Sub-hourly modeling and 'hourly' DC loss adjustments

  • caseyzak24
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27 Mar 2018 19:49 #6170 by caseyzak24
Sub-hourly modeling and 'hourly' DC loss adjustments was created by caseyzak24
According to the SAM help docs:
"The SAM CSV format supports hourly and sub-hourly data with up to a one-minute resolution. SAM recognizes the weather file's time resolution based on the number of data rows in the weather file. For example, SAM recognizes a file with 8,670 data rows as an hourly data file, and a file with 35,040 rows as 15-minute data."

Given the ability to handle sub-hourly input data, how does SAM handle the
dc_adjust:hourly
variable? The sdktool indicates that it is an array constrained to be 8760 elements in length, so is it applied on an hourly basis regardless of the time-resolution of the simulation? Or is it just required to be the same length as the input data such that each element is applied to a single time-step of the simulation (which is 1 hr for the standard TMY use case)?

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  • sjanzou
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29 Mar 2018 08:39 #6171 by sjanzou
Replied by sjanzou on topic Sub-hourly modeling and 'hourly' DC loss adjustments
caseyzak24,

The SDKtool is correct, the dc_adjust:hourly is always an 8760 array that is applied on an hourly basis to the kWh output of the array regardless of the time resolution of the simulation.

Ther relevant code for the computations is at github.com/NREL/ssc/blob/develop/ssc/cmod_pvsamv1.cpp line 1727 for setup and application at line 2627 and 2628 (search for "dc_haf").

The setup of the adjust factors is at github.com/NREL/ssc/blob/develop/ssc/common.cpp line 336 with the default for nsteps being 8760 used for dc_haf.

Let us know if you have further questions...

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  • caseyzak24
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29 Mar 2018 20:15 #6172 by caseyzak24
Replied by caseyzak24 on topic Sub-hourly modeling and 'hourly' DC loss adjustments
No that answers my question and thank you for pointing me to the pertinent spots in the source code

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