Earth temperature evaluation

Discussion in 'Geothermal Loops' started by CivilLizard, Dec 19, 2015.

  1. CivilLizard

    CivilLizard New Member

    Hi,

    I'm thinking of experimenting with a GeoThermal system for cooling mostly, but first I would need to know what's the average temperature around where I am.

    I was thinking of setting up temperature loggers at the depth of the supposed loops to know if it'll be worthwhile or not. I'm not quite familiar with the averages of temperatures around where I am, it being at Riyadh, Saudi Arabia, but I'm interested in exploring it because it does sound fun. :)

    To get an idea on the above surface weather here click: http://www.weather2travel.com/climate-guides/saudi-arabia/riyadh.php

    I would like to find a device I can bury for a couple of days and then extract to read how the temperatures were down there.

    Any recommendations?

    /CivilLizard
     
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Pretty much any temperature probe thermometer will work. Your temperature is not going to change over the course of the few days.

    Easiest thing to do is just to dig a trench and stick your probe into the side of the excavation.
     
  3. CivilLizard

    CivilLizard New Member

    Hi,

    Would the temperature change of the course of summer and winter? Down here it's dry, sort of like Tucson, AZ. Temperatures get below zero and above 50c (122+f).

    Great idea about the trench! I'll use that.

    /CivilLizard
     
  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Yes. You will get seasonal fluctuations in shallow earth (<3.5m). The extremes, around here, are about a month behind the air extremes.
     
  5. CivilLizard

    CivilLizard New Member

    Umm.

    Recommend I try temperature scans at 2, 3 and 4 meters in extremes?
     
  6. CivilLizard

    CivilLizard New Member

    Recommend temperature sensors? I can pick them up from amazon.
     
  7. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    What type of soils are you working with?
     
  8. CivilLizard

    CivilLizard New Member

    It's pretty rocky.

     
  9. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

  10. CivilLizard

    CivilLizard New Member

    Would there be a way to dig a narrow hole and dangle down a probe that's long enough to do this?
     
  11. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    It will be challenging. The reason why geo is not really prevalent in cooling dominated climate like the middle east is because you are rejecting so much heat in the ground that your loop field has to be enormous, and it would not be very efficient, due to high loop temperatures.
     
  12. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Agree - it is hard enough to justify geo away from the coast in Florida with deep ground temps low mid 70s. Our design high outdoor air temps are low 90s.

    Thinking a bit out of the box I wonder if some sort of thermal storage system utilizing the fact that nighttime temperatures in the mid east are much lower. The daily swing is much higher than in temperate regions

    That said, though a 5 minute browse found nothing, maybe Riyadh's deep ground temp is fairly mild owing to nigttime lows. Geo could still work, even with elevated entering water temps since air source systems really lose ground when outdoor air temps climb into 100s.
     
  13. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Been to Riyadh. Looked at solutions there.
    The problem is is that the peak loads are so high and for a prolonged amount of time, that you would simply heat up the ground too much. It does not matter what the current ground temps are, you will quickly heat up the ground to inefficient levels.
    Open loops would work much better, but there is not much water at all, and the deep well water is depleted and of bad quality.
    Nights are cooler during the winter, but bad during the summer. Tried to reject the high loop temps with a water-air coil during the nights, worked badly during winter, did not work during summer.
     
    Last edited: Dec 29, 2015
  14. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Why is it that prolonged cooling operation overheats the ground to such a problematic degree, but prolonged heating operation in hostile climates such as Buffalo doesn't overchill the ground to the same problematic degree? Mind you, I only do open loop reinjection systems in sunny Fla.
     
  15. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    I always look at it as the difference between thermoconductivity and thermodiffusivity. Ground can store heat too well in the heat rejection side of things.
     
    Palace GeoThermal likes this.
  16. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I explain it with the phase change. Once you make ice you release a large amount of energy, that is why you really have to screw up your loop field to over chill the ground.
    The opposite would happen in cooling mode when water turns to gas, which consumes large amounts of energy in form of heat (that what chillers do in a certain way). Unfortunately, in the ground we never get to that point in cooling mode.
     

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