Techno-economic assessment of long-distance supply chains of energy carriers: comparing hydrogen and iron for carbon-free electricity generation

The effective usage of renewable energy sources requires ways of storage and delivery to balance energy demand and availability divergences. Carbon-free chemical energy carriers are proposed solutions, converting clean electricity into stable media for storage, long-distance energy trade and on-demand electricity generation. Among them, hydrogen (H₂) is noteworthy, being the subject of significant investment and research. Metal fuels, such as iron (Fe), represent another promising solution for a clean energy supply, but establishing an interconnected ecosystem still requires considerable research and development. This work proposes a model to assess the supply chain characteristics of hydrogen and iron as clean, carbon-free energy carriers and then examines case studies of possible trade routes between the potential energy exporters Morocco, Saudi Arabia, and Australia and the energy importers Germany and Japan. The work comprises the assessment of economic (levelized cost of electricity - LCOE), energetic (thermodynamic efficiency) and environmental (CO₂ emissions) aspects, which are quantified by the comprehensive model accounting for the most critical processes in the supply chain. The assessment is complemented by sensitivity and uncertainty analyses to identify the main cost drivers. Iron is shown to be lower-cost and more efficient to transport in longer routes and for long-term storage, but potentially more expensive and less efficient than H₂ to produce and convert. Uncertainties related to the supply chain specifications and the sensitivity to the used variables indicate that the path to viable energy carriers fundamentally depends on efficient synthesis, conversion, storage, and transport. A break-even analysis demonstrated that clean energy carriers could be competitive with conventional energy carriers at low renewable energy prices, while carbon taxes might be needed to level the playing field. Thereby, green iron shows potential to become an important energy carrier for long-distance trade in a globalized clean energy market.