A solar energy collecting system and method suitable for hot water generation using solar energy. The system includes multiport tubes between inlet and outlet manifolds. The tubes are formed of a metallic material, each tube has oppositely-disposed first and second flat surfaces between lateral edges thereof, longitudinally-opposed first and second ends, and multiple fluid channels between the first and second ends that are in fluidic parallel to each other. The inlet and outlet manifolds are coupled to the first and second ends of the tubes so that chambers within the inlet and outlet manifolds are fluidically connected to the fluid channels of the multiport tubes. During operation of the system, a fluid flowing through the fluid channels of the tubes is heated by direct solar radiation impinging the first flat surfaces of the tubes and optionally by reflected solar radiation impinging the second flat surfaces of the tubes.