Parametric Analysis on PV System Size or DC-AC Ratio

For the Detailed Photovoltaic model, before you run a parametric analysis on Desired DC-AC Ratio (desired_dc_ac_ratio) or Desired Array Size (desired_size), be sure to check Estimate Subarray 1 configuration on the System Design page. Otherwise when you run a parametric simulation, it will appear that changing the DC-AC ratio or system size has no effect on results.

For example, here are results for a parametric simulation on system size without checking the estimate Subarray 1 configuration option, where you can see that the annual energy and net present value do not vary with the desired sytem size:

 
By adding the System Nameplate DC Rating (nameplate_dc_rating) output to the list, you can see that SAM did not vary the actual size of the system:


Now, if we rerun the parametric simulation after checking Estimate Subarray 1 configuration on the System Design page, we get the results we expected:


If you are modeling a system with more than one subarray and want to do a parametric analysis on system size or DC-AC ratio, then you will have to adjust the numbers of modules in each subarray, and possibly the number of inverters:

Subarray 1 modules per string (subarray1_modules_per_string)
Subarray 2 modules per string (subarray2_modules_per_string)
Subarray 3 modules per string (subarray3_modules_per_string)
Subarray 4 modules per string (subarray4_modules_per_string)

Number of parallel strings 1 (subarray1_nstrings)
Number of parallel strings 2 (subarray2_nstrings)
Number of parallel strings 3 (subarray3_nstrings)
Number of parallel strings 4 (subarray4_nstrings)

Number of Inverters (inverter_count)

Best regards,
Paul.

Perfect post that answers why I have been struggling with parametric results after modeling systems with all subarrays checked and specified. 

One follow up and clarification:
If I want to keep subarrays checked and the module distribution ratio--is the only away to check different total array size via parametrics to figure out distribution for each subarray at each possible array size I want to test the financials around? I assume that is what you're specifying at the bottom but I want to double check before I spend the time calculating each string and module number for each sub for each array size I want to test.

Thanks!

Yes, your follow-up comment is correct. For a system with more than one subarray, you'll have to set the number of modules per string and strings in parallel (and possibly number of inverters) for each parametric scenario.

Thanks,
Paul.

Thanks for the confirmation. One followup question:
Can one just enable subarray variables in parametric quick-setup?

PV System Design/Enable Subarray 2 (subarray2_enable)
PV System Design/Enable Subarray 3 (subarray3_enable)
PV System Design/Enable Subarray 4 (subarray4_enable)

Thanks.

Yes. For example set subarray2_enable = 1 to enable subarray 2, and subarray2_enable = 0 to disable it.

Best regards,
Paul.

Hello, I am trying to narrow down the optimal solar PV system size but am having issues with the desired DC-AC ratio in parametric analysis.
I have checked the estimate subarray 1 configuration as suggested but this does not change the annual energy output.
Besides the mentioned checkbox, is there something else that could be stopping this?