STRUCTURAL ANALYSIS OF CARBON STEEL PIPELINES FOR HYDROGEN OFFSHORE TRANSPORTATION: STATE OF THE ART AND CASE STUDY

The transition to a low-carbon energy system is one of the most pressing challenges facing Europe today. As part of the European Union's broader climate goals, reducing greenhouse gas emissions to net-zero by 2050, the focus on alternative energy sources has intensified. Offshore renewable energy, particularly in the form of hydrogen, has emerged as a key component of this strategy, offering both a means to harness Europe’s vast offshore wind potential and a versatile energy carrier that can be stored, transported, and utilized across various sectors. This thesis explores the technical and strategic aspects of developing offshore hydrogen infrastructure, with a specific focus on pipeline design and transportation challenges. Beginning with an examination of Europe’s offshore energy frontier, the study delves into the current and future hydrogen demand, the EU's hydrogen strategy, and the strategic importance of hydrogen production within the continent. It emphasizes the need for a robust hydrogen network, highlighting the differences in design criteria between natural gas and hydrogen pipelines, as well as between offshore and onshore infrastructure. The core of the thesis, though, delves into critical technical considerations for designing offshore pipelines specifically tailored for hydrogen transportation. The second chapter begins indeed with a general analysis of pipeline sizing, which is essential for ensuring that pipelines can efficiently and safely carry gas, hydrogen or a blend across long distances under the seabed. The study explores various failure modes that could compromise pipeline integrity, such as bursting, collapse, and local buckling. Understanding these potential failure scenarios is vital for designing pipelines that can withstand the unique pressures and environmental conditions found offshore. In addition to these factors, the thesis also addresses free span analysis, which examines the behavior of pipeline sections that are unsupported by the seabed. Spans can be vulnerable to fatigue and other stress-related issues, making their analysis crucial for ensuring the long-term durability and reliability of the pipeline. By thoroughly investigating these aspects, the thesis provides a comprehensive framework for the design of offshore pipelines, helping to mitigate risks and optimize performance in hydrogen transportation. The third chapter provides a detailed examination of the unique challenges associated with hydrogen transportation, including hydrogen embrittlement and its effects on material properties. The analysis further addresses the existing standards and codes relevant to hydrogen pipelines, evaluating their applicability and suggesting revisions where necessary. Finally, the thesis presents a case study on the structural analysis of an offshore pipeline subjected to free span. Static, dynamic, and fatigue analyses are performed to assess the feasibility and safety of both gas and hydrogen transportation in offshore environments. Through this comprehensive study, the thesis aims to contribute to the understanding of offshore hydrogen infrastructure development, offering insights that are crucial for the successful integration of hydrogen into Europe's future energy mix.