Is there a reason ground-coupled geat exchangers wouldn't work?
https://en.m.wikipedia.org/wiki/Ground-coupled_heat_exchange...
https://en.m.wikipedia.org/wiki/Ground-coupled_heat_exchange...
Aside from a single sentence mentioning homeless people mid way, nothing else in the article was geared towards the homeless.
Even the splash image at top was people lounging on a beach midday. Not something you'd associate with homeless people doing.