Solar Thermal Water Heating - Solar Thermal Domestic Hot Water Systems

Types of Solar Thermal Domestic Water Heating Systems

There are two main types of solar thermal system (Indirect and Direct) and two main types of solar thermal panel or collector ('Evacuated Collector' & 'Flat Plate').

Indirect
Sometimes known as 'Closed Loop', this system pumps an antifreeze solution through the solar collector. The heated solution flows through a coil within the new solar thermal water store and exchanges its heat with the stored water above. The now cooler antifreeze solution returns to the collector for re-heating and the process begins again.

Direct
A direct system (also known as 'Open Loop') uses the water already stored in your system and pumps it through the solar collector. The heated water is then stored in the conventional hot water tank. This type of system is susceptible to freezing in many climates unless additional safeguards are added.

Evacuated Tube Collectors An Evacuated Tube Collector, or 'Vacuum Tube Collector', is made up of a number of vertical tubes. Each tube consists of two glass tubes made of extremely strong Borosilicate glass. The outer tube is transparent - allowing light to pass through - and the inner tube is coated with a special heat absorbent. Both tubes are fused together and the air between them is removed to create a vacuum, aiding the efficient transfer of light and heat. Within each inner tube is a u-tube copper pipe containing the heat transfer fluid - this pipe connects to the main manifold above and on through the system.

Flat Plate Collectors A Flat Plate collector is a metal or polycarbonite box with a glass covering, often dark in colour to help absorb heat and fully-insulated inside to minimise heat loss. Light passes through the glass and strikes an absorber plate, which has the water or antifreeze solution flowing through its piping.