in November 2019 Engineers commissioned the 18th and final turbine at Belo Monte Dam in Brazil: the final stage in an odyssey of planning and construction that began nearly 50 years ago. The massive hydroelectric complex – the fourth largest in the world – completely upends the northern section of the Xingu River, one of the major tributaries of the Amazon. Water held by the main dam created a reservoir that flooded 260 square miles of lowlands and forests, displacing over 20,000 people,
Major hydroelectric dams can have disastrous consequences – flooding homes and habitats and changing the flow, temperature and chemistry of rivers over decades. Although few are as big as Belo Monte, there are a slew of new hydroelectric dams around the world. In 2014 researchers estimated that at least 3,700 Major Hydroelectric Dams globally in planning or under construction. Most of these new projects are located in low- and middle-income countries eager to fuel their growing economies with a significant source of low-carbon power: in 2020, hydroelectric dams will generate as much electricity nuclear and wind power combined, But the race to tap the world’s rivers for renewable energy presents something of an environmental conundrum: Do the benefits outweigh the environmental chaos that dams can eliminate?
Some researchers think there is a smart way out of this dilemma. Instead of building more dams, why don’t we figure out a way to get the most out of the dams we already have? Most of them are not generating electricity – they are used for irrigation, water supply, flood control, or for fishing and boating. If we can figure out a way to put turbines in those dams so they can also produce hydroelectricity—a process known as retrofitting—we could unlock a vast renewable energy potential that hasn’t been tapped. He is going.
In a retrofitted system, water falling through a dam would spin newly installed turbine blades connected to a generator—and that spinning would generate electricity that could be distributed to local homes or connected to a larger power grid. . “How much more can we get from revitalizing existing infrastructure, rather than expanding and building new infrastructure?” asks co-author Ryan McManmay, an ecologist at Baylor University in Texas of a paper Exploring the untapped potential of non-operated dams. (McNamame’s own office in Waco is a short walk from one of these dams on the Brazos River. A wasted opportunity at his door, he explains.)
McNamame and his colleagues estimated that retrofitting dams and upgrading existing hydroelectric plants could increase their maximum output by 78 gigawatts. This is roughly the electricity generated by the Seven Belo Monte Dam, or more than twice that. Average electricity demand across the United Kingdom, And in parts of the world where new dams are being planned and built, the change could be huge. Retrofitting and upgrading dams in the Amazon River basin could unlock 1.6 gigawatts of new electricity generation. This is roughly the amount of energy produced by a natural gas-fired power station and enough to completely avoid the construction of 17 new small dams. Upgrading and retrofitting dams in the Mekong River basin in Southeast Asia could generate so much electricity that all new dams to build in the region would be a surplus.
Some countries are already using this capability. Since 2000, 36 dams in the US have been retrofitted with turbines, adding more than 500 MW of renewable generation capacity. There’s even more potential: A 2016 US Department of Energy report found that an additional 4.8 gigawatts of electricity could be generated. Repair of non-operated dams over the next three decades. In places such as the US and Western Europe, where the pace of dam-building has long faded in the mid-20th century, retrofitting may be the only option for governments looking for a little more hydropower. “If there are dams that are going to remain in place, let’s try to find a solution and work together to find the most optimal solution,” McManame says.
But before one starts upgrading all these dams, they would like to take a second look at the numbers. It is not easy to accurately predict how much electricity a retrofitted facility will actually produce, as it turns out that not every dam is suitable for conversion. Suppose one wants to install turbines in a dam which was built to hold water so that it can be used to irrigate farmers’ fields. During the growing season, a lot of that water would normally be directed toward crops, rather than flowing over the dam to generate electricity. Or perhaps it is in an area where the water is only high enough to generate electricity for some part of the year. Suddenly those retrofitted dams may not seem like such a smart idea.
a recent study on Rebuilt Dam in America, also commissioned by the Department of Energy, found that their electricity production estimates skewed toward the optimistic side: on average, those estimates were 3.6 times higher than actual output. The study found that the most successful retrofits were concrete dams initially built to aid navigation. (Dams are often used to widen or deepen waterways so that boats can easily cross.) “This is a complex issue. “It’s not an easy fix,” McManame says.
But big dams are still on the agenda in countries like Brazil. “If they are going to grow and really raise the standard of living across the country, they need energy. This is the long and short of it,” says Michael Golding, a senior aquatic scientist at the Wildlife Conservation Society Nine new large dams have been outlined in the country’s most recent 10-year energy plan scheduled to be completed before 2029. Rather than hoping that these dams will not be built, it is important to ensure that proper studies are carried out to ensure that they are built in a way that minimizes environmental destruction, Golding says: ” Often environmental impact frameworks are not very good. They will define an area of interest close to the dam and do not include all downstream impacts and also upstream impacts in that area of interest.
The Belo Monte Dam is a good example of the impact large dams have on the surrounding environment. The dam complex diverted 80 percent of the Xingu’s flow from a 62-mile section of the river, known as the Big Bend. This section of Xingu also happens to be the only known wild habitat of the zebra pleco – a fascinating striped catfish beloved by aquarists. “This species is at great risk of extinction,” says Thiago Bea Couto, a postdoctoral researcher at Florida International University’s Tropical River Lab. The effect of dams on fish species is well documented elsewhere in the world. In Washington state, the Elva Dam intersects the Upper and Lower Elva watersheds, reducing the water 90 percent of available habitat for salmon, Some species endemic to the river have disappeared entirely, while populations of others—such as the Chinook—have declined to a fraction of their previous levels.
Ultimately, however, even large dams can outweigh their usefulness. In 2014, the last remnants of the Elva Dam were removed forever. Chinook salmon that was locked behind two dams for decades is now slowly make your way back up above. A full recovery is expected to take decades. “Dams don’t last forever,” Couto says. “There are many that are abundant, but they are not providing the minimal benefits they need.”
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