The achievement of climate neutrality by 2050 requires a profound transformation of industrial sectors characterized by high energy consumption and significant greenhouse gas emissions. Among these sectors, the steel industry represents one of the most challenging industries to decarbonise, accounting for approximately 7% of global carbon dioxide emissions while producing nearly 1.9 billion tonnes of steel annually. Despite the progress achieved in renewable energy deployment and industrial efficiency improvements, conventional steelmaking remains heavily dependent on fossil fuels, particularly coal and natural gas, which act as both energy sources and reducing agents in ironmaking processes. Consequently, the development and implementation of innovative low-carbon technologies are essential to ensure the sustainability and competitiveness of the steel sector while contributing to international climate objectives.

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This thesis investigates the potential role of green hydrogen as a key enabler for the decarbonisation of the steel industry, focusing on the techno-economic feasibility of large-scale hydrogen production integrated with hydrogen-based steelmaking routes. The research was developed within the framework of the HYDRA project, coordinated by RINA-CSM and funded under the European IPCEI initiative, which aims to demonstrate and validate innovative hydrogen technologies along the entire steel value chain. The study evaluates the technical and economic implications of producing renewable hydrogen through offshore wind-powered electrolysis and its utilisation in hydrogen-based direct reduction and electric arc furnace technologies, considered among the most promising pathways towards carbon-neutral steel production.

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The work begins with an overview of the global energy transition and the increasing penetration of renewable energy technologies. Special attention is devoted to the evolution of wind power and electrolysis systems, which constitute the foundations of future hydrogen economies. Offshore wind energy is identified as a particularly suitable renewable source due to its high energy yield, technological maturity, and large-scale deployment potential. The thesis reviews current developments in offshore wind installations, including fixed and floating turbine technologies, highlighting their strategic importance for supplying sustainable electricity to hydrogen production facilities.

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A comprehensive analysis of hydrogen production technologies is also presented, focusing on water electrolysis as the primary pathway for obtaining green hydrogen. Different electrolysis technologies, including Alkaline Electrolysers (AEL), Proton Exchange Membrane (PEM), Anion Exchange Membrane (AEM), and Solid Oxide Electrolysis Cells (SOEC), are assessed in terms of efficiency, operational flexibility, technological maturity, and integration with renewable energy systems. Among these solutions, PEM electrolysers are identified as particularly suitable for coupling with intermittent renewable sources because of their rapid response, high current densities, compact design, and operational flexibility.

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The thesis subsequently examines conventional steelmaking technologies and their environmental impacts. Special emphasis is placed on the comparison between the traditional Blast Furnace-Basic Oxygen Furnace (BF-BOF) pathway and alternative Direct Reduction-Electric Arc Furnace (DR-EAF) routes. While the BF-BOF process remains the most widespread production method worldwide, it is also the most carbon-intensive, generating approximately 2.2 tonnes of CO₂ per tonne of steel produced. Conversely, hydrogen-based direct reduction technologies can significantly decrease direct emissions by replacing carbon-based reducing agents with hydrogen, producing water vapour instead of carbon dioxide during iron ore reduction.

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The research further explores ongoing international efforts to develop hydrogen-based steel production, examining major initiatives such as HYBRIT, SALCOS, H2 Green Steel, and other industrial demonstration projects. These initiatives collectively demonstrate the growing interest in hydrogen-enabled steelmaking and confirm the technical feasibility of replacing fossil fuels in iron reduction processes. The study places particular emphasis on the HYDRA project, which aims to create an integrated experimental platform for testing hydrogen-based steel production technologies, including hydrogen-compatible materials, direct reduction processes, electric arc furnace operations, and hydrogen-fired heating systems.

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A central contribution of the thesis consists of the development of a detailed simulation model for a large-scale green hydrogen production system designed to supply a hydrogen-based steel plant. The study considers the case of the Taranto steelworks, one of Europe's largest industrial steel production sites, with an assumed annual production capacity of six million tonnes of steel. Based on process requirements for hydrogen-based direct reduction, electric arc furnace operations, and reheating processes, the annual hydrogen demand of the plant was estimated at approximately 439.2 kilotonnes.

