Introduction

Solar thermal systems collects energy from the sun and converts it into hot water. It is typically comprised of solar panels which are usually a flat plate collector consisting of a metal box with a glass or plastic cover and a black absorber plate at the bottom of the panel.

solar thermal schematic

Absorber plates are painted with selective coatings that absorb and retain heat more effectively than ordinary black paint. The plates are normally made of metal, usually copper or aluminum because these metals prove to be a good conductor of heat. The collectors are insulated along the sides and bottom to minize heat loss.

Solar collectors are usually mounted on the roof oriented towards the true-south at an appropriate angle, and are connected to a circuit containing water with propylene glycol (anti-freeze). The heated liquid flows through the circuit with the aid of a pump typically supplied with energy with a small photovoltaic module attached to the collectors. The heated liquid is stored into a solar water storage tank that then feeds in-floor heating systems or the hot water tank.

Solar Thermal Systems Explained

The illustration below depicts at a conceptual level the key components which comprise a solar thermal system of a "closed-loop" configuration (the water-glycol heat transfer solution does not mix with the consumable water in the heating/domestic system). The relevant components are explained in more detail below the illustration.

1. solar collector(s) absorb solar energy and converts that energy into heat in the form of heated water-glycol heat transfer solution,
2. photovoltaic module converts solar energy into electricity which powers the solar pump pumping the water-glycol solution through the collects and heat transfer unit,
3. solar powered pump powered by the photovoltaic module pumps the water-glycol heat transfer solution through the system,
4. heat transfer unit is the point in which the heat captured by the heated water-glycol heat transfer solution is transferred to the consumable hot water distribution, e.g. in-floor heating systems, domestic hot water tank, etc. These heat transfer units can come in the form of heating coils within a solar water storage tank, or be integrated into a domestic hot water tank, or as a separate water tank unit integrated with the consumable hot water supply,
5. hot water tank is the component that feeds the consumable hot water supply,
6. Note : what is not depicted on the illustration are the numerous check valves, pressure gauge, temperature gauge, pressure relief valve, etc. which are included in any installation and in which the number or type of components may vary per installation.

In general, the application of solar thermal systems will be comprised of the above components with variations due to differences in manufacturers designs.