I once saw a documentairy on National Geographic Channel, about the parabolic mirror system, and they used molten salt (!) (=the salt keeps fluid because of the high temps of course) as fluid in their pipes.
Salt melts at 801°C
Also i though that salt can capture very much heat. More than water (i think).
That was also the reason i was thinking of storing the heat in a vat/tank, filled with salt. Have been searching on this, but couldnt find many.
Ok, very interesting comments already. I'll do some further reading for now, so i can better understand the basic principles.
The only thing i would be glad to have figured out here is this:
if (if!) you can transport the heat fast enough, away from your concentrated collector, why do you still need fluids that can handle the higher temps ?
It seems to me that, if you 'cool' your concentration point fast enough, temperature wont get to high. Or isn't that possible ?
Yeah i'll do some more reading now