Research advances on metal fuels without carbon dioxide emissions

Nowadays we are gradually transitioning from fossil to renewable energy in our energy consumption, but the green electricity, represented by solar and wind power, is highly fluctuating and difficult to use efficiently. Hydrogen production from electrolysis of water is currently an important pathway to consume green electricity, yet hydrogen still faces difficulties in large - scale long - term storage. Subsequently, a new pathway for the efficient use of renewable energy has been proposed: powering by renewable energy - preparing metal by electrolysis - heating by metal combustion. Metals are easy to store, and transport and its market is large. This makes it possible to realize the large - scale long - term storage of fluctuating renewable energy. In this new technical route, metal combustion is a crucial element. This work reviews the combustion models of iron and aluminum as fuels, and discusses their combustion characteristics under different particle sizes and microgravity conditions, as well as the flame propagation process. We hope that our work will benefit the development of this field.