> But then there’s the dunkelflaute and its evil brother, cold dunkelflaute. ... It’s a shame there aren’t any umlauts in the word, otherwise it’d make a great

> But then there’s the dunkelflaute and its evil brother, cold dunkelflaute. ... It’s a shame there aren’t any umlauts in the word, otherwise it’d make a great name for a metal band. That made me laugh. Sabine is absolutely right that storage is the key, and it's a presently unsolved problem. The technologies she lists mostly can't scale up to world scale: pumped hydro and CAES need particular geography/geology, flywheeels and falling blocks have too low energy storage density, and lithium is needed for mobile applications. Thermal storage can work for durations of a day or so, but it's very capital intensive and has all the problems of thermal engines. Not really confidence-inspiring. There are a couple of infant/ancient technologies that Sabine doesn't mention. Iron is plentiful and rechargeable iron-based batteries could supply energy at week-long duration. Ammonia is under active research as an energy storage medium. That could supply seasonal storage. We have well over a century of experience with both materials, and they are already produced at the necessary scale for the rapid scale-up we need in energy storage. Both storage technologies are near commercial deployment. I also think that Sabine may be focusing a little too much on efficiency. This is because I expect the price of PV production to drop fairly quickly to low single cents per watt, so PV plus storage could end up in the low double-digit cents per watt.[1] At these prices we could perhaps our relax efficiency requirements a little. Synthesis of methane from air-captured carbon is one possibility if we do that. That has the advantage of using existing storage and distribution structures, already present at the required scale. The recent ESA proposal for space-based solar[2], though, is just sad. The fact that it even exists shows that European officials have not yet faced up to the reality of their situation, and they are still expecting the technology fairy to wave her magic wand to rescue them by lifting a million tonnes of PV satellite into orbit in less than a decade, more or less for free. Such passivity is very disappointing. 1. The path to this is via PV cells printed on flexible plastic film laid directly on the ground, with the strips laid side by side and bonded together. (Think greenhouse plastic strips hundreds of meters long, and with hundred-meter widths). No panel glass covers or aluminum frames, no galvanised steel stand mounts bedded in concrete, no inter-panel wiring, avoiding looming bottlenecks in glass, aluminum, and copper production. Minimal site prep and construction labor, and good land-use efficiency. (Legacy panel farms are only around 50% covered by panels because of shading and the need for access to fix wiring problems or replace panels with broken glass.) Erthos is half-way to this installation design, but still uses legacy panels. Perovskites are this year at the point where roll-printed PV cells are feasible. 2. https://arstechnica.com/science/2022/08/european-space-chief-says-continent-will-lead-in-space-based-solar-power/ https://arstechnica.com/science/2022/08/european-space-chief...