House Pictures Chat Corner - Show off your house pictures!

Well, I wouldn't have done that... where is the heat supposed to come from? The basement unheated? And then the costs to push the heat back in during the summer? A air-to-water heat pump is certainly much more efficient and cheaper.

Yes, technically it is difficult to understand, since neither sun nor precipitation reach there. Where does the regeneration come from?

Wooden cellar is also interesting, because if there is ever a water ingress, how can it be repaired? Is it permanently sealed >20 years? Etc.

But I don't want to unsettle you with this, experience shows that it apparently works.

The manufacturer of the films gives a 50-year warranty (which is completely sufficient for me now, at 51 years old; after me the deluge), but only because legally more is not possible. They probably last much longer. There are empirical values from 35 years now (with these films), but only above ground. If neither light nor other weather influences reach them (as they are underground), this should rather benefit their durability (so when I look at the plastic tarp we dug up that probably slept in the soil since the construction of my parents' house, I have absolutely no concerns; it looks like new).

The cables lie in the sand and that is probably decisive. I don't know the technical details, I simply believed the empirical values. In summer, the excess heat of the solar system is conducted through these cables, which warms the soil again (at the aforementioned daughter’s place the soil is now probably about 24° warm). But I can ask in detail again at the next meeting. For me as a layman it was plausible, although I must admit that I have never heard the thing about "needing sun and precipitation".

Where does the regeneration come from?

First of all, I would claim that in soil that is not too fine-grained, capillary forces can draw water in from the sides. That would then also be THE main mechanism to introduce solar energy from the sides (stored as heat in the water).
Differences in temperature compared to the case without BP above could be compensated by more collector surface area.
Roughly my theory. Otherwise, I wouldn't know how it works.

The fact that it's placed in sand, in my opinion, supports that.

To me as a layperson it was plausible, although I must admit that I have never heard of the thing with "needs sun and precipitation".

A mass of earth from which heat is to be extracted should be rechargeable by solar radiation. The earth mass itself is more sluggish in passing on stored thermal energy to neighboring molecules than percolating water. One might not think of that by oneself, but it should be easy to understand.

I can ask again in detail at the next meeting. As a layperson, it made sense to me, although I must admit that I have never heard of the thing with "needs sun and precipitation" before.

With classical collectors, the heat reaches the ground through the sun and the warm precipitation water, and this regenerates it. Therefore, building over it is an absolute no-go.

However, I have also heard of brine pipes under the floor slab, but there is nowhere near as much experience with that. Even targeted googling for it is not quite easy.
The general consensus is roughly:
Quite daring
Less effective than classic surface collectors
Can work, but can also go wrong

Furthermore, the floor slab needs to be more strongly insulated because you are additionally extracting heat from the ground.