... in a frigid environment collector.Corrosion resistance and long service life (long life)Groove high standard borosilicate glass, linear expansion coefficient 3 ... (super-heat absorbing)Germany OPT monitoring process monitoring, quality of the only solar-absorption more than.945, ε more than 0.05 ... hail impacts damaged voltage 1Mpa, excellent mechanical properties. All-glass Evacuated Solar Collect Tube