... water produced, anti-insolate, water heater in the copper pipe, reliable quality, free maintenance, can stay for 15 years ... and aluminum unified core, or all copper core, heat pipe diameter: 22mm/25mm. Few welding line, high intension, and ... maintenance, can stay for nearly 20 years8. Special preservation: Glass wool/ high dense polyurethane foam. Working principleSunlight passes through the glazing ...