife doesn't think much of my ideas. But I know YOU GUYS wont horse
laugh me too much. Right?  Well its LATE... I wanted to make this more
detailed, but its enough to give you-all something to think and comment
about.  I may add more later but this is about 90percent of it.

Underground Air Cooling | 17 comments (17 topical, 0 editorial)

Re: Underground Air Cooling (3.00 / 0) (#1)
by domwild (domwild at hotmail dot com) on Thu Nov 1st, 2007 at 12:35:04 AM MST
(User Info)

Hi,

You are rediscovering an age-old method to cool a mosque or house. The arabs use a howzah, a tower to catch the hot desert wind, the same tower the muezzin does his chant from. The air travels underground below any damp area, e.g., the area of the ritual baths or any other wet area. The air cools adiabatically and enters the mosque or house at ground level.

Another clever trick is to heat the house through the black attic space in winter. This requires fans to push the hot air down.

Cheers,

dom There is one thing money cannot buy: POVERTY!



Re: Underground Air Cooling (3.00 / 0) (#2)
by Jeff (ruralmcguyver at yahoo dot com) on Thu Nov 1st, 2007 at 06:50:56 AM MST
(User Info)

Congrats! I'm definitely one of those that won't "horse laugh" ya'! (See my diary on this site).
Another method of drilling, or putting a pipe into the ground I was reminded of by my kids. One day I found a little piece of garden hose sticking up in the middle of the lawn. When I tried to pick it up, I found it was stuck pretty good! Even a little digging revealed it was down ther a ways. My kids did this, little boogers! The only way I could get it out was to hook it up to the water supply, and let the water pressure loosen the dirt around the hose. This thing turned out to be buried about 12 feet! Now, whenever I have to sink a pipe, or make a hole, I use this method. I can't use a post-hole digger anymore, but this works even better!
This year, all of my hot water, heating, and cooling will be from a solar/geothermal system. I had a friend help me bury 2 plastic 55-gallon drums under the center of my home. Most of the "digging" was done by the method I described above, my friend couldn't believe it at first, and balked at the idea of having to "dig" in such an in-accessible place.
We set down a 2x6 frame bottom that was insulated, and once the barrels were in, we insulated around them. This winter, the solar water heater will be circulating hot water into those. A couple of on/off valves will allow me to circulate that hot water inside at night, thru an old car radiator with a 12v fan behind it. This, and keeping a large pot of hot water on the gas stove will be my only heat.
This coming summer, the insulation will come out from around those barrels, and they will be cut off from the solar water heater. I'll still circulate that water thru the same radiator/fan setup, but with the opposite effect.
I'm using two pumps from those cheap 12-15 foot plastic swimming pools you see, but they are 110volt, 0.75amp. I'd rather have two 12volt pumps!

Keep up the good work!
Rural McG



Re: Underground Air Cooling (3.00 / 0) (#16)
by iamatthews (OklahomaPioneers) on Mon Jan 28th, 2008 at 08:55:59 AM MST
(User Info)

Hello RuralMcGuyver ... We have enjoyed reading your comments. We are new to the board and in reading Framistan's Underground Air Cooling adventure, you included a comment about a hose that turned out to be buried 12 feet in the ground by your kiddos. You said you use "this method" to bury pipes now. Unfortunately, I can't see where you describe the actual technique. Don't mean to be dense here, but could you share?

Thanks,
OklahomaPioneers

Independence is true freedom.
[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#17)
by Jeff (ruralmcguyver at yahoo dot com) on Tue Jan 29th, 2008 at 10:47:30 AM MST
(User Info)

