There are two main forms of solar panels on the market here in Ireland
Flat Plate collectors and Evacuated Tube collectors.
The main component of each is the absorber, which absorbs solar radiation and converts it into heat. In a plate collector, the absorber is in the form of a flat, black plate in a shallow metal container covered with one or more layers of transparent glass or plastic; either air or a liquid is circulated through the cavity of the container. Heat is directly transferred from the absorber to the circulating liquid (air, water)
The absorber in an Evacuated tube collector consists of a relatively narrow strip of copper with a selective black coating bonded to a single copper tube. The tube contains a special fluid which evaporates when heated. This vapour rises and transfers heat to the water circulating in the systems primary circuit.
Evacuated tubes are the most efficient solar collector used for solar water heating systems. These units perform excellent in any location and the improvement is particularly noticeable in colder climates and on darker days. Evacuated tubes are also more efficient than flat plate collectors; consequently they take up less space. They are, however, more expensive that flat plate. Generally speaking, to produce a given amount of hot water, whether using flat plate or evaporated tubes Solar Panels, the installation costs will be roughly the same.