Geothermal heating with cooling function - adjustable?

Well, I thought that if I only get 1 degree down for 1300€, that's pretty little.

As already said, we hope for 4°C. That would already be a huge difference for me and worth every cent.

AAC can achieve more of what I imagine under cooling. I also didn't think of a professional split unit with installation, rather a small combo with a condensate water tank. It's apparently only about one room of 15-20m² (?) and maybe for about 20 days a year, right?

Yes, in an emergency you can always set it up. But the water changing thing is pretty annoying. We currently have a device where you have to constantly empty the water - it's annoying. Yes, for us summer is from June to August - some years in a row. ;) The climate is supposed to get worse and worse anyway.

As already said, with the passive cooling as you plan it there, no more than 1-2 degrees can be expected. If then the sun shines on the house for a few days in mid-summer and it heats up... then it is questionable whether there is any cooling effect at all...

As already said, we will report. I find it pointless to argue the matter down without personal experience. So far, I have only read positive reports from those who actually own the thing. And if it doesn't work - well, then it's just bad luck - then something else will have to be done. :)

before you want to overwhelm the case with expensive high-tech: have you thought about external shading?

The situation here in our top-floor apartment with south-west orientation and lots of south-west windows:
external sun protection made of white awning fabric, which still lets in a lot of light. The rooms are not dark and unusable.
In summer, outside partly 35 °C, inside 28 °C, if the sun protection is consistently down during the day or when there is sunlight. The house was built in 1980 and is rather poorly insulated.

Morning,

I'm chiming in once again. So, 4K is definitely realistic. There is more than enough cooling capacity available, the only problem and thus the reason why "only" 4K below outdoor temperature can be achieved is that the dew point must not be undershot. A more elegant solution would be heating the house using chests, which would then be used both for heating and cooling the house. (Chest --> ventilation unit with heat exchanger and forced ventilation) In these chests, the 10°C supply temperature from the primary circuit of the heat pump could be fully utilized since the condensate formed is directly drained out of the chest and uncontrolled dew point undershooting (condensate formation) does not occur inside the room.

Regarding the effort, any cooling realized with an active cooling unit is and remains an energy guzzler. The expensive split air conditioning units would still be the cheaper alternative, the "cheap" split air conditioning systems without performance control are not even the most expensive option. The mobile units with the exhaust hose are hardly to be outdone, except by an air-water heat pump used for cooling....

Incidentally, even large companies with technical applications use this type of cooling. The only thing that is not optimal is simply the arrangement of the heat exchanger surface in the building. Heat rises upwards, which is why underfloor heating is often used. Actually, the heat exchanger surface for cooling should be installed at the top (there are cooling ceilings for this), whereby the dew point undershooting must be prevented here as well (there are control systems that prevent this). Alternatively, there is also the option to realize heating and cooling by means of ventilation systems (partial air conditioning systems). And the solution with the chests falls into this category. This chest solution is or was successfully used by a large house construction company. This would also be feasible with a ventilation system if you have a heat pump using geothermal energy in operation.