Importing DNI data for model validation

Hello all,

we were creating a Sandia Model for one of our CPV modules. Now I would like to validate this model with real measured data from one of our sites. I want to put in hourly DNI, T_amb and Windspeed data and compare the hourly-energy output with the measured energy output.

However, I tried some days do incorporate our DNI measurements somehow into the TMY format, which can be imported into SAM. It doesn't work, as we don't have any DHI (difuss) or GHI measurement. As a result, the "incident beam irradiation" is almost always lower than the one I put into the TMY.

In PVsyst, they have the special CPV-option, where GHI or DHI will be neglected, and only the DNI has to be imported. This enables validation of any CPV module in PVsyst.

Could somebody tell me how the same is possible in SAM?

Thanks in advance,

Jakob

I assume that you have documentation of the Sandia model and test procedures:

Photovoltaic Sandia PV Array Performance Model: King, D.L.; Boyson, W.E.; and Kratochvil, J.A. (2004). "Photovoltaic Array Performance Model." 41 pp.; Sandia Report No. 2004-3535. [url=PDF 1.8 MB t=_self] photovoltaics.sandia.gov/docs/PDF/King%20SAND.pdf [/url]

You can use the Entech 22x module in SAM's Sandia module library as a guide. As far as I know, the Sandia model is suitable for low-X concentrators, but not high-X.

As for the weather data, SAM should read the DNI data from your TMY file. The FD parameter for a CPV module should be zero to eliminiate diffuse radiation from the calculation.

There are a couple of things that could be causing the Nominal Incident Beam Radiation value from being lower than the weather file's DNI value:

• The tracking option on the Array page is set to something other than 2-axis.
• The soiling derate factor on the Array page is less than 100%.

Finally, we are preparing a new high-X CPV model for SAM that will be in the Beta version we plan to release for testing and comments next week. We will send an email announcement when the Beta is ready and would appreciate your taking the time to give us feedback on the model.

Best regards,
Paul.

Dear Paul,

The module parameters for our CPV module have been assessed by Sandia directely.

Now we would like to validate the Sandia model in SAM.
Thanks for your comments, it is indeed depending on the limit angles and the Soiling. I corrected them and now I find the correct DNI output values

On which module exactly will your new high-CPV model be based? Is it the one from our company, or from a different company?

Best regards,
Jakob

The new high-X CPV model is not based on a specific module. It is similar to the "Concentrating PV Simple Efficiency Model" in the current version of SAM, but is based on a table of cell efficiency values instead of module efficiency and includes adjustments for spectral effects.

We're preparing the Beta version for release this week, so you will be able to test it soon.

Best regards,
Paul.