Thermal Characteristics of Hybrid Photovoltaic Solar Thermal System during Summer.

A hybrid photovoltaic (PVT) solar thermal system combines a simultaneous conversion of the absorbed solar radiation into electricity and heat. In this study the design of an experimental PVT dual system, both air and water circulation with modifications in the air channel is presented. First modification is to place a thin flat metallic sheet (TMS) inside the air channel and second one is to use painted Black ribbed surfaces at the bottom of the air channel. To observe the variations of heat transmittance with change of the shape of the ribs four experimental setups with a Trapezoidal, Saw teeth forward, a Saw teeth backward ribbed surfaces and a flat plate have been used. Natural convection is applied instead of forced convection to increase the system’s net electrical output & thereby the overall system efficiency. All setups were of the same capacity, projected area, and water heat extraction method and average depth. Performance study was carried out during the months of February to June, 2012 at IUT campus, Gazipur, Bangladesh. Significant performance has been observed with the above stated modifications. In an intense sunny day of March, the maximum temperature of water was found to be 45°C for Trapezoidal, 44°C for Saw teeth forward, 43°C for Saw teeth backward and 41°C for flat plate setup. Maximum temperature of air inside the air channel was found to be 39°C for Trapezoidal, 38°C for Saw teeth forward, 37°C for Saw teeth backward ribbed surfaces and 36°C for flat plate in an intense sunny day of march 2012 with an ambient temperature of 34°C. The average efficiency from all calculated values is found to be 64% for Trapezoidal, 62% for Saw teeth forward, 61% for Saw teeth backward and 58% for flat plate setup.