OklahomaPioneers,

There's not much to putting almost any kind of pipe into the ground with that method...providing the ground is "soft" enough. You just hook up a good, pressurized water source to the pipe you want to sink into the ground. Point the other end (the end that the water is now rushing out of) straight down into the ground, and the water pressure pushes away the dirt under the pipe. Once the end of the pipe is into the ground a ways, you'll see the water is pushing the dirt up & out from the outside of the pipe. Providing you don't encounter any rocks, the pipe will practically sink from it's own weight into the ground. Well...it did here anyway, the ground around here is mostly sand. This is how most people around here put in a well. There's a special end fitting, called a "screen point" you can get in most hardware stores that sell PVC pipe. It comes to a point on the downward end, has little tiny slits in it all around to let in (or out!) the water & not the dirt, and the other end is sized to fit whatever size pipe you are using. My well here for example, is a 2" PVC pipe with a screen point. I had a local farmer with a huge water tank he used to water & spray his fields help put it in. We just hooked up his tank to a 12ft. piece of PVC with a screen point on the other end. Once he turned on the pressure, it took all of a couple minutes before almost the whole thing was buried. I attached another 12ft. piece to the one in the ground, and we sunk that one too. That's my well! I've measured the water at 12ft., to about 18ft. during the dryest spells.
       New news!!!: I got a 12volt pump for christmas from my family. They got it from surplus center, and it's working great! For anyone who wants to know, their part # is: 2-924, the model # on the pump is: DC-4T Marine/Camper Utility Pump. It draws only 1.8amps under full load. Well, here's the URL for it: http://www.surpluscenter.com/item.asp?UID=2008010212515618&catname=&item=2-924
It worked great for the heating section of my system. I was using an old 24volt motor from a wheelchair for the fan, and the dash-dimmer switch from an old T-Bird to reduce & control the power going to both. Just the fan motor would draw up to 5 amps connected directly, but with the dimmer switch, I was able to reduce that to about 1.8-1.9 amps & still get plenty of air-flow. The pump worked well on this reduced voltage, and the total for the new pump, fan, and solenoid was just over 3amps (3.06-3.08). The solenoid is connected to a standard thermostat, and the solenoid is what handles most of the "juice", as I didn't think just a standard thermostat would handle 3amps or more.
     After about a week of use, I found the radiator I'm using for heat indoors, would overflow when the pump turned off. The solar water heater is on the roof, and there's an 8ft. difference between it, and the lowest portion of my system (which happens to be the radiator). When the pump was off, the water in the solar water heater would have a tendency to flow back down. Remember, this is what is called a "closed system" technically. BUT, a car radiator is only made to handle 14 lbs. of pressure before it overflows. This is what was happening. Easily fixed (I thought). My father sent me a couple of RV check valves, and one of them did the trick & stopped the back-flow problem.
     Then, I noticed I wasn't getting ANY water flow from the new 12v pump! All that was, was the new check valve needed more pressure from the pump to open it. I hooked it directly to my 12v source, and presto! Everything worked fine! I just couldn't reduce the volts to the pump and save about 1/2 of an amp. So...total system draws about 3.75 amps now.
Rural McG
[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#3)
by wdyasq on Thu Nov 1st, 2007 at 07:13:00 AM MST
(User Info)

You have discovered the temperature of the ground is the mean temperature of the area. There should have been a reference somewhere to avoid  the hole digging ... and a years  time. Saving the years time for an hours research is a good trade for me.

If one cares to get the reverse effect of 'heat rising' they may use a brine solution in the pipes. As the water/salt mixture heats, it has the ability to hold more salt in solution, it gets heavier and sinks.

Another efficient method of heat transfer is the 'heat pipe'. This is a pipe where a liquid that evaporates at a low temperature. It is placed where the heat is at the lower end and the vapor resulting boils, condenses at top and runs back down the pipe to start the process over.

Be aware there is a limited amount of thermal mass in any area. Eventually, the ground where the heat/cool is 'pulled' will more closely resemble the mean of where the heat/cool is being used. The 'Geo-thermal' folks found in some soils the heat from air-conditioning raised the ground temperature above where it was more economical to revert back to air to air evaporators/condensers.

Well, have fun,

Ron
Adventure is just bad planning." -- Roald Amundsen



Re: Underground Air Cooling (3.00 / 0) (#4)
by BigBreaker on Thu Nov 1st, 2007 at 09:53:59 AM MST
(User Info)

Ground water flows are extremely powerful "rechargers" of the ground temperature near your heat wells.

It may be worth drilling down near ground water to take advantage of it.

[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#5)
by electrondady1 on Thu Nov 1st, 2007 at 02:50:07 PM MST
(User Info)

i did that same hose trick when i was a kid
i got it down about three or four feet .
there is a guy around here that puts in whats called sand point wells using the same method
the equipment consists of a pointed steel end bonded to a few feet of stainless steel mesh tubing . then a few more feet of steel pipe.
he just hooks it up to a water hose and starts pushing it into the ground.
 

[ Parent ]


Re: Underground Air Cooling (3.00 / 0) (#9)
by Jeff (ruralmcguyver at yahoo dot com) on Fri Nov 2nd, 2007 at 08:02:15 AM MST
(User Info)

Electrondady,
   That's the kind of well I have here. Of course, the soil is predominantly sand here, guess that's why they call this area "the SandHills".
   We did essentially the same thing digging a large hole under my home, and used a "dirty water" pump to pump the dirt & water away!
Rural McG
[ Parent ]


Re: Underground Air Cooling (3.00 / 0) (#6)
by feral air on Thu Nov 1st, 2007 at 04:22:48 PM MST
(User Info)

In your sketch the black part should probably be a section of metal pipe instead of pvc. Metal should loose/lose (for once both loose and lose are correct!) more heat than pvc but it might be worth testing to know for sure, I could easily be wrong.

Cool project and one I'd like to try at some point. I like the idea to slant it too - it makes perfect sense yet it's one of those things I'd have never thought to do. take it easy



Re: Underground Air Cooling (3.00 / 0) (#7)
by etownlax on Thu Nov 1st, 2007 at 05:04:22 PM MST
(User Info)

I second that. Metal  has a better thermal conductivity(how easily the substance can transfer heat). If you put a metal pipe down the hole then it would be able to transfer the heat to the ground a lot better. Also if the radiator was metal it would work better too.

