Geothermal Cooling

Discussion in 'Homesteading Questions' started by jim/se kansas, Jul 22, 2004.

  1. jim/se kansas

    jim/se kansas Well-Known Member

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    Give me your thoughts on this.

    I have a drilled well and I am getting ready to build a cabin on our land. If I would take one half inch copper pipe and make a loop down inside my well (70 ft.) then under ground to the cabin through an A coil with fan and a pump to circulate water or a good conductor. Would this work to cool my cabin? I know that thee will be water condensate to contend with. Will I need a de-humidifier?

    Thanks for your thoughts,
    Jim
     
  2. TX Poet

    TX Poet Member

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    The temperature a few feet down in the ground is remarkably constant throughout the day and year. In Chicago, for example, that deep soil remains approximately 52°F, day and night, summer and winter. In the summer, the hot house air is blown through some underground tubes and that hot house air is cooled by contact with the cool (52°F) walls of the underground tubes. It turns out that it is also de-humidified, too! By the time the air has returned to the house, it is exactly the same as the cooled air that would have come out of a standard central air-conditioner. Air conditioning is accomplished without running an energy-expensive compressor, virtually eliminating air-conditioning expense. In the winter, there is even a bonus effect! Make-up air for the house, that might sometimes enter the house at -10°F, would enter the house at around 52°F instead! The heat load of the house can be significantly reduced, minimizing heating bills.

    This is a quotation from this site: http://mb-soft.com/solar/saving.html

    It was posted recently in the Cooling w/o ac for Okla. thread...I THINK. Lots of interesting info here, diagrams, instructions...but I haven't tried anythng like this, so I can't vouch for it.

    A
     

  3. TX Poet

    TX Poet Member

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    Me again. I was just reading the ground tubes thread, which has A LOT of information on it. I like the idea of the heat chimney to help channel the heat away from the rooms and with the ground tube system, to help pull the cool air up into the house. I am not sure how this would serve in winter, though. Seems like it would steal away your heat...maybe there is some kind of closing or blocking off mechanism. (I am in Texas, so we get a lot of warming sun on winter days.)
     
  4. agmantoo

    agmantoo agmantoo Supporter

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    You can obtain cooling from the well water. Some changes are needed in your proposal. The cool water needs to be extracted from you well water and delivered to the A coil where a fan can blow across the fins thus extracting the cool from the water. The water thusly becomes heated and should not be dumped back into the well as the well water will become tempered (warmer) and the efficiency of the system will deminish. You need a once through pass with the water then dump the water where it can be reabsorbed into the ground. The condensation from moving the humid inside house air across the A coil can be collected and dumped using a small condensate pump designed for the purpose. The volume of water delivered to the A coil and the coils size will need to be calculated to the task. Expect the volume of water to be 6 gallons per minute or greater so you will need a good well.
     
  5. charles

    charles Well-Known Member

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    Sufficient air volume across your cooling coils will keep most condensation off them. Less volume, however, will allow condensation and help dehumidify your house air and will help you feel cooler. Typical HVAC collector can carry the water outside.

    The cost of pumping 6 gallons a minute might be cost prohibitive for long cooling runs - but I redily defer to Agmangtoo. I'd want to use or dump that water into something usefull. A source resevoir?, a shallow pond?
     
  6. Cyngbaeld

    Cyngbaeld In Remembrance Supporter

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    In the winter your fresh air has to come from someplace. It is better to have it coming in somewhat prewarmed, hopefully close to yrly average for your area. You certainly do not want to close off all air exchange even in the winter. You would, however want to decrease the air circulation over the summer volume or you would cool the house off too much.
     
  7. Dreams30

    Dreams30 Lady Rider

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    TX Poet,

    It seems to me that if air coming through those tubes is cooled by the ground to cooler than outside temp in the summer ......wouldn't it follow that in the winter, the air coming through those tubes would end up in the house warmed by the tubes in the ground and be warmer than the outside air?

    Ya'll if I read that thing wrong, please, let me know BEFORE I start digging holes!!! ;) :haha:
     
  8. peanutgreen

    peanutgreen Well-Known Member

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    Maybe you could use some of the water that you're cooling with to fill your hot water heater. After it runs through the coils and warms up, divert part of it to the water heater. Then it's pre-warmed to save money on heating it up to a useable temperature. Just a thought.
     
