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Pumpless Geothermal Cooling

No moving parts needed
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[edited to simplify design of, and cooling of, the geothermal field]

Design and build an in-wall radiant cooling system, with good "upward drainage", so that if any gas enters the system, it can rise to the highest point, without being trapped anywhere by the shape of the piping.

Design and build a geothermal loop. No special properties will be necessary, except that it will need to be constructed of materials that won't collapse due to the sub-atmospheric pressure of the liquid within.

Place several heat pipes in the geothermal field, leading upwards to the surface, and ending above the frost line. The working fluid should be some substance whose freezing point is below typical winter time lows... ethanol would be a good choice.

Add a gas/liquid separator, and a direct contact condenser, as would be used in a solar bubble pump water heating system.

The radiant system, geothermal system, separator, and condenser are all connected in a manner directly analogous to the solar bubble pump -- the radiant system corresponds to the solar collector, and the geothermal system corresponds to the hot water heat exchanger.

When cooling is needed, a thermostatic valve allows cool liquid from the condenser into the radiant system. The combination of low pressure in the system and the heat of the house causes the liquid to boil. The pipe diameter is selected so that the boiling produces a vapor pump effect, moving liquid to the gas/liquid separator. The liquid from the separator descends (via gravity) into the ground heat exchanger, and back up into the condenser (whose height is below the separator). Gaseous working fluid from the separator descends into the condenser, joins with the cool liquid from the ground heat exchanger, and flows back into the radiant panels.

Separate rooms can, of course, have separate thermostats.

Whenever the temperature of the ground near the tops of the heat pipes is cooler than the temperature of the ground near the bottom of the heat pipes, the heat pipe working fluid condenses at the top of each pipe, drips downwards, and evaporates at the bottom, transferring heat upwards, and cooling the geothermal field. This heat transfer is entirely passive, and unidirectional (upwards).

goldbb, Mar 29 2010

Solar Bubble Pump http://www.bubbleactionpumps.com/
Or, how to passively move heat downward [goldbb, Mar 29 2010]

Using the night sky for cooling http://www.google.c...sky+radiant+cooling
[goldbb, Mar 29 2010]

(?) http://www.patentst...47/description.html [2 fries shy of a happy meal, Mar 31 2010]

[link]






       Cool. There is a similar but opposite pumpless system using geothermal and ammonia to make your driveway or yard just steam all winter long no matter what the snow-load.   

       Really?   

       While I could easily imagine using a shallow in-ground heat exchange loop, under the driveway or yard, as an alternative means of recharging (cooling) the geothermal resource, I question whether there would be enough available heat to melt *all* of one's winter snow/ice, without making use of a heat pump.   

       I'm assuming, of course, that the primary source of heat for warming the geothermal field is the home's heat, and that natural warming/cooling is negligible.
goldbb, Mar 30 2010
  

       I'm thinking that a run-off pit would be a must.   

       I'll see if I can find the link.
It had to do with the pipes dipping down below the frost line. The ammonia is pressurized in a closed loop so that the temperature below the frost line causes it to evaporate where it condenses at the top of the loop and runs back down again.
  

       Give me a sec.   

       <later> Ok I found the [link], but when I linked it originally on [snarfy guy]'s electric driveway idea I swear it was for melting snow and nothing to do with air conditioning.   

       Wierd.   

       Although the patent you cited does cool the ground passively (using heat pipes), it doesn't cool the *house* passively:   

       //During the summer cooling months, when air conditioning is required by the house thermostat, the pump in the well is started, bringing up cool water from the bottom of the well, to cool the coils in the heat exchanger//   

       In my scheme, no pumping is required, only the opening of a valve or two... heat from the house, boiling the thermal fluid, provides all the motive power necessary to circulate the fluid.
goldbb, Mar 31 2010
  

       In-wall systems are great, until you want to hang a picture up.
moomintroll, Apr 01 2010
  

       Pictures are no problem -- just use adhesive picture hooks, instead of nails.   

       Shelves, on the other hand...
goldbb, Apr 05 2010
  
      
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