In this document
We will explain how to verify the PV simulation models. It can be achieved by breaking down the models into individual components, enabling a more detailed and precise analysis of the various calculations involved.
Overview
The verification of PV simulation models is critical for ensuring the accuracy and reliability of energy yield predictions. This verification process, applied to key simulation steps, ensures that the software correctly represents real-world conditions, including complex scenarios like partial shading and variable irradiance.
The verification of Solargis PV simulation software is presented here for three core models: ray-tracing, electrical simulation under shading, and inverter performance.
Solargis ray-tracing algorithm
The Solargis ray-tracing algorithm was validated using Radiance, a reference model known for its robust optical simulations. The study focused on comparing global tilted irradiance (GTI) including front and rear side of modules, leveraging ray tracing and Solargis anisotropic sky model. Test cases across diverse sites and configurations were examined to cover a wide range of lighting conditions, including clear skies, overcast scenarios, and complex shading setups.
Under clear sky conditions, Solargis and Radiance results demonstrated strong alignment, indicating high accuracy. In overcast scenarios, the outputs were equally consistent, validating the models’ performance under diffuse lighting. Complex shading and rear-side irradiance simulations highlighted minor deviations due to differences in ray-tracing configurations.
Solargis electrical simulation under partial shading conditions
The Solargis electrical simulation is able to handle complex layouts and shaded scenarios for PV plants. The electrical model was validated using advanced tools like LTSPICE to simulate various PV modules and configurations under partial shading conditions. Simulations included single-module setups and string-level configurations with different module orientations.
For Single Module Validation, power outputs showed near-identical results across simulators, with small deviations in some cases, primarily due to differences in diode parameters. For string-Level Simulations, accurate IV and power calculations were achieved, demonstrating reliability for both landscape and portrait orientations under partial shading.
Solargis inverter model
Unlike other PV software, the Solargis inverter model can employ subhourly data inputs. The model was tested spanning diverse climate zones using input data at time resolutions of 1-minute, 15-minute, and 60-minute intervals. The study evaluated the impact of time resolution on clipping losses and energy yield predictions.
Simulations revealed that lower temporal resolutions, such as 60-minute data, underestimated clipping losses and overestimated energy yields. This discrepancy was most pronounced in regions with high irradiance variability due to cloud cover or atmospheric conditions. High-resolution data (1-minute) captured rapid irradiance changes, leading to more accurate predictions of clipping losses and system performance.
Conclusions
The verifications proved the validity of Solargis PV simulation, including the following key steps of both optical simulation and electrical simulation.
The tests confirmed the accuracy of the Solargis ray-tracing algorithm and Perez sky model for both the front and rear side of modules. Differences in results were primarily attributed to variations in sensor density, with angular and spectral losses excluded from this validation. The close agreement across diverse scenarios establishes Solargis as a reliable tool for PV simulations under varying lighting and shading conditions.
The tests verified the single-diode model and the capability to simulate substring and string calculations. The circuit-solving algorithm was accurately implemented, ensuring reliable simulation results under real-world shading scenarios. Minor deviations underscored the importance of precise diode parameters and temperature coefficients for accurate modeling. These results confirm the reliability of Solargis for simulating partial shading conditions, supporting improved PV system design and performance assessments.
The tests confirmed that using high-resolution data improves PV system design by better accounting for clipping losses, optimizing component sizing, and preventing underperformance during operation. This verification underscores the importance of temporal granularity in simulation data for optimal PV system performance.