Performance Optimization of Bifacial Module PV Power Plants Based on Simulations and Measurements

Abstract

In contrast to monofacial photovoltaic (PV) systems, bifacial PV systems are able to harvest sunlight from both front and rear side, hence increasing the generated energy yield. The biggest contribution to the additional generated energy comes from the ground reflected irradiance, which depends on the module installation design. In this work, the optimum geometry of system design for bifacial PV power plants is found. For this objective, the individual and combined effect of the installation parameters on the energy yield of bifacial were studied through simulations and measurements. To empirically validate the used simulation model, measurements for different tilt angles were carried out and compared with the simulation results. In addition, a compilation of published data of the bifacial gain for bifacial PV plants with different system design geometry was done. Analyzing the variance of the results of the simulations, it was found that the parameter that has the biggest contribution on the bifacial gain in energy (BGE) is the reflection of the ground surface. To study this effect, short-term measurements for different reflecting surfaces are carried out and compared with calculations based on the view factor. It was found that the BGE is directly dependent on the albedo of the surface by a factor of 0.40. Carried out simulations yielded bifacial gains of up to 30 % for a stand-alone module. For big scale power plants with a distance between rows of 2.3 m, bifacial gains of 4 % were yielded and by using a white reflective cover underneath the modules, BGE could be increased up to 8 %. It was also found that modules in large scale systems generate comparably lower energy levels up to 12 % less bifacial gain in comparison to neighboring modules due to large shadowing areas.