Examining the spectral and thermal properties and electricity production efficiency of organic photovoltaic modules with regard to possible application as greenhouse cover

The present study examines the radiometric and thermal properties of an organic photovoltaic (OPV) semitransparent flexible module. Transmissivity of the module was measured under outdoor conditions in the wavelength range of 390 to 1100 nm using a transmittance measuring box. Measurements were done at four different angles of sun incidence: 0, 21, 41 and 46 degrees. Simultaneous, to the transmittance measurements, the open circuit voltage and close circuit current of the module were recorded, to allow power and efficiency calculations of the OPV modules as function of the tilt angle. Supplementary laboratory measurements of transmissivity, reflectivity and absorptivity as function of wavelength, were done with a spectroradiometer equipped with an integrating sphere for wavelengths between 390 to 1100 nm. The overall heat transfer coefficient (U value) of the module was determined during several winter nights, using a standard hot box. The OPV module examined in this study had about 20% transmissivity, 15% reflectivity and 65% absorptance in the photosynthetically active radiation (PAR) range (400-700 nm). The boundary efficiency of electricity generation (product of Voc and Isc) of the module was about 2% and the overall heat transfer coefficient about 6.0 (W m^-2 K^-1).