Importing input files from json to PySAM for Pvwattsv8

J.vanantwerpen@unsw.edu.au
Topic Author

12 Mar 2024 22:58 - 13 Mar 2024 16:12 #12978 by J.vanantwerpen@unsw.edu.au

Importing input files from json to PySAM for Pvwattsv8 was created by J.vanantwerpen@unsw.edu.au

Hello,
There are two parts to my question.
The first is that I am unable to achieve comparable results when building a Pvwattsv8 No financial model in pySAM compared to those obtained in the SAM application. Specifically comparing achieved capacity factors. The pySAM model consistently produces lower capacity factors compared to the SAM application.

A link to those files can be found here .

The second part is in regard to issues when importing JSON inputs.
This was done following the example code from the documentation below, however I encounter the error:
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb0 in position 41: invalid start byte.
The json file was downloaded from the code generator, and the SAM application and pySAM versions are 2023.12.17. and v5.0
Could you please advise on what might be causing this problem?

Code:

import json
import PySAM.Pvwattsv8 as pv # import the PVWatts module from PySAM

# create a new instance of the Pvwattsv8 module
pv_model = pv.new()
# get the inputs from the JSON file
with open( 'untitled1_pvwattsv8.json', 'r') as f:
        pv_inputs = json.load( f )

# iterate through the input key-value pairs and set the module inputs
for k, v in pv_inputs.items():
    if k != 'number_inputs':
        pv_model.value(k, v)

# run the module
pv_model.execute()

# print results
print('Annual AC output for {capacity:,.2f} kW system is {output:,.0f} kWh.\n'.format(capacity = pv_model.value('system_capacity'), output = pv_model.Outputs.ac_annual) )

Thanks in advance for your help.
Jaco

Last edit: 13 Mar 2024 16:12 by pgilman. Reason: Please attach images as files and then insert them into your message

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pgilman

13 Mar 2024 16:17 #12982 by pgilman

Replied by pgilman on topic Importing input files from json to PySAM for Pvwattsv8

Hi Jaco,

Please attach the .json and .sam files for the first part of your question, and the .json file for the second part if you would like me to help troubleshoot. I could not access the files the Google Drive link you provided.

You should be able to attach each file individually, or you can zip them into an archive and attach the .zip file.

Best regards,
Paul.

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J.vanantwerpen@unsw.edu.au
Topic Author

13 Mar 2024 18:34 #12983 by J.vanantwerpen@unsw.edu.au

Replied by J.vanantwerpen@unsw.edu.au on topic Importing input files from json to PySAM for Pvwattsv8

Hi Paul,

Please find attached.

Kind Regards,
Jaco

Attachments:

... Pvwattsv8.zip

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pgilman

15 Mar 2024 10:40 - 15 Mar 2024 10:42 #12986 by pgilman

Replied by pgilman on topic Importing input files from json to PySAM for Pvwattsv8

Hi Jaco,

Thank you for attaching the files.

For the first question, in your SAM file, the array type is set to "1-axis tracking." In the Python script, array_type = 1, which is the fixed roof mount option. That explains the difference in capacity factor between the two.

For the second question, we are investigating this UnicodeDecodeError. I think you can work around the problem by deleting the five "adjust" variables from the JSON file:

Code:

"adjust_constant" : 0,
"adjust_en_timeindex" : 0,
"adjust_en_periods" : 0,
"adjust_timeindex" : [ 0 ],
"adjust_periods" : [ [ 0, 0, 0 ] ]

Best regards,
Paul.

Last edit: 15 Mar 2024 10:42 by pgilman.

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pgilman

21 Mar 2024 09:35 - 21 Mar 2024 09:36 #13014 by pgilman

Replied by pgilman on topic Importing input files from json to PySAM for Pvwattsv8

Hi Jaco,

It turns out that the SSC variable names that start with 'adjust_' are named without the "adjust_" in PySAM. For example, for Pvwattsv8, 'adjust_constant' in SSC (the name used for defaults and JSON generated by SAM) is 'constant' in PySAM.

We will fix this in an update to PySAM: github.com/NREL/pysam/issues/164 .

For now the workaround is to rename the "adjust" variables when you read them from defaults or a SAM-generated JSON file. For example:

Code:

for k, v in pv_inputs.items():
    if 'adjust' in k:
        k = k.split('adjust_')[1]

Sorry about that! Thank you for helping us find this problem.

Best regards,
Paul.

Last edit: 21 Mar 2024 09:36 by pgilman.

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Proton7430

11 Jun 2024 08:07 #13247 by Proton7430

Replied by Proton7430 on topic Importing input files from json to PySAM for Pvwattsv8

I ran into the same issue.

However, I had to adjust the workaround as the provided code triggered on "cec_adjust" in my json file. I added the underscore after adjust to prevent it from triggering on that entry.

Here is the code I had to use:

Code:

    for k, v in pv_inputs.items():
        if k != 'number_inputs':
            if 'adjust_' in k:
                k = k.split('adjust_')[1]
            pv_model.value(k, v)

I'm just providing this in case someone else had a similar issue.

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