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An Arizona energy company wants to build a new lake in the desert for hydropower

ARI SHAPIRO, HOST:

An Arizona energy company wants to build a new lake in the desert outside Phoenix. The company says it'll help fight climate change. From member station KJZZ, Katherine Davis-Young reports.

KATHERINE DAVIS-YOUNG, BYLINE: In the mountains about an hour east of Phoenix along the Salt River sits Mormon Flat Dam. It's managed by one of Phoenix's electric providers, Salt River Project.

(SOUNDBITE OF MACHINERY WHIRRING)

DAVIS-YOUNG: Inside the dam, Waylon Johnson, a hydrogeneration supervisor, shows me the underside of a hydropower turbine. It looks like a huge propeller.

WAYLON JOHNSON: It's 15 foot in diameter, and it weighs approximately 55 tons.

DAVIS-YOUNG: When water spins it, this can generate enough power for 13,000 homes. But this isn't typical hydropower. SRP describes this dam more like a giant rechargeable battery. During times when energy is abundant and cheap to produce, SRP pumps water from a lower elevation lake uphill to this reservoir. Then, as needed, it can release that same water back downhill to produce power. Principal engineer Eric Hannoush says this method of storing electricity has become especially critical as SRP has invested more in solar power.

ERIC HANNOUSH: They can take that energy that's generated during the day when our customers don't necessarily need it and store it for the nighttime when solar power falls off.

DAVIS-YOUNG: Now SRP wants to build another lake like this as part of its plan to reach net-zero carbon emissions by 2050. It would be Arizona's largest pumped storage hydropower system, generating about 10 times as much power as the utility's current pumped storage output. Hannoush says it makes more sense than investing only in utility-scale batteries for storage.

HANNOUSH: When you compare battery systems that are continuously being replaced compared to a resource that's going to last a hundred years, there's a real economic benefit to building a pumped storage facility.

DAVIS-YOUNG: Batteries last about four hours per charge. The proposed project could power nearly half a million homes for 10 hours each cycle. That's important as demand soars. Amid a population boom, expansion of the data center industry and warming temperatures, Arizona's utilities are all looking for ways to generate more power, and Arizona-based energy consultant Amanda Ormond isn't surprised pumped storage is part of SRP's plan.

AMANDA ORMOND: The electric system as a whole is moving from generators that turn on and run all the time, like coal and nuclear, to a more flexible system.

DAVIS-YOUNG: There are currently about 40 pumped storage systems nationwide, but the U.S. Department of Energy reports more than 90 of these projects are now in development. Ormand says SRP's project is ambitious, but she doesn't think it's unrealistic.

ORMOND: The viability of this project, I think, is pretty good.

DAVIS-YOUNG: Still, she says, it's likely at least 10 years down the road. SRP hasn't announced an estimated price tag for the project but says it will be in the billions. And before it can break ground, the utility faces lengthy reviews from government agencies as well as public stakeholders. Don Steuter is with the Sierra Club's Grand Canyon chapter.

DON STEUTER: When it comes to, like, creating an upper lake in the desert, you know, it does - immediately, it raises all kinds of questions.

DAVIS-YOUNG: The two locations SRP is considering for the lake, the dam and the transmission lines he says are currently home to saguaro cactuses, desert tortoises and bighorn sheep. At least six tribes have connections to the areas under consideration, and archaeological findings have turned up at both sites. Steuter wants to see thorough environmental and cultural reviews from SRP.

STEUTER: We realize that we need energy storage, but the devil's always in the details.

DAVIS-YOUNG: SRP plans to hold public meetings about the project later this month. For NPR News, I'm Katherine Davis-Young in Phoenix.

(SOUNDBITE OF HI-TEK, JONELL AND CORMEGA SONG, "ALL I NEED IS YOU") Transcript provided by NPR, Copyright NPR.

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Katherine Davis-Young