On Sunday, possibly the hottest days on record, California managed to avoid an energy bullet and conserve enough energy during a critical time to avoid rolling blackouts up and down the Golden State.
The California Independent System Operator (ISO) updated the public on the impact of the heat on the power grid at a press briefing on Labor Day.
Speakers included Operations Vice President Eric Schmitt and Real-Time Operations Director John Phipps.
The press briefing presents an interesting look into how the state’s energy grid operates during what amounts to an emergency on a holiday weekend when demand could have exceeded supply. It is a story of jockeying resources from one part of the state to the other as some sources are lost for a time and others need to be rerouted.
The main takeaway of the briefing was that there were no power outages on Sunday, the hottest day in at least a decade. But it was a close run thing. Schmitt said, “Consumers were the key to this success.”
ISO plans for extreme contingencies and takes into account others failures in the grid that happen in real time. At some point supply begins to approach demand. “When that happens that margin begins to narrow and we have grid conditions like we had yesterday undoubtedly the most stressful day that we had this year maybe in the last 10 years,” said Schmitt. “The conservation from consumers increased our margin and that’s what happened yesterday because we had no outages.”
That was true even though from 5-7 p.m. they lost some transmission and generation. “We were still able to ride through that because of the margin that was increased by consumer conservation. So it’s hard to describe how thankful and grateful we are,” said Schmitt.
Phipps added, “It was a very stressful day. We did have several contingencies happen so it did push us toward the edge.” Earlier in the day the grid lost some power generation due to fires in Imperial Valley as well as a fire in a power generation plant.
As the afternoon wore on, around 4 p.m. on Sunday the ISO began calling in resources and issued a warning on demand response customers to shift their usage to off-peak hours. Such customers agree in advance to shift usage when requested. They did that “as we moved closer to the time that we knew we were going to be tight on resources and that did help,” said Phipps.
At 5:40 p.m. they lost power from five smaller generators, “Within a matter of ten minutes we lost nearly 2,000 megawatts of capacity—so that pushed us right to the edge,” said Phipps.
This caused them to declare a Stage 2 Emergency, with ISO warning residents to expect rotating blackouts and advising them to conserve energy. A Stage 2 Emergency means, literally: “The ISO has taken all mitigating action and is no longer able to provide its expected energy requirements.”
This, said Phipps, “allows us to begin pulling out some more of our emergency response actions and tools and one of those is that it allows us to get additional assistance from our neighboring utilities.”
At this point it was “very, very tight,” said Phipps. “The operators were really doing a balancing act here where they were managing multiple transmission constraints while trying to make sure there was enough energy for the load. We did make it through: we set a peak load for the year at 5:43 p.m. of a 47,236 megawatts. But thank goodness, it actually was a little bit below forecasts. It came in around 1,900 megawatts below forecast—definitely from conservation.”
Because the region was looking at cooling temperatures for the next few days, the ISO appeared to draw a collective sigh of relief.
Of course, when there are large wildfires, such as the Valley Fire burning near Alpine, the utility must always be on the lookout for threats to power lines from high Santa Ana winds. Schmitt said, “We have given got heads up from all of our transmission owners and those serving entities that they will be activating some of the Public Safety Power Shutoffs so that they can prepare for the winds.” Those include San Diego Gas & Electric Co, which on Tuesday warned “Due to elevated fire weather conditions and forecasted Santa Ana winds, San Diego Gas & Electric (SDG&E) has notified backcountry residents that it may have to turn off power to reduce wildfire risk in the coming days. Public Safety Power Shutoffs (PSPS) are approved by state regulators as an important safety tool of last resort to mitigate fire risk during dangerous weather conditions.”