Re: [TRNSYS-users] Solar Types 194 and 94

[David BRADLEY <d.bradley@tess-inc.com>]

Sascha,
  You are correct about the error in the effref equation in Type94. It has been fixed and will be released in an update.

  As far as looking at response to small time steps is concerned there are two issues that you need to consider. First, Type94 (and Type194) are quasi steady state models meaning that they are designed to be used at time steps that are longer than their transient response times. You would need to modify Type94 to add transient effects such as thermal response. I would imagine that the transient electrical response of the module still has a time constant a good bit shorter than 1 second. Secondly, you need to carefully consider your solar radiation data. Weather data files read by Type15 contain hourly total solar radiation data. The algorithms in Type15 that are used to compute subhourly radiation values were developed to give good accuracy (i.e. represent reality) down to about 15 minute intervals. Beyond that point the algorithms that break total radiation up into diffuse and beam radiation over short time periods begin to be less correct, especially if you are dealing with a day that has a highly variable degree of cloudiness. If you look over a 15 minute period, the average solar radiation follows a fairly predictable pattern. If you look over a 1 minute (or even more so a 1 second) period then whether there is currently a cloud obscuring the sun has a very strong impact on the amount of solar radiation incident on your PV.

Kind regards,
 David

On 8/27/2014 01:08, Lindig Sascha wrote:

Hello

I`m comparing Type 194 and Type 94 to see the differences between the types.

It occurred that the calculation for effref is different while the calculation the cell temperature of the type.  It seems to me that the equation for Type 94 is wrong (effref = (imr/nprl)*(vmr/nser)/(sunr)) since it does not include the area of the module?

Another thing is the calculation of it. I want to simulate small timesteps  (1s) to see how the temperature and the behavior of the system changes when changing the ambient conditions. But after the first timestep steady state conditions are already reached. Is there a way to improve that or maybe another type which is better suited for this purpose?

Thanks in advance

Sascha

_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@lists.onebuilding.org
http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org

-- 
***************************
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.com
http://www.trnsys.com