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Capacity Factor Difference between PVWatts-Battery and Detailed PV-Battery Model
22 Apr 2024 15:11 - 22 Apr 2024 15:59 #13113
by Ondrea
Capacity Factor Difference between PVWatts-Battery and Detailed PV-Battery Model was created by Ondrea
Hello,
I am running SAM v. 2023.12.17 and when I model a detailed PV- Battery system, I get a very low Yr 1 DC capacity factor of 5.3% for a system in Virginia. I then duplicated the detailed PV - Battery model and changed the duplicate to a PV Watts - Battery model. The PV Watts - Battery model produces a more reasonable Yr 1 DC capacity factor of 15.6%. See screenshots below:
Detailed PV - Battery System Design and Summary
I am running SAM v. 2023.12.17 and when I model a detailed PV- Battery system, I get a very low Yr 1 DC capacity factor of 5.3% for a system in Virginia. I then duplicated the detailed PV - Battery model and changed the duplicate to a PV Watts - Battery model. The PV Watts - Battery model produces a more reasonable Yr 1 DC capacity factor of 15.6%. See screenshots below:
Detailed PV - Battery System Design and Summary
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22 Apr 2024 16:15 #13114
by Paul Gilman
Replied by Paul Gilman on topic Capacity Factor Difference between PVWatts-Battery and Detailed PV-Battery Model
Hi Ondrea,
The low capacity factor for the Detailed PV case is caused by inverter clipping. You can see that on the Losses tab of the Results page:
Note the information on the System Design page indicating that the array's nominal maximum string voltage is higher than the inverter's maximum MPPT input voltage:
You can solve this problem by reducing the number of modules per string so that the string Voc at reference conditions is less than the inverter maximum MPPT voltage (Vmppt_high). If you want to maintain the same DC/AC ratio, you will also have to change the number of strings in parallel. For example, I changed modules per string to 24 and strings in parallel to 7100, which resulted in a DC capacity factor of 16.5%.
Best regards,
Paul.
The low capacity factor for the Detailed PV case is caused by inverter clipping. You can see that on the Losses tab of the Results page:
Note the information on the System Design page indicating that the array's nominal maximum string voltage is higher than the inverter's maximum MPPT input voltage:
You can solve this problem by reducing the number of modules per string so that the string Voc at reference conditions is less than the inverter maximum MPPT voltage (Vmppt_high). If you want to maintain the same DC/AC ratio, you will also have to change the number of strings in parallel. For example, I changed modules per string to 24 and strings in parallel to 7100, which resulted in a DC capacity factor of 16.5%.
Best regards,
Paul.
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