[sionnsar]

I'm somewhat familiar with ground-loop heat pumps. The Reichstag went to those (really deep ones!) in its renovation in the later 1990s. I've also seen industry standards for sizing same for sale, but for our locale there's a pretty high upfront cost in drilling for the downloop end. OTOH, the subsurface water flow through our property could significantly reduce the size of the required wellhole if we planted the downloop in the path of that flow.)

We're way up on a hill on glacial moraine; there are no ponds nearby as indicated by my annual tally of mosquitoes usually being less than what I can count on my fingers & toes.

[NicknamedBob]

"OTOH, the subsurface water flow through our property could significantly reduce the size of the required wellhole if we planted the downloop in the path of that flow."

There you go! If all you want is the cool, you can have it for almost free.

Trying to get heat the same way is a bit more work. What makes it worthwhile is that in mid-winter, the ground below frost level is warmer than the air.

Heat pumps that work on extracting heat from the air are at a bit of a loss to find any when the air is below freezing. They usually turn to straight electrical resistance heating. (Very inefficient.)

Contrariwise, ground source heat pumps can essentially cycle heat on an annual cycle. Note also that such set-ups can easily be supplemented with a passive solar gain for the heat source. Just pass a portion of your collector piping through something like a "cold frame".