How California kept the lights on
The recent heatwave showed grid scale battery storage has arrived in California in a big way. In 2020, the state had a mere 250 megawatts of batteries installed on its grid, out of a total statewide peak load of 52 gigawatts (GW). During last week’s heat wave, California had more than 3.2 GW of batteries supporting the grid, more capacity than the Diablo Canyon nuclear power plant. These batteries typically provide four hours of energy, so that’s 150 times more energy from just two years ago. Batteries played a critical role in keeping the grid running, and without them we would have experienced rolling blackouts.
California’s grid has the most installed battery capacity installed of any grid worldwide, and the United States led global investment in grid scale battery storage with nearly half of all investment last year. By investing in energy storage, the state has increased its resilience to extreme weather.
But this is just the start – more and more batteries are coming online in California. Earlier this year, the California Public Utilities Commission issued its preferred system plan, which includes 15 GW of new storage and demand response resources to be installed by 2032. More than 90 GW of batteries are proposed in the California ISO’s interconnection queue, showing strong commercial interest in battery storage. Batteries will be a crucial resource for meeting California’s ambitious clean energy goals, ensuring sufficient firm capacity to keep the grid running even in times without solar or wind energy.
Demand response, where customers reduce their usage either voluntarily or through compensation, plays a critical role in grid reliability and is a key building block in the resource portfolio balancing supply and demand. In extreme cases like the heat wave last week, grid operators don’t always have enough generation online to meet load. In fact, most grids plan to have some small number of outages, as it is very costly to plan to meet load all the time.
Tuesday’s extraordinary text alert asking customers to reduce their electricity demand was successful in avoiding rolling blackouts – it was followed almost immediately by a roughly 2 GW drop in demand. But that sort of mechanism can only work in limited situations, and can’t be called on more than once or twice a year.
Some localized outages were caused by distribution transformers overloading due to heat, and the City of Healdsburg misunderstood the grid operator’s emergency level and started load shedding (rolling blackouts) before they were asked to, but overall the grid held up well.
The weather facing the state, and the rest of the West, was prolonged and extreme. Not only does the hot weather mean record breaking load for the grid, it also means punishing temperatures can force equipment offline. Grid planners need to acknowledge climate change is pushing historic temperatures from extreme to normal and plan for more of these extreme, West-wide, long lasting heat storms.
Solar provided a consistent 13 GW of power to California’s grid last week from 9:00 a.m. to 5:00 p.m. each day, roughly a quarter of total demand. The evening hours from 4:00 p.m. to 9:00 p.m. were the times of greatest grid stress, as solar output drops but demand remains high. This is when batteries helped the grid, charging during midday and discharging in the early evening. On Tuesday, heat wave’s hottest day and the day of greatest grid stress, wind picked up in the evening and provided 2.7 GW of power.
While we made it through last week with the grid intact, California shouldn’t have to suffer such close calls in the future. The state is racing to install more solar, wind, batteries, as well as transmission to connect all these new resources to the grid.
However, supply chain challenges with both solar and batteries have delayed many projects, leaving the state short of meeting its goals. In addition, the pace of transmission development has not kept up with the demand, leaving many projects stuck in the queue waiting to connect to the grid. The state needs a comprehensive plan to deploy new projects and unblock the logjam of transmission development so it can meet its clean energy goals.