High-resolution, parametric BIPV and electrical systems modeling and design

The design of building integrated photovoltaics (BIPV) often involves complex geometries, non-uniform irradiance conditions and partial shading. This can lead to high energy losses if not considered adequately. This paper presents a BIPV modeling and optimization method which uses a parametric 3D modeling tool, coupled to a high-resolution ray-tracing irradiance simulation and an electrical model based on the single diode model on a subcell level. With the use of a genetic algorithm, electrical interconnections of the modules are optimized for maximum yield. The presented approach allows the simulation and optimization of BIPV in urban environments where complex shading occurs and high electrical mismatch of photovoltaic cells and modules is to be expected. It allows specific geometric design and optimization of photovoltaic installations and their electrical layout. The electrical simulation is validated for both flat and curved thin-film CIGS modules, as well as for two connected thin-film CIGS modules under deferring irradiance and partial shading conditions. The presented method is further applied in a case study on a double-curved roof shell. The results show that by using genetic algorithms the layout can be optimized to minimize the string mismatch losses for BIPV networks with a variety of modules. The detailed electrical simulation allows to quantify effects of module designs and inverter concepts on the system performance. This is demonstrated for the case study, indicating that thin-film modules with longitudinal cell direction outperform modules with orthogonal cell direction by up to 8%. Furthermore, module-integrated bypass diodes show little benefits for the best performing module technologies. Post-processing the results allows the evaluation of annual, seasonal, daily and hourly losses on a highly disaggregated level.