Comparison of the energy performance between flat-plate and heat pipe evacuated tube collectors for solar water heating systems under mediterranean climate conditions

In this paper, the energy performance of a flat-plate collector and a heat pipe evacuated tube collector exploited for domestic hot water production in the Mediterranean climate is compared. For this purpose, yearly data obtained from two field-trial solar water heating systems are used. The selected systems are with forced circulation and installed near each other. The studied solar collectors are installed on the roof with the same slope angle of 45° and the surface azimuthal angle of 10°. The installed surface area of the flat-plate solar collector is 4.41 m ² , whereas for the heat pipe evacuated tube collector is 1.5 m ² . The annual irradiation on solar collector plane was 1,456 kWh/m ² year. Obtained results showed that the annual solar yield for the flat-plate collector was 664 kWh/m ² year, whereas for the heat pipe evacuated tube collector was 885 kWh/m ² year. The annual average collector efficiencies were 0.494 and 0.62, respectively.