The drawing on the right seems like a neat setup.
It's moving solar heat into the copper heater.
I'm not concerned about the molecules inside the evaluated tubes.
We know they work really well and reach high temperatures.
But what would happen to CO2 or some other refrigerant inside the
Copper Header.?.
If the heat expanded the refrigerant inside the header, could that
expansion
/ increase in pressure, be used to 'pump' refrigerant around a loop??
The indoor part of the loop would be the HX, where the gas would be cooled.
(Transferring it's heat to water).
When cooling dropped the pressure inside the HX, more hot gas would
enter the input check valve.
Header
Collector_______HX
|--------->---------|
|---------<---------|
The pressure inside the Header would equalize to the whole loop.
As the HX cooled the gas, more gas would be drawn in from the header.
But as cool water dropped the pressure in the HX, some gas would
be drawn back up to the Header, (via the bottom check valve).
Maybe kinda like a Stirling engine action..?.
Would it flow? Or just equalize and the HX stays cold??