[TRNSYS-users] Solar PV System Analysis

Fri May 27 11:41:49 PDT 2016

Chaminda,

  I did not have a chance to look deeply into why you are getting 
different results if you split up your two PV simulations into two 
projects. However, I did notice a few things about your project in 
looking at it.

  First, I do not think it is adviseable to have two instances of Type99 
that are both reading from the same file. This might be the cause of the 
different results when you move one of the PVs to its own project. 
Either make a copy of the weather file and give it a different name or 
just use one instance of Type99 that feeds its outputs to both of your 
PV simulations.

  Second, there are errors and inconsistencies in the solar radiation 
that is passed to the PV. In all cases the total radiation input is 
connected. However, in some case the beam radiation is connected from 
another component's output and in other cases it is not. The diffuse 
radiation input is not connected. This means that the PVs think that 
there is 0 diffuse radiation at all times. It is very important to be 
consistent about the radiation inputs to the PV and to make sure that 
all three (total, diffuse, and beam are all being passed to the PV from 
another Type.

  Third, while you can use Type30 as an approximation for shading on a 
PV it assumes that the impact of shading a PV is linear (i.e. if you 
shade half the PV you will get half the power output that you would from 
an unshaded PV). This linear shading impact is often not the case with 
PVs. There is an alternative model (Type551) in the TESS Electrical 
library that offers a somewhat improved model for shading PVs.

kind regards,

  David

On 05/27/2016 04:41, Chaminda Ranaweera via TRNSYS-users wrote:
> Hello,
>
> I made analysis for two surfaces. South and West. When I run both West 
> and South programs run in same Trnsys file, then I get wrong result 
> (Different result). But when I run it in two different files, then I 
> get another result. Can anyone explain me the reason for this? Please 
> help me. Trnsys Hotline is no longer helping to me.  I think this 
> problem is due to inherent problem of Trnsys. Before sselling the 
> product, they were replying to university. Now they are silent.
>
> Can anyone help me. Actually I am doing my final modelling for thesis. 
> Nobody will give money to me to go for training on Trnsys and nobody 
> knows whether it is useful or not.
>
> (I hereby attach Program File and results)
>
> Thank You,
>
> Chaminda Ranaweera
>
>
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-- 
***************************
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.com
http://www.trnsys.com

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