How Pressurized Anti-Freeze Solar Thermal Systems Work

Pressurized anti-freeze solar thermal system diagram

1: In an active, indirect heat-exchange closed loop system, non-toxic polypropylene glycol or anti-freeze is used as a heat transfer fluid. An anti-freeze solution works well in climates with freezing temperatures.

The heat transfer fluid circulates through solar collectors, capturing and storing solar heat energy when the solar collector is exposed to sunlight.

2: A single pump moves the glycol through solar thermal collectors, allowing it to collect heat energy from the sun.

3: After making its way through the collectors, the glycol continues through a heat exchanger, which transfers heat energy from the glycol to water in a storage tank.

Because the heat exchanger transfers heat from the glycol to potable water in the storage tank, these two liquid substances never mix.The circulating heat-collection fluid operates in a pressurized self-contained loop, with very little or no noise.

This type of closed-loop system requires additional maintenance, as the polyproplene glycol must be changed every 3 to 5 years.