One idea
Which I really like simply because it was a bit of an "of course, that should havve been so obvious" moment is using a wax (or wax like) material in the walls of homes that, when the temperature is warm, melts thus storing energy and then freezes again when it gets cold thereby releasing the energy.

I'm not entirely convinced that it's particularly effective but it's certainly the sort of creativity we need to solve these problems.
( Captain V, Tue 23 Dec 2008, 11:39, Reply)