BESS stored vs. Direct use from Solar

[Mariyam]

Hello, I am simulating a grid-connected 10MWh BESS PV system. From the losses diagram, I gather that the stored energy (usage from BESS) is 8.5% of generation = 1595.195 MWh/year; and the remaining 91.5% is direct use from solar = 17171.805 MWh/year.

However, when I look at these values from tables: the EDirUse = 17432MWh/year and EBatDis = 1399 MWh/year; which doesnt match with the above values. Am I looking at the wrong values? Or does PVsyst give a highly approximate % of values from batteries and direct use? I have attached the table of values and losses diagram FYI. 

[André Mermoud]

In the loss diagram, the energies are always evaluated from the previous energy.

In this case, the Stored energy sharing is evaluated from the charging energy rather than the discharging.

You can evaluate the available solar energy as   20'443 MWh * (1-2.3%)*(1-0.5%)*(1-0.4%*(1-2.8%)*(1-1.0%) * (1-0.6%) = 18'933 MWh. 

Then:  18'933 MWn * 8.5% = 1609 MWh.  This is the charging energy.

The direct use is   8'933 MWh  * 91.5% = 17'323 MWh.

Here is the detailed calculation in EXCEL: you can check that the final result is very close to the loss diagram.

NB: You can get the detailed calculations of the loss diagram directly in EXCEL. In the menu of the report, you can use "Export => Loss diagram values", that you can simply paste in EXCEL.