Input / Output decimals consistency

[MicheleANE]

Hello,

We are able to display the report using 1 to 3 decimal places but, in several places of the software, the input is limited to 1 or 2 decimals (soiling, aging, etc).

Often we are requested to run simulations with input values calculated separately and, as they are often given with 3 or more decimals, it would be nice to be able to keep the same precision in the input and output.

This is especially true for losses that just use the input value. These should not be rounded more than the report precision requires.

Best regards

[Michele Oliosi]

Hi,

Thank you very much for the feedback.

In fact, being able to display 3 decimals for loss percentages in the report is completely artificial. It was added probably because of some request.
You should always keep in mind that in PVsyst changes below 0.1% are to be considered as irrelevant, and in some cases you will even find differences when saving and reopening a variant (some values are recalculated based on other variables, and the saving precision is fixed). In any case this is justified by the large inaccuracy of measurements and basically most inputs, but especially the meteo.

That is to say, we will likely not increase the number of decimals in the losses. However I agree with you that at least the default 2 decimals should match in the output and input. We will check that that is the case.

[MicheleANE]

Thank you for the prompt response.

I perfectly understand your point about accuracy and agree.

It's more about coherence and being able to show that we used the input values as requested.

It would actually be fine if all losses and inputs were fixed at 2 decimals without other options as long as they were all compatible.

Thank you in advance for your support and best regards.

[MicheleANE]

Hello,

Any news about this?

2 decimals are more than enough. Just, please make it so the parameters inputs are 2 decimals as the results and that those 2 decimals are kept the same for losses that are directly calculated using those parameters (ex.: soiling loss).

Also, recently I noticed that the mismatch loss keeps the input value only on the first run of that variant. If ran twice, it will sometime change (usually x-0.01%).

Best regards

[Michele Oliosi]

Hi Michele,

The ticket is assigned, but we are clearing some other issues at the moment. It may take a few patches for an update on this.

The mismatch loss may change when there is aging (we use a statistical model to change the impact of aging on the mismatch). Apart from that and since it is such a small difference (0.01%) this is maybe due to some other edge effect of a rounding. I will keep an eye open about it.

[MicheleANE]

Hi Michele,

Thank you for your response.

It is nice to know this is being given thought. Couldn't ask for more.

Best regards.

[Brij.Modi]

Hello PVSyst team,

Version 7.4.2

When We are try to create loss diagram from hourly. Illumination Losses are accurate with 2 decimal (x.xx), While Electrical losses have mismatch with PVSyst Report.  

For Example:

Input side LID = 1.00%,

Output side,

A) sum of LID = -6,002 MWh

B) sum of Array nominal energy (at STC effic.) = 629,849 MWh

PVSyst display for LID = 1.00%

Modelled LID(%) =  A/B = 0.95%

 

How to deal with this errors? May I know the solutions?

Thanks,

Brij

 

 

[Michele Oliosi]

Dear Brij,

It is incorrect to refer as the LID loss with respect to the nominal energy value. You have to consider the loss diagram flow:

The LID is only accounted after the irradiance level, temperature, module quality losses (and other losses that may appear in your project). I.e. you need to change the value you use in B in your equation to account for these.