[TRNSYS-users] Possible data error in TM2 Weather File and circumventing solar radiation error messages

[Flynn Ciaran]

Hello everyone,

I have a question concerning the validity of the solar data in the FI-Helsinki-Airport-29740.tm2 weather file.

After running my simulation with a typical year of Helsinki weather, I got the following errors concerning solar data:
"The calculated total horizontal radiation exceeded the horizontal extraterrestrial radiation and was set to the extraterrestrial for 1212 timesteps during the simulation"
"The calculated horizontal beam radiation exceeded the provided total horizontal radiation and was set to the total horizontal radiation for 4 timesteps during the simulation"

To get the typical solar data for Helsinki, I modified the global horizontal, direct normal and diffuse horizontal solar data in the tm2 file (according to: Development of weighting factors for climate variables for selecting the energy reference year according to the EN ISO 15927-4 standard. Kalamees, T., Jylhä, K., Tietäväinen, H., Jokisalo, J., Ilomets, S., Hyvönen, R. and Saku, S. Vols. Energy and Buildings 47 (2012) 53-60.), leaving the extraterrestrial data untouched.

I found out that one reason behind the errors was that the extraterrestrial solar data do not seem to be valid. For example, in the tm2 file, there are only 5 hours of extraterrestrial solar data for the shortest days of the year. In reality however, the minimum daylight hours is just under 6 hours...

So my question is, does anyone know of a valid method to circumvent this inconsistent extraterrestrial data problem? Can I simply set all of the extraterrestrial radiation values to a high number throughout the year (and how useful are these if non-extraterrestrial radiation data are already provided)?

Thank you for your help,
Ciarán

----------------------------------------
Ciarán Flynn
Project Researcher
Aalto University - Department of Energy Technology
P.O.Box 14100, 00076 Aalto
Otakaari 4, 02150 ESPOO

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