Definition
The absorber is the metal plate inside a solar collector that captures sunlight and passes the heat to the fluid in the tubes bonded to it. A selective coating, usually applied by vacuum sputtering, absorbs about 95 % of sunlight while emitting only around 5 % as thermal radiation, so the absorber stays efficient at high temperatures. Absorbers are made of copper or aluminium sheet with copper tubes in harp or meander form.