Future-proof your home
with Solar PV & Thermal Panels

How do solar thermal panels work?

Solar thermal panels collect energy from the sun and convert it into heat. For optimal performance, they should be installed on south-facing roofs. However, they still work efficiently on any roof facing between southeast and southwest. They are commonly mounted on pitched roofs but can also be installed on flat roofs or ground-mounted structures. In most cases, installation falls under permitted development, meaning no planning permission is required.

Closed-loop system

Most solar thermal systems operate in a closed-loop circuit using a glycol-based heat transfer fluid with antifreeze. The system works as follows:

1. The panels capture solar energy and heat the transfer fluid.
2. This heated fluid flows through a twin-coil hot water cylinder inside the home.
3. Heat is transferred to the water in the cylinder, which is then used for showers, taps, and other hot water needs.

Since the system is closed-loop, the heated liquid in the collector never directly mixes with the household water supply.

Types of solar thermal collectors

1. Flat Plate Collectors:
   • Feature an absorptive panel covered with a transparent layer (usually Perspex) and insulated to retain heat.
   • Better suited for snowy conditions as snow melts and slides off.
2. Evacuated Tube Collectors:
   • Consist of double-layered tubes with a vacuum in between to minimize heat loss.
   • More efficient in heat retention but can struggle with snow accumulation.

Since solar thermal panels use antifreeze in the collector fluid, they are unlikely to freeze in winter.

Twin-coil hot water cylinder

A twin-coil cylinder has two heat sources:

• Solar Coil (Bottom Coil): Positioned at the base of the cylinder, where the water is cooler, to maximize heat transfer from solar energy.
• Boiler/Auxiliary Coil (Top Coil): Used when solar energy isn’t sufficient, often powered by a boiler, air-source heat pump, or ground-source heat pump.
• Immersion Heater (Optional Backup): An electric backup that can be used if necessary, though it should be rarely needed with effective system controls.