(Bloomberg) – China’s Three Gorges Dam is an awe-inspiring sight, a vast barrier across the Yangtze River that contains enough concrete to fill seven Wembley Stadiums and more steel than eight Empire State Buildings. Its turbines alone could power the Philippines.
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But this summer, the world’s largest power plant was eerily quiet.
During a late August visit to the facility, the water on both sides of the dam stood still. There was no sign of the white jet that usually rises from the spillway or the roar of water coming out of the turbines. Scorching temperatures and drought upstream reduced the reservoir to a bare minimum, dramatically reducing the plant’s ability to generate electricity.
Water problems at China’s iconic mega-dam are part of a global hydropower crisis that is being made worse by global warming. From California to Germany, heat waves and droughts have shrunk the rivers that feed reservoirs. Hydropower generation fell 75 terawatt hours in Europe this year through September – more than Greece’s annual consumption – and fell 30% across China last month. In the United States, production is expected to fall to its lowest level in six years in September and October.
It’s a cruel irony that is forcing utilities to reconsider the traditional role of hydroelectricity as a reliable, instant source of green power. Dams are the world’s largest source of clean energy, but extreme weather conditions make them less effective in fighting climate change.
The cycle is “a warning signal in terms of power system design,” said Wenxuan Xie, management consultant at Wood Mackenzie Ltd. “You really have to think about the possibilities of extreme events, and maybe what you once thought was extreme could happen more frequently.
The problem is that there are few renewable alternatives that are as flexible or widespread. Globally, hydroelectricity generates more electricity than nuclear and more electricity than wind and solar combined. In countries like Norway and Brazil, dams generate more than half of the total electricity. Additionally, large dams have historically been more reliable, generating electricity on average about 42% of the time, compared to 25% for wind and 12% for solar, according to data from BloombergNEF. And grid operators can use them as a distributable source – a source that can be turned on almost instantly when needed, like coal or gas.
Except when there is no water.
“The worsening drought conditions under climate change will begin to limit the availability and dispatchability of hydroelectric reservoirs and reduce the capacity factor in places like southwestern China and the western United States. United,” said Xizhou Zhou, managing director of power and renewables at S&P Global Commodity Insights. . This will affect both the revenue generated by the dams and the reliability of the networks they feed, he said.
The worst drought in 1,200 years this year in the western United States means that dried-up reservoirs can only produce half the electricity they normally supply to California, increasing the risk of blackouts electricity throughout the state. Nationwide hydroelectric generation fell to 17.06 terawatt hours in September and is expected to fall further in October, according to the Energy Information Administration, the lowest since September 2016.
In Europe, dried up rivers reduced September hydropower output to the lowest since at least 2015, according to climate think tank Ember. This forces utilities to rely more on coal and gas, using the fuel stocks the continent is trying to hold onto to avoid a winter power shortage caused by supply disruptions from Russia.
In Brazil, which typically depends on hydropower for more than 60% of its electricity, a drought last year brought the country to the brink of power rationing and forced it to depend on rising imports of its neighbors Uruguay and Argentina, or to buy expensive fossil fuels. to fill the gap.
Dam operators must also balance competing demands for their water. Large dams ensure the irrigation of crops, the water supply of cities and the navigation of ships. The main purpose of the Three Gorges Dam, for example, was to control the annual Yangtze floods that periodically devastated towns and farms downstream. This summer, as drought reduced the flow of water in the river, the dam had to retain enough water to maintain navigation to Chongqing, the largest city in central China located nearly 2,000 kilometers away. of the sea.
Lake Mead, the reservoir behind the Hoover Dam on the Colorado River in the western United States, provides 90% of Las Vegas’ water supply, powers cities like Los Angeles, and irrigates hundreds of thousands of acres of cultures. The lake level has fallen so low this summer that human bones have been dug up from the lake bed, prompting police investigations.
However, no country has built more dams than China, where the worst drought in at least 60 years in Sichuan, a province the size of Germany, cut production by 50% in August, when even where the demand for air conditioning was skyrocketing to counter a heat wave. Officials had to cut power to many local factories for nearly two weeks, disrupting supplies for manufacturing giants including Apple Inc. and Tesla Inc.
“When such an event occurs, it does two things: it reduces the power supply and increases the demand for electricity, so there is a double whammy,” said Li Shuo, an analyst at Greenpeace.
Even after the end of the Sichuan drought in late August, the effects persist. In neighboring Yunnan province, aluminum smelters are forced to operate at reduced capacity to save energy and give reservoirs a chance to fill up before the drier winter months, when electricity supplies could be tight. again tested by strong demand. To fill the energy gap, China has had to rely more on polluting coal and gas, even as global fuel costs hit record highs.
“A prolonged severe drought like the one we have experienced this year can have a crippling effect,” said David Fishman, Shanghai-based analyst at The Lantau Group. “Reservoirs take progressively longer to fill up and be ready to generate again.”
Short of reverting to using more coal or gas, countries struggling with less reliable supply from hydroelectric turbines can invest in nuclear power or battery storage for wind and solar. Another option is to build more power lines to spread the load across more power sources in different regions.
Floating solar panels on hydroelectric reservoirs can also help, generating electricity when it’s sunny and slowing evaporation, said Lei Xie, energy policy officer at the International Hydropower Association. “The combination of hydropower and solar works well,” she said, and the Chinese government has used the strategy to increase the flexibility of hydropower facilities.
Yet extreme weather conditions can affect all sources of clean energy. Smoke from wildfires and dust storms cloud solar panels, while plummeting winter temperatures can freeze wind turbines. Drought in Europe has curtailed production at nuclear power plants that rely on river water for cooling.
Worries about the reliability of dams as the planet warms are compounding growing resistance to new hydropower projects in many countries. Dams have been blamed for disrupting ecosystems, loss of wetlands and extinction of aquatic species. Major projects displace local people to make way for reservoirs – more than 1.3 million people in the case of the Three Gorges.
These headwinds mean that hydropower is unlikely to maintain its leading role in clean energy for long. BloombergNEF predicts an 18% increase in global hydropower capacity by 2050, compared to a more than 8-fold increase for solar power and at least a 3-fold increase for wind power.
In fact, hydropower development may be shifting to what was once a niche in the industry: pumped storage. For these, water is pushed back into the reservoir during times of excess electricity generation, and then allowed to flow through the turbines when more electricity is needed. The technology can be combined with intermittent wind and solar power to provide carbon-free electricity around the clock. Because the pumping systems operate in a closed loop, they are less affected by droughts, according to the hydropower association. .
China could develop 270 gigawatts of such projects by 2025, according to the major state-owned dam builder, compared with the country’s plans to add 60 gigawatts of traditional hydropower generation over the same period.
Hydro’s struggles underscore the difficulty of building a robust renewable energy grid to replace fossil fuels, especially in developing countries which also face growing electricity demand as per capita consumption rises . At the same time, drought concerns underscore the need to accelerate efforts to curb rising temperatures as the cost of the energy transition rises, Greenpeace’s Li said.
“If we don’t tackle the problem that is causing climate change and reduce emissions, we have to admit that there will be things that we can’t plan for or that are too expensive to plan for,” he said. he declared. “There will be catastrophic losses.”
–With help from Mark Chediak.
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