August 29, 2017 - Sr. Project Leader, Jim Green, opens the doors on the Flex manufactured battery enclosure,1 MW, 1 MWh rating, using lithium ion batteries from LG, at the Battery Energy Storage System, owned and operated by NREL for grid integration research at the NWTC. (Photo by Dennis Schroeder / NREL)

The California Blackout that Wasn’t

Both batteries and demand response played roles in keeping the lights—and AC—on in California on June 17 and 18. We're going to need more of both.

People pay a lot of attention when the power goes out, but we tend to not notice when the grid remains stable—even under trying conditions. On June 17 and 18, record heat in California led the state’s grid operator to call on residents to reduce electricity usage through issuing a “flex alert.” And despite clickbait headlines in the press warning that the grid could fail, as it did last August when nearly half a million Californians lost power, the power stayed on both days.

There were many factors in why the state’s electricity system was able to withstand the heat. In this blog, we will focus on battery storage and demand response—voluntary reduction in electricity usage for specific periods of time. Both of these resources delivered last week and helped stabilize the grid, and both are going to be more and more important as California moves to achieve its clean energy goals.

However, extreme weather continues to intensify due to climate change—as was seen in the Pacific Northwest last weekend. As our grids decarbonize, we are going to need a greater volume and faster deployment of these resources to ensure that we can keep the lights on.


Grids Feel the Heat

Across the West, we’ve been seeing extreme heat in June. While temperatures in California that weekend fell short of all-time highs, there were a number of temperature records set for the day and the month. In short, it hasn’t been this hot, this early, in the more than 100 years that we’ve been keeping records. And in Palm Springs, the temperature matched the all-time high of 123°F.

High heat puts additional pressure on power grids, and this affects multiple parts of the system. On the supply side, thermal power plants, such as coal, gas, and nuclear plants, can shut down when the water they use for cooling gets too warm. And on the transmission side, due to increased risk of wildfires, over the past few years California utilities have at times de-energized power lines in areas of particularly high risk.

The demand side is more obvious: people turn up their air conditioners and keep them on for longer when it is hot, meaning more power demand.

In California, the pressures change depending on the hour. While heat and electric demand peak in the afternoon, these hours are not as much of a challenge for California’s grid, as the state’s massive installed solar capacity means that there is less need for other forms of power. But in the evening, when demand is still high and solar output falters, there is more pressure on the state’s fleet of conventional power plants to deliver.

All of these came together last summer, when California had rolling blackouts on August 14 and 15, which affected nearly half a million people. Specifically, a heat wave led to very high demand, some gas plants reduced output or shut down under the heat and due to system issues, and imports were limited by transmission capacity.

In a final root cause analysis, California’s electricity authorities found other factors such as market design challenges and inadequate procurement as causes in the 2020 blackouts. But the number one cause identified was extreme weather. It is also notable that the August 2020 blackouts came around 6:30 p.m., not at 5–5:30 p.m. when demand peaked.


What Was Different This Year?

June 17 and 18 were different in a number of respects. First off, demand was not nearly as high: peaking at only 41 GW and not 47 GW. Some of this may be due to the success of demand response, and the California Independent System Operator (ISO) praised the response of consumers to the flex alert as a factor in keeping the lights on.

Demand response can be done both at the industrial level, where facilities reduce power under special programs, and at the consumer level through means such as flex alerts. Either way, this resource has been identified as an important tool to integrate more renewable energy into grids. But it can be difficult to measure, particularly when done through flex alerts. And California ISO doesn’t have dashboards to show the contribution of demand response the way it shows renewable energy output and demand.

Another factor was the additional power available in the evening. While it hasn’t added many gas plants, California has been aggressively adding batteries. An ISO document released in May states that a total of 675 MW of batteries were expected to come online between June 1, 2020 and June 1, 2021, and another 343 MW by July 1. This does not account for many of the batteries at homes and businesses, as resources on the customer side of the meter are not measured in California ISO’s figures.

This increase is confirmed by the dashboard on the California ISO’s website, which shows battery discharge reaching 773 MW on June 18, 2021. This is much more than the 310 MW of discharge on August 15, 2020.

Source: California ISO

There is also the critical matter of how these batteries are used. Batteries can do many things besides meet evening peak demand, and battery owners often take advantage of the market for other services, such as frequency regulation.

California’s state agencies have noted that batteries were not fully utilized during the August 2020 outages. As evidence of this sub-optimal alignment with system needs, on August 15, 2020, battery discharge peaked at 2:50 p.m. Solar output was still strong at this time and it was well before these batteries were needed during the evening outages.

Source: California ISO

This is an area where the California ISO says that it is actively working to better understand the behavior of the state’s battery fleet. It also notes that it is working with battery providers to “better incentivize and align storage charge and discharge behavior with the needs of the system.”


More to Be Done

These figures need to be put in perspective, as the difference in battery output on these two dates is more than 10x smaller than the difference in demand. And maximum battery discharge on June 17 was about 15x smaller than the state’s peak solar output, so there is room for a lot more batteries to charge using daytime solar and provide power in the evening.

California ISO is putting more batteries on line this summer and plans to add another 472 MW between July 1 and August 1. Also, there are more opportunities for expanded demand response—both at the industrial, commercial, and residential levels. California ISO has identified 1.2 GW of demand response resource available on its system, but it is not clear how much of this is being utilized.

There is a role for energy services companies in building out the capabilities of demand response. A recent deal between OhmConnect and East Bay Clean Energy to mobilize 150,000 consumers to reduce demand in the evening could point the way for greater deployment of this resource. OhmConnect is also planning to give away 1 million smart thermostats to California customers that will enable them to help balance the grid during heat waves as the summer progresses.

Both batteries and demand response will be needed this summer, as will all system resources—including solar, wind, hydroelectric power, gas plants, nuclear power, and imports. Because despite the extreme heat, we aren’t in what is traditionally the hottest part of the summer yet. An analysis by California ISO says there is a 1 in 5 chance that demand will go above 47.7 GW again this summer, and a 1 in 10 chance that it will reach around 51 GW. And one factor making the grid operator’s task more difficult is the drought, which has led to lower levels of hydroelectric output.

California’s efforts to deploy clean energy solutions to meet power demand during heatwaves are a race against time. And with the changing climate, this is a race we are all in, regardless of where we live.