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[Sloppy_Snood]

Chemist's Explanation:  Deep in the earth, the temperature of ground itself is pretty much the same at 50°F to 60 °F throughout the four seasons.   Geothermal takes advanatge of this situation. 

Geothermal How Does It Do That:

For cooling purposes:  A geothermals hot (i.e. warmed) refrigerant (cooling season) is cycled down into the ground into this 50°F to 60 °F zone in order to cool the refrigerant (i.e. lose excess heat to the earth) and then returned to lines within the air handling system of a house/building in order to remove heat from the air.  The heated refrigerant returns to the earth through a coiled loop system and the process repeats itself.

For heating purposes: A very cold refrigerant fluid is cycled within a copper tubing coil deep in a well hole within the static 50°F to 60 °F zone of the earth.  The refrigerant fluid absorbs heat from the earth in order to increase the refrigerant fluid to the 50°F to 60 °F temperature range.  The earth-heated refrigerant fluid then cycles from the coil back to a compressor. 

The refrigerant fluid compressor is what "makes the magic happen."

When the refrigerant fluid is compressed, the 55°F refrigerant fluid is pressurized and heats from 55°F to over 100°F (in physics, this is thermodynamics; pressure is directly proportional to temperature; in other words, as the refrigerant fluid pressure increases, so must the temperature of that refrigerant fluid).  The compressed, 100+°F temperature refirgerant coolant is circulated through thin finned tubing within the cold air return of an air handling ductwork system.  The colder air absorbs the heat from these thin finned tubes and heats the air passing through the fins.  A blower then pushes the warmed air through the ductwork of the home to supply heat. 

That's all there is to it! 

[Scott7m]

Wish I could drill deep enough into the earth to get down to the 150 degree material   then I'd be excited

[mlappin]

Wish I could drill deep enough into the earth to get down to the 150 degree material   then I'd be excited

Like Iceland?

[mlappin]

Chemist's Explanation:  Deep in the earth, the temperature of ground itself is pretty much the same at 50°F to 60 °F throughout the four seasons.   Geothermal takes advanatge of this situation. 

Geothermal How Does It Do That:

For cooling purposes:  A geothermals hot (i.e. warmed) refrigerant (cooling season) is cycled down into the ground into this 50°F to 60 °F zone in order to cool the refrigerant (i.e. lose excess heat to the earth) and then returned to lines within the air handling system of a house/building in order to remove heat from the air.  The heated refrigerant returns to the earth through a coiled loop system and the process repeats itself.

For heating purposes: A very cold refrigerant fluid is cycled within a copper tubing coil deep in a well hole within the static 50°F to 60 °F zone of the earth.  The refrigerant fluid absorbs heat from the earth in order to increase the refrigerant fluid to the 50°F to 60 °F temperature range.  The earth-heated refrigerant fluid then cycles from the coil back to a compressor. 

The refrigerant fluid compressor is what "makes the magic happen."

When the refrigerant fluid is compressed, the 55°F refrigerant fluid is pressurized and heats from 55°F to over 100°F (in physics, this is thermodynamics; pressure is directly proportional to temperature; in other words, as the refrigerant fluid pressure increases, so must the temperature of that refrigerant fluid).  The compressed, 100+°F temperature refirgerant coolant is circulated through thin finned tubing within the cold air return of an air handling ductwork system.  The colder air absorbs the heat from these thin finned tubes and heats the air passing through the fins.  A blower then pushes the warmed air through the ductwork of the home to supply heat. 

That's all there is to it! 

Sounds like the earth takes the place of the condenser in a standard AC system.

[agriffinjd]

<snip>
For heating purposes: A very cold refrigerant fluid is cycled within a copper tubing coil deep in a well hole within the static 50°F to 60 °F zone of the earth.  The refrigerant fluid absorbs heat from the earth in order to increase the refrigerant fluid to the 50°F to 60 °F temperature range.  The earth-heated refrigerant fluid then cycles from the coil back to a compressor. 
</snip>

This is accurate on how it works, but what they don't tell you is it's not coming into the house at 50 degrees F.  The heat that's extracted from the dirt around the coils doesn't get replaced by other 50-degree-heat molecules to replenish it.  When they've done actual studies of real systems in cold climates, it's coming into the house right around 33 degrees F. 

Still easier to extract heat and compress it from 33 degree fluid than to use an air-source heat pump and try to extract heat from sub-zero air, so it's still more efficient.  And it's more efficient that propane or oil. 

If I didn't have the option of an OWB, I'd probably look at doing a ground-source heat pump to avoid propane.  It would eventually pay for itself, especially with the latest propane prices.  But I think the payback would be about 10 years or more, not the 3-5 years that some claim.

[Sloppy_Snood]

Still easier to extract heat and compress it from 33 degree fluid than to use an air-source heat pump and try to extract heat from sub-zero air, so it's still more efficient.  And it's more efficient that propane or oil. 

Enter "auxillary electric heating coil."