A fully transient novel thermal model for in-field photovoltaic modules using developed explicit and implicit finite difference schemes

Three fully transient numerical thermal models have been developed for photovoltaic (PV) modules in MATLAB environment, using 2-D finite difference (FD) method. One of the thermal FD model is based on explicit time scheme, while the other two are based on implicit time schemes. Out of the two implicit FD models, one has been modeled using preexisting toolboxes of MATLAB, while the other has been modeled using a self-developed novel method. All the three FD models are based on energy balance of different control volumes, which as a whole constitute the complete solid domain of the PV panel. The models have been tested against a variety of experimental data, ranging from sunny clear days, sunny cloudy days, rainy overcast days and consecutive sunny clear days. All the three models are found to agree very well with experimental results, i.e. the errors between the modeled and experimental data ranges between 0.2–0.7 °C. The main difference is between their computational speeds. In terms of average execution time per iteration for transient analyses, the self-developed novel implicit method (referred to as implicit BB throughout the work) was about 1200 times slower than the explicit method. However, overall, the implicit BB method took less time for the entire transient analyses, as it requires less number of iterations due to its tolerance to adapt longer time steps for each iteration. In other words, the explicit method although slightly more accurate, took approximately 900 times more CPU time to simulate the same time span test compared to implicit BB method. Thus, the self-developed novel method (implicit BB) has been recommended for these types of thermal models.