Solar panel

Solar panels vary in size and your installer will advise on the panel that suits your home and hot water needs. There are two main types of solar panel available:

Flat Plate Collector
This type of collector is made up of a metal sheet (usually copper, stainless steel or aluminium) called the absorber plate to which a selective surface coating has been applied allowing for very efficient heat absorption (i.e. it gets very hot!). Copper pipes are soldered to the back of the absorber plate. The pipes and the absorber plate are then placed in a well-insulated box and covered by a transparent material like glass or perspex which has a coating that allows for good light absorption and low light emissivity.

As water is circulated through the solar panel, heat is transferred from the absorber plate to the water, which is then circulated through the system to the hot water cylinder.

Evacuated tubes
Evacuated tubes are individual tubes that fit to a manifold to make a solar collector.

Full flow evacuated tubes work in a similar way as flat plate panels. They consist of an absorbent coating on a metal plate with pipes attached to the back of the plate through which a fluid passes to absorb the heat and then travel back to the hot water cylinder.

However, this time the collector absorber is encased in a glass tube that has had the air removed from it. This ensures that very little of the energy collected by the absorbent surface is lost by conduction or convection.

Although this is a more efficient system, the gaps between the tubes when they are attached to the manifold to form a panel mean the output per square meter differs very little to that of flat plate panels.

A popular variation on this theme is the hot pipe system where the tube is mounted vertically with a copper pipe attached to the back of the collecting surface in the vacuum. The pipe is filled with alcohol that boils as the collector heats up. The hot gas rises to the top of the pipe, which is fitted into a heat exchanger. Water flows through the heat exchanger drawing off the heat of the hot gas causing it to condense back to a liquid and return to the bottom of the collector. The heated water in the heat exchanger then passes onto the heat exchange coil in the hot water cylinder.

In all these systems the solar circuit is a closed loop and does not contain the water that you use. Instead the water is pumped around the circuit absorbing heat in the solar panel and transferring it to the water in the hot water cylinder.