Thermoelectrical Modeling of Wavelength Effects on Photovoltaic Module Performance—Part I: Model

A better understanding of the factors that affect the performance of photovoltaic (PV) modules will improve the design, optimization, and development of them. Researchers have introduced thermal models to predict module temperatures, and thermoelectrical models to study the interaction of electrical and thermal module characteristics. However, these models have relied on the assumption that the short-circuit current is proportional to the total incident irradiance, neglecting wavelength-specific effects. While it is true that the main input power to the PV module is the incident solar irradiance, various optical properties of module materials vary with wavelength. At each wavelength some energy is reflected, some is absorbed in the PV cells (contributing to electricity production), some is absorbed in other module materials, and some is transmitted through the module. A model capable of predicting this wavelength-specific behavior will generally allow a better assessment of the module performance especially when it is combined with subsystems such as optical filters. In this study, a wavelength-based thermoelectrical model is proposed to predict the PV module temperature and output power. A lab-built PV module is used to validate both the temperature and output power results. The predicted results are shown to agree with the experimental measurements.