PV Array modelling using TRNSYS 17

asked 2021-07-06 06:14:53 -0500

kkotenidisGRtuc's avatar

updated 2021-07-12 04:48:34 -0500

Hello to everyone! I'm student at Technical University of Crete and I'm trying to model a PV Array using TRNSYS 17. In my research I'm trying to see how the PV reacts with a cool material underneath it. In this case I'm using Sikalastic 560 as a cool material. It seems that the roof temperature is being lowered due to the material's high reflexivity, so the same occurs also about the PV's temperature, but the problem is that the PV's power is also less than expected. Physics says that; hotter electrical device == less performance, cooler electrical device == better performance. In my models occurs the opposite, as the temperature of the Array is less, also the production is less. So the question is; Am I doing something wrong in the models? Am I looking the wrong perspective?

Here is the PV specs (SunPower mono-crystalline 345W SPR-X21-345)

  1. http://www.solardesigntool.com/compon...
  2. https://www.renugen.co.uk/sunpower-x2...

Here are the link for there TRNSYS models

  1. https://www.mediafire.com/file/29xosp...

It contains 2 folders; (1) named "Plain" with simple concrete flat rooftop and (2) named Sikalastic560 which has the model with flat rooftop but added this material on the outside roof as mass-less material (also included in this folder the Sikalstic560 layer and Sikalstic560 wall)

I also attach the .xlsx files with 2 different states of the PV; (1) resistance set to -1 and (2) resistance set to 0.5

  1. https://www.mediafire.com/file/gnhjuk...
  2. https://www.mediafire.com/file/ssbhve...

As you will see in the .xlsx files I've made the diagrams for PV's temperature and PV's power (ignore Elastokryl columns). The roof temperature is less due to the material, also is less due to lower temperature of the roof, and the problem comes to surface when we see the PV's Power diagram. With the Sikalastic560 it produces less ammount of watts and I don't know why.

Could someone please help me? What I'm doing wrong with this modelling? The watts should be more due to lower temperature, right?


I found my fault. I had as Voltage input 24V, so that means that the panel works always at the maximum and with the lowered temperature the Amps were a little bit less (still 24V), so that's why it gave me less power. As it shown at the image below, the amps are a little bit less with lower temperature and the volts are much more with lower temperature. But in my care due to stable voltage only the amps were variable.

image description

So my (new) question is, how could I have variable Voltage depending on the sunlight for my simulation? Is there any way? I don't wanna simulate an IV-Curve (I have already done it), but I need a whole year simulation for the panel's production.

Thank you all for your time


Kotenidis Konstantinos

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