What is solar thermal system?
Solar Thermal works by collecting heat energy from a collector which is usually fitted on a roof.
Pipework from the collector connects a solar pump station and then to the solar cylinder. The cylinder typically has twin coils – one for solar and one for a heat pump/fossil fuel boiler (gas, oil, electric).
The solar pump is switched on and off by the solar controller switch depending on the collector & solar coil temperature. The pump switches on and transfers heated fluid to the bottom of the cylinder when there is approx 7°C temperature difference between the roof collector & cylinder.
The solar coil is where heat transfer takes place from the solar primary circuit to the water in the bottom of the hot water cylinder.
A solar primary circuit is a term used for a continuous flow and return loop. This is where the fluid within the pipework is mixed with water & anti-freeze (glycol). The reason for this is to ensure that the fluid does not freeze or crack the solar collector during colder months.
There are two types of solar thermal systems – these are on-roof or in-roof.
On-roof is usually cheaper to install & is generally installed as part of a renovation or retrofit system.
In-roof is typically a higher installation cost but is more aesthetically pleasing. This is because the flow and return pope from the solar collector is hidden. In-roof is also more efficient as there is less wind loss to the collector.