[TRNSYS-users] Weather generator T54

Tue Apr 29 07:34:57 PDT 2008

oOOps... so obvious i couldn't see it. I needed to adjust the timestep of my brain.
  I was about to ask about these annoying peaks in the diffuse radiation at sunrise, and i've realized that when using T54 the solar time has to be advanced by 15 degrees in T16. I haven't seen this mentioned anywhere, so now it is at least once.
  I've read in an old message by Michael Kummert that type 16 with radiation smoothing had several known "issues". I intend to use it with the weather generator, for a distributable of a PV system. I haven't observed anything abnormal yet, do you think it can be used without risk? 

  Thanks.

  Gabriel Colomer
Industrial Engineer
41.23N/2.11E 
    I'm trying to use the weather generator T54 with version 15.3, and i'm getting confusing results. 
For example, using the data in nrel.dat for Orcata, CAL (#11), and integrating daily, i get this:
    RADIATION
TIME            GLOBAL      DIRECT      DIFFUSE   
[HR]                                              
  +4.05400E+03 +2.89376E+04 +2.89096E+04 +7.45607E+03 -> SUNNY DAY, SUMMER
+4.16800E+03 +6.36239E+03 +1.91064E+02 +6.22575E+03 -> CLOUDY DAY, SUMMER
+4.90000E+01 +8.42967E+03 +1.47342E+04 +2.42320E+03 -> SUNNY DAY, WINTER 
+1.68000E+02 +1.77229E+03 +6.80880E+01 +1.74991E+03 -> CLOUDY DAY, WINTER
  The sum of direct and diffuse is much superior to global radiation, only gets close when direct is small.
In winter, sunny days, direct radiation is much greater than global (almost double).
  Should i ignore direct radiations and use global and diffuse? Am i missing something?

  Thanks for your help

  Gabriel Colomer
Industrial Engineer

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