How can renewable energy surpluses from summer be stored in the long term and used in winter? While hydrogen is seen as a beacon of hope, iron could fill a crucial gap – as the new E+E Insight Paper from the Energy and Environment research field at TU Darmstadt shows.

The concept is as simple as it is innovative: iron powder is burned, releasing energy in the form of heat – without CO₂ emissions. This produces iron oxide, which can be converted back into iron using green hydrogen or electrolysis. This cycle can be repeated as often as required and enables long-term energy storage which, unlike batteries, does not self-discharge.