Arizona’s biggest electric utility is going big on batteries.
Arizona Public Service Co. plans to spend hundreds of millions of dollars to add large, building-size batteries to the power grid, aiming to use their capacity to store surplus power available early in the day when solar power plants are productive.
The power stored in batteries then would be used in the evening when customers need the energy after solar panels power down for the night, the Arizona Republic reported .
“Arizona is already a national leader in solar energy. The challenge is, no one has figured out how to stop the sun from setting at night,” said Don Brandt, APS chairman and CEO. “As storage technology improves and declines in cost, we will increasingly be able to store the power of the sun cost-effectively to deliver when our customers need it.”
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Phoenix-based APS serves about 2.7 million people in 11 of Arizona’s 15 counties.
One megawatt is approximately enough energy to power 250 homes, meaning that 850 megawatts of the batteries APS plans could supply about 212,500 homes for three to four hours.
APS didn’t provide cost estimates for the entire project because of proprietary information from its construction powers and because not all work has been put out to bid.
But the battery technology’s price has fallen and company officials said 100 megawatts of battery capacity with four hours of storage generally costs about $120 million, the Republic reported.
That would put the total cost of the projects at more than $1 billion, with APS owning some of the projects and purchasing power from others.
Like many other utilities, APS is already phasing out most of its power supply that comes from coal-fired power plants.
The batteries will displace traditional power plants, particularly natural-gas-fired generators, and increase the amount of renewable energy APS uses.
APS now gets about 14 percent of its power supply from renewable sources such as solar and wind, and the batteries will help the utility meet a state mandate to get 15 percent of its power from renewable sources by 2025.
APS already has two batteries on its power grid, and plans for a larger project to be online by 2021.
“We believe now we are at the right stage as an industry and from a technology standpoint to begin to go down this path,” said Daniel Froetscher, APS executive vice president of operations.