Climate irony: Clean hydropower faces a dry patch

livemint.com:

The world’s biggest source of renewable energy has been going through a dry patch. Generation from solar farms roughly tripled between 2018 and 2023, while the output of wind turbines almost doubled. That provided enough extra clean energy to power Japan and Russia put together.

Meanwhile, the hydroelectric dams that generate about one-seventh of the world’s electricity stood still: The additional 52 terawatt-hours in 2023 was only enough to fuel Greece. That’s not surprising. Hydro’s problems resemble those of the other veteran form of clean power, nuclear.

Unlike wind and solar, it’s been an established technology for decades, so much of its growth potential has already been exploited. Like nuclear, it’s dependent on the building of costly and time-consuming projects to move forward, and shows little sign of reducing its costs. Compounding problems, a drought related to La Niña in 2022 and 2023 caused a collapse of generation in China, home to about a third of the world’s hydro dams.

It would be nice to dismiss this as a temporary setback. When drought conditions recede, generation should surge back, as we appear to be seeing in China now, where wetter weather has been filling reservoirs and drove coal to an estimated record-low 53% share of generation in May. A recent study of 610 US hydropower projects shows there may be more long-lasting issues.

The productivity of a power plant can be measured by its capacity factor—the kilowatt-hours it generates as a proportion of a theoretical maximum. For 24/7 nuclear facilities, this is close to 90%, while for solar panels, which mostly operate for a few hours around midday, it’s 15-20%. Hydro facilities typically have capacity factors in the region of 40%—but it’s a mistake