INDIRECT solar water systems are usually recommended for areas that are susceptible to frost. Water treated with a heat transfer fluid is run through the panels of the solar water systems and the heat that is absorbed is transferred to the water in the storage tank through heat exchangers.
These solar water systems are often recommended in southern and elevated regions in Australia.
Solar water systems are placed on roofs from where rainwater may be collected. There exists the possibility that a leakage in a system could result in contamination of potable water by heat transfer fluid that may result in injury.
The possibility of leakage of heat transfer fluid varies with system design and placement of the solar water system. The manufacturer and the installer can assess this.
The most commonly used heat transfer fluids for freeze protection in solar water systems are water-ethylene glycol solutions and water-propylene glycol solutions.
Exposure to ethylene glycol heat transfer fluid has produced ill effects in test groups and exposure levels have been regulated.
An alternate heat transfer fluid for solar water systems is pharmaceutical grade propylene glycol USP/EP from AnglomOil.
Propylene glycol USP/EP from AnglomOil, with a suitable inhibitor package, is available from Anglo Design , and makes an excellent choice for use as a heat transfer fluid in applications where contact with potable water, food or beverages might occur.