IF you’re looking for an iconic example of humanity’s ability to harness nature to produce clean energy on a massive scale, it’s hard to ignore the Three Gorges Dam.
Built through the 2000s just as China’s rise was at its most headlong, the world’s largest power station can generate 22.5 gigawatts, equivalent to 20 nuclear plants.
Two more of the world’s six biggest generators are upstream of its reservoir on the Yangtze River. Together, they pump out enough electricity to light up Poland.
That makes the problems being experienced in the backyard of the Three Gorges a warning to other economies in Asia that would seek to follow China’s path to development. Daily hydro generation has fallen 51% amid the worst drought on the Yangtze since the early 1960s, part of a worldwide drying that’s also closed the Rhine to barge traffic.,
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That’s led to factory shutdowns as soaring demand from air conditioners collides with the constraints of a provincial grid that depends on dams for four-fifths of its electricity.The hydro potential of the Yangtze and its sister rivers originating in the Tibetan Plateau is crucial to the future of Asia. Nearly half of humanity lives in countries dependent on the vast rivers fed by the glaciers and snowpack of the plateau and Himalayan mountains. It’s hotly debated how that frozen store of water will fare as the climate warms – but this year’s events in Sichuan, in southwestern China, show that even a change in rainfall conditions downstream can affect output from major dams.
That’s important, because these rivers provide a large slice of the clean energy set to be installed over the coming decade.
While China’s current crop of dams are likely to be the last it builds for many years, India has about 29 gigawatts on the way, with another 13 gigawatts in neighbouring Pakistan, Nepal and Bhutan. Nine more gigawatts will come from Vietnam and Laos, heavily dependent on the Tibetan Plateau-fed Mekong, according to the International Energy Agency.
Renewable energy – dependent as it is on the vagaries of planetary forces, rather than the certainties of fossil fuels’ industrialised commodity supply chain – always suffers from variability in output. Dams, however, are often seen as being exempt from the worst effects. With reservoirs acting as a vast battery of stored energy, they have a great deal of freedom to determine their output on any given day. So-called pumped hydro stations can even move water between two different elevations, providing a surge of electricity at the touch of a button.
The drought on the Yangtze is showing how the climate can scramble that logic. Solar’s major variability can be measured in hours, governed by the rise and fall of the sun, and relatively easily fixed by using batteries to shift the midday peak in output to the early evening peak in grid demand.