Thermal Efficiency Comparison of Flat Plate and Evacuated Tube Solar Water Collectors

Flat plate and evacuated tube solar water collectors are widely used for supplying hot water for domestic and industrial applications in the world. However, there is no enough information regarding thermal efficiencies of different type solar water collectors for various environmental and climatic conditions. Therefore, in this work; thermal efficiencies of different types of flat plate solar water collector panels  such as aluminum, copper, 304 chromium and evacuated tube have been compared. It was seen from the results that the efficiencies of aluminum and copper collector panels are changing between 56%...68% while  the efficiencies of 304 stainless steel chromium panels are varied between  67%...88. In addition, evacuated tube type solar water collectors have less heat loss but lower absorber surface area to gross area ratio (about 70%) when compared with flat plate solar water collectors. Based on absorber surface area, evacuated tube type solar water collectors have more efficiency than equivalent flat plate collectors. However in practical applications, gross area of any solar water collector should be considered for comparison. In this case, the efficiencies of evacuated tube type solar water collectors are changing between 50%...70%. Besides, it should be kept in mind that evacuated tube type solar water collectors can be preferred for cold environmental and climatic conditions because of their less heat loss and cold resistant.