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Result data mismatch between hourly electricity and lifetime hourly data

  • Sreemohan
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06 May 2021 17:51 #9557 by Sreemohan
Result data mismatch between hourly electricity and lifetime hourly data was created by Sreemohan
Hello,
I am running a PV+Battery simulation with "input battery power target dispatch" and the battery is set to charge from the system.
When looking at the results there is a mismatch between Lifetime hourly data-"Electricity to load from the system" and Hourly data-"Electricity from system to load". The sum over the first 8760 hours does not match. At some points, the hourly data is non-zero while the lifetime data is 0 which does not make sense.
Another mismatch I'm seeing is in lifetime hourly data the "Energy produced without battery and curtailment" is 0(or negative i.e PV is not generating) and the System power generated is non-zero. This does not make sense since the PV system is not generating any power at that time. 
For reference, if you run the model I have attached and look at row 19 fin all the variables I have mentioned you shall see the mismatch.
here is the file

File Attachment:

File Name: NREL-SAM-Q...5-06.sam
File Size:172 KB

Please let me know what you think
Regards,
Sreemohan
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  • pgilman
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07 May 2021 22:34 #9560 by pgilman
Replied by pgilman on topic Result data mismatch between hourly electricity and lifetime hourly data
Hi Sreemohan,

The Hourly/Subhourly  "Electricity to/from" variables in the hourly outputs are from the electricity bill calculations. These variables are reported to help you account for how energy charges, demand charges, and excess generation is calculated. For these outputs, the "Electricity from system to load" is negative at night to account for the inverter nighttime consumption. Comparing the "Electricity from grid," "Electricity from system to load," and "Electricity load" might help you see how these values are being reported.

The Lifetime Hourly/Subhourly  "Electricity to/from" variables are from the battery dispatch calculations. These variables are to help you understand how the battery is being charged and discharged. The "Energy produced without the battery or curtailment" shows the power generated by the PV array, while system power generated is power from the PV array and battery discharging. System power is non-zero when energy produced without the battery is zero when the battery is discharging at a time when the PV array is not producing power.

The output variables are separate because they are generated by different parts of the underlying code.

We are working to improve the labeling and documentation of these variables.

Best regards,
Paul.

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  • Sreemohan
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10 May 2021 21:18 #9582 by Sreemohan
Replied by Sreemohan on topic Result data mismatch between hourly electricity and lifetime hourly data
Hi Paul,
Thanks for your reply. 
What does the annual energy in kWh in the Summary dashboard refer to?
This value seems to be different from the "Energy produced without curtailment or battery" 
Regards,
Sreemohan

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  • pgilman
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11 May 2021 15:18 #9585 by pgilman
Replied by pgilman on topic Result data mismatch between hourly electricity and lifetime hourly data
Hi Sreemohan,

The annual energy value in the table on the Summary tab of the Results page is the sum of the System power generated values:

Annual Energy (kWh/year) = SUM( System Power Generated (kW/h) * Time Steps Per Hour (1/h) )

For hourly simulations, this comes out to:

Annual Energy (kWh/year) = SUM( System Power Generated (kW/h) * 1 (1/h) )

For systems with battery storage, the annual energy represents the total amount of electricity delivered to the grid, including electricity discharged from the battery.

"Energy produced without curtailment or battery" is equivalent to the electricity generated by the PV array.

Best regards,
Paul.

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