The performance evaluation of a dual flat-plate solar thermal collector suitable for diurnal heating and nocturnal cooling applications is presented. Two collectors, each with estimated area of 0.784 m2 were designed, developed and experimentally investigated. The plates were made with mild steel and coated with matte black and polyethylene terephthalate (PET) powder. The results obtained showed that in the diurnal heating mode, the hybrid plate attained a maximum temperature of 68.8oC while the ambient temperature ranged from 25.3oC-30.4oC, at a peak insulation of 937.3W/m2during the test period. In the nocturnal cooling phase, the hybrid plate attained a minimum temperature of 21.3oC, while the ambient temperature ranged from 23.4oC-24.3oC. During the nocturnal phase at clear sky, the maximum water temperature drop recorded was about 10.3oC. Also,8oC difference in temperature occurred between the top water zone and the bottom zone in the tank, signifying a clear thermal stratification in the tank. The overall performance of the system revealed that the device is a promising technology in locations that have similar climatic conditions as Owerri; thus, showing a dual-purpose seasonal adaptability and energy saving capabilities. Therefore, an installation of the device into a building can ensure a supply of domestic hot water for domestic and other activities all year round. The system can also deliver heat for comfort heating in cold seasons or for comfort cooling during periods of elevated ambient temperatures, hence offsetting the seasonal energy bills in a building.
