How do solar panels work?

Indirect Systems

The Principles of an Indirect System

Roof tubes

The collector solar panels work by absorbing the solar radiation and the heat is transferred to a hot water storage cylinder by means of an indirect system, which often uses a water/antifreeze and inhibitor solution as the heat transfer fluid (see Fig. 3). The pump, often controlled by a differential temperature controller, but alternatively controlled by a PV panel or light sensitive control circulates the heat transfer fluid from the collector panels through the heat exchanger in the hot water cylinder and back to the collector panels for re-heating. Where used, the temperature sensors of the differential temperature controller are situated at the collector panel outlet and on the hot water cylinder, and ensure that fluid is only circulated when the fluid in the collector panels is hotter than in the cylinder.

Indirect system diagram

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