Aperture areas, panel outputs and test reports

[wookey]

Interesting find, ericw. I thought the Apricus explanation (or reflection onto the backs of tubes) seemed reasonable (although I'm still not quite sure why tube->tube reflection is more significant than reflector->tube reflection).

Those results given on the colorado state pages seem to have increasing outputs past 50 degrees, all the way to 80 degrees, which seems wrong.

The code compiles and runs with no trouble. If you set the last transverse incidence angle to 89 (90 is not allowed) then it gives results like an IAM of 7.5! There is definately something wrong with the model/code at high angles. (The right answer for 90 degrees and 8 tubes is 0.125, or threabouts).

I set up and ran the numbers for a 20x47mm panel (with a planar reflective backplane) but have no faith in the results it gives:

   0.   20.   40.   60.   80.
   0.   10.   20.   30.   40.   50.   60.   70.   80.   89.
1.000 1.223 1.502 1.576 1.436 1.772 1.926 1.949 2.010 3.504
1.001 1.219 1.499 1.592 1.435 1.789 1.928 1.936 1.983 3.518
1.003 1.212 1.475 1.570 1.439 1.764 1.955 2.003 2.007 3.575
0.933 1.114 1.372 1.472 1.377 1.725 1.931 2.000 2.066 3.563
0.515 0.600 0.758 0.857 0.874 1.205 1.546 1.780 1.970 3.604
 
tau_alpha normal                    =  0.4464
tau_alpha diffuse                   =  0.6707
aperture area [m^2]                 =  2.4000
backplane area/aperture area        =  1.0933
backplane-tube center distance [cm] =  4.3500
backplane diffuse reflectance       =  0.0000
backplane specular reflectance      =  0.6000
backplane semi-specular reflectance =  0.0000
backplane r_d power                 =  0.0000
backplane r_ss power                =  0.0000
glass thickness*extinction coef.    =  0.0195
index of refraction                 =  1.5000
outside radius of glass             =  2.3500
radius of collector cylinder        =  2.0500
length of cylinders                 =  150.00
tolerance                           =  0.0100