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Stand alone P50 - P90?


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Is it possible to do the P50 and P90 calculations in a stand alone system. For example i need the system to be 100% reliable, year on year. I use currently Meteonorm data, which is averaged so there is a chance one year could under perform. Usually what is done is the system is over sized, so the battery autonomy will always save you in the case of under production but it is also the most expensive part of the system. Is there anyway to model this variability so i can optimize my battery size?



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This is an excellent question.

In the present time, PVsyst provides a pre-sizing of the battery capacity, which is computed using one meteo yearly distribution (from monthly meteo data).

This yearly meteo is randomly generated (synthetic generation), so that you have a different result at each execution. The PLOL is highly dependent on the worst conditions, i.e. the duration of the periods without sun in the meteo series.

We plan, in a near future, to extend this sizing evaluation over a set of multiple years generations, and give a distribution of the PLOL, allowing to establish a P90 (or any Pxx) probability.

NB: if the battery is slightly oversized, for a given charging/discharging balance its lifetime will be extended. Therefore the higher investment price will be balanced by a lower "operating" cost (i.e. provision for the replacement of the battery). The important parameter here is the cost of the stored kWh, taking the number of cycles into account.

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