Physical Trough Model Optical Efficiency

Dear Paul,

I am in the process of running a simulation using molten salt in a parabolic trough plant.
I am using the FLABEG Ultimate Trough with a 70mm receiver. When I calculate the design point optical efficiency I get the same figure as SAM: 0.882677. However when I run the simulation, the optical efficiency reaches a maximum of approximately 0.77. The cosine efficiency and IAM are both close to 1. I am unsure what is causing the additional loss in optical efficiency.

Any help would be great!

Thanks,
Ian

Are all optical parameters identical?
(Slope error, tracking errors, reflectance, soiling)

Could you provide the SAM file?

Dear Ian,

The design point optical efficiency assumes the zenith angle = 0 degrees. In many locations, the sun is never actually directly overhead, which results in the observed difference. You can verify this in SAM's time series results by looking at the value of the "Resource Solar Zenith" output variable at noon on June 21.

Best regards,
Paul.