[TRNSYS-users] Radiation processor / printer

Fri Nov 19 08:32:49 PST 2010

Hello David, hi Jerome
for many years I have made measurements of solar energy in short time
 intervals (e.g. 1/2 minute). Sometimes it happens, that on the fixed
 place of your measuring instrument the global solar energy is indeed
 even a little bit greater than the extraterrestrial solar input.
The explanation is easy: you get not only the direct solar energy but
 also the reflections from atmosphere and it can happen, that the
 reflections from a cloud side to your place are so big, that the
 total global solar energy exceeds even the extraterresstrial input. A
 good solar simulator should also reflect this behavior. 
In a greater area and over a long time, this effect levels out and the
 measured input is naturally always smaller than the extraterrestrial
 input.
Best regards,
Gerhard Luther

meine Adresse:
  Dr. Gerhard LUTHER
  FSt. Zukunftsenergie (FZE)
Technische Physik - Bau E26
  Universität  des Saarlandes
D-66041 Saarbrücken
EU - Germany
Tel.: (49) 0681-302-2737
Fax: (49) 0681-302-4676
luther.gerhard at vdi.de 
luther.gerhard at mx.uni-saarland.de  (auch für größere Dateien)
homepage: http://www.uni-saarland.de/fak7/fze/-

------------
Jérôme,
   There isn't much that you can do about the second error (radiation 
exceeding extraterrestrial). It happens quite often and has to do with

the sub-hourly interpolation used. If it happens a lot during your 
simulation (5 percent of the timesteps?) then it might be worth having

your distributor look at it.

   For the issue about having the printer rounding. Trnsys takes the 
timestep that you indicate (in decimal hours) and tries to fit it to a

ratio of two integers. If you enter a 10 minute timestep as 
0.16666666666666666666667 (in other words lots of decimal places) then

chances are good that Trnsys will find 10/60 for the best 
representation. If you put in 0.1667, however, it can find a crazy 
representation of the time step and what ends up happening is that the

printer is trying to print at the end of the hour and there is no time

step at the end of the hour (0.1667 does not divide evenly into 1).
 The 
safest approach is as follows:

in your control cards, set the simulation time step to a "string" and 
enter "DELT" in the field.

in the small window at the bottom of the control cards, enter the
 following:

EQUATIONS 1
DELT = 10/60

in this way you are giving TRNSYS the exact ratio of integers that you

want it to use and your printer and timestep will line up with each
 other.
Best,
  David

On 11/19/2010 08:32,  wrote:
> Hi everybody,
> i have 2 warning messages in TRNSYS16 that i dont succeed in fixing
 them.
>
> The first one refers to output printers Type25a :
> the printer has rounded the reset time to an even number of 
> steps.-Please check to make sure that it doesnt adversly affect your

> simulation results.
>
> I think it is because i have put my steptime (in control cards) to 
> 10min that is to say 0.1667h. I havent this message when i put back
 1h 
> as a timestep.
> I think the cause in printer is the 1st parameter set to STEP with 
> unit=hr. Could you tell me what STEP represents? I was thinking this

> value to be the steptime in control cards.
>
> The second message refers to irradiation :
> "the direct beam is greater than the maximum allowed for this 
> timestep. The extraterrestrial radiation has been used for this time

> step."
>
> this message refers to unit 60 which is type16c (radiation
 processors).
> i read my total horizontal radiation from datareader (type 9c). the 
> maximum value in my file for radiation is 975W/m² (3510kJ/hr.m²).  I

> use a multiplication factor in data reader for radiation (3.6) in 
> order to switch to kJ/hr.m² and i send the output to radiation 
> processor which solar constant parameter is seto to 4920kJ/hr.m².
>
> Maybe the problem is about units of the input from data reader. I
 have 
> tried to send the output of datareader to unit conversion routine 
> (type57). I put parameter 1=17 parameter 2 and 3=1.
>
> Thank you for reading. I hope i have put enough details in order you

> can understand and help me.
>
>
>
>
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at cae.wisc.edu
> https://www-old.cae.wisc.edu/mailman/listinfo/trnsys-users

-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.commeine Adresse:
  Dr. Gerhard LUTHER
  FSt. Zukunftsenergie (FZE)
Technische Physik - Bau E26
  Universität  des Saarlandes
D-66041 Saarbrücken
EU - Germany
Tel.: (49) 0681-302-2737
Fax: (49) 0681-302-4676
luther.gerhard at vdi.de 
luther.gerhard at mx.uni-saarland.de  (auch für größere Dateien)
homepage: http://www.uni-saarland.de/fak7/fze/
http://www.trnsys.com