Soiling losses at different azimuths

[Sebastian.stan]

Hi Andre,

I'm wondering how is the overall soiling loss factor calculated from the monthly soiling values.

I was surprised to see that for one project with unlimited sheds facing south the soiling loss factor is shown as 8.5% and for facing east (-90 azimuth) the soiling loss becomes 7.4%.

This is for the same project inputs (and same monthly soiling values), the only value I changed was the azimuth.

This tells me that the azimuth is somehow part of the equation for soiling, but I don't see why or how.

Could you shed some light on this?

Thanks,

Sebastian

[Sebastian.stan]

Hi,

What I failed to mention was that my monthly soiling losses are significantly larger in winter than in summer.

Looking closer at the irradiance for the east facing project, it seems that the values are quite a bit lower in the winter compared with the south facing project.

This means that the soiling losses in the winter don't affect that much the overall project losses as they would in the case of south facing.

The values make sense now.

Hope my reasoning is right.

Best Regards,

Sebastian

[André Mermoud]

Yes your reasoning is right: the soiling loss is specified in terms of percentage of the yield.

Therefore if low irradiance in winter, the loss will be lower in absolute value.

For your monthly analysis you have to consider the absolute losses, not the percentages.