Solar hot water system using hydrualic fluid.

[arcandspark]

My friend wants me to build a solar hot water system that will me maintenance free for ten twenty years. Unlike water or glycol systems that require the transfer fluid to be replaced periodically due to thermal breakdown and acid corrosion issues, I am thinking of using a high temperature transfer fluid. I have worked for years with hydraulics. The hydraulic fluid has to handle high temperature and last for years. I am looking for a good hydraulic fluid similar to Exxon NUTO32,something that can handle 220 degrees for a long time. I will have to use a little larger pump due to the higher viscosity and the heat absorption properties are only about half as good as water so I will have to use two flat plate collectors instead of one, but other than that the system should work fine. Anyone have any suggestions (other than the usual ones that keep telling me to use water glycol) ? I am thinking outside of the normal design box, water and glycol just will not work for me. The reason is I am also going to use heat exchangers to extract all the heat energy out of the generator engine while its running, using hydraulic fluid, but that is another story. arcandspark

[cheap&cheerful]

I just know John is going to find these really interesting.

Jill..