-Randy

[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#10)
by BigBreaker on Fri Nov 2nd, 2007 at 08:24:57 AM MST
(User Info)

True, metal conducts heat better, but the metal transfers that heat top/from the soil it faces and that is the limiting factor.  The only way to get appreciable thermal flux from these wells is to maximize the surface area of the soil interface.  Metal is nice but plastic or concrete is great too and the latter two will generally last longer.

Earth tube experiments showed little difference in performance across different "tube" materials.

[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#13)
by feral air on Fri Nov 2nd, 2007 at 01:56:05 PM MST
(User Info)

"True, metal conducts heat better, but the metal transfers that heat to/from the soil it faces and that is the limiting factor."

It's not guaranteed that the soil is the limiting factor though.

[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#15)
by BigBreaker on Wed Nov 7th, 2007 at 07:40:19 AM MST
(User Info)

From Wikipedia:

Material   Thermal conductivity W/(m·K)  
Air            0.025
Wood           0.04 - 0.4
Alcohol or oil 0.15
Soil           0.15
Rubber         0.16
Epoxy (unfilled) 0.19
Epoxy (silica-filled) 0.30
Water (liquid) 0.6
Thermal grease 0.7 - 3
Glass          1.1
Ice            2
Sandstone      2.4
Stainless steel 15
Lead           35.3
Aluminium      237
Gold           318
Copper         401
Silver         429
Diamond        900 - 2320

Looks like soil is pretty similiar to rubber / oil / epoxy, all good proxies for plastic.  I just looked up PVC, it's 0.19, so again... similiar to soil.  Metal is massively more conductive.  Also the tube material is quite thin compared to the thickness of soil it pulls or pushes heat through.  So it's not that important anyhow.

[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#8)
by spinningmagnets (velmis1450bc(at)aol(dot)com) on Thu Nov 1st, 2007 at 10:22:15 PM MST
(User Info)

Dear Framistan, great project! There's a lot of info about similar projects at "builditsolar.com" Here's one pic:

http://www.daviddarling.info/encyclopedia/G/AE_geothermal_heat_pump.html

My home is now on lava rock, with just a couple feet of soil, but when I retire to another property soon, this was one of the ideas that I'm interested in. Renting a backhoe for a day to make 6'-10' deep trenches was my previous best option (hiring a driller for dozens of vertical wells is VERY expensive).

I've never read of anyone using angled wells, or using your drilling method. 20-feet is an excellent result, and I now consider this to be the best way to go, so thanks for posting this!

The tube flowing down will shed heat into the soil, so I would recommend insulating the cold up-flowing tube. Lay them out in a honey-comb pattern, about 6 feet apart, and I would guess you won't run out of cool soil. Just keep adding wells until your system can keep up with your highest demands.

Natural flow in a closed loop that is induced by temperature change is often referred to as "thermo-siphon". I have a suggestion for you to consider. Scavenge materials to put a drop-ceiling in the garage that is hanging about one foot below the existing, but only covering half the ceiling. Cut a circular hole in the drop-ceiling next to the wall and insert an old small ceiling fan (from the trash?) that you only need to run on its lowest speed. Suspend the rows of copper pipe that you already have just an inch below the fan. Even when the fan isn't running there should be a small amount of thermo-siphoning because of the drop-ceiling "ducting" the room air-flow.

Best of luck! Please post the finished design, and how it works out!




Re: Underground Air Cooling (3.00 / 0) (#11)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Fri Nov 2nd, 2007 at 10:59:22 AM MST
(User Info) http://wooferhound.com

Hey that is a Cool system, I hope.
interesting that you are doing your own Research and Development

Here is a bunch more information about Earth Air Conditioning

http://mb-soft.com/solar/intake.html
http://www.fieldlines.com/story/2007/5/17/44838/3837
http://www.fieldlines.com/story/2006/2/16/03029/6284
http://www.fieldlines.com/story/2005/8/8/12943/89666
http://www.fieldlines.com/story/2005/6/10/192944/611
http://www.fieldlines.com/story/2005/3/14/25815/7076
http://www.fieldlines.com/story/2004/1/14/7289/14572
http://www.fieldlines.com/story/2003/5/12/9815/83446

W o o f -={(



Re: Underground Air Cooling (3.00 / 0) (#12)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Fri Nov 2nd, 2007 at 11:57:16 AM MST
(User Info) http://wooferhound.com

Here is even more . . .

http://www.fieldlines.com/story/2007/8/23/222653/062
http://www.fieldlines.com/story/2007/5/19/17221/5531
http://www.fieldlines.com/story/2005/10/7/214025/629
http://www.fieldlines.com/story/2005/1/10/14924/6884
http://www.fieldlines.com/story/2004/7/27/20637/4835

W o o f -={(

[ Parent ]



Re: Underground Air Cooling (3.00 / 0) (#14)
by Shadow on Fri Nov 2nd, 2007 at 11:33:54 PM MST
(User Info)

A BIG part of your garage being alot cooler is because you insulated it. The more insulation the cooler it will stay. Its not so much the ground thats keeping it cool, but more likely the Suns inability to heat it up.
              Interesting experiments , keep them coming!



Underground Air Cooling | 17 comments (17 topical, 0 editorial)
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