Detailed Losses

[astha.saxena542]

I am simulating a 50MW ground mounted project. I am a beginner at PVsyst. Can anybody help me how to define detailed losses in PVsyst? What are the inputs to be given?

[André Mermoud]

You define the losses in the "Detailed losses" dialog.

PVsyst proposes default values (for your first simulations). And for several of them you have a detailed Help for understanding their meaning.

However most of the values are closely related to the situation and the conditions of your project. You have to evaluate them by yourself.

[akshay3207]

You define the losses in the "Detailed losses" dialog.

PVsyst proposes default values (for your first simulations). And for several of them you have a detailed Help for understanding their meaning.

However most of the values are closely related to the situation and the conditions of your project. You have to evaluate them by yourself.

 

Hello Andre,

I have noticed that in the AC cable Loss section, say if I have chosen a Solaredge Inverter of 27.6KW, the Pac value under STC it shows it to be 32KW. Same I have experienced with other Inverters as well such as Delta & SMA, the Pac values are very high. I tried searching in the Inverter Manufacturer Data from the Datasheet as well as the data available within PVsyst, but couldn't find the source how a higher value Pac was being arrived at. In all the cases the voltages shown against the power were nominal , but the current values indicated were more than the nomical AC current specified in the data sheet.

Also is it possible to retrieve the PVsyst resistance values of different cable sizes , which in turn is used to calculate the Loss fraction at STC. These resistance values vary to a great extent from the ones specified by the cable manufacturers and hence the loss fractions that I calculate doesn't exactly match with PVsyst. Can you please confirm will the relation of the Energy loss to Loss at STC still be value near around 60% , as you had said in one of you other posts.

Request you to please guide me with these two issues.

Thanks & regards,

Akshay

[André Mermoud]

The Pac(STC) is indeed used as reference when defining the external transformer losses.

See the FAQ How to determine the parameters for External Transfo Losses ?

But this is a reference value, not a realistic one. Remember that the STC values concern a run under 25°C. Under 1000 W/m2, the temperature may attain say, 60°, i.e. a loss of roughly 15% ((60°-25°) * 0.44% = 15.44%).

Therefore the yield under 1000 W/m2 ad 60° is roughly equivalent to a yield under 1150 W/m2 and 25°C.

I am aware that this definition is not very convenient for the evaluation of the transformer losses parameters. We will improve this in a next version.

The resistivity of the wires is defined in "Detailed Losses > Ohmic losses > Detailed computations > Wires". It corresponds to pure copper (or alumuînium), but you can change it as you like. The default value is specified in the "Hidden Parameters".

The final energy loss evaluation is explained in the FAQ Why the losses in the results are different of those specified ?.

This is a pure calculation result of quadratic losses, there is nothing to confirm.

[lenergy]

The Pac(STC) is indeed used as reference when defining the external transformer losses.

But this is a reference value, not a realistic one. Remember that the STC values concern a run under 25°C. Under 1000 W/m2, the temperature may attain say, 60°, i.e. a loss of roughly 15% ((60°-25°) * 0.44% = 15.44%). Therefore the yield under 1000 W/m2 ad 60° is roughly equivalent to a yield under 1150 W/m2 and 25°C.

I am aware that this definition is not very convenient for the evaluation of the transformer losses parameters. We will improve this in a next version.

 

I'm using the latest version 7.0.15 and still seeing the confusing "Generic Reference Pac(STC)" in the transformer losses section. Suggest eliminating it and replacing with "Inverter Max. Output Pac" - which is what the transformer losses are actually based upon, not STC or any other test conditions.