Design, production and determination of parameters which effects efficiency of pv-thermal modules

In this study, Photovoltaic/Thermal (PV/T) modules which can convert solar energy both to heat and electrical energy were investigated. Hence, during the production of 5 different PV/T modules, identical photovoltaic (PV) cells were used, however different diameter, quantity and design of absorber pipes and absorber sheets were used. Thermal absorber and PV module were attached each other with lamination method. Additionally 1 unit PV module were produced with identical photovoltaic cells used in PV/T modules due to compare electrical efficiency. As first step, electrical efficiencies of 6 samples were determined from the results of I/V testing in STC (Standard Test Conditions) with solar flash testing unit. In standard test conditions efficiency results were between 12.56% and 12.68%. With the experimental system for investigating both electrical and thermal efficiency of PV and PV/T modules, measurements were performed in between 01.04.2012 – 30.09.2012. Due to calculate efficiencies, some parameters were measured such as sun radiation, output of current & voltage of all samples, input and output temperature of liquid in PV/T modules and its flowrate and ambient temperature. It was figured out that electrical conversion efficiency of PV module under higher working temperatures decreased remarkably because of the decrease rate on solar cell voltage was higher than the increase of solar cell current. It is also seen that PV/T modules' electrical efficiencies were higher than PV module's efficiency with the cooling effect of water flow. Under outdoor conditions, PV/T modules' highest efficiencies (electrical and thermal) were obtained between 60.68% and 67.14%. Overall, the most efficient sample were designated among PV/T samples. The reason of increased efficiencies is lamination method which caused better contact and thermal conductivity between PV cells and thermal absorber. Furthermore, it was proposed the way of using PV/T modules in a biogas system.