Techno-economic assessment of aluminum as a clean energy carrier to decarbonize remote industries†

Abstract

The energy sector is transitioning to a low-carbon era requiring the wide use of renewable energy sources, mainly wind and solar. In this context, aluminum could serve as a sustainable energy carrier as it stores energy in a safe and compact way. It could be used to help decarbonize remote communities and industries, trade energy on a global scale, or provide seasonal energy storage. The Hall–Héroult process, reducing aluminum oxides to aluminum, is already a technology deployed at an industrial scale. The maturity of this industry could therefore be leveraged to store electricity. To convert aluminum back to power, it can be fully oxidized with high-temperature liquid water. The hydrogen and high-temperature heat produced can then be converted to power using a combination of heat engines and/or fuel cells. For this concept to be viable, the oxides produced must be collected and reduced in a sustainable way. In this work, aluminum recharging costs were evaluated by reviewing the current reduction process and the literature available on the development of inert anodes, a technology enabling carbon-free smelting. Results show that aluminum can be cost-competitive on a chemical energy basis with most common hydrogen carriers discussed in the literature. To contextualize the findings, a remote mine case study integrates transportation, storage and power generation costs for aluminum, compared to liquefied hydrogen and ammonia. The analysis reveals that aluminum is comparable to other carbon-free solutions, although they all currently remain more expensive than diesel fuel at an input electricity price of $30/MWh_e. Aluminum emerges as marginally more expensive than the direct use of ammonia, while avoiding concerns related to toxicity and NO_x emissions. This study thus positions aluminum as a promising energy carrier that merits further consideration in various other applications.