Technical specification of hot water storage tank inner tank : gi sheet 2.0 mm thickness insulation : puf 50 mm outer cladding : color coated sheet 0.4 mm thickness technical specification of evacuated tube collector (etc) tube material : borosilicate glass tube size : dia. 58 x 1800 mm absorptive coating : graded al-nal vacuume : < 5x10-3 pa absorptance : >92% glass thickness : 1.6 mm emittance