POA Irradiance for SAM Input

Hi Paul,

When assessing the performance of an existing PV system, is it possible to use measured plane of array irradiance and temperature data as input to SAM? Is it necessary to transposed POA into GHI, DNI, and DHI (such as by using NREL DISC program) to convert the hourly POA data into the TMY3 format, or is there an easier more direct approach. Thanks.

Dear James,

In the current version of SAM (SAM 2015.6.30 r2), it is not possible to use POA irradiance as input to SAM's detailed photovoltaic model. However, we are working on that capability now, and it will be part of the next version of SAM, which we plan to release late this calendar year or early next.

For now, you would have to convert the POA data to its components. I would recommend using the SAM CSV format rather than the TMY3 format to do that. The SAM CSV format is simpler and only stores the data that SAM requires. The format is described in SAM's Help system, under Weather Data, Weather File Formats.

Best regards,
Paul.

Hi Paul,
I have two questions:
1) I want to confirm if the simulations of the different POA are always generated hourly between 7 a.m. and 6 p.m.?
2) If I want to compare the different POA with those generated by another model for a specific year, is it correct to cut the Lifetime Hourly Data series for the first year and then whether to compare them?

Thanks for the answer. 

Hi Diego,

SAM's Detailed Photovoltaic model reports POA irradiance values when the "Sun up over horizon" output variable is not zero. See the Detailed Photovoltaic Model Results topic in Help for a description of that variable: samrepo.nrelcloud.org/help/pv_results.htm .

You can extract the first year of POA (plane of array) data from the lifetime hourly data to compare it to data from a different model.

Best regards,
Paul.