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Modeling & Graphing Load Data vs. PV Output Data on 15-min. Intervals

  • Jan_C_Hubbard
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15 Mar 2022 01:04 #10686 by Jan_C_Hubbard
I have built a 1MW (AC) PV array in SAM 2021.12.2 (r1) with a 2020 15-minute weather file and entered annual building electrical load data (35,040 records) in 15 minute intervals for the purpose of sizing the PV system (kW) to the electrical load (kW) and exporting very little or no PV energy to the grid with the largest possible PV array for the load.  

I can successfully run the simulation and view "System power generated (kW)" and "Electricity from  Grid (kW)" data in "Data tables" tab in the "Lifetime 15-minute" category, but when I try to graph the same data in the "Graphs" tab,  then SAM goes into a loop (spinning circle appears) for more than an hour with no graph results. After  an hour, I have to close SAM or my PC is in a seemingly endless loop. Perhaps 35,0440 records per year is too much for SAM over the 30 year system lifetime.

I don't necessarily need lifetime data, but there is no "System power generated (kW)" for year1 in the 15-minute data category, only "Electric peak from system to load (kW)" and "Electricity to/from grid peak (kW)".  I believe there used to be "System power generated (kW)" year 1 data available in earlier versions of SAM. 

Is there a way to create a graph in SAM of year 1 data showing "System power (kW)" output vs. "Electric load (kW) in SAM 2021.12.2?

Thanks
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  • pgilman
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15 Mar 2022 16:39 #10690 by pgilman
Hi Jan,

I was able to display the 15-minute data over the 30-year analysis period on the Time Series tab on my computer, so it may be a memory issue.

Sometimes it is possible to avoid display problems for lifetime data by only displaying part of the data (for example Jan-Dec of Year 1) instead of the entire data set. You might try closing all other applications when you run a  simulation and display results in SAM to see if that helps. You can also monitor the memory in the Windows Task Manager (Activity Monitor in macOS, or a suitable task manager in Linux) to see if that is the problem. My Windows computer's task manager reports that SAM requires 744 MB of memory to display the data from your file. Immediately after the simulation, the memory requirement briefly spikes up to 1.2 GB, so you'll need to make sure at least 1.2 GB of memory is available when you run the simulation.

If you can't get the graph to display, you may have to export the data from the Data Tables tab and use a spreadsheet program or other graphing software to create graphs of the time series data.

We plan to address the confusion caused by some outputs covering only one year vs covering multiple years: github.com/NREL/SAM/issues/978. Outputs generated by the performance model simulation are over the analysis period (multiple years), and outputs generated by the electricity bill calculator and sun position calculator are over one year.

Best regards,
Paul.

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