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Re: [TRNSYS-users] Radiation processor / printer
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@vdi.de
luther.gerhard@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@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@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@vdi.de
luther.gerhard@mx.uni-saarland.de (auch für größere Dateien)
homepage: http://www.uni-saarland.de/fak7/fze/
http://www.trnsys.com