News wrote:
Nick,

Is Chicago north of the arctic circle, with
no sun for months at a time?

I recall a girl from Chicago living in London. She said she liked
England
because at least you see sun in the winter. She said in Chicago they
can go
months on end without seeing any significant sun.

If you are trying to make a "rechargable thermal battery" for thermal
storage, wouldn't a material that phase changes be a better bet, ie
something like freon that evaporates and condenses or freezes and
melts. These have a much higher heat capacity.

Mark