Combustion of Iron Particles in Oxygen and Air as a Regenerative Energy Carrier on Earth and the Moon

Worldwide, metal particles are being researched as carbon-free fuels and energy storage systems. Many metal particles exhibit combustion behaviour similar to that of coal dust, possess comparable or higher energy densities, and can be recycled in an environmentally friendly and cost-effective manner using renewable energies. In addition to aluminum and silicon, current research focuses on iron particles (about 100 µm) that can ignite and burn spontaneously in air at 800°C. The energy density during oxidation to Fe2O3 is 7.4 MJ/kg and 58 MJ/m3. The carbon-free regeneration of the resulting iron oxide can be achieved either through reduction with hydrogen or directly via electrolysis. The electrolytic reduction of iron oxide into iron and pure oxygen enables a combustion cycle on the Moon for power generation. Consequently, iron has been identified by the German Aerospace Center (DLR) as a potential energy source for a lunar station to bridge the 14-day lunar nights. Iron is the third most abundant element in lunar rock (regolith) after oxygen (43%) and silicon (21%), with a mass fraction of 13%. Several in situ resource utilization (ISRU) processes exist to separate iron from regolith.