Solar Hot Water Systems

Solar Hot Water Systems

A Typical Domestic Solar Heating System for Hot Water

Solar heating system for domestic hot water (Credit: Vaillant)

A typical solar panel domestic hot water heating system layout uses a twin coil cylinder which is fed by both a boiler (or other heat source) and the solar panels. The solar panel system and the conventional heating system work together to heat the domestic hot water. They share the hot water storage cylinder (which you would normally have to change to a suitable twin coil cylinder).

The solar panel hot water system has its own pump, expansion vessel, pressure relief valve, air vent and controller.

The solar panels are mounted on a roof or suitable wall selected to maximise the exposure to the sun’s energy – so ideally a south facing roof with a 45 degree angle.

The solar panels are then connected via pipe work to the lower coil of a twin-coil hot water storage cylinder. The energy in the sun’s rays is collected by the solar panels and the heat is transferred into the pipe work. The pipe work is filled with a suitable heat absorbing liquid (a glycol and water mix) that won’t freeze in cold weather. The liquid is circulated by a pump to the coil in the hot water cylinder to exchange heat. The solar heating system is equipped with a simple controller to regulate the flow of energy from the panels to the storage cylinder to maximise the use of the available free solar energy.

The conventional boiler tops up the heat provided by the solar heating system as required and continues to supply hot water for the central heating system.

Effectiveness of Siting of Solar Panels

Effectiveness of solar panel positioning (Credit: Vaillant)

Ideally the solar heating panels should be installed in a southerly direction at an angle of around 45 degrees. Where this is not possible the installation should move towards a westerly facing direction. East and North facing directions should be avoided.

Hot Water Storage Cylinders

The solar panel system and the conventional heating system work together to heat the domestic hot water within the twin coil storage cylinder – which you would normally have to swap for your existing cylinder.

To make the most of summer sunlight and the higher potential solar energy gains a 2 panel solar hot water system should ideally be combined with a 300 litre cylinder. If this is not possible it is recommended that a storage cylinder of at least 200 litres storage is used.

Planning Permission

In general the installation of solar panels is reasonably straight-forward with most local authorities regarding the solar panels as similar to flush fitting roof-light windows, where planning permission may not be required.

However it is wise to seek the opinion of the local authority on planning matters prior to starting work on the solar panel hot water system installation. Requirements vary from one authority to the next both with planning permission and building control procedures.