  9. owhn

    owhn Well-Known Member

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  10. barbarake

    barbarake Well-Known Member

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    You're right - in the winter, the air coming through ground tubes would be warmed up by the ground and would be warmer than the outside air. But that's not necessarily what you want.

    I've installed ground tubes and will be reporting on how well they work once I actually get everything hooked up. I live in a warm climate (upstate SC) so I'm more interested in cooling. The ground temperature around here is approx. 62 degrees. So hopefully the tubes will cool the air down to (let's say) 70 degrees.)

    So, in the summer, the air will come through the tubes directly into the house. The hot air in the house will be pulled out via a solar fan. Hopefully that will be all I need. In other words, I want air circulating (hot venting out, cold coming in through tubes.)

    But the situation is different in the winter. Let's say the outside temperature is 35 degrees but the ground tubes will warm the air up to 55 degrees. (I'm making these numbers up.) But that's colder than I want my house to be. If I am using just the ground tubes, the temperature in my house will be 55. That's better than 35 but still not comfortable.

    I've heard of people who - in the winter - feed the ground tube air into the furnace. Then the furnace doesn't have to work as hard - it has to heat 55 degree air up to 65 degrees (instead of starting with 35 degree air). In other words, the tube air doesn't go straight into the house, it goes through the furnace first.

    Same principle would work with central airconditioners. Let's say I really like it cool in the summer - like 60 degrees. But the tubes alone won't cool the air down that much. So I feed the tube cooled (70 degree) air into the airconditioner - then it only has to cool it from 70 to 60. This is better than having to cool it from the 90 degree outside air down to 60.

    I hope this makes sense.
     
  11. Dreams30

    Dreams30 Lady Rider

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    Barbarake,

    Thank you. It makes a lot of sense now.
     
  12. Godot

    Godot New Member

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    Hi all. (my very first post at this forum) :)

    I'd like to build an earth-sheltered home into a hillside. The use of ground tubes for both cooling and heating has caught my attention and is partially described at this site:

    http://www.earthshelters.com/Other_const.html

    The author really wants us to buy his book so it's no surprise that he doesn't offer much info about the potential drawbacks like those described in the ground tubes thread at this forum:

    http://homesteadingtoday.com/showthread.php?t=39057

    However, the author remains convinced that the temperature of the soil around the tubes will be push to it's annual high point just in time for the heating season and will drop to it's annual low point just ahead of the cooling season. I suppose the full amount of annual fluctuation will depend on many factors including:

    - tube depth/spacing/length/area
    - soil moisture
    - groundwater proximity
    - heating/cooling demand
    - etc

    Nonetheless, the ground tubes could be up around 75 degrees when used for pre-warming winter air for heating and down at around 45 degrees when called upon for cooling early summer air.

    What an interesting topic!
     
  13. agmantoo

    agmantoo agmantoo Supporter

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    I think you need to consider doing a recirculation on the house air. Bringing fresh air thru the ground tubes and exhausting the house is going to IMO overload the the ground tubes with heat.
     
  14. Dreams30

    Dreams30 Lady Rider

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    It explained about moisture/condensation in the pipes also and said some way to deal with that but, I couldn't understand it. Does anyone here understand that part?
     
  15. Godot

    Godot New Member

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    Jim, a lot depends on the aquifer that your well is dug into. A highly permeable aquifer (sand/gravel) might have a high enough groundwater flow velocity to conduct away the heat that you are sending down with a closed loop system. A nearby river or sloping terrain might offer some indication of high groundwater flow velocities in the area. However, if your well seems to have relatively low yield then you can probably assume slow groundwater movement which would likely result in rapid heat build up.

    How deep is the groundwater? My main concern with discharging any heated water somewhere near surface level out of an open system would be the amount of work your pump would have to do to raise all that water as much as 70 ft (?) just for its cooling effect. At least with a closed loop there wouldn't be any effort spent pushing water uphill.

    And for efficiency's sake, try to restrict the copper piping to what's down-well and use plastic tubing for the rest, all the way to the heat exchanger.
     
  16. Godot

    Godot New Member

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    I think the main idea is to drill/cut enough holes in the bottom of the ground tubes so that any condensed moisture can drain away.
     
