Earth Cooling Tube

[clone477]

 For those using them, will it be enough to completely keep a home cool in the summer months??  My ground temps here in Ontario are 8C.  But summer can get as hot as 35C.  If I run excessive tubing for a closed loop system, will it be enough to do the job??  My second question is how is the annual ground temps found??  Do they measure the temp every day out of the year, and then just take an average to reach that nember.  Or, is the ground always going to be that 10C no matter whether it is winter or summer.  Thanks guys.

[pwr]

Air weighs about .0809 lbs per cubic foot and has a specific heat of about .238, which means a change of one degree F in 52 cubic feet of air is one Btu.  If you want a 10,000 Btu per hour air conditioner you need to move about half a million cubic feet of  air per hour with a temperature difference of 1 F.  Divide that amount by the difference in your house air and the earth's air to find out how much you have to move for your application.

Keep in mind that we've neglected the heat transfer efficency on both ends of the apparatus, which can be significant, depending on the materials and design used.

Moving air takes a lot of volume, which is why a liquid such as a 50/50 mix of water and antifreeze is preferred.

[neelin]

get the NASA Surface "meteorology and Solar Energy" data for your Lat/Long at:

http://eosweb.larc.nasa.gov/sse/

There is a wealth of info on this site & about as detailed as you want.

apply this (I will have this available for download for a month or so):

http://neelin.ca/temp/GroundTempPenetrationTemperature.gif

hope it helps,

Robert

[GaryGary]

Hi,

There is some material on my site on earth tube cooling here:

http://www.builditsolar.com/Projects/Cooling/passive_cooling.htm

The last link on the page "Earth Tubes 2003 ..." gives some actual test data that you might be able to apply to your case.

A rule of thumb on earth temperatures is that by 20 ft down the the temperature is nearly constant year round, and is equal to the year round average air temperature for that location.  This is from the "Passive Annual Heat Storage" book by John Hait -- which also has quite a bit of earth tube material in it.  There is some rundown on the book here:

http://www.builditsolar.com/Projects/SolarHomes/constructionps.htm

The Hait houses manage to maintain inside temperatures that are in the comfort zone year round without any active heating or cooling in 8000 deg-day Montana -- partly through the use of earth tubes.

Gary

[clone477]

Thanks for all the info guys,  Everything looks very promising.  I was wondering what the opinion is on whether to use a thin plastic pipe, or some metal(copper/galvenized steel) for better conductivity.  From what Ive read it doesnt make that much of a differance, because the dirt is already such a poor conductor of energy.

[BoneHead]

I doubt plastic (pvc) is the best option but it is the most affordable. Even thin wall sewer pipe has a little insulatory value. The object is to bring the new air to the temp of the ground at the depth the pipe is buried at. To be the most efficient, you would want some kind of metal that will loose heat well, painted with asphalt paint or something for moisture protection.

[bob g]

from what i have read  on the subject

earth tubes efficiencies are all over the board.

basically it comes down to many factors, some known

some unknown

is there a sufficient temperature differential to start with?

and what are the thermal properties of the earth that you are

going to use at your site?

some of the systems work well, others because of poor thermal

conductivity of the soil saturate with heat and the performance

goes down substantially.

earth loop, or ground source heat pumps have this problem in some

locations.

i would do a lot of research before i spent alot of money trenching and laying

pipe.

bob g

[benjamindees]

I would think of it this way, unless you are paying somebody to dig the trench for you:

If plastic is, say $0.25/foot, and copper is $1.00/foot, then is 100 ft of copper better than 400 ft of plastic?  In other words, is $100 worth of copper better than $100 worth of plastic?

As you said, I would expect plastic to be better, since the earth is a relatively poor conductor anyways.  And I also think that's what's usually used.

[kell]

Can't find it now, but a few days ago I saw a thread here that had a link to an earth tube website.

[GaryGary]

Hi,

I read this book a while back, and it provides quite a bit of info on using earth tubes.

PASSIVE ANNUAL HEAT STORAGE, IMPROVING THE DESIGN OF EARTH SHELTERS

By Hait. Spiral bound 1983 original, 152 pages, 8.5 x 11 inches. Still the world's most advanced text on earth sheltering. PAHS heating & cooling systems, underground water control, convection powered earth tube ventilating systems, heat flow control, radiant, convective, conductive, "transportive." All PAHS publications below are supplementary to this book.

You can buy it from Hait's web site, but I got a copy from my interlibrary loan.

His website is:   http://www.earthshelters.com/Catalog.html

His whole concept for storing heat in the dirt around the house under an insulation "umbrella" is pretty interesting, and unlike a lot of earth sheltered design concepts he has quite a bit of data to back it up (something like 50 temperature and humidity sensors surrounding his first test home).  But, even if only the earth tubes part is of interest to you, there is quite a bit of both practical and design information on earth tubes in the book.

Gary

[clone477]

Thanks for the info, my next thing will be going to the libary to find some books.  I was the one who posted that site, but they deleted the link because it had conspiricy theories.

[wooferhound]

Heres a few links to try . . .

http://mb-soft.com/solar/intake.html

http://www.bagelhole.org/article.php/Housing/337/

http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12350

[clone477]

I was doing some research, and found that HEPA furnace air filters will remove microorganisms, mold and bacteria.  Is this true???   If it is the case then the problem about mold and microorganisms growing in the earth tubes would be eliminated.  Also I read that the RH(relitive humidity) has to be hight than 55% for this to be a concern in cooling tubes.  Whats the feedback on this?

[julien]

Hi Guys,

I'm looking for some information on the design principles underlying the design of earth tubes.I am about to start the construction of my house and I just came across the earth cooling tube.

I've read on a website (http://www.azsolarcenter.com) that "when properly built and sized, underground tubes can supply cool air durin the peak load daytime even in the hottest climates".

Does anybody have the design requirements of earth cooling tube?

Also,I have not yet fully study the wind pattern on the construction site.But as a general rule which one of these two is the determining factor:micro-climate or general wind pattern?According to my micro-climate(since I'm in the Southern Hemisphere)the South side of the house is cooler and the intake vent should be found in the south side but where should I place the intake vent if the cooling breeze generally blows from the North?

Thanks for your help

Cheers,

Julien    

[crosscaliber]

hi there, i'm new to earth cooling tube. here's my question, what happens if we use a depth deeper than 3m? can the earth cooling tube be able to make a difference in air temperature? in my opinion, we can save cost if we do it vertically instead of horizontally for the pipes...