Summer heat for the winter

Can thermal solar energy be stored until wintertime? Within a European research consortium, scientists have spent four years studying this question by pitting three different techniques against each other.

3 different approaches were studied
see empa link on right side

like "thermal batteries" that use solar heating panels to charge themselves

here is report one one of the three
https://www.sciencedaily.com/releases/2017/01/170110121112.htm

Summer heat for the winter

https://www.empa.ch/web/s604/naoh-heat-storage

I believe in Minnesota they did.

What they wanted to know was; could the black top of a section of paved street retain enough heat during the winter to keep it ice free? Their way of testing was to sink wells in the test section letting the heat of summer acts as heat sinks. Not only did it heat the road surface enough to keep it from freezing, and thus snow and ice free as well, but heated a 6 floor apartment adjacent to the test road.