[TRNSYS-users] Type1288 IAM

[Maximilian Stahlhut]

Hey,

I am using Type1288 for modeling a Parabolic Trough Collector with  
single-axis tracking.
In Type 1288, the IAM values are read from an external data file which  
contains the biaxial IAMs of the collector. For reading this data  
file, the longitudinal and transversal incident angle are needed. As  
far as I know, they are calculated by:

Tranverse = ATAN(SIN(Zenith  
angle)*SIN(ABS(Azimuth-SolarAzimuth))/COS(IncidentAngle_Beam))

Longitudinal = ABS(ATAN(TAN(Zenith  
angle)*COS(Azimuth-SolarAzimuth))-CollectorSlope)

For Tranverse=0° and Longitudinal=0° I would have expected an IAM of  
1. However, Type1288 calculates a smaller one at this timestep.


Does anyone has experience using this Type or using a different type  
with a biaxial IAM input file and a similar problem occurred? Or have  
I missed something in my calculations?



Regards,

Maximilian