I have heard of some form of silicone fluid being used in active solar collectors, which carries more btu's per gallon, and is not as likely to have air dissolve in it.

If the air aspect is correct, wouldn't this be a better fluid to use in a liquid filled compass?

I have also heard that Australia is very big on solar and hot water panel use for electricity and heating. Can any of our Australian members give us a "heads up" on the best current technology regarding the liquids used for heating panels?

Bountyhunter