Best fluid for solar panel

[osolemio]

Working on my project (still), now getting closer to getting the solar panels.

As they are focused and user higher than normal temperatures, temperatures could potentially reach 200 C (about 400 F) in worst case scenario. In normal operations, they shouldn't, but in case they do, what fluid is better for the purpose?

Also, in the winter, temperatures could reach down (rarely) to -30 C (about -22 F).

I realise there are many other parameters to consider, but any suggestions? I heard mention of some kind of spirit which is even less dangerous to the environment than glycol.

Most of the system is water based anyway, it is only between the solar panels and down to two heat exchangers, where the anti-freeze and above-boiling scenarios could exist.

Thank you