Solar Hot Water full copper TP2 tubes 3 years warranty,>15 years lifespan pressurized, high efficiency OEM is ok Cheapest & Efficient Chinese Solar Hot Water There are mainly 3 kinds of flat solar collectors with different coating1, Black Chrome Coating series: absorption:~95%, thermal emission:~10%2, Blue Titanium Sputtering series: absorption:~95%, thermal emission:~5%3, Anode oxidaiton coating ...