Michele Oliosi Posted June 5 Posted June 5 Two corrections impacting electrical shading results Release note: Shadings: the bottom cell size is now taken into account also when computing the shading factor table from the Near shadings window. Between versions 8.0.0 and 8.0.11, the bottom cell width was not available in the Near shadings window calculations. Therefore, recomputing the shading factor tables by clicking the “Recompute” button, or computing the tables when prompted when closing the Near shadings window could lead to slightly incorrect results, especially for low sun heights. Version 8.0.13 corrects this bug. Shading factor table calculations will be consistent no matter where they were called from. If you were using the "according to module strings" model in "Fast", it is possible that electrical shadings will slightly increase due to this correction. Release note: Shadings, thin objects: the partition model results in presence of thin objects have been corrected. This may impact the simulation results, by increasing the electrical shadings slightly in some cases. In previous patches of PVsyst 8, the electrical shading factor in the presence of thin objects, when using the fast simulation mode (table interpolation), was not calculated correctly. This could lead to an underestimate of electrical shading losses. Note that this bug was not present in version 7. Moreover (also in previous PVsyst versions), whenever the total irradiance loss was lower than the electrical shading loss from normal objects (case with many thin objects), the electrical shading loss could also be underestimated. Although very rare, this case is now corrected as well. Improvements of the bifacial view factor model Release note: Bifacial: corrected calculation of the sky diffuse contribution on the rear side of the PV modules This patch addresses several issues in the modeling of the sky diffuse on the rear side. The impact of the number of rows has been reassessed; it now better captures the fact that the rows at the extreme end of the array do not experience mutual shadings, for all diffuse components. The rear side diffuse view factor has been revised; a normalization factor now correctly depends on the tilt. A discretization effect that caused an East-West asymmetry for trackers has been fixed. These issues were most impactful in the following two cases: systems with vertical tables, and systems with few rows of tables. With this correction, the modeling of irradiance on the front and on the rear have been harmonized and generally have a better match. However, the impact on the total system output remains small, amounting to less than 0.5% for most bifacial systems. Note: Systems with a single table, or a single row of tables, can currently only be designed with “unlimited” orientations. A workaround duplicate all the elements in your 3D scene and place it sufficiently far away so that mutual shading effects are negligible. Considering the power factor in the System window for sizing assistance Release note: System design: Overload losses are now adjusted when a Power Factor is specified in “Energy Management”. When requesting an inverter to produce reactive power, its overload conditions may be impacted. This will depend on its nominal power specifications. If the nominal power (PNom) is specified as apparent power ([kVA]), a power limitation will apply in terms of active power according to the formula: PNom(active) [kW] = PNom(apparent) [kVA] × cos(φ). Since PNom(active) is lower than PNom(apparent), overload losses increase and depend on the chosen power factor (cos(φ)). Once a yearly power factor is specified, the estimation of overload losses in both the System and Sizing windows will take this effect into account, indicated as “Overload loss, with PF”. This estimation now more closely reflects the values shown in the loss diagram. Future versions will include the estimation of overload losses for monthly power factor as well. A more detailed explanation is available in the Help section: https://www.pvsyst.com/help/project-design/grid-connected-system-definition/power-factor/index.html Warning message “inverter is slightly/strongly undersized” Release note: System Sizing: warning and error messages for inverter slightly and strongly undersized are now triggered at 2% and 4% overload losses, respectively. These errors are not fatal anymore. In addition to the previous point (considering the power factor in the System window), the fatal error message “the inverter is strongly undersized” is no longer triggered at 3% overload loss. Instead, it is now issued as a warning that does not block the simulation. For new projects, the threshold for displaying this message has been updated to 4%, acknowledging that moderate inverter overloading has become a common practice. For older projects, the threshold is still set at 3%, which can be modified in the parameters of the project.
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