sunlight IR trap

A black body to be heated. surounded by a broad range IR reflector (gold or copper work) that allows higher freq light to pass thru. Vacuum for insulation. Photon intensifier thru mabye up jump phosphors (unfort work both ways and tend to scatter output) or a GaN micron-LED array..anyway it needs to bump a chunk of IR into the vis and above spectrum without filtering any of the already present vis/UV etc

Its a solar heat collector. You heat water to higher temperatures than are currently used..this could generate modest amount of electricity or reduce water power bills or sterilise water. Its prob redundant cause I found out some systems already claim 95% efficiency.

OK so you have a medium to heat right...if you insulate it with a vacuum then only real heat loss is radiation. If you have a IR reflective coating then the majority of radiation is going to be contained. So most of the heat gets trapped. as an example a 80deg body in a 20 deg enviroment loses 600W/m2 compared to the 200W/m2 of sun radiation gained. This ive found out this is common practice already.

The shifting of IR into the vis spectrum allows more of the energy to get passed the IR reflector. mechanism is a bit dubious but involves multiple IR range photons being absorbed by a molecule and pooling to produce a higher energy state of the electrons and so a higher energy photon can be expelled. With some compounds (phosphors) this requires near simultaneous collision of photons with the molecule but GaN systems (which can act as a photon intensifier) I think has a semiconductor aspect that allows for considerably longer delays in collisions