Shading losses in PVSYST 5 and 6

[Konstantina]

Dear Andre,

I have seen some differences in shading losses between the version 5 and 6.

1. In version 6 the horizon losses are higher than 5 (I have done some simulations for different sites in Europe with always using the same mountain size in my horizon).

Why is that happening?Should not be the other way around?

2.The shading losses in 6 are smaller than in 5. That is due to the direct shading factor calculation that tha last version uses? So, there are no interpolation in time uncertainties in the shading factor table?So, no time interpolation uncertainties regarding mutual shadings too?

3.Also, using the same inverter and PV modules the mismatch losses and the quality losses are in every case for each version the same.For 5 they are higher than 6 but in every site the same.The same results in the quality losses are due to the fact that I use the same PV system in every case and the exact same scene? But about the mismatch losses, why in every simulation is fixed?Should not be the same for every site that I use because they have to do with the shading or not to a cell that can drive the current of the whole string. And in different geographical sites that differs or not, (although I have the same PV system and the same scene)?

Thank you very much.

[André Mermoud]

1. In version 6 the horizon losses are higher than 5

Nothing has been changed in the Horizon loss calculation. This may be an effect of the Transposition model, which is, by default, the Hay model in version 5 and Perez model in version 6.

The shading losses in 6 are smaller than in 5.

Same answer as above. There are in principle no differences in the near shading calculations.

So, there are no interpolation in time uncertainties in the shading factor table?

Yes of course there are interpolation uncertainties. The solar geometry (therfore the sun's position) is calculated in the middle of the hour, and the shading factor in interpolated in the table.

However these uncertainties are averaged over the whole yearly calculation.

NB: with version 6, you can avoid the interpolation in the shading factor table by asking the Calculation mode: "during the simulation", i.e. the shading factor is fully computed at each simulation step.

3. Also, using the same inverter and PV modules the mismatch losses and the quality losses are in every case for each version the same.

See "Which are differences in yield between version 6 and version 5 ?", especially "Losses with derate factors".