Tomorrow's Hydropower Begins With Retrofitting Today's Dams

Big dams that are as bad as fossil fuels can be turned green

3 min read
dam and reservoir of Jose Toran
The Jose Toran dam and reservoir in Spain.

With wind and solar prices dropping, it can be easy to forget that two-thirds of the globe's renewable energy comes from hydropower. But hydro's future is muddled with ghostly costs—and sometimes dubious environmental consequences.

Most dams weren't, in fact, actually built for hydropower. They help stop floods and supply farms and families with water, but they're not generating electricity—especially in developing countries. Nearly half of Europe's large dams are primarily used for hydropower, but fewer than a sixth of Asian dams and a tenth of African dams generate substantial amounts of electricity—according to Tor Haakon Bakken, a civil engineer at the Norwegian University of Science and Technology (NTNU).

People like Bakken see such dams as opportunities. He's one of a few researchers proposing to retrofit old, non-generating dams by installing turbines at their bases. That, he thinks, would create electricity without adding an ecological burden.

Bakken's group and one of his graduate students, Nora Rydland Fjøsne, modeled theoretically doing just that for numerous dams in a part of southern Spain. Their study found that, in many cases, retrofitting was an economically viable approach.

Bakken hopes that hydro developers consider retrofitting before building anew. “I think, for the case in Spain, we have proven that this is both a technically and economically viable alternative," he says. “And I think it's the case in many other places too."

Even power-generating dams could also be productively retrofitted. The Brazilian Energy Research Office estimates that updating aging hydro plants could add 3 to 11 gigawatts of generating capacity—above and beyond Brazil's existing 87 GW hydropower base. Meanwhile, scientists at the National Renewable Energy Laboratory (NREL) in the US have proposed using reservoirs as beds for floating solar panels, something they think could theoretically generate terawatts of power.

But if you do need to build new hydropower facilities, other scientists believe the best course of action is to stay small: focus on establishing so-called “run-of-the-river" dams, which try to keep the river and its environmental conditions intact.

“This kind of turbine, you don't need to flood large areas," says Michael Craig, an energy systems researcher at the University of Michigan, and formerly of NREL.

Craig and some of his colleagues from NREL and the private-sector Natel Energy modeled a sequence of run-of-the-river dams on a river in California, all linked such that they could be easily controlled. They found that this approach was, like retrofitting dams, economically viable.

“The smaller the facility, the more energy you can get out of that, I think is definitely a great strategy," says Ilissa Ocko, a climate scientist at Environmental Defense Fund.

Righting the course of old hydro

Hydropower's behemoth dams of old can singlehandedly rewrite the courses of rivers, creating winding reservoirs in their wake. They can prevent floods and supply water, but they can also displace countless communities upstream and constrict river flow downstream. Such dams disproportionately hurt rural and indigenous people who rely on rivers for a living.

Moreover, some hydro plants generate alarming amounts of greenhouse gases. The culprit, scientists now know, are those very reservoirs—and the biological material trapped underneath. “You're basically flooding a whole area that has all this vegetation on it that now is just decomposing underwater," says Ocko.

The result? Greenhouse gases. On top of carbon dioxide, it can generate methane, which—while not as long-lasting in the atmosphere—is more potent at warming. Reservoirs that are larger in surface area, and reservoirs that have warmer waters—such as those near the equator—are especially prone to burping up copious amounts of methane.

Take the Brazilian Amazon, for instance. “Over the last decades, basically all the potential for hydropower expansion that Brazil had close to consuming markets has been exhausted, and Amazonia became the new frontier," says Dailson José Bertassoli, Jr., a geochemist at the University of São Paulo.

But many dam reservoirs in the Amazon are comparable to fossil fuel plants in their capacity to generate greenhouse gases. So too are their counterparts in Western Africa. In fact, one Environmental Defense Fund study found that nearly seven percent of the 1500 hydro plants around the world they examined emit more greenhouse gases per unit energy than fossil fuel plants.

That's ample reason to eschew building new dams and instead look to what we have. “In terms of environmental impacts, it makes sense to focus on areas that already are not in their natural conditions," says Bertassoli.

So, in the face of its mounting environmental costs, does hydro have a future?

Yes, say climate scientists, but with a caveat. The key is to minimize the future of those large, greenhouse-gas-excreting reservoirs.

“I would never say that we should stay away from hydropower. From a climate perspective, I think we need all the solutions we can get." says Ocko. But, she adds, “We can't make an assumption and put it into this bucket of being a renewable energy source just like solar and wind. It's not."

This article appears in the September 2021 print issue as "Righting Hydropower's Course."

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Smokey the AI

Smart image analysis algorithms, fed by cameras carried by drones and ground vehicles, can help power companies prevent forest fires

7 min read
Smokey the AI

The 2021 Dixie Fire in northern California is suspected of being caused by Pacific Gas & Electric's equipment. The fire is the second-largest in California history.

Robyn Beck/AFP/Getty Images

The 2020 fire season in the United States was the worst in at least 70 years, with some 4 million hectares burned on the west coast alone. These West Coast fires killed at least 37 people, destroyed hundreds of structures, caused nearly US $20 billion in damage, and filled the air with smoke that threatened the health of millions of people. And this was on top of a 2018 fire season that burned more than 700,000 hectares of land in California, and a 2019-to-2020 wildfire season in Australia that torched nearly 18 million hectares.

While some of these fires started from human carelessness—or arson—far too many were sparked and spread by the electrical power infrastructure and power lines. The California Department of Forestry and Fire Protection (Cal Fire) calculates that nearly 100,000 burned hectares of those 2018 California fires were the fault of the electric power infrastructure, including the devastating Camp Fire, which wiped out most of the town of Paradise. And in July of this year, Pacific Gas & Electric indicated that blown fuses on one of its utility poles may have sparked the Dixie Fire, which burned nearly 400,000 hectares.

Until these recent disasters, most people, even those living in vulnerable areas, didn't give much thought to the fire risk from the electrical infrastructure. Power companies trim trees and inspect lines on a regular—if not particularly frequent—basis.

However, the frequency of these inspections has changed little over the years, even though climate change is causing drier and hotter weather conditions that lead up to more intense wildfires. In addition, many key electrical components are beyond their shelf lives, including insulators, transformers, arrestors, and splices that are more than 40 years old. Many transmission towers, most built for a 40-year lifespan, are entering their final decade.

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