Soiling Loss Calculation

[Enginerd]

Hello,

I am trying calculate monthly soiling loss as a % using the monthly losses in kWh. I was using the equation (kWh Loss/(kWh Loss + Energy Injected into Grid)). However, I found that if I use this same equation on the Annual Soiling Loss and Annual Energy injected into Grid, I do not get the same % Loss that is in the Loss diagram. In this situation, I have the following annual values:

Soiling Loss (from output table): 45255 kWh

Energy Injected into Grid (from Loss Diagram): 1289957 kWh

Soiling Loss (from Loss Diagram): 3.1%

45255/(45255+1289957) = 3.39%

I also tried dividing the loss by the Nominal Array Energy at STC (1627062 kWh), which gave 2.78%

Could you tell me what value I should be using to find Soiling Loss as a percent?

Thanks

[André Mermoud]

In the version 5, the soiling loss parameter (to be defined in the "Detailed losses" and appearing in the first page of the report) was defined as a percentage of the STC energy value.

Now during the simulation, the corresponding energy loss is indeed calculated as a percentage of the STC energy as specified.

But the result on the loss diagram is referenced as a percentage of the remaining energy just before the loss, therefore a slightly different percentage value.

In the versionn 6, it is accounted in the optical losses, and is a loss by respect to the remaining irradiance (after shading and IAM losses). The value on the loss diagram is identical to the specified parameter.

[Gayathridevi]

How to assume soiling loss for different geographical zones(snow area, desert or tropical zones)?

[André Mermoud]

There are some few references for particular cases.

But I don't know any general study nor methodology for the estimation of the soiling factor in any situation.