Matthew Hutson writes:

The German word Dunkelflaute means “dark doldrums.” It chills the hearts of renewable-energy engineers, who use it to refer to the lulls when solar panels and wind turbines are thwarted by clouds, night, or still air. On a bright, cloudless day, a solar farm can generate prodigious amounts of electricity; when it’s gusty, wind turbines whoosh neighborhoods to life. But at night solar cells do little, and in calm air turbines sit useless. These renewable energy sources stop renewing until the weather, or the planet, turns.

The dark doldrums make it difficult for an electrical grid to rely totally on renewable energy. Power companies need to plan not just for individual storms or windless nights but for Dunkelflaute that stretch for days or longer. Last year, Europe experienced a weeks-long “wind drought,” and in 2006 Hawaii endured six weeks of consecutive rainy days. On a smaller scale, factories, data centers, and remote communities that want to go all-renewable need to fill the gaps. Germany is decommissioning its nuclear power plants and working hard to embrace renewables, but, because of the problem of “intermittency” in its renewable power supply, it remains dependent on fossil fuels—including imported Russian gas.

The obvious solution is batteries. The most widespread variety is called lithium-ion, or Li-ion, after the chemical process that makes it work. Such batteries power everything from mobile phones to electric vehicles; they are relatively inexpensive to make and getting cheaper. But typical models exhaust their stored energy after only three or four hours of maximum output, and—as every iPhone owner knows—their capacity dwindles, little by little, with each recharge. It is expensive to collect enough batteries to cover longer discharges. And batteries can catch fire—sites in South Korea have ignited dozens of times in the past few years.

Venkat Srinivasan, a scientist who directs the Argonne Collaborative Center for Energy Storage Science (ACCESS), at the Argonne National Laboratory, in Illinois, told me that one of the biggest problems with Li-ion batteries is their supply chain. The batteries depend on lithium and cobalt. In 2020, some seventy per cent of the world’s cobalt came from the Democratic Republic of the Congo. “Unless we have diversity, we’re going to be in trouble,” Srinivasan said. Any disruption to the supply chain can strongly affect prices and availability. Moreover, a lot of water and energy are required for mining the metals, which can cause environmental damage, and some cobalt-mining operations involve child labor. Experts doubt that Li-ion prices will drop more than thirty per cent below their current levels without significant technological advancements—a drop that is still too small, according to the Department of Energy. We need to expand our capacity; by one estimate, we’ll require at least a hundred times more storage by 2040 if we want to shift largely to renewables and avoid climate catastrophe. We may somehow find clean and reliable ways to mine, distribute, and recycle the ingredients for Li-ion batteries. And yet that seems unlikely. Although we usually think about renewable energy in terms of its sources, such as wind turbines and solar panels, that’s only half the picture. Ideally, we’d pair renewable energy with renewable storage. [Continue reading…]