The Absorber Pipe, also called heat collection element (HCE), is made up of a several-meter-long metal tube and mostly a glass envelope covering it. In between these two usually resides either air or a vacuum to reduce convective heat losses and allow for thermal expansion. A glass-to-metal seal is crucial in reducing heat losses as well. The metal tube is coated with a selective material (black chrome , cermet etc.) that has high solar radiation absorbance (filters out infrared rays) and low thermal remittance (attracts more visible light). The HCE is the core part that enables PTPP to acquire high efficiency (with only a 10% heat losses). , .