On June 1, the Tumbleweed project in California\u2019s Kern County became the first major battery installation in the U.S. that can discharge power for up to eight hours at a\u00a0time \u2014 twice as long as typical energy-storage facilities.<\/p>\n
The U.S. power sector now builds more battery storage capacity<\/a> than any other form of on-demand power, like gas, nuclear, or geothermal. But battery developers typically design their projects to discharge at maximum capacity for four hours before running out of juice; that\u2019s what has made sense, so far, given equipment costs and market opportunities. Analysts have concluded that longer-duration storage is needed to cost effectively power the grid with clean energy 24\/7<\/a>.<\/p>\n \u201cThis was one of our first eight-hour contracts in the country for batteries, and now it\u2019s one of the first projects online, and it\u2019s a\u00a0complex deal with a\u00a0bunch of members coming together,\u201d said Alex Morris, general manager of California Community Power. \u200b\u201cIt\u2019s designed to be part of the clean energy mix, helping capture the solar and discharge that later when they need\u00a0it.\u201d<\/p>\n Granted, the system\u2019s 125\u00a0megawatts of instantaneous capacity are modest compared with the multi-hundred-megawatt batteries getting built elsewhere in the West. But Tumbleweed is far bigger than the 6-megawatt, eight-hour battery installed in Nantucket<\/a> in 2019 for a\u00a0special-case island power role, and larger than the 50-megawatt, eight-hour battery that went live in Australia<\/a> in May. Tumbleweed has finally delivered eight-hour storage at a\u00a0meaningful scale to test what this emerging resource means for the\u00a0grid.<\/p>\n How to build an eight-hour grid battery<\/p>\n The patch of inland Southern California that surrounds Tumbleweed resembles Texas, said Cody Hill, who leads storage development for Rev Renewables<\/a>, which built the project. It\u2019s a\u00a0flat, scrubby desert that\u2019s hosted ample oil production for decades and more recently turned into a\u00a0hot spot for wind turbines, vast solar arrays, and batteries. Rev picked up a\u00a0parcel there that was too small to fit serious solar capacity but just right for an energy-dense battery installation.<\/p>\n Rev built the site in two phases, first activating 125\u00a0megawatts with four hours of duration back in the summer of 2024. Ava Community Energy, the locally governed nonprofit that secures electricity for customers in Alameda and San Joaquin counties, paid for 50\u00a0megawatts to serve its capacity obligations. For two years, Rev used the rest of the available capacity as a\u00a0merchant power plant, bidding into the markets run by the California Independent System Operator.<\/p>\n To convert this very regular four-hour battery into a\u00a0groundbreaking eight-hour battery, Rev <\/a>\u200b\u201cliterally doubled the number of battery boxes on the site,\u201d Hill said. \u200b\u201cTechnology-wise, the differences are pretty trivial.\u201d<\/p>\n