# Unavailability of the system (V. 6.5.2)

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i got confused about unavailabiliy loss function and how it calculate on PVsyst 6.5.2. I have got Solar Rooftop Project for Car Factory, self consumption in factory.

So i have a vacation schedule plane (that is factory will not utilize electricity) for factory and condition to shut down as following,

1.) 106 days a year for vacation.

2.) shut down electricity in factory every 1 hour a day , 256 days a year .

So the calculation is,

1.) 106 days* 5hour (5 is average hour a day that is Solar system produce electricity) = 530 hour a year.

2.) 256 days*1hour = 256 hour a year.

Total days that is Solar system can not produce electrical due to unavailabiliy system is 530+256 = 786 hours a year.

So unavailabiliy system fraction is [786/(365*5)]*100= 43%.

this calculation that i have shown above is resonable or not. if not cloud you advise or suggest me how to calculate for this situation or how this function works.

Thank you very much for your support.

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This is not the right way of taking the not-used energy into account.

You should use the option "Net metering", and consider the energy injected ito the grid as lost energy.

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Thank you for your support, let me tell you that system is grid-connected and what i am evaluating is PR because i have to warranty system and we have zero export system that not allow energy injected to grid (in my country, if the system is consumption type. they not allow enrgy inject to grid).

In my understanding, in case of shut down system to maintenance, it directly impact to PR because of Zero export system.so PR will go down. So i want to know that if i known the exact schedule for matenance or their vacation that is the system cannot product energy what PR value i have to warranty due to such condition.Therefore, i think it relate to this function,"unavailability", right? . and if the caculation that i have shown you is not work how can i solve this solution.

Thank you very much

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Technically, I don't see how your system will work.

If it is really forbidden to reinject electricity into the grid, your system will only run when the full production is indeed consumed internally.

As soon as the consumption goes below the inverter nominal power, unless there is a very special control device within the inverter for running at partial load (I don't know any device of this kind), this will stop working.

Now the unavailability tool is not suited for this use. You cannot define more than 5 periods. The only way is the definition of the load in hourly values, and discard the energy reinjected into the grid. In this case you can recalculate the PR by yourself according to your hypothesis.

You can also create an hourly file when performing the simulation, and calculate your balances by yourself in EXCEL.