André Mermoud

The usual tracking strategy defines the tracker's angle in order to minimize the incidence angle for a given sun's position. This new strategy determines the orientation according to the best irradiance received by the trackers. This may be different than the previous strategy as the transpositon of the diffuse component is proportional to (1 + cos(i) / 2), where i = incidence angle. Therefore the higher tilt, the less transposed irradiance. For a fully covered weather, the optimal tracker's position will be horizontal (Phi = 0) In practice on real systems, this strategy may be easily applied by putting 2 irradiance sensors on the tracker, separated by a black wall perpendicular to the tracker: the best orientation is obtained when the measured irradiances are equal.

Some answers to your questions. 1. - I don't understand well your doubts. The fixed sheds are obviously usually aligned East-West, i.e. facing the south. Except when you are using domes. The single axis trackers have always an axis orientation close to N/S, for tracking the sunrise and sunset "sun's height" positions. An axis oriented E/W would only track the height of the sun on the horizon. It is not useable with PV systems. 2. - The "Edge effects" When you have 2 narrow tables one behind the other, in the morning or the evening a part of the shade is falling on the ground instead of the table behind. We don't have this situation in "unlimited sheds". 3. - Difference between "Unlimited trackers" and "Tracker arrays" defined in the 3D scene. The "Unlimited trackers" shades calculation (from tracker to tracker) is a 2-dimentional analytic calculation. The "Trackers arrays" defined in the 3D scene use the full 3D calculation of the mutual shadings from the sun's position. It is a much more complex calculation, taking the real sizes of the tables into account ("edge effects"). Now each of these very different calculations are using not quite perfect models, it is normal that there are some little discrepancies.

We don't envisage to develop a simulation of both options mono and bi-facial at the same time. As these would be 2 different systems, therefore 2 different sets of result variables, etc. This involves a very complex simulation process. I really don't see how to do that in PVsyst, and how to present it on a report. The right way is to perform 2 different simulation, and compare the results (eventually the losses, like for example the overload losses).

The bifacial model is rather complex (and specific, still involving "ulimited sheds"). It is not useable with stand-alone systems.

The integral for the diffuse involves an incidence factor of each irradiance ray on the receiving surface. I.e. each "cell" of irradiance should be multiplied by cos(i) (i = incidence angle). Therefore: - the effect depends on the plane orientation - It cannot be approximated by surfaces on the sphere.

This part of the report gives indications about the system, taken mainly from general features of the 3D scene. Of course if the system is complex, with different pitches or sizes, or different groups of sheds, this determination becomes unsure and very difficult to evaluate. It is quite impossible to give accurate measurement of any complex system. Should we completely suppress it when ths system is not "perfect" ? I don't think so, but people should understand that the values are only indicative.

The thumb rule is to consider a shading object as "Far shading" when it is at a distance of at least ten times the sizes of your PV system. So if your PVsystem has a size (width or length) less than 27 meter, you can indeed use the "Far shadings". In the opposite case, you can create a ground object for simulating your mountain. Don't define a too detailed grid as the calculation time may become prohibitive. Don't forget to check the option " Enable shadow casting" in the object's properties.

In PVsyst, the parameters of all trackers should be identical. So that at a given time, the orientation of all trackers is the same. Therefore it is not possible to distribute trackers on a hill, with axis following the slope. We will develop this feature in a next version. But in this case the backtracking will be totally impossible (either in PVsyst and in the reality).

This depends on the version. In the latest versions you have indeed the item "SAM CSV format - Hourly TMY or time series".

This depends on when you evaluate the solar geometry. In PVsyst, for normal intervals the geometry is computed in the middle of the hour (eventually shifted for some measured data). Now the first interval of the day begins at the sunrise time (say, 6:20). And the solar geometry is evaluated in the middle of this interval (in this case 6:40). I don't know whether the Synthetic generation managed by Meteonorm uses this convention. Please ask the Meteonorm team.

This service has been suppressed by PVGIS in october 2018. It is no more supported. PVsyst can now import CM-SAF data in a new format, as hourly files, directly from the PVGIS site. Please choose the option "PVGIS V5 Hourly time series"

PVsyst can import meteo data from many sources, in many formats, and creates internal *.MET files. But it doesn't create files in external formats.

SolarEdge has very specific and constraining rules. These rules involve specific devices (inverters and optimizers) and their associations. These are implemented in PVsyst according to the requirements of the SolarEdge team. Please ask them. NB: There will be a new implementation of these rules in the next version 6.80, with some new devices.

The irradiation conditions in the nord of Chile are really exceptionnal (due to altitude and very dry weather). You should increase the limit for this warning in the Hidden parameters, topic "Sites and Meteo", item "Upper limit for monthly clearness index"

Perhaps you are using an old version. In the Weak grid definitions you have this option: Group "Operating conditions", checkBox "Allows solar injection into the grid."

Usually no more than 1-2 working days.

There is a short explanation in the help "Project design > Shadings > Near Shadings: Import > Helios 3D" But we should indeed write a complete description of this tool.

Before analyzing the economic evaluation, please analyze first the energy output of your simulation. I don't understand well what you have specified on your CSV file: with CSV reading, PVsyst only accepts hourly consumption values, not daily values. If you want to create a PV system ensuring 100% self-consumption, it should be of sufficiently low power for never exceeding the User's needs, even by clear sky conditions.

For importing PVGIS data, PVsyst now uses a "Web service": it reaches directly the PVGIS site, and downloads the requested data. You don't need to open the PVGIS web site anymore. NB: With this new service, the PVGIS database has been deeply updated. The data are now provided in really measured hourly values, either as real years, or as TMY.

This calculation "according to strings" corresponds to an upper limit of the possible shading for each specified string. A "Fraction for Electrical effect" of 100% means that the full beam component is lost when the rectangle si shaded. A value higher than 100% would mean that more irradiance than the beam would be lost, which doesn't make sense.

The Voc(Tmin) requirement corresponds to a safety requirement. The procedure used in PVsyst for the evaluation of the max. voltage is a universal common practice, adopted by everyone in the PV community (not only PVsyst). We will certainly not modify this procedure. See the FAQ How to adjust the design temperatures ?.

This "Ground reflexion on front side" contribution had to be introduced with the bi-facial mode. It is due to the reflexion of the ground just between each row of collectors. It is mainly dependent on the tilt (low tilts will give lower contributions). This was quite necessary especially for the treatment of vertical bi-facial systems. It is also related to the pitch, as with big pitches, the contributing area in front of the PV table is higher. You can do some trials for this estimation in different situations. NB: This contribution is theoretically also present in usual not-bifacial systems. However it has always been neglected, as the calculation is quite complex, it requires all the hypothesis of the bi-facial systems - definition of the ground albedo, the geometry, etc. We were not aware of it until working on bi-facial systems. I doubt that any other PV simulation software takes this contribution into account and calculates it accurately.

The "Unbalanced" feature is a very special mode, only available for 2 MPPT imputs with very dissymetric inputs. When you have more than 2 MPPT inputs, you cannot define this mode and its very specific behaviour. But you can always define Sub-arrays of different powers on each MPPT. In this case you should use the "Power sharing" option for attributing a given PNom to each MPPT input. See the help "Project design > Grid-connected system definition > Multi-MPPT inverters: power sharing" for further details.

The back-up current is specified for your system, as a property (setting) of the back-up generator. It is specified in the "System" dialog, page "Genset". It is supposed to be constant at any time, when the genset is activated.

Th PNom limitation is applied on the apparent energy, therefore earlier. This is fully explained in the help "Project design > Grid-connected system definition > Power Factor"