Water battery: Utah company advances Wyoming pumped-storage project

The 900-megawatt power plant would provide renewable electricity even when there is no wind or sun

(rPlus Hydro) This rendering shows the Seminoe pumped storage site. Wind and solar energy are used to pump water from Seminoe Reservoir to a new upper reservoir. When power is needed, the water flows back down through a hydroelectric turbine.

This story is part of The Salt Lake Tribune’s ongoing commitment to identify solutions to Utah’s biggest challenges through the work of the Innovation Lab.

Salt Lake City-based rPlus Hydro announced Thursday that it has submitted its final application to the Federal Energy Regulatory Commission to build a 900-megawatt pumped storage project north of Rawlins, Wyo.

Pumped storage projects function as massive batteries. Wyoming has been adding wind and solar farms in the area, and those farms would provide the power to pump water uphill from a lower reservoir to an upper reservoir.

Then, when the power is needed, the process is reversed. The water flows out of the upper reservoir through an underground hydroelectric turbine to the lower reservoir, producing electricity on demand.

Called the Seminoe project, it would use the existing Seminoe Reservoir north of Rawlins, Wyo., as the lower reservoir. An upper reservoir would be built 1,000 feet higher in mountains near Seminoe. When filled, the upper reservoir can provide up to 10 hours of 900-megawatt power, enough to power thousands of homes. It takes 12 hours of available wind or sun to fully recharge, but its cycles will depend on the availability of wind and solar. It’s intended as a backup to those sources that can pick up when wind stops and the sun is down.

“This project will help to extract all the values of the wind and solar and transmission lines,” said Luigi Resta, president of rPlus Hydro. This is the first project to reach the final application stage for the four-year-old company, which is backed by the real estate and development firm Gardner Group.

There are two major transmission lines under construction near the project. One is the Gateway South line PacifiCorp is building from southeastern Wyoming to Mona, Utah. The other line, the Transwest Express line, will run from Wyoming to the Intermountain Power Plant near Delta, where it can connect to another transmission line to southern California.

Those lines give the project access to several power providers who could be potential customers for the power. That includes Rocky Mountain Power’s customers in Utah, but it could also include other systems as far away as California.

It’s a $2.5 billion project that would take until 2031 to become operational. The cost ultimately will be borne by the electricity customers who use the power, although as much of half the cost may be covered by the federal government through the Inflation Reduction Act, Resta said.

This month’s filing will begin the environmental analysis, including writing an environmental impact statement. Three federal agencies are involved, and the process could take more than two years. The existing Seminoe reservoir is operated by the U.S. Bureau of Reclamation. The upper reservoir would be built on Bureau of Land Management land, and the Federal Energy Regulatory Commission oversees all power plant development in the country.

Resta said the company has done preliminary research to find there are no environmental or cultural resources that would prevent construction. The environmental analysis will include a public comment period.

Currently, there are 43 licensed pumped storage projects in the country, most of them east of the Mississippi River. This would be the first in Wyoming. Utah has no licensed pumped storage projects, although several are proposed.

As more solar resources come online, the need for storage has become more acute. The so-called “duck curve” describes the issue when power providers have to power down other sources when the sun is shining, and then power the other sources back up when the sun sets. Pumped storage can provide on-demand power that comes online quickly when the sun sets.

Tim Fitzpatrick is The Salt Lake Tribune’s renewable energy reporter, a position funded by a grant from Rocky Mountain Power. The Tribune retains all control over editorial decisions independent of Rocky Mountain Power.