At the centre of the project is an innovative cycle of energy and substance as important contribution to the energy transition. Electric energy from renewable sources is accumulated in iron with a high energy density and thus becomes storable and transportable. This can be done directly by electrochemical reduction or by using green hydrogen in a thermochemical reduction. The chemical energy is released again with high power densities via high-temperature thermochemical oxidation and reconverted into electricty in thermal power stations. Iron is a carbon-free energy carrier. Thus, the release will not emit carbon dioxide as greenhouse gas. Well packed, iron can be stored for long periods of time. This makes iron a chemical energy carrier to guarantee the supply by controllable power station capacities.