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In 2013 the California Independent System Operator (CAISO) published this image, dubbed it "the duck curve", and took the internet by storm (or, at least the part of the internet that tracks trends in renewable electricity generation):

enter image description here

Here's an explanation of the duck curve from Wikipedia:

[The] curve comes from the Net Load ("the difference between expected load and anticipated electricity production from the range of renewable energy sources"). In certain times of the year (namely Spring and Summer), the curves create a “belly” appearance in the midday that then drastically increases portraying an “arch” similar to the neck of a duck, consequently the name “The Duck Chart.”

Essentially, solar production causes a reduction in net demand in the mid-day (the belly). Later, sunset coincides with increased demand, causing a sharp ramp in demand (the neck).

This image generated lots of interest and people are still talking about it today -- lots of search results in the past year are still showing the same image.

But the most recent actual data on the chart is from 2013, and the duck shape was created by the projected net load curves from 2014 through 2020.

I tried to find some recent data from CAISO to see where things stand. To do this, I assume I'll need hourly historical demand and solar production data, in order to calculate net load.

CAISO's OASIS tool includes historical load data, but as far as I could tell solar data is only included lumped with wind, and only goes back to 2016.

Has someone published an updated version of this chart? If not, where can I find historical hourly solar generation to reproduce it myself?

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  • \$\begingroup\$ It might be helpful to actually say what exactly this graph is showing, because it's not at all clear to me. \$\endgroup\$ – Hearth Mar 26 '19 at 23:08
  • \$\begingroup\$ @Hearth I think it's showing how system load during peak solar generation hours is decreased and how it was expected to decrease at the time and illustrating that the more daytime solar decreases system load the more other types of generation capacity must ramp up for the evening peak hours. I'm guessing it's used to argue against the value of solar without storage. Ugh... I guess I'll risk the link... Hmm was expecting hyperpolitical stuff, wasn't too bad. Wikipedia article confirms duck curves are used to analyze change in overall system demand. \$\endgroup\$ – K H Mar 27 '19 at 1:42
  • \$\begingroup\$ @OP you should edit your question as senor Hearth indicates. I have no idea if someone has published an updated version of this specific chart(as they appear to be just a "thing" that is generated to analyze every single largescale system, but you don't need to know the hourly solar generation, you just need to know the hourly load, as solar generation without batteries simply directly decreases the load the generators see. Hourly solar generation could be estimated but would be hard to measure as you have to measure it at the installation. \$\endgroup\$ – K H Mar 27 '19 at 1:46
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    \$\begingroup\$ The belly in the graph simply appears as a result of the reduction in load caused by the solar. If you wanted to compare to this specific graph, you'll have to figure out who made it and ensure that the updated graph used for comparison uses the same dataset from the same source. \$\endgroup\$ – K H Mar 27 '19 at 1:49
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    \$\begingroup\$ I particularly like all the data provided at eia.gov/realtime_grid . I couldn't find the hourly data for solar specifically, but perhaps it is buried amongst all the options in the "Sources & Uses" menu. \$\endgroup\$ – 1N4007 Mar 28 '19 at 13:55