Giant Batteries Are Transforming the Way the U.S. Uses Electricity.
They’re delivering solar power after dark in California and helping to stabilize grids in other states. And the technology is expanding rapidly
By Brad Plumer and Nadja Popovich at The New York Times
May 7, 2024
California draws more electricity from the sun than any other state. It also has a timing problem: Solar power is plentiful during the day but disappears by evening, just as people get home from work and electricity demand spikes. To fill the gap, power companies typically burn more fossil fuels like natural gas.
That’s now changing. Since 2020, California has installed more giant batteries than anywhere in the world apart from China. They can soak up excess solar power during the day and store it for use when it gets dark.
Those batteries play a pivotal role in California’s electric grid, partially replacing fossil fuels in the evening. Between 7 p.m. and 10 p.m. on April 30, for example, batteries supplied more than one-fifth of California’s electricity and, for a few minutes, pumped out 7,046 megawatts of electricity, akin to the output from seven large nuclear reactors.
Across the country, power companies are increasingly using giant batteries the size of shipping containers to address renewable energy’s biggest weakness: the fact that the wind and sun aren’t always available.
“What’s happening in California is a glimpse of what could happen to other grids in the future,” said Helen Kou, head of U.S. power analysis at BloombergNEF, a research firm. “Batteries are quickly moving from these niche applications to shifting large amounts of renewable energy toward peak demand periods.”
Over the past three years, battery storage capacity on the nation’s grids has grown tenfold, to 16,000 megawatts. This year, it is expected to nearly double again, with the biggest growth in Texas, California and Arizona.
Most grid batteries use lithium-ion technology, similar to batteries in smartphones or electric cars. As the electric vehicle industry has expanded over the past decade, battery costs have fallen by 80 percent, making them competitive for large-scale power storage. Federal subsidies have also spurred growth.
As batteries have proliferated, power companies are using them in novel ways, such as handling big swings in electricity generation from solar and wind farms, reducing congestion on transmission lines and helping to prevent blackouts during scorching heat waves.
In California, which has set ambitious goals for fighting climate change, policymakers hope grid batteries can help the state get 100 percent of its electricity from carbon-free sources by 2045. While the state remains heavily dependent on natural gas, a significant contributor to global warming, batteries are starting to eat into the market for fossil fuels. State regulators plan to nearly triple battery capacity by 2035.
“The future is bright for energy storage,” said Andrés Gluski, chief executive of AES Corporation, one of the world’s largest power companies. “If you want more renewables on the grid, you need more batteries. It’s not going to work otherwise.”
When power companies first began connecting batteries to the grid in the 2010s, they mainly used them to smooth out small disruptions in the flow of electricity, say, if a power plant unexpectedly tripped offline. Many battery operators still earn most of their revenue by providing these “ancillary services.”
But power companies also use batteries to engage in a type of trading: charging up when electricity is plentiful and cheap and then selling power to the grid when electricity supplies are tighter and more expensive.
In California power prices often crash around midday, when the state produces more solar power than it needs, especially in the spring when air-conditioning use is low. Prices then soar in the evening when solar disappears and grid operators have to increase output from gas plants or hydroelectric dams to compensate.
California now has 10,000 megawatts of battery power capacity on the grid, enough to power 10 million homes for a few hours. Those batteries are “able to very effectively manage that evening ramp where solar is going down and customer demand is increasing,” said John Phipps, executive director of grid operations for the California Independent System Operator, which oversees the state’s grid.
Batteries can also help California’s grid handle stresses from heat waves and wildfires, Mr. Phipps said. “It made some differences last summer,” he said. “We were able to meet high load days and wildfire days when we might lose some power lines.”
In Texas, batteries are still largely used to provide ancillary services, stabilizing the grid against unexpected disruptions. Texas is also more reliant than California on wind energy, which fluctuates in less predictable patterns.
But Texas is quickly catching up to California in solar power, and batteries increasingly help with evening peaks. On April 28, the sun was setting just as wind power was unexpectedly low and many coal and gas plants were offline for repairs. Batteries jumped in, supplying 4 percent of Texas’ electricity at one point, enough to power a million homes. Last summer, batteries helped avert evening blackouts by providing additional power during record heat.
The two states built their battery fleets in distinct ways. In California, regulatory mandates were a key impetus: In 2019, officials worried that too many older gas plants were closing, risking blackouts, and ordered utilities to quickly install thousands of megawatts of storage.
In Texas, market forces dominate. The state’s deregulated electricity system allows prices to fluctuate sharply, rising as high as $5,000 per megawatt-hour during acute shortages. That makes it lucrative for battery developers to take advantage of spikes, such as in locations where power lines periodically get clogged.
“Anywhere we think the market is going to get tight, you can put batteries in and even things out,” said Stephanie Smith, chief operating officer of Eolian, a battery developer. “Then, we’re making bets all day about when to charge and discharge.”
One battery, for instance, sits near Fort Worth, absorbing excess wind power from West Texas during the nighttime, when no one needs it, and feeding it into the grid when demand surges.