Pumped storage along North Platte could use water to store surplus wind power 

Developers of a pumped storage hydropower project planned for Carbon County believe the technology, which has been deployed in the U.S. for nearly a century, could unlock future energy development in Wyoming.

Pumped storage has emerged as a possible answer to the inherent variability of wind and solar. It’s a pretty straightforward concept: Surplus energy is used to pump water from a lower reservoir to an upper reservoir, where it’s stored. When more electricity is needed, that water is released, and flows back down to the lower reservoir through turbines that generate power.

Staff at rPlus Hydro, the Salt Lake City-based partnership behind the Seminoe Pumped Storage Project, have been eyeing the Wyoming site for more than a decade. They’re hoping to construct an upper reservoir to connect to the North Platte’s Seminoe Reservoir below.

After years of honing the pumped storage proposal, developers now anticipate building a 900-megawatt facility – comparable in output to the 832-megawatt Naughton coal plant and 922-megawatt Dave Johnston coal plant – that can run at full capacity for up to 10 hours.

“We’re just saying, you know, if there’s going to be wind energy built, and transmission lines built to deliver that wind to market, let’s make that as much of a reliable power source that we can,” said Matthew Shapiro, CEO of rPlus Hydro.

The project comes with a price tag of roughly $2 billion. A comparable utility-scale battery storage project would be similarly costly, but wouldn’t be able to retain power for as long as pumped storage.

Shapiro estimates that the facility would create 400–500 construction jobs and 30–35 permanent jobs. Once built, he said, it would have a lifespan of at least 75 years; unlike the lithium-ion batteries primarily being deployed to ease renewables’ intermittency, its storage capacity wouldn’t degrade over time. Most of the infrastructure would be underground.

Since rPlus Hydro formed in 2019, the company has conducted numerous site studies as it progresses through the licensing process. It enlisted sustainable design firm Stantec to complete a geotechnical investigation and feasibility study, in which it will identify preferred locations and designs for both the underground and above-ground components, by early 2023.

According to Vik Iso-Ahola, the project manager leading Stantec’s engineering study, the company has been the design engineer of record for the last two pumped storage projects built in the U.S.

“There’s a huge need for it, for energy storage and clean batteries,” he said. “Pumped storage is a promising technology. It’s proven, and it’s been around for a long time, and it can be developed, but there’s still a lot of untapped potential for developing pumped storage throughout the country and the world.”

Stantec’s review will lead to another round of engineering studies and another round of geotechnical studies, likely done in parallel to permitting and licensing work, Shapiro said. He hopes to begin construction in 2025 or 2026, and have the project operational by 2030.

While the company is still in the process of securing a power purchase agreement with a utility, it sees the facility as an important addition to the regional power supply.

“There aren’t an unlimited number of great locations for pumped storage,” Shapiro said. “There’s only a few great locations. And this, we believe, is one of them.”

Correction 11/1/2021: This article has been updated to more accurately represent the cost of utility-scale battery storage.