Heat and power storage using aluminium for low and zero energy buildings

A new concept for seasonal energy storage (both heat and power) for low and zero energy buildings based on an aluminium redox cycle (Al→Al3+→Al) is proposed. The main advantage of this seasonal energy storage concept is the high volumetric energy density of aluminium (21 MWh/m3), which exceeds common storage materials like coal. To charge the storage, oxidized aluminium (Al3+) is reduced to elementary aluminium (Al) in a central processing plant using renewable electricity in summer. In winter, during discharging process, the energy stored in aluminium is released in form of hydrogen and heat via the aluminium – water reaction. Hydrogen is directly converted to electricity and heat in a fuel cell. The discharging phase has been investigated using a laboratory-scale experimental setup. In optimized conditions, heat and hydrogen is reliably produced for all types of aluminium forms (grit, pellets, foil). A high efficiency of the conversion to hydrogen was obtained (>95%). The remaining challenge is to optimize the entire cycle, e.g. the aluminium recovery process via the use of climate-neutral inert electrodes.