Pumped-storage hydropower could help renewable energy flow

Back in the 1970s, the Tennessee Valley Authority built what remains one of the largest energy storage facilities in the world — a pumped-storage hydropower plant.

Here’s how it works. A pump takes water from the Tennessee River, shoots it up a giant shaft and holds it there until electric power needs peak during the day. At that point, the water is allowed to drain back down, spinning turbines that can generate enough power for a million homes.

It’s almost like a gravity-powered battery as big as a cathedral … buried deep inside a mountain.

Marketplace’s Lily Jamali spoke with Robert Kunzig, a freelance journalist who recently wrote about this in depth for the publication Science. He said pumped-storage hydro is attracting a lot of interest, thanks in part to generous tax credits from the 2022 Inflation Reduction Act.

The following is an edited transcript of their conversation.

Robert Kunzig: To solve the climate crisis, we’re going to need to decarbonize the electric grid. And to do that, we’re going to need to build a whole lot of renewable energy, solar and wind. And the trouble with those energy sources is they don’t emit carbon, but they’re very variable. So you need some way of storing the electricity they produce when they’re producing more than you need, so that you have it available when they’re producing less than you need at night or when the wind is calm. And pumped-storage hydropower is a proven technology for storing a lot of energy that you could use to tide you over a whole day or even longer when the renewable energy is not producing what you need to meet the needs of the grid. It would just be a very reassuring energy bank to have if you’re a grid operator.

Lily Jamali: Yeah, and you describe in your article how this allows utilities to bank that power on a scale that’s way more significant than what they can do with lithium-ion batteries, which is another technology that’s used to store power.

Kunzig: Yeah, I mean, there are plants — the Tennessee Valley Authority plant I visited can basically supply a small city for a day. There aren’t battery plants that can do that. So this is the sort of thing that would give you confidence that you can build all the renewables you want and still have a grid that will be reliably present, even on a rainy winter day or week in winter.

Jamali: That’s interesting because we always obsess about those hot summer days and trying to get through that hump when people are coming home and turning on all of their appliances. But it’s this wet winter day scenario that’s really the true test for this technology.

Kunzig: Yes because that peak lasts longer. So that example you just mentioned, getting over the daytime hump, batteries are actually helping with that already in places like California, where you have a lot of solar energy. People are building a lot of batteries to get over that late-afternoon peak. But if you’re trying to store energy for a whole day, then you just keep having to add more and more batteries. And the trouble is, the cost doesn’t go down much. Each battery you add to increase the amount of energy you stored costs about the same as the first. And that’s where a technology like pumped storage comes in.

Jamali: But this is incredibly expensive, right?

Kunzig: It is very expensive upfront. It costs billions of dollars to build one of these things because you’ve got to tunnel into a mountain to build your power plant in a cave, and you have to build a giant shaft straight up through the mountain to connect that cave to the upper reservoir. So there’s tremendous civil engineering costs upfront, but afterwards, there are pumped-storage hydropower plants around now that have been operating for about a century. And they just don’t wear out. And the cost per kilowatt-hour delivered, per electricity delivered over that time period, is much cheaper than batteries, say. So they have high upfront costs, but low operating costs over the long term.

Jamali: In reporting your story, you visited a place called Goldendale, Washington. I believe this is on, the kind of near the Washington-Oregon border. Is that right?

Kunzig: Yes. It’s right on the Columbia River, which is the border between Washington and Oregon.

Jamali: Yeah, and so there’s this facility that is in development, right? Tell me about that.

Kunzig: Yeah, it’s a company called Rye Development, a private merchant power developer specialized in hydropower. And they are trying to develop several different facilities. One of them they already have a license from the Federal Energy Regulatory Commission, which is a quite cumbersome process that any hydropower project has to go through. But Goldendale is a project that, they’re on the verge of getting a license, and it’s in many ways technically a perfect project. The upper reservoir will be 2,000 feet above the lower one, it’s right on this bluff overlooking the Columbia River, the two reservoirs will be quite close together so the tunnels would not have to be so terribly long, and the lower reservoir is on an old industrial site and a derelict aluminum smelter. The trouble is, this site is also a site that is sacred to the Yakama Nation.

The site where Rye Development proposes to put a pumped-storage hydropower plant, it’s called Juniper Point, but in the Yakama language, it’s called Pushpum, and it’s a site that is sacred to them. It figures in their creation stories, and it’s a place where they forage for foods. They follow sort of a traditionally seasonal round of collecting these foods that is important to their rituals. And they’ve been doing this for thousands of years, so there are also archaeological sites that are located in this area that would be affected by the proposed plant. So there’s just very strong, emotional, historical heritage reasons, very strong opposition on the part of the tribe to this development.

Jamali: What occurred to you as the biggest hurdle to seeing this really flourish as an energy solution in the U.S.?

Kunzig: I would say the biggest hurdle is our difficulty in building big things that pay off over the long term. And for part of the country or for a large part of the country, it’s an electricity system that has been deregulated and turned over to the market. And the market does not plan decades ahead.

Jamali: Yeah, it’s a great point. Markets tend to be very focused, notoriously so, on the short term.

Kunzig: Yes. And from their point of view, this is a tremendously volatile time right now in the electricity business. And so it’s very hard if you’re, you know, sitting in the seat of responsibility in one of these utilities to commit to spending billions of dollars on a plant that’s going to last many decades when there’s so much else going on. And there are new technologies being developed that could maybe ultimately outcompete pumped-storage hydropower.

More on this

There’s a real push to develop new forms of battery technology. Finland, for example, installed the world’s first working sand battery in 2022.

There are also iron-air batteries, which capture the energy released when water, oxygen and iron are mixed together.

During our conversation, Robert Kunzig and I also discussed lithium-ion batteries, a staple of electric vehicles. “Marketplace Tech” recently spoke to Reuters correspondent Ernest Scheyder about controversies around mining lithium and other minerals that are critical to storing energy.