Sandia Model_Modules Database

Hi,

I'm a student at the Faculty of the Renewable Energy Engineering at the Munich University of Applied Sciences . I am working this semester on my bachelor thesis, which is about simulating the behaviour of a PV-generator installed in Europe using different mathematical models of photovoltaic cells.

So for applying the Sandia Model, I have read the publication "Photovoltaic Array Performance Model" of the Sandia National Laboratories, published in 2004. I've contacted the "SNL" regarding the coefficients needed to apply the model, but they told me that they don't maintain a public database anymore for the different types of modules and that "NREL" may help you with this issue, as they apply the Sandia Performance Array Model in their (SAM) software.

So I've downloaded your new Beta Version of the software, and it is a pretty interesting software, not just for my project, but also for simulating other renewable energy systems. But unfortunately what is available for the different modules is the temperature coefficients for the Voc, Isc and for the mpp-points.

So my question is, do you have a modules database, where all coefficients needed to apply the Sandia Model i.e (A0,A1,..,B1,B2,..,C1,C2,..,fd, the reference voltages and currents, a and b coefficients used to in the thermal model,...etc) are listed for each module?

Thanks you

Eid Maraqah

Dear Eid,

You can use SAM's library editor to view, edit, and export the Sandia module model paramters. In SAM 2012.5.11, open the Library editor from the File menu. In SAM Beta 2012.9.27 and later, open the editor from the Tools menu.

Best regards,
Paul.

Hi,
thank you very much, this is exactly what I was looking for.

But I would like to ask another question about the Sandia Model. Within the listed parameters of each module, the value of the thermal voltage d(Tc)or DTC can also be found.

Typical values are around the 0.026V (thermal voltage at n=1 and Tc=25°C), while almost all values in your data base are equal to "3".

When I tried to plot the IV-curve of a solar module (using d(Tc)), I got a curve with negative voltages. So I decided to apply 0.03 instead a of the 3 in my calculations and by doing so, I got a nice smooth IV-curve which conforms to the typical curve shape after interpolating the currents and voltages.

I guess you used the following formula to calculate it:

d(Tc)=n.k.(Tc+273.15)/q

Which units do the d(Tc) values have in the your database?


Thanks in advance

Eid

Dear Eid,

The equations and values you are describing are from King D, Boyson W, Kratochvill J. (2004) Photovoltaic Performance Model. Sandia Report SAND2004-3535 .

The dT parameter in the Sandia module library, and also visible on the Module page is different from the thermal voltage value that you describe, which is Equation 8 on p 8 of King (2004). The thermal voltage is used to calculate the points on the module I-V curve.

The dT parameter, on the other hand, is part of the "temperature correction" algorithm of the performance model, which calculates the module's operating temperature. It is the temperature difference between the cell and module back at 1000 W/m^2 incident irradiance. See Equation 12 on p 18 of King (2004). I have also reproduced these temperature correction equations in the SAM Help topic for the Module page.

Best regards,
Paul.

Hi,
I would like to know if the formulas regarding the "angle of incidence" and the "absolute air mass" mentioned in the first publication of the Sandia Model, published in 1997 (pages 7 & 9), can still be used in modelling PV-Generators, as the author David L. King hasn't mentioned anything about them in the edition of the year 2004.

AM = {cos(Zs)+0.5057 (96.080- Zs)-1.634}-1 (6)
AMa = (P/P0 ) AM where: P0 = 760 mm Hg (7)
P/P0 » e (-0.0001184 h)
where: h = altitude (m) (

AOI = cos-1 {cos(Tm) cos(Zs)+sin(Tm) sin(Zs) cos(AZs-AZm)} (9)

Thanks a lot

Eid

Dear Eid,

You may find the new Sandia website for the PV Performance Modeling Collaborative to be helpful. It includes a set of PV performance modeling steps intended to help standardize modeling approaches and facilitate comparison between different models. Here's the link to the Incident Irradiance chapter of "Modeling Steps:" 

[url=https://pvpmc.sandia.govmodeling-steps/incident-irradiance/ t=_self]Sandia PVPMC Modeling Steps: Incident Irradiance[/url]

Best regards,
Paul.