I can't dig up my suburbun yard...
 

I have PV on my all my sun-facing roof, and I'm looking at DIY converting all my PV panels to PVT panels, to opportunistically gather heat, and then make a liquid to liquid heat pump with R290 in the style of this forum.

While googling I came across this company: triplesolar.eu/en/pvt-heat-pump-with-propane-as-refrigerant/

Here is a thread on the diysolarforum that I made: diysolarforum.com/threads/interesting-product-i-came-across.35043/

I'm confused. A couple of questions:

What does that pv/t heat pump use for heat transfer outdoors? Directly plumbed refrigerant lines? Water or glycol?

Are you planning to DIY or buy some strange new phase change unit? If it's for dhw only, it wouldn't be much work to modify a smallish window a/c unit.

The plan for my own system is to have water/glycol or a drainback system, circulate through pex with heat spreaders on the back of my PV panels to a low grade heat tank, and then essentially use that tank as the heat well in place of a ground loop - that I'll pump heat out of for home heating and domestic hot water. During summer when there is just domestic hot water pumping heat out, I'll probably circulate at night too, as to radiate off heat so I can cool the PV panel temperatures during the day.

For the link I pasted up, it looks to me like they circulate the refrigerant directly behind the panels? It isn't clear, I just thought it was funny that the two things PVT, and using R290 propane as the refrigerant intersected with the project I'm planning.

I'm doing all DIY. I already have a few used working window units that I've acquired over the last few years. I'll paste up a logical drawing of the system I have in mind in a little bit.