A basic solar thermal installation consists of a solar panel (often called a collector) and a cylinder (often called a tank) that stores the hot water. The connecting pipe work that transfers energy from the panel to the cylinder is filled with environmental friendly antifreeze. A control panel monitors the temperature difference between the cylinder and panel that activates a pump when appropriate.

There are two types of collector - flat plate and evacuated tube. Our site visit will assess which is the most suitable for your house.

Flat plate collectors

A flat-plate collector consists of an absorber, a transparent cover, a frame, and insulation. Usually an iron-poor solar safety glass is used as a transparent cover, as it transmits a great amount of the short-wave light spectrum. Only very little of the heat emitted by the absorber escapes the cover (greenhouse effect). In addition, the transparent cover prevents wind and breezes from carrying the collected heat away (convection).

Together with the frame, the cover protects the absorber from adverse weather conditions. Typical frame materials include aluminum and galvanized steel; sometimes fibre-glass or reinforced plastic is used. The insulation on the back of the absorber and on the side-walls lessens the heat loss through conduction. Insulation is usually of polyurethane foam or mineral wool.


Evacuated-tube collectors

There are essentially two types of evacuated tube collectors. In the first, the absorber strip is located in an evacuated and pressure proof glass tube. The heat transfer fluid flows through the absorber directly in a U-tube or in counter-current in a tube-in-tube system. Several single tubes, serially interconnected, or tubes connected to each other via manifold, make up the solar collector.

The alternative is a heat pipe collector which incorporates a special fluid which begins to vaporize even at low temperatures. The steam rises in the individual heat pipes and warms up the carrier fluid in the main pipe by means of a heat exchanger. The condensed liquid then flows back into the base of the heat pipe. The pipes must be angled at a specific degree above horizontal so that the process of vaporizing and condensing functions. There are two types of collector connection to the solar circulation system. Either the heat exchanger extends directly into the manifold ("wet connection") or it is connected to the manifold by a heat-conducting material ("dry connection"). Evacuated tubes offer the advantage that they work efficiently with high absorber temperatures and with low radiation.