ETC: Evacuated tube collector (ETC) consists of single tubes that are connected to a header pipe. To reduce heat losses of the water-bearing pipes to the ambient air, every single tube is evacuated.
FPC: A typical flat-plate collector is a metal box with a glass or plastic cover (called glazing) on top and a dark-colored absorber plate on the bottom. The sides and bottom of the collector are usually insulated to minimize heat loss.
Heat Pump: An air source heat pump is usually placed along with the system. It takes heat from the air and boosts it to a higher temperature using a heat pump. The pump needs electricity to run, but it should use less electrical energy than the heat it produces