Efficiency Improvement of Solar Modules under Low and Oblique Light Conditions

Within the framework of the research project ESOSWA (“Improvement of efficiency of solar modules under oblique and low light conditions”, funded by the BMBF, German Ministry of Education and Research), the Cologne University of Applied Sciences is conducting a detailed investigation on different textured module covers to increase the energy yield of solarsystems under unfavorable conditions. Using textured cover surfaces for PV-modules seems to be an appropriate answer to improve the performance of modules under oblique light conditions. As opposed to earlier studies [1], this paper investigates the influence of the optical behavior of textured covers on the energy yield of PV systems as a function of module orientation and module location. Additionally, there is a need to develop a simulation-model for textured surfaces that can be implemented into currently used forecasting programs. In a first step, the analyzed deep textured cover glass was compared to a standard solar glass. For this purpose, modules with and without deep surface texture were measured under different incident angles in the university’s testing facility. In a second step, the results of the measurements were used to simulate the enhancement of the energy yield for different European locations by using the textured glass cover. The simulations were realized with the software INSEL for all azimuth and tilt angles and took long-term diffuse and direct solar radiation data of Cologne, Germany, into account. The simulations of the energy yield of textured surfaces in comparison to standard solar glass show increases for all module orientations. For the location Cologne, Germany, with an orientation to the west or east and a tilt angle of 40°, the module with the textured surface showed a higher annual energy yield of 5.8 % compared to a standard solar glass module. The energy yield increases to 7.6 % for a north oriented module.