  17. barbarake

    barbarake Well-Known Member

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    Well, if I pull cool tube air into the house, air has to be vented somewhere (otherwise the house will explode :eek: :D ). Seriously, the trick will be to pull in just enough cool air to keep the temperature where I want it. I'm sure I'll have to experiment with it.
     
  18. barbarake

    barbarake Well-Known Member

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    Quote:
    --------------------------------------------------------------------------------
    Originally Posted by Dreams30
    It explained about moisture/condensation in the pipes also and said some way to deal with that but, I couldn't understand it. Does anyone here understand that part?
    --------------------------------------------------------------------------------

    The sites I've seen mentioned sloping the pipes and having some way for it to drain in the low spot. I did this in the ground tubes I installed but still felt uncomfortable with it. I really don't want to have to worry about mold and having to amend the system (i.e. dig it up) would be a major pain.

    So I made a couple of changes. First of all, I ran a nylon rope through each of the pipes (I have four, each approx. 100 feet long). The rope comes out each end where the pipe comes out of the ground. Near the other end - where the four pipes physically come together prior to going in the house - I build a cement block 'box' (four feet square). The four pipes each have an outlet there (pointing up) from where the other end of the rope comes out. This outlets are normally capped. This 'box' has a cover and will normally be covered by dirt/mulch (will be in a flower bed area). It has a stainless steel cover and can be walked on but I'll probably put something there to keep people away from it.

    So - when I want to check the lines - I merely clear off the mulch and open the 'box'. I now have access to the four outlets (each with a rope coming out). I can now tie a towel or something to the end of the rope along with a second rope. Go to the other end of the pipe and pull on the other end of the rope which will pull the towel *and* the second rope through the entire length of the pipe. This will allow me to see how wet it is inside, dry it off a bit, etc. I can keep pulling the towel back and forth if I want to. I might soak the towel in bleach water to help kill any mold.

    Also in the 'box' is another outlet for each pipe that points down (into gravel). This is the 'low spot' in the pipes where everything should (theoretically) drain. This 'down' outlet is right next to the 'up' outlet with the rope. I can cap the 'down' outlets. Right at the point, the four pipes then start a fairly steep climb up to the house. Theoretically, I should be able to pour bleach water into the far end of the pipes and fill them completely up and then pump the bleach water out through the 'up' outlet. Hopefully I would never need to do this but it should be possible.

    Before you laugh at any of this, remember - I'm basically winging it. :) Any comments/suggestions would be appreciated but - be kind. :D
     
  19. agmantoo

    agmantoo agmantoo Supporter

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    What I am trying to communicate is that the hot outside air coming into the tubes is going to overhelm the tubes and the air being delivered to the house is going to be too warm. By recirculating the the house air to the inlet of the tubes you will not be heating the tubes as much since the house air is going to be cooler than the outside air.
    Another way of viewing what I am inadequately stating is that by doing what you state you will in essence be attempting to warm the area inside the tubes with hot outside air and the tempered outside air is then going to be introduced into the home in an attempt to cool the home. It will take a lot of tubing buried to accomplish the cooling in the setup in this manner. A lot more!
    I have seen zone cooling for confined animals where the cooling is only directed to the animals head using the method you described. The zone cooling worked but it was only a small percentage of cooling as compared to cooling the interior volume of a home.
     
  20. barbarake

    barbarake Well-Known Member

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    Ah yes, I see what you mean. I have heard of doing it that way but decided against it for some reason (now what was that reason??) Heck, you hit forty and your memory goes right down the tubes :)

    I think I decided against it (at least for now) because of the significant added cost it would have involved. The four tubes I have basically run at an angle away from the house. The far end is 150' away from the house (that's the end where the pipes stick out of the ground and pull in the air). Those ends are in the woods so hopefully the air would be a bit cooler. Long story but I had to put it that way.

    If I ran more pipes (from the house to the far end) to do what you're saying, they would have had to go around some buildings and through the woods (which would have involved lots of trees having to be removed).

    My house is small, approx. 1,400 sq. ft. The house is well insulated but not *super* insulated. I guess I'll just have to see how it goes. Doing as you suggest makes sense in many respects and is something I could add in the future.