The absorber is the part of the solar collector that collects (absorbs) the incoming solar radiation and transforms it into heat.
The absorption specifies the percent of the radiation on the absorber area that is transformed into heat.
Air heat pump
System that uses heat in the air to heat buildings.
Important figure for assessing the energy efficiency of boilers. The annual efficiency designates the percentage ratio of the heat energy used to the energy used across the entire year.