Median P50 AC Energy vs. AC Energy Injected into the Grid

[kjs55]

It is reported in literature [1] that the p50 (median) derived from a Monte Carlo- or convolution-based uncertainty analysis [2] is more appropriate to use (and not always the same) as the primary AC energy into grid value (E_Grid simul) that comes out of PVsyst. e.g., Not all the distributions that feed into the Monte Carlo are normal Gaussian distributions (e.g., the Gamma-shaped degradation rate distribution from Dirk Jordan [2]-[3]). Does the p50 in the PVsyst p50 estimation directly use E_Grid simul? Or is the p50 derived from the uncertainty analysis? Is it really a median p50 (or is it simply E_Grid simul)?

[1] https://www.researchgate.net/publication/318259323_A_Framework_to_Calculate_Uncertainties_for_Lifetime_Energy_Yield_Predictions_of_PV_Systems/

[2] https://www.eupvsec-proceedings.com/proceedings?paper=19917/

[3] https://onlinelibrary.wiley.com/doi/10.1002/pip.3566/

Edited September 8, 2022 by kjs55
Add convolution option (requires significantly less computational work)

[Michele Oliosi]

Hi @kjs55,

In PVsyst we assume the normal Gaussian distribution, and the assumed P50 value (since the distribution is Gaussian, it is the median and the average) is E_Grid simul. In order to perform a Monte-Carlo evaluation, multiple simulations should be run, which is not how the tool works in PVsyst at the moment.

Intuitively, I would assume that since the uncertainties are large and partially ad-hoc (and usually the main factor is the climate variability, for which I don't know the customary distribution -- I should check) that the details of the distribution don't matter much. However I can see how when you take into account aging, or when the weather statistics are well-defined, this could change.

But yeah, indeed, adding a Monte-Carlo tool, maybe on the basis of the batch mode, as well as a distribution function selection would be interesting.

[PVsystUser]

On 9/9/2022 at 3:12 AM, Michele Oliosi said:

and the assumed P50 value (since the distribution is Gaussian, it is the median and the average) is E_Grid simul.

What could be the possible source of difference in P50 and E-Grid simul.  here: 

 

[PVsystUser]

I saw the help page below but E_Grid calculated based on TMY which itself is a statics entity.

[Michele Oliosi]

You have 1% "climate change" this parameter will make P50 and E_Grid(Sim.) differ. It represents the fact that the weather data used for the simulation is not representative for the P50 (e.g., the P50 may change in the future, or has changed since the data was recorded).