Negative Values of "Energy injected into grid" in Hourly Output File with Unavailability Loss Applied

[kjs55]

Operating PVsyst V6.12

It is uncertain whether the negative energy values correlate with the randomized dates / times when the systems is not operational.

It appears that summing the 8760 hourly energy values (both positive and negative) in Excel yields the same annual value as what is reflected in the PVsyst output report.

I would have expected energy production to be zero during the times when the system is not operating (not negative).

Please advise as to whether this is a bug or not.

Edited April 15, 2021 by kjs55

[André Mermoud]

In PVsyst the final yield is meant as the net energy delivered to the grid (produced - consumed).

The not-operating loss (by night) is apparent on the loss diagram as parts of the transformer MV losses and the eventual auxiliaries loss (if arising by night).

If we don't include them in the final yield, we should represent them as an input arrow representing an input gain drawn from the grid, which may be confusing.

And still more confusing if we consider that these losses arise indeed during the full operating time (not only the night).

[kjs55]

During system downtime due to "unavailability in the system" (new loss in PVsyst V6), the external transformer losses remain proportional to the square of the current even though the system is not operating and no current is flowing (open-circuit). I think the external transformer losses should be constant (not irradiance-dependent) when the system is not operating.

I think this indicates that there is a bug (e.g. the transformer loss is calculated and applied before taking into account the system is down).

Edited December 16, 2019 by kjs55

[André Mermoud]

OK, I will check this in the program.

But please admit that this will have a marginal effect...