I haven't read the entire thread but will do so today. About the ice caves, I've visited two in Arizona and saw nothing that might compress the air in interesting ways. What I did notice is that they occur in what appears to be lava rock (btw, make sure you wear a hardhat and DON'T hit your head when it gets low, very painful). This lava rock is a wonderful insulator and you could call these places "super insulated". I surmised that, they also occur in climates that have very cold winters. Cold air sinks and, theoretically, collects in these lower spaces. There was no detectable air movement so it appears that the air collects, displaces any warmer air and, being super insulated, they stay cold. I'm looking into the vortex tube coolers and the fact that they are inefficient does not bother me if the power source is solar. My $.02.
