By Vik Iso-Ahola

The energy transition is upon us. And it has governments around the world turning to solar and wind power to help meet aggressive renewable energy targets. However, grid operators face challenges when the sun isn’t shining or the wind isn’t blowing. That’s just the intermittent nature of some of these renewable energy sources. If we want to take advantage of all that energy, we need the capacity to store it. 

Energy storage helps to quickly bring large amounts of power online to fill the gaps during times when wind or solar generation isn’t possible. Generally, when we think about energy storage we think about batteries. But when we talk about hydroelectric projects, energy storage can come in the form of pumped storage. 

In the US, pumped storage accounts for 95 percent of the energy storage capacity. And we will need to see more of these projects come online as we continue to navigate the energy transition. The good news? We are seeing pumped storage projects in development. However, there are several barriers to progress in the industry that we will need to overcome. 

Let’s look at what pumped storage is, how it can help us, the barriers to adoption, and some examples of projects across the US, particularly in the west where pumped storage projects are desperately needed to meet rising energy demands.

Pumped storage in a nutshell

Pumped storage has the capability to pump water from a lower reservoir to an upper reservoir in periods where there is excess electricity on the grid or when energy prices are low. The water can then be released back through the reversible turbines as needed to meet energy demand. Essentially, it is a utility-scale “water battery” with virtually immediate response time.

How does pumped storage work? Well, pumped storage projects have two reservoirs close together with a significant elevation difference. These reservoirs are connected by pipelines that pass through a powerhouse. The powerhouse contains reversible pump turbines that can generate electricity while in turbine mode and store energy while in pump mode. This ability to store energy for times of high demand works great for days when the sun isn’t shining and the wind isn’t blowing. The ability to use excess energy that would otherwise be lost due to lack of battery storage capacity makes pumped storage even more impactful. 

Pumped storage projects will grow increasingly more popular as the US weens itself off fossil fuels. Why? Because they have the unique ability to provide energy reserves and grid reliability. An estimated 36 gigawatts (GW) of new pumped storage capacity could be added to the US grid. Both operators and consumers see pumped storage as a proven and sustainable solution to our energy storage needs.

Challenges for pumped storage projects

Pumped storage projects can be complex to say the least. Challenges for new pumped storage plants include size, capital cost, reliance on specific geographies like mountains, and prolonged development timelines. In recent years, developers and experts are revisiting these challenges with a new enthusiasm exploring potential sites outside of the typical geography and involving new technologies.

But the biggest barrier for pumped storage projects? Regulatory roadblocks. The current regulatory framework and energy market structure in the US require a long-term commitment and vision for these projects to be built. This causes a lengthy permitting process and leads to projects not going ahead. In fact, the Federal Energy Regulatory Commission (FERC) has issued only a small handful of pumped storage facility licenses in recent years. Policy changes are needed to support the timely development of additional grid-scale energy storage. 

The Seminoe Pumped Storage Project

Recently, our team was selected by rPlus Hydro to conduct a detailed feasibility study for the Seminoe Pumped Storage Project. The project is located on the Seminoe Reservoir, approximately 30 miles outside Rawlins, Wyoming.

The proposed ~900-megawatt (MW) project will help to address energy storage needs in the western US. It is needed as more renewable energy is integrated onto the grid. The project will be the ideal “water battery” for Wyoming wind energy, which is abundant. This will allow a more efficient use of new transmission infrastructure responsible for delivering that wind power to the market.

Our teams will identify and analyze the alternative intake and outlet structure types. We will also identify the location and type of upper reservoir to complete the pumped storage scheme above Seminoe Reservoir. After that, we will plan and perform a geotechnical investigation that will support the feasibility design of the underground facilities, identify pump-generating equipment, identify routing for a transmission line that will lead to nearby grid interconnection, evaluate project constructability, and provide an opinion on probable construction cost.

The Seminoe Pumped Storage Project is just one example of the work my Company has been working on in the US. In fact, Stantec has developed a global footprint in pumped storage through 57 years of experience working with clients to provide 16,000 MW in pumped storage capacity at new and existing hydroelectric pumped storage plants.

In the US, the three most recent pumped storage projects include the 40-MW Lake Hodges Pumped Storage Plant in California, the 1,035-MW Rocky Mountain Pumped Storage Plant in Georgia, and the 1,800-MW Gregory County Pumped Storage Project in South Dakota. Furthermore, we are the engineer of record for the 3,000-MW Bath County Pumped Storage Plant in Virginia—the largest pumped storage project in the world.

Heading forward with pumped storage

As energy consumers, we might take for granted that at every instant, grid operators are balancing the supply of electricity with the demand.  

The significant expansion of solar and wind energy pose even greater challenges for these grid operators, who can’t control when the sun is shining or the wind is blowing. A very sudden change in supply—like the drop of solar power at sunset—means other generation sources must quickly make up the difference.

While it’s difficult for some types of generators to respond quickly enough to keep the grid reliable, pumped storage excels at rapidly bringing large amounts of generation online to fill the gap. That’s why I’m excited to see future developments in the industry. If we hope to successfully combat climate change, pumped storage will need to play a big part. 


Vik Iso-Ahola is Vice President, Power & Dams.