Geothermal HVAC, tank vs groundwater?
Geothermal HVAC, tank vs groundwater?
(OP)
Hi folks.
I'm considering geothermal for the house and the weekend discussion was using a reservoir vs putting in wells. Using the buried coils in this GA dry clay is the last resort. I could dig out my Marks handbook and do the thermal calc, but I figured somebody here probably already has this available.
Georgia will not allow circulation between wells - you can't return water - so it would have to be 1 or 2 new 12" wells with downhole coils. $$ and a lot of mess - my house well is 230ft deep.
The option is one of the large direct burial plastic tanks, I figured about 5000 gallons, at least 4 ft below the surface, surrounded in fine sand for support and contact area. Heat exchanger inlet/outlet would be at opposite ends. Adding coarse sand or clean crushed rock internally would increase the thermal mass.
Assuming 3 ton HVAC unit, outside temp 100F, well insulated house, ground temp 60F, how long to raise the water temp 10F?
PART 2 - If anyone has done this, please share your experience, advice, comments, warnings, etc!!
THANKS!!
I'm considering geothermal for the house and the weekend discussion was using a reservoir vs putting in wells. Using the buried coils in this GA dry clay is the last resort. I could dig out my Marks handbook and do the thermal calc, but I figured somebody here probably already has this available.
Georgia will not allow circulation between wells - you can't return water - so it would have to be 1 or 2 new 12" wells with downhole coils. $$ and a lot of mess - my house well is 230ft deep.
The option is one of the large direct burial plastic tanks, I figured about 5000 gallons, at least 4 ft below the surface, surrounded in fine sand for support and contact area. Heat exchanger inlet/outlet would be at opposite ends. Adding coarse sand or clean crushed rock internally would increase the thermal mass.
Assuming 3 ton HVAC unit, outside temp 100F, well insulated house, ground temp 60F, how long to raise the water temp 10F?
PART 2 - If anyone has done this, please share your experience, advice, comments, warnings, etc!!
THANKS!!
It's only a complete day when you Learn something and Teach something!





RE: Geothermal HVAC, tank vs groundwater?
5000 gallons is 42,000 pounds. so in 1 hour you'll raise the temperature 1 degree F.
one problem I see is how to get the water to give back the heat to the ground. Because the water is stagnet ther will only be natural convection, not forced, so heat transfer rate will be slow.
RE: Geothermal HVAC, tank vs groundwater?
How about a gray-water spray onto the condenser coil? No holes to dig and probably similar performance improvement.
RE: Geothermal HVAC, tank vs groundwater?
I planned to place the inlet at one end of the tank, outlet at the other so there would be slight circulation across the length. I can oversize the circulation pump slightly to get more flow or add one that circs inside the tank at a preset temp. Depending on the thermal transfer of the plastic, the 6 degrees gained during the day (assume 6 hr run, really hot days) should be lost at night.
Mint - I don't generate enough gray water here. What I'm doing on the existing heat pump is adding a misting line, connected to a solenoid that opens when the fan starts - this just runs off house water pressure. The downside would be long term build up of clay or calcium from the well, but this unit will be upgraded within a year so it doesn't matter.
It's only a complete day when you Learn something and Teach something!
RE: Geothermal HVAC, tank vs groundwater?
RE: Geothermal HVAC, tank vs groundwater?
It's only a complete day when you Learn something and Teach something!
RE: Geothermal HVAC, tank vs groundwater?
Down side is that you have to increase the size of your circ-pump and that adds $$ to the overall running cost.
RE: Geothermal HVAC, tank vs groundwater?
RE: Geothermal HVAC, tank vs groundwater?
RE: Geothermal HVAC, tank vs groundwater?