Somehow I missed this post. I have always been fascinated by this heating/cooling system which is sometimes referred to as "Canadian well" or "Geothermal Exchange". This started when I visited some Navaho ruins in the Arizona desert several years ago and found that they were using underground caves for living in very comfortable 18-20 degrees C (64-70 F) while the outside temp in the desert was 43c / 110F.Okay, I have the other type of geothermal heating with a ~220 meter deep borehole, works great with very low heating expenses over winters.
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The whole idea that temperatures at between 2 and 6 meters below the ground surface anywhere in the world are very stable at between 10 to 16C (50 to 60F) and that we can simply run air pipes from a house down there to cool the air in the summer or reverse it to heat the house in the winter is just fascinating. It takes a little work to get it done right but in the long term, it is a fantastic clean and energy efficient way to deal with seasonal temperatures. I will definitely try to implement that in our next house.
https://en.wikipedia.org/wiki/Geothermal_heat_pump
However I wonder why you went as far as 220 meters / 660ft. That seems incredibly deep. Is there any benefit in going that deep?