Solar Water Heating Panels
There are two main types of solar water heating panels; flat plate and evacuated tube. These panels, also referred to as collectors, are a vital part of any solar thermal system.
Flat Plate Collectors
Flat plate collectors look more like traditional solar panels. They have a flat, glazed, dark-surfaced absorber plate which contains metal tubing. The plate covering the tubing, which is normally copper or aluminium, absorbs the solar energy and the casing stops heat from escaping from it. A fluid is constantly run through the tubing which is heated up by the solar power captured from the sun.
Evacuated Tube Collectors
Evacuated tube collectors have a very different look. The panel is a collection of glass tubes in a parallel row which have an absorber insulated by a partial vacuum. They are generally more expensive than flat plate collectors but provide an alternative aesthetic option and are argued to be the more efficient option.
There are two different types of evacuated tube solar panels:
Direct Flow, where the fluid flowing in the absorber also flows through the pipes to the hot water cylinder.
Heat Pipes which have fluid in them that evaporates at a low temperature. When the fluid evaporates it rises up in the tube and condenses, transferring the heat it was carrying and the latent heat of condensation into the pipes into the hot water cylinder. The fluid then runs back down the tube again ready to be re-heated.
Unglazed collectors are also available but they are designed to be used in conjunction with lower temperature applications like swimming pools rather than as a household hot water heating source.