[TRNSYS-users] Total solar radiation, beam, diffuse, ground reflected solar radiation are not balanced

[Shengteng Li]

Hi all,

The total solar radiation on a tilted surface should equal the sum of the beam radiation on the tilted surface, sky diffuse radiation on the tilted surface, and ground reflected radiation on the tilted surface, as shown in following:

It_tot = It_beam + It_sky + It_gnd
           = It_beam + I_d * f_sky + I_h * refl_gnd * f_gnd

f_sky = (1 + cos(slope) ) / 2
f_sky = (1 - cos(slope) ) / 2

And I connect the each variable between Typed15-6 and a Equation I set , as shown below:

[cid:image001.png at 01D951BF.DC3E8AF0]

In the Equation, I calculated
I_balance=It_tot-( It_beam+I_d*f_sky+I_h*refl_gnd*f_gnd)
I_balance should be zero. However,  it is not zero and it varies with time. It is only zero when slope=0, i.e., a horizontal surface.

Also, I compared the It_beam with I_b*Rb, and It_d with I_d* f_sky, and they all not even.



Can you tell me where I made mistakes?

Thank you for your suggestions.



Regards,
Santo

Santo Li
PhD student, Sustainable Buildings Research Centre
University of Wollongong

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