system unavailability

[sarah95]

Hi all 

i have 2 system proposals for same project where i set system unavailability pvsyst default values for both (2%)

 but at loss diagram of the reports i found different value in each , one report with -1.98% and the other -2.45%

How does that happened?

[Robin Vincent]

Dear sarah95,

The unavailability figure defined in PVsyst represents the time fraction during which the system won't be able to produce electricity.

The unavailability losses are not directly linked to the unavailability fraction, but also to when the system is not available (day, night, summer, winter, ...).

Thus a same unavailability duration can give dissimilar unavailability related losses. 

 

You can find more details on our help page related to the subject :

https://www.pvsyst.com/help/index.html?unavailability_loss.htm

 

 

[sarah95]

1 hour ago, Robin Vincent said:

Dear sarah95,

The unavailability figure defined in PVsyst represents the time fraction during which the system won't be able to produce electricity.

The unavailability losses are not directly linked to the unavailability fraction, but also to when the system is not available (day, night, summer, winter, ...).

Thus a same unavailability duration can give dissimilar unavailability related losses. 

 

You can find more details on our help page related to the subject :

https://www.pvsyst.com/help/index.html?unavailability_loss.htm

 

 

yes i  understand ur points but how it varies for same project the only difference between the 2 proposals is the type of inverter (central , string inverters) and all other things are the same 

[Auxi Madero]

3 hours ago, Robin Vincent said:

Dear sarah95,

The unavailability figure defined in PVsyst represents the time fraction during which the system won't be able to produce electricity.

The unavailability losses are not directly linked to the unavailability fraction, but also to when the system is not available (day, night, summer, winter, ...).

Thus a same unavailability duration can give dissimilar unavailability related losses. 

 

You can find more details on our help page related to the subject :

https://www.pvsyst.com/help/index.html?unavailability_loss.htm

 

 

Hello, and sorry for stepping in.

I have a question regarding this matter.

I am not clear about the concept of unavailability for simulations.
Could you confirm how I need to indicate in the system losses that the current availability provided by a client for the simulation of a site is 95%?

Thanks in advance.

Best regards

[Robin Vincent]

@sarah95 When setting the unavailability factor to default, PVsyst will split the total duration onto 3 separate periods of equal length.

These periods are randomly selected when you enable the unavailability factor for your different variants the 1st time.

Thus, two variants using the default (random) unavailability period may end-up with very different unavailability losses.

If you consider the unavailability of both systems should be the same, you can specify the same date, time and unavailability duration manually.

 

@Auxi Madero In your variant, detailed losses ==> unavailability you can set a unavailability probability to 5%. With the rest of the settings unchanged, it will generate three random unavailability periods for a total duration of 5% of the whole year. 

You can find more information in the help page dedicated to the topic : https://www.pvsyst.com/help/index.html?unavailability_loss.htm

[Auxi Madero]

23 minutes ago, Robin Vincent said:

@sarah95 When setting the unavailability factor to default, PVsyst will split the total duration onto 3 separate periods of equal length.

These periods are randomly selected when you enable the unavailability factor for your different variants the 1st time.

Thus, two variants using the default (random) unavailability period may end-up with very different unavailability losses.

If you consider the unavailability of both systems should be the same, you can specify the same date, time and unavailability duration manually.

 

@Auxi Madero In your variant, detailed losses ==> unavailability you can set a unavailability probability to 5%. With the rest of the settings unchanged, it will generate three random unavailability periods for a total duration of 5% of the whole year. 

You can find more information in the help page dedicated to the topic : https://www.pvsyst.com/help/index.html?unavailability_loss.htm

Thanks a lot for your answer.

So, recapitulating, in the "unavailability time fraction" box I include the percentage of unavailability that the plant has. But isn't it relevant to modify the number of periods? considering that I have no further details beyond 95% availability.

Thanks again.

[Robin Vincent]

We cannot help you in the definition of the periods themselves, as they are only related to your project. This information must be provided by your client or be part of your simulation assumptions.

[dtarin]

@Robin Vincent Is there a reason for a limit of 5 periods?

[Robin Vincent]

There is no real justification for limiting the number of periods to 5. It will be changed in a future PVsyst release.