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To satisfy this demand, a renewable energy system based on offshore wind farms located in the Gulf of Taranto was designed and modelled. The analysis employed six years of meteorological data obtained from the Copernicus ERA5 database and considered a reference 15 MW offshore wind turbine model. A detailed wind power production model was developed to estimate hourly electricity generation and evaluate system performance under realistic operating conditions. The simulated offshore wind infrastructure includes multiple wind farms with a total installed capacity of 4.2 GW.

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The renewable electricity generated by the wind farms is converted into hydrogen through PEM electrolysis systems. A detailed electrochemical model was developed in Python to simulate electrolyser performance, including cell voltage, activation losses, ohmic losses, concentration losses, Faraday efficiency, and overall stack efficiency. The model allows the prediction of hydrogen production under variable power conditions and enables optimisation of electrolyser operation in response to fluctuating renewable electricity availability.

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The developed simulation demonstrated that offshore wind generation alone is insufficient to satisfy the continuous hydrogen demand of a large-scale steel plant. The installed wind farms produce approximately 10.1 TWh of electricity annually, enabling the generation of around 171.7 kilotonnes of green hydrogen. Consequently, additional electricity supplied from the national grid becomes necessary to ensure continuous hydrogen production. The integrated wind-plus-grid configuration allows annual hydrogen production of approximately 440 kilotonnes, effectively covering the entire hydrogen requirement of the steel plant. Under these conditions, approximately 39% of the electrolyser energy demand is supplied by offshore wind generation, while the remaining 61% originates from the electricity grid.

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The techno-economic assessment focuses on the calculation of the Levelised Cost of Hydrogen (LCOH), considering capital expenditures, operating costs, stack replacement requirements, and electricity costs. The results indicate that green hydrogen production remains significantly more expensive than conventional fossil-based hydrogen. Depending on technology cost assumptions, the estimated LCOH ranges from €6.8 to €9.5 per kilogram under 2024 conditions and between €5.9 and €8.1 per kilogram under projected 2030 scenarios. These values demonstrate substantial progress towards cost competitiveness but also highlight the need for policy support mechanisms, financial incentives, and continued technological innovation.

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From an environmental perspective, the study demonstrates the substantial decarbonisation potential of hydrogen-based steelmaking. By replacing conventional BF-BOF processes with hydrogen-powered H₂-DR-EAF routes, annual carbon dioxide emissions could be reduced by approximately 11.4 million tonnes, corresponding to an 87% reduction compared to traditional steel production pathways. These findings confirm that hydrogen-based steelmaking can make a transformative contribution to European climate objectives while supporting industrial sustainability.

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The thesis further discusses the remaining barriers to large-scale deployment of green hydrogen in the steel industry. Key challenges include the high cost of electrolyser technologies, renewable electricity availability, hydrogen transport infrastructure, long-term storage solutions, and material compatibility issues related to hydrogen embrittlement. Potential solutions include stronger public and private investment mechanisms, targeted industrial support policies, development of the European Hydrogen Backbone infrastructure, advancement of hydrogen storage technologies, and potential integration with emerging low-carbon electricity sources such as Small Modular Reactors (SMRs).

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In conclusion, this research demonstrates that hydrogen-based steel production represents one of the most viable pathways for the decarbonisation of the steel sector. Although significant economic and infrastructural challenges remain, the results confirm the technical feasibility of integrating large-scale renewable hydrogen production with modern steelmaking facilities. Projects such as HYDRA provide critical platforms for technological validation and industrial learning, accelerating the transition towards a carbon-neutral steel industry. Achieving this vision will require coordinated efforts across technology development, renewable energy deployment, policy support, infrastructure investment, and industrial collaboration. Nevertheless, green hydrogen has the potential to become a cornerstone of sustainable steel production, contributing significantly to climate change mitigation while ensuring the long-term competitiveness of European industry.