Hi there,

I'm new at DIVA/RHINO and I'm having some trouble running the daysim-based hourly method to obtain the radiation map on a bifacial PV panel. Everytime I try to run the simulation I get the error attached. Can you please help me?

Thank you so much,

Sofia

Tags: Bifacial, Error, Hourly, PV, Radiation, Simulation

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Hi Sofia,

Apologies that I missed your original post. The issue is that Daysim, the climate-based calculation engine in DIVA, doesn't accept the ashik2 Ashikhmin-Shirley material model. Luckily, for calculating the irradiation map across a grid of sensors on the PV panel, the material of the panel itself doesn't matter. You should be safely able to (1) remove the ashik2 material from your material.rad file in the .\Filename - DIVA\Resources\material.rad file and (2) assign a default material (such as 50% wall) to the panel in DIVA.

Best,

Alstan

Thank you for your reply!

I understand the problem now, but why does it run the radiation map (daylight images) and seems to assume the material at RHINO?

Images attached.

Thank you again,

Sofia 

Hi Sofia,

The image-based and GenCumulativeSky nodes-based image maps use a different method that employs standard Radiance, so the ashik2 material will work in that case. I know it is a little confusing, but if you want hourly information the ashik2 material cannot currently be used.

Best,

Alstan

Hello Alstan,

Thanks for the clarification!

However I will need to define a material for PV to know the radiation that strikes the cells after passing the glass and also to count reflection effects. Do you have some sugestion?

Thanks again,

Sofia

Hi Sofia,

If you need reflective effects, then that becomes a little trickier. Can you explain how the glass and ashik2 materials are working in relationship to your sensor placement in the current model?

Alstan

Hello Alstan,

I'm using the material's definition from http://lighting-materials.com/materials/665, so the code is

void texfunc Pucker
6 puck_dx puck_dy puck_dz pucker.cal -s 4.0
0
1 0.0035

Pucker ashik2 Sunpower_PVCells
4 0 1 1 .
0
8 0.006995137 0.008994048 0.021037648 0.029284513 0.029518141 0.030717789 100 100

I assume this material has already the effects of glass+cells because it was measured considering the PV module as a whole.

I have sensors at the front and back of the panel (since I'm studying bifacial) with a 5 cm spacing.

Thanks,

Sofia

Hello Alstan,

I forgot to leave here the "Pucker" function that is called and I had to install in radiance library:

{
This puckered texture is used on the Cabin Bedspread
to provide it with a bumpy look.

A1 - The degree of puckeredness.
}

puck_dx = A1 * noise3a(Px, Py, Pz);
puck_dy = A1 * noise3b(Px, Py, Pz);
puck_dz = A1 * noise3c(Px, Py, Pz);

Thanks again,

Sofia

I see -- so the reflections are indeed important. Since you need hourly data, I think that the best course of action might be to use a plastic material with specularity (0.0299) and an equivalent roughness factor. I estimated the roughness of the material during the measurement study, so I can look up the value for you once I am back at the office.

Best,

Alstan

That would definitely help, since I do not have the instruments to measure the properties of a PV cell. The value for specularity (0.0299) has already the glass+cell effects?

Thanks,

Sofia

Hello Alstan,

I've already defined the plastic material acording to the parameters from http://lighting-materials.com/materials/665, and it gave me something like this:

# material PVCells
void plastic E20_PVCells
0
0
5 0.03603818 0.038340619 0.053256422 0.0299 0

I have another question, in the new version of DIVA - DIVA Grasshopper v4.0.2.33 - there is the option to produce hourly irradiance data when using the Radiation Map. However, if I select the daysim option I can't see the results, it gives me the exactly outputs that I obtain using the GenCumulativeSky method. How can I see hourly results?

Thanks again,

Sofia

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