Requirements Evaluation for the Implementation of Offshore Electrolysers in Green Hydrogen Production: An Approach for the Marine Industry

Abstract

The marine industry is increasingly evaluating offshore green hydrogen production as a pathway to decarbonize key energy-intensive sectors. However, offshore electrolysers face unique technical, economic, and operational challenges that require adaptation to withstand harsh marine conditions. This thesis evaluates the requirements, feasibility, and techno-economic performance of integrating offshore electrolysis and wind resources. It combines a comprehensive state-of-the-art of electrolyser technologies and floating offshore foundations with a European case study and a techno-economic framework. The state-of-the-art identifies key strengths and limitations of the main types of electrolysis technologies, as well as the current market trends and gaps of floating platforms concepts, connection schemes, demonstration projects, and regulatory frameworks. It highlights that PEM offers the greatest offshore readiness due to its compactness, pressurized hydrogen output, low minimum load, and fast dynamic response despite its reliance on precious metals. The case study applies a multi-criteria site-selection which identified Viana do Castelo as the optimal Atlantic location for a 500 MW offshore hydrogen project. It is based according to market demand, infrastructure and resource availability for the 3 configuration schemes considered. Experimental testing and hydrodynamic modelling of a semi-submersible platform with PEM modules confirm an acceptable performance under marine motions with mitigation and operational strategies, including ramping controls, buffering, marine-grade protection, and integrated water treatment. Finally, a techno-economic evaluation estimates LCOH of 4.00 €/kg for centralized onshore, 4.57 €/kg for centralized offshore, and 4.82 €/kg for decentralized offshore electrolysis at the case study site. A sensitivity analysis shows that wind availability appears as the dominant cost driver. Export distances over ~120 km favor HVDC or hydrogen pipelines due to electrical losses in HVAC, while port distance increase O&M significantly until SOVs become viable at ~150 km. Water depth does not influence results significantly for the deep-water range considered. Centralized onshore electrolysis remains the most cost-effective for near-shore sites with strong wind and proximity to shore, while offshore configurations gain advantage when long export distances or space limitations occur.