1) Water does not flow in vacuum tube, works normally if one tube is damaged 2) Twice heat transfer: first heat transfer to solar tube collector via copper heat tube, then solar tube collector as a heat exchanger to heat liquid (anti-freezing liquid or water) which flow in it 3) Vacuum tube: 47/1,500mm 4) Outer tank: aluminum alloy or color steel 5) Inner tank: SUS304 stainless steel 6) Insulation: polyurethane foam 7) Bracket: stainless steel or aluminum alloy