Prediction of PV module nominal operating cell temperature using electromagnetic wave modeling

Nominal operating cell temperature, NOCT, defined by module heat generation and loss mechanisms, is an important factor relating to energy conversion efficiency of PV modules. Development of simulation tools for predicting NOCT is an important element of designing modules that may function to operate at lower NOCT. When modeling the heat generation from incoming radiation, it is highly desirable to accurately simulate the solar energy conversion in the cell, glass, encapsulant and anti-reflective layers, as well as the spaces between the cells. We present herein an approach that starts from the fundamental of electromagnetic wave (EMW) propagation based on Maxwell's equations. This approach enables the EMW energy in individual layers and at different regions of the PV module to be evaluated from the dielectric constants and thickness of each material. Once the light intensity in the cell is known, it becomes possible to predict cell electrical parameters using established electrical models. This methodology was applied to a packaged back-junction-back-contact (BJBC) cell and compared with parameters derived from an experimental I-V curve. Good agreement was observed for both electrical parameters and external quantum efficiency. The distribution of solar energy conversion within the module was further combined with heat transfer and 3D finite element analysis models to enable a prediction of thermal profiles of the module. The simulated temperature distribution was found to agree well with experimental measurements using a thermal imaging camera and thermocouples.