DNI and field output energy

[JFO78]

Hello,

I have some problems understanding the results of a simulation with
SAM and I would like a confirmation on how the field output energy is
calculated, based on the DNI :
DNI * Aap * cos (TH) * IAM(TH) * ηopt * ηth_loss
where Aap is the aperture area of the solar field
cos(TH) is a the cosine loss, related to the incidence angle
IAM(TH) is the value of the incidence angle modifier, related
to the incidence angle
ηopt is the optical efficiency, assuming it is not dependant
on the incidence angle (tracking error,geometry defects ...)
ηth_loss that takes into account the the thermal losses in
the receiver

Besides, is it possible with SAM to draw the value of the incidence
angle over the year ?

Thanks a lot for your help,

Regards,

Jérémy

[Paul Gilman]

Hi Jeremy,

It's not clear from your message what kind of system you are
modeling.

In general, for the CSP system models, SAM uses a version of your
equation to calculate the hourly thermal output of the solar field.
The specific equations, and how SAM calculates the values of each term
in the equation depends on the technology (dish, power tower,
parabolic trough, etc), and on the performance model (physical trough,
empirical trough, etc.).

If you are using SAM's physical trough model to model a parabolic
trough system, you can read detailed descriptions of the calculations
in the trough reference manual:

Wagner, M. J.; Gilman, P. (2011). "Technical Manual for the SAM
Physical Trough Model." 124 pp.; NREL Report No. TP-5500-51825.
http://www.nrel.gov/docs/fy11osti/51825.pdf

For the other models, please see SAM's help system for a list of
references describing the calculations.

SAM does not explicitly report the incidence angle, but it does report
the hourly DNI values from the weather file and the calculated
incident DNI values (DNIxCosTH for the physical trough model).

Best regards,
Paul.