Concentrated Solar Energy Across the Iron and Steel Value Chain: From Ironmaking to Advanced Processing and Residue Valorization

The decarbonization of the iron and steel industry requires alternative energy and process routes that reduce dependence on fossil fuels and conventional high-temperature heat sources. Concentrated solar energy (CSE) offers a renewable source of high-temperature process heat that could be integrated into selected stages of the iron and steel value chain. This review critically examines CSE applications ranging from iron ore preparation, beneficiation, agglomeration and reduction to prospective solar smelting, electric arc furnace (EAF) steelmaking, downstream steel processing and the valorization of iron- and steel-bearing residues. Particular attention is given to solar-assisted sintering and hydrogen-based direct reduction, hybrid reduction routes, solar integration with EAFs, heat treatment, powder metallurgy, welding, surface modification and residue processing. Experimental investigations, reactor developments, process modelling and system-level assessments are compared to distinguish demonstrated process feasibility from conceptual configurations and model-based projections. The literature provides experimental evidence for selected agglomeration, iron oxide reduction and materials-processing operations, but the level of validation varies substantially, and several routes remain at the laboratory or modelling stage. The review also examines solar-resource availability and the geographical distribution of iron ore mines and steelmaking facilities as a preliminary framework for identifying locations warranting further assessment. Techno-economic and environmental analyses indicate that the prospects for implementation depend on process configuration, operating conditions, thermal storage, backup supply, system boundaries and the origin of electricity and hydrogen. Key challenges include intermittent solar availability, heat transfer and thermal losses, reactor integration, scale-up and economic competitiveness. Further progress will require pilot- and demonstration-scale validation, continuous operation, improved process control, and integrated techno-economic and life-cycle assessments under realistic conditions. Overall, CSE is best regarded as a complementary source of renewable high-temperature process heat whose contribution to steel decarbonization will depend on the technical maturity and integration requirements of each application.