Grid-connected with self-consumption strategy

[julmou]

Good morning,

I am using the DEMO Residential Geneva Project, with the variant VC5 "Self consumption with storage".

I have a question about some of the information when we open the "Storage" dialog box.

Under the "System information" part, there is "Charging Time during full sun conditions". Now what are these "full sun conditions" exactly? The STC conditions (1000 W/m2, 25°C) or the summer clear sky conditions? Because, on the next tab "Self-consumption", we have the PV array max. output power (clear sky) at 7.79 kW, which would take the 10.7 kWh potential stored energy 1.4 hours to recharge, not 1.2 hours. But under STC conditions, the 9.0 kWp of the array would produce 9 kW which would indeed charge the 10.7 kWh in 1.2 hours.

So I just want to clarify, because the "during full sun conditions" confuses me... Specially because in the same tool, we also see the "(summer clear day)" and "(clear sky)" terms.

What does "full sun conditions" mean in this case?

[Bruno Wittmer]

This value is indeed calculated for STC, which are meant to be close to plain sun exposure, therefore the wording.

This is arbitrary, and one could use the maximum power for the clear sky calculation as well. This figure is there to give a quick feedback on whether the battery size is within a reasonable range. One should not draw precise conclusions from this value, but rather from the simulation results.

Please note also, that this is the nominal DC power of the PV modules, so it is the value shown in 'PV array Pnom'. In the simulation the charging power is also limited by the inverter nominal power and the maximum charging power given in the tab 'Self-consumption'. This can potentially lead to much higher charging times.

[julmou]

Thanks for the clarification :)