Earth Tube used to moderate air source heat pump condenser operating temps
Long time reader first time posting.
Has anyone tried or thought of using an Earth Tube to pre-heat or cool the air for an outside condensor of an Air Source Heat Pump or Mini-split?
Earth tubes are new to me and not common in most of MN. I have read about the downfalls of these poorly designed or installed earth tube systems for indoor air quality. Radon is a considerable problem in MN and I see an earth tube system only adding to it.
I like the efficiency of ASHP or mini-split systems, and the newer systems are now able to provide heat even on the coldest of days. My understanding is that when those below 0 degrees F days are upon us, or any large DeltaT for that matter, the systems aren’t as capable of producing heat efficiently.
Could the outside condensor be enclosed in a small, insulated, exterior space (similar to a porch or breeze-way) where a few 100′ runs of burried earth tube loop starting and ending with a small fan system to move air through the tubes?
Air from the Exterior, enclosed room that houses the condensor enters the tube is moved by the fan through the earth tubes to either warm it or cool it prior to re entering and being used by the ASHP condensor to make interior heat or cooling more efficient with lower DeltaT values theoretically.