parabolic trough model: question on IAM

Hello John,

I had a look at the incicent angle modifiers in the SAM library and
all exept one are identical. [1,0.0506,-0.1763]

The second coefficient is positiv for these collectors, so
the incident efficiency will be slightly greater than 1
for small incicent angles. Is this a realistic scenario?

Since I would like to compare commercially available trough collectors,
do you know where I can find the IAMs?
I was searching for a paper or other publications but could not
find anything.

Kind regards,
Joe

I also came across a small typo in the SAM documentation.
(Images are attached to the first post show it).

The equation for the IAM (physical trough model)
is different in the SAM documentation and the
"Technical Manual for the SAM Physical Trough Model"

As I believe the technical manual is correct, the factor
for IAM_2 is theta^2/cos(theta), not (theta/cos(theta))^2 .