Physically-based irradiance model for photovoltaic applications

Abstract

The installation of photovoltaic systems in the urban environment is becoming increasingly common. These photovoltaic systems are affected by a large fraction of reflected irradiance as well as partial shading. In a similar way these issues also have an important effect on bifacial photovoltaic power plants. Irradiance models that are able to take these issues into account are therefore gaining interest. For an accurate economic assessment of a PV system and the calculation of delivered power it is becoming very important to be able to accurately determine the irradiance on a PV system. Therefore there is a rising demand for accurate irradiance models that are able to take into account the effects that arise in complex geometric scenarios. The research in this thesis report aims to develop such a model which is able calculate the irradiance incident on bifacial modules and PV arrays in complex landscapes by combining the concepts of ray tracing and 3D view factors. The implementation of the proposed model decouples the irradiance simulation into independent blocks that allow to efficiently calculate the spectrally-resolved irradiance incident on a PV module. This decoupling makes the proposed model suitable for simulation of tandem devices in the near future. The developed simulation has been experimentally validated using measurements from the PVMD monitoring station and also in comparison with other sophisticated irradiance simulation models. Experiments with a large fraction of specular reflected irradiance showed a good match between the measured and the simulated irradiance. Validation over a longer time period was also performed for 3 different sensors on the PVMD monitoring station roof. The results show an overall low mean bias error between the measured and simulated irradiance for the time period between mid-August 2020 to mid-October 2020. The proposed model is able to model the irradiance impinging on a PV system in a complex urban environment using a decoupled structure and its performance is comparable to sophisticated existing ray tracing models. The performed simulations show a good match with the measurements for different situations. Further improvements are the implementation of higher order reflections, computational optimization and more extensive validation.