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Comment by jeffbee | Hacker News Reader

Would love to know what changes day-to-day. According to CAISO dashboard, they are currently delivering 45 GW, while yesterday they were shedding load before they hit 44 GW. So, what aspect of supply changed? We're importing the same amount but we're getting 5 GW more natural gas supply than yesterday. Are there ... are there nat. gas plants that only operate on weekdays?

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The issue is time of day. Everything is fine while the sun is still up. Once the sun starts setting and the ~10GW of solar power California has goes away things get challenging.

Yes but the sun is up right now and they are already shedding loads (the dashboard is bouncing off a ceiling of 45 GW).

That is likely natural fluctuations in demand. The grid operator has not announced any load shedding (they have not even announced any imminent need to shed load) and there's still another 5GW of available capacity according to the dashboard.

We're just in the last few minutes getting the stage 2 warning that capacity limits could be reached soon.

It doesn't seem very likely that the actual behavior of a large-scale stochastic system and the hour-ahead forecast of that system would part ways to the extent we're seeing, just by coincidence. If it wasn't an intentional curtailment of demand, perhaps there is simply an outage somewhere?

Maybe there was unintentional curtailment of some sort, idk. There's still no announcement of stage 3 emergency (intentional curtailment).

I am going to try to use "unintentional curtailment" in a future post-mortem report.

California declared a Stage 2 Emergency at 15:30 PDT today which begins curtailment of interruptible loads, a less drastic form of load shedding. A Stage 3 Emergency begins to affect firm load using rotating outages.

Yes, when I wrote that the Stage 2 Emergency had not yet been announced.

Hence the Pacific DC intertie: https://en.wikipedia.org/wiki/Pacific_DC_Intertie "The Pacific Intertie takes advantage of differing power demand patterns between the northwestern and southwestern US. During winter, the northern region operates electrical heating devices while the southern portion uses relatively little electricity. In summer, the north uses little electricity while the south reaches peak demand due to air conditioning usage. Any time the Intertie demand lessens, the excess is distributed elsewhere on the western power grid (states west of the Great Plains, including Colorado and New Mexico).[3]"

(that predates solar, boy do I wish we could store that daylight 12-16 hours)

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