An idea that's been in my head for a few years.
Could we not consider an outdoor swimming pool
1) fairly well insulated on its side and top walls (why not a greenhouse above the pool and walls with high thermal resistance)
2) with a coil at the bottom of the pool and use it as a reversible heat pump with glycol water.
In summer, calories could be brought in, both by the sun and the cooling of the house, calories that would diffuse into the depth of the ground.
On the contrary in winter, the heating of the house would draw the calories from the bottom of the swimming pool.
The swimming pool would behave like a well from which heat would be drawn or brought in.
After a few years, a large mass of soil under the pool could be at 20-25°C, maybe more. A fairly optimal temperature, whether you want to heat or air-condition (the COPs of the machines are then at least 5)
I say that with a wet finger, this idea came to me with
DLSC.ca which applies this principle much more "industrially".
I would have liked to see simulations of thermal diffusion in the ground with weather scenarios, there is enough to model in my opinion.
