... solar energy converting it into heat for use in water heating. Evacuated tubes have already been used for years in Germany, Canada, China ... co, CO2, n2, o2, H2O and h2 out-gassed from the evacuated tube during storage and operation, thus helping to maintaining the vacuum ... ( m2oC )< 0.8W/ ( m2oC )< 0.8W/ ( m2oC )Bearing HailD25mmD25mmD25mmD25mmLife Span15years15years15years15years Solar Vacuum Tube