SOL Perpetua System
How the Sol-Perpetua System Works
4. WORKING FLUID
The working fluid is non-toxic propylene glycol and distilled water. Where there is no danger of frost, distilled water alone can be used. Being under vacuum, the fluid boils at between 45 and 80 C (113 and 176 F) depending on the strength of the sun and the water temperature at the bottom of the tank.
The propylene glycol used in solar heating has a pH of 8, and inhibitors to reduce geloamic action (carrosion) where the copper tubing may be in contact with other metals.