[TRNSYS-users] (no subject)

[Erik Boschek]

Dear TRNSYS users,

I have a simple question regarding weather reading and interpolating direct normal radiation (DNI) values for time steps less than an hour.

As long as I have been using TRNSYS (using TRNSYS 16.1) I have understood this can be done in a few ways as follows, including the consequence for an example TM2 file (see attached screen shot for clarification):

1.) Do not interpolate, using Type 15 with output DNR (not interpolated): you end up with a "steppy" profile
2.) Using Type 15, but with 2-axis tracking and the output "Beam radiation for surface": you get a discontinuous "spikey" profile, but the integration of energy across the hour is respected
3.) Same as 2, but using Type109-TMY2: You get a smooth profile, but often there appear inexplicable spikes at the beginning or end of the day. The one in the plot obviously is an extreme case.


For reference: I just used the Daggett profile "US-CA-Daggett-23161.tm2" which came with TRNSYS, but the behavior is not specific to this file.

Generally, I have been using 2, but it can cause problems if there is, for example, some triggering function based on DNI and the DNI hovers around the threshold. Is there another option for getting a smoother profile or is it best just to not interpolate? Any opinions? Feel free to point me to an earlier post on this topic in case I missed it.


Thanks,

Erik Boschek
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