When wind and sun are weak in winter, Europe needs power plants that can deliver energy at the push of a button—and in a climate-neutral way. So far, hydrogen and carbon capture and storage (CCS) are considered the favorites for this. Both require infrastructure that doesn't yet exist. An expert report by the Energy Economics Institute at the University of Cologne (EWI), commissioned by the Metal Energy Hubs project of TU Darmstadt and the DESERTEC Foundation, is now examining a third option: iron. TU Darmstadt and KIT have been collaborating on the Clean Circles project on iron as an energy source since 2021.