Abstract
We analyze the output of various state-of-the-art irradiance models for photovoltaic systems. The models include two sun position algorithms, three types of input data time series, nine diffuse fraction models and five transposition models (for tilted surfaces), resulting in 270 different model chains for the photovoltaic (PV) system simulation. These model chains are applied to 30 locations worldwide and three different module tracking types, totaling in 24,300 simulations. We show that the simulated PV yearly energy output varies between −5% and +8% for fixed mounted PV modules and between −26% and +14% for modules with two-axis tracking. Model quality varies strongly between locations; sun position algorithms have negligible influence on the simulation results; diffuse fraction models add a lot of variability; and transposition models feature the strongest influence on the simulation results. To highlight the importance of irradiance with high temporal resolution, we present an analysis of the influence of input temporal resolution and simulation models on the inverter clipping losses at varying PV system sizing factors for Lindenberg, Germany. Irradiance in one-minute resolution is essential for accurately calculating inverter clipping losses.
Highlights
Irradiance models are among the most important elements of the complex model chain for simulations of photovoltaic systems
Model quality varies strongly between locations; sun position algorithms have negligible influence on the simulation results; diffuse fraction models add a lot of variability; and transposition models feature the strongest influence on the simulation results
To highlight the importance of irradiance with high temporal resolution, we present an analysis of the influence of input temporal resolution and simulation models on the inverter clipping losses at varying PV system sizing factors for Lindenberg, Germany
Summary
Irradiance models are among the most important elements of the complex model chain for simulations of photovoltaic systems. The irradiance incident on the module plane is measured beforehand in-situ in high resolution, so that this time series can directly be used as an input for the electrical PV simulation. The models have to deliver estimates for the sun position, for the diffuse fraction of the horizontal irradiance and, most importantly, for the global irradiance on the plane of the module. By altering the model chain, we combine all selected models of one category with the all models of the other categories, which leads to a considerable amount of simulations With this analysis, we are able to answer questions about the importance of choosing the right sun position algorithm, the required temporal resolution or the best model for the diffuse fraction. We can make statements about the variability of the simulation results under given conditions
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