CEC Module Library vs. User Specified Inputted Module Differences

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CEC Module Library vs. User Specified Inputted Module Differences

I am working with a SolarWorld 345 XL Mono module, however it is not in the CEC library (or the Sandia). I was able to input specifications based off of the datasheet SolarWorld has online. I wanted to make sure that these results were going to be the same as if it had been in the library.

I took a SolarWorld 335 XL Mono from the CEC library and ran a simulation. Then I inputted a SolarWorld 335 XL Mono based off the datasheet online and ran the same simulation. The Nominal POA answer was very different. I was wondering what would possibly account for that difference. The Nominal DC energy was exactly the same. After that there were differences in the module losses as well, however it did not change the overall energy output dramatically.

If you have any insight as to why the Nominal POA is so different, I am all ears. I am assuming that the module losses were different due to small differences in the specifications of the user and the library.


Paul Gilman


I would not expect the value of the "Subarray [n] POA total irradiance (nominal) (W/m2)" output array to be different for two different modules, as long as the subarray orientation for both cases is identical. Because that value is in Watts per square meter, and is the nominal value before any reduction caused by shading, soiling, or module cover losses, it should be the same, regardless of the module you choose. I would expect the monthly and annual "POA total radiation (nominal) kWh)" values to be different for the different modules if the module areas are different. Please check your two cases and make sure that 1) the array orientation (tilt and azimuth) are the same, and 2) the module area is the same.

When you use the "user specified data" version of the CEC module model, SAM calculates the values of the model coefficients based on the manufacturer data that you provide. When you use the "database" version of the model, those parameters come from the database and may be slightly different than those that SAM calculates. SAM's coefficient calculator is described in the Dobos (2012) publication listed on the Performance Model Documentation page under "CEC Module Model."

For a module that is in the CEC library, like the SolarWorld module you mention, you can compare the values from the database listed on the Module page under "additional parameters" with the six output variables of the "user specified" option listed on the Results page Data tab under "Single Values" and beginning with "CEC 6 parameter."

Best regards,


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