Evacuated solar tube collectors can harness some seriously scalding BTU's due to the vacuum being such a good insulator.
Unfortunately, the shape has to be a tube as the pressure difference would be too much for a flat panel. This puts such a phenomenal solar collector out of reach of us hobbyists.
Until now. :)
(Maybe. :} )
As you know, homemade aircrete is a surprisingly good insulator and more or less competitive with commercial insulation... but... It's also concrete, so it has a high compressive strength!
So, crazy idea. What if we cast an aircrete block, pressed our heat collector plumbing into it, then when it dried, sucked all the air out!??
Below is my design. For simplicity, I'm calling for mylar wrap on 5 sides, and recycled window glass on the sixth. (Note the only unsupported span of glass is directly over the pipes, which is very narrow so it should be able to withstand the force.)
(I could also see doing ultra-efficient wall slabs sealed in pouches like a giant brick of Folgers. But that's another enchilada.)
Anyway, I hope to fiddle with this once I get my aircrete skill up and going -- but if you want to beat me to it, be my guest! ;)
If you don't "know enough"... try anyway! (Cuz that's how you learn.)
Concrete is very alkaline and will eat copper if it's in direct contact. Is the plan for pex? I would suggest sourcing tempered glass panels as the thermal differential between the hot and cold side can be too much for regular glass. Usually old patio doors are tempered.vI dont know how your array would perform. I think probably in line with a flat plate collector. It would be fun to see though.