ABSTRACT
The solar collector mounted on the roof converts the light that penetrates its glass panes (short-wave radiation) into heat. The collector is therefore the link between the sun and the hot water user. The heat is created by the absorption of the sun’s rays through a dark-coated, usually metal, plate – the absorber. This is the most important part of the collector. In the absorber is a system of pipes filled with a heat transfer medium (usually water or an antifreeze mixture). This takes up the generated heat. Collected together into a pipe it flows to the hot water store. In most solar water heating systems – by far the most commonly used type of solar thermal systems – the heat is then transferred to the domestic water by means of a heat exchanger. The cooled medium then flows via a second pipeline back to the collector while the heated domestic water rises upwards in the store. According to its density and temperature, a stratified system is set up in the store: the warmest water is at the top (from where it leaves the tank when the taps are turned on) and the coldest is at the bottom (where cold water is fed in).
