[extropy-chat] Greenhouse Power? (was A Grim Vision ...?)

[Lee Corbin]

Keith writes

> Think about how hot it gets inside a parked car in the summer 
> and you will get an idea of how hard it would be to seal up a 
> greenhouse.  You could also look up the power bills for cooling
> Biosphere II.

Why doesn't this furnish a productive energy source?  That is, the
temperature difference generated between such an enclosure and
the outside sounds as though it could be useful.

Lee