The vision of a clean-energy future — where wind turbines and solar panels are knit into a new kind of power grid — hinges on a humble savior: the battery. Giant versions of the same technology that powers toothbrushes and smartphones are being plugged into electrical systems at breakneck speed, forming a critical part of plans around the world to fight global warming. The scale of the effort is daunting: Meeting the battery needs just for California’s green energy buildout, widely considered a global test case, will require five times the world’s current capacity of utility-grade electrical storage.

1. Why are batteries key?

Because relying on renewable energy means storing power for when the sun doesn’t shine or the wind isn’t blowing. Utilities are also deploying batteries to replace small “peaker” plants — mostly powered by natural gas — that only run when electricity demand surges. But large-scale storage has yet to be tested to support grids as big and complex as the ones in the U.S. Batteries will tie together decentralized energy sources based on a gaggle of new technologies and form an essential part of President Joe Biden’s ambition to make the electricity system carbon-free by 2035. Other countries doubling down on grid batteries include China and Australia.

2. Aren’t batteries already better?

Yes. They’ve come a long way since Sony Corp. first commercialized lithium-ion storage cells in the 1990s to power video cameras and other gadgets, and even since the inventors of the technology won the Nobel Prize in chemistry in 2019. Soaring worldwide production, mainly in China, has slashed the average cost by more than 88% from 2010 to 2020, as smaller and longer-lasting cells powered the digital revolution. But we’re going to need to store a lot more electricity for the switch away from fossil fuels used in transport, buildings and industry.

3. How’s it going so far?

The transition hasn’t exactly been smooth. When the worst heat wave in a generation taxed California’s power system in the summer of 2020, the state suffered its first rolling blackouts in 20 years. Part of the problem: Older gas-burning plants have been closing faster than batteries have replaced them. California is projected to have 1,700 megawatts of new battery capacity in place by August, enough to power 1.3 million homes and, in theory, avert another grid emergency. Another issue is that most battery packs now available hold enough juice for just four hours. That makes them a good fit for California, where supplies are strained in early evenings for a few hours after solar power shuts down. But they’re of little help during events like the winter storms that pummeled Texas in February and left millions of people without power for days.

4. Who builds batteries now?

China produces 79% of the world’s supply. That’s no accident — years ago the government put batteries on the list of high-tech industries it wanted to dominate with its “Made in China 2025” initiative, funneling subsidies to domestic suppliers. The U.S. ranks a distant second, with 7% of global production, though Europe is poised to overtake it this year. Becoming overly reliant on Chinese supplies has raised concern in Washington, particularly at a time of heightened tension between the two countries. More domestic plants are planned for Georgia, New York, North Carolina and Ohio. One limiting factor, however, has been U.S. access to the minerals needed, lithium in particular, most of which now comes from South America, Australia and China.

5. What is Biden’s agenda?

Biden wants more batteries built in the U.S. to generate jobs, supply American automakers and catch up in a key industry of the future. While there are few details so far, plans include pumping money into researching new chemistries and technologies, with a goal of cutting costs by 90%. Prices for lithium-ion batteries used in electric vehicles are forecast to drop from about $125 per kilowatt-hour now to less than $100 by 2024 according to BloombergNEF, a long-awaited milestone that will mean EVs will no longer cost more than their gasoline-powered brethren.

6. What about other technologies?

Pumped-hydro plants, which use water and gravity to store and release energy, are a time-tested solution, but they take years to build and require the right terrain. Lithium-ion batteries are now so widely used and so many new plants to make them are under construction that any radically different battery technology could have a hard time breaking in. That doesn’t mean innovation is dead. When renewable power is plentiful, it can be used to make hydrogen fuel out of water, which can run fuel cells or be burned in turbines instead of gas. Other possibilities include storing compressed air in underground formations or in above-ground tanks, releasing it when needed to provide energy.

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