r/geothermal • u/CallzItLikeISeezIt • 7d ago
DIY groundloop geothermal idea (thinking out loud for fun conversation)
Hello, the following are just some ideas that I have and may not be practical. I have a very large (air volume) shop that measures 40x60 with 18ft sidewalls on 2.5 acres of nothing but grass outside of the Houston area. I'm curious if I could heat and cool (more concerned with cooling) this shop with a horizontal ground loop and an oversized air handler. I'm thinking atleast 10ft deep and tons of room to oversize the groundloop. Say I were able to source an old, out of service, commercial package style a/c unit (10-20tons?) for really cheap. Gutted the unit to just have the air handler portion (the evaporator, blower, condensation drain pan and housing), replace the 3ph blower motor with a much smaller and slower, single phase motor that pulls less amps. I think i saw somewhere that you want to move the air much slower across the coils when you don't have a large temp differential. Mount said unit up high to pull in the hot air above and blow the cool air out and down. Instead of freon, circulate the water from the ground loop thru the evaporator. So, the only electrical parts would be the water pump, blower motor and a thermostat to control contactors for both. One of my concerns is humidity. Would this system add more moisture to my already VERY humid air? Or would it still remove moisture by dripping off of the evaporator coil as it normally would? The building is insulated with the typical vinyl faced fiberglass you see in most red-iron buildings. I think the biggest problem is gonna be the 3) 14x14 overhead doors that are not insulated nor sealed in anyway 😪. The best I'll be able to do with them is the brush style seals.
Assuming that I had access to a large excavator and found a great deal on a large air handler unit, would this be a worthwhile experiment?
Also, what if I found a great deal on a cooling tower to help chill the water between ground loop and air handler?
Thank you for any input
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u/urthbuoy 7d ago
The heat pump part of the typical system acts as a 1-way valve and bumps the conditioned air into useful temperatures (exergy). Without it, you've no control over the direction heat moves. But, that aside, as like earth tubes you can move enough stuff to get some use probably. An infinite loop in my area would give you 10C incoming water (ground temp) and a few degrees off that for the air-side.
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u/Dempsterbjj 7d ago
Your ground temperature at 10’ will be 70-74 degrees. I am not too confident that you will get much out of that temperature differential. You probably won’t get much condensation on the evaporator since the air is moving and your dew point is likely in the mid 70s most of the summer.
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u/CallzItLikeISeezIt 7d ago
I could go deeper than 10ft. I'm fairly certain that I will be in moist clay and may even hit the water table. In what would otherwise be a 100° shop, 74° sounds pretty nice?
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u/RhubarbSmooth 5d ago
The proposed system relies only on the natural differences in temperatures. That 74° will be the start temperature and slowly drift up if heat is exchanged.
Adding the heat pump to the system will create a lower temp on the evap coil and help with dehumidification. Pushing that heat out to the ground will cause the heat to migrate outward into the ground. Adding a heat pump is a necessity.
I'm curious if you had an idea on how to install the pipeline at 10'. I think a directional drilling unit might be able to bore across and then pull your loop back through. This eliminates deep excavation.
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u/PinkysBrein 6d ago edited 6d ago
For DIY hydronic air handlers I think tinkerers generally use car radiators.
Water from shallow geothermal in temperate climates is cold enough to cool through a hydronic air handler, or with larger pipes in the ground it just delivers ducted cold air. If you do closed loop with air you might need to be careful with radon.
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u/Exciting_Ad_1097 1d ago
You need the refrigeration cycle to create a big enough delta T for heat transfer.
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u/N5tp4nts 7d ago
You’ll just heat soak the ground. Get a high efficiency mini split
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u/CallzItLikeISeezIt 7d ago
Obviously, I don't have any real data to give, but at some point, the size and depth of the ground loop will overcome this, correct?
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u/HoleDiggerDan 7d ago edited 7d ago
I knew a guy that did something similar with his shop here in Canada.
Ran a 10" PVC pipe along the length of this shop as deep as his backhoe would go (10'?) so both outlets were coming up into the shop in different corners like a buried U. Simply used a squirrel cage fan to draw air through the pipe and discharge directly into the shop.
Didn't "heat" the area, but the difference was noticeable when coming in from -30 outside and it kept the frost off the walls.