When I was going to technical college many years ago, solar panels were in their infancy, one of my lecturers was "inventing" a new system. He used anti freeze in the panels as the heat absobtion/transfer was quicker than using water alone, thus making them more efficient as well as providing protection from freezing conditions. He then used a fridge compressor to extract the heat from the fluid, run this through a tank of water and hey presto, hot water.
Just a bit of useless information.
Baz
