[TRNSYS-users] Solar radiation comparison

[Michał Klimas]

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 at msn.com] 
Sent: Sunday, April 26, 2015 10:42 AM
To: TRNSYS users mailing list at OneBuilding.org;
michal.klimas at 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 at put.poznan.pl
To: trnsys-users at 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

 

From: Michał Klimas [mailto:michal.klimas at put.poznan.pl] 
Sent: Saturday, April 25, 2015 4:23 PM
To: trnsys-users at lists.onebuilding.org
Subject: [TRNSYS-users] Solar radiation comparison

 

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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