Anyone who is following this subject, quick sum-up.
According to Sunliang’s answer I’ve verified model using different ground reflectance from 0,1 to 0,9.
This gave (in best case scenario) reduction of solar radiation by 1kWh/month.
Other things that Sunliang has suggested is to check pyranometer condition during winter time:
· whether it was covered by ice, dust and so on,
· check the occurrence of any heating element that removes snow.
Other possibility is to check other numerical models for solar radiation.
Sunliang thank you for your help !
kind regards
Michal Klimas
From: SUNLIANG CAO [mailto:caosunliang@msn.com]
Sent: Sunday, April 26, 2015 10:42 AM
To: TRNSYS users mailing list at OneBuilding.org; michal.klimas@put.poznan.pl
Subject: RE: [TRNSYS-users] Solar radiation comparison
Hi, Michal.
When you compare the measured data with the output from the Type16a, large percentage error in the winter time might be resulting from the wrong input of the ground reflectance (4th input).
If your applied location in a higher latitude country, such as Northern European countries, during the winter time, the ground diffuse radiation will have a quite higher proportion in the total radiation compared to the summer time. In this situation, the result from Type16a will be more sensitive to the ground reflectance in the winter season than the summer season.
On the other hand, during the summer season, the proportion of ground diffuse radiation in the total radiation is much lower than that of winter time (because beam radiation will have a much higher proportion), leading to much less percentage error.
Moreover, the relatively lower total radiation will also make your percentage error higher as the denominator in the percentage error equation is smaller.
Therefore, try to calibrate your ground reflectance parameters in your model compared to the measured data. In winter time, if there is snow in your applied location, then put a relatively higher ground reflectance, such as 0.7-0.8.
Kind Regards,
Sunliang Cao, Dr.,
Department of Energy Technology,
Aalto University,
Finland
From: michal.klimas@put.poznan.pl
To: trnsys-users@lists.onebuilding.org
Date: Sun, 26 Apr 2015 07:25:17 +0200
Subject: Re: [TRNSYS-users] Solar radiation comparison
Just for clarification.
I'm comparing measured solar total tilted radiation with output from Type 16a- Total radiation on surface 1.
kind regards
Michal Klimas
Dear All,
I'm having an issue with comparing tilted (45 deg) total solar radiation with measurements.
I have connected measured total horizontal radiation to Type16a, and taken as an output Total horizontal radiation.
I have a significant difference in January (50%) , February (30%) and December (40%). Remaining months are ok.
I have verified the Solar shift time, Latitude and checked whether any radiation occur during night - everything is fine.
Can anyone suggest any solution ?
kind regards
Michal Klimas
Poznan University of Technology
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