Most Suitable Future-Proof Energy Supply for a New-Build Semi-Submersible Crane Vessel

Abstract

Currently, our society faces a pressing challenge: global warming. The solution lies in the energy transition, which replaces fossil fuels with clean sources. This requires a global effort across all sectors, including shipping. While a significant portion of shipping relies on polluting fuels, the European Union’s Green Deal aims for climate neutrality by 2050, which applies to shipping as well. Emission reduction technology and low-to-zero emission energy supplies are emerging, yet choosing the right energy supply for new vessels remains complex, especially in meeting EU targets.
This study focuses on supporting the decision-making process for the energy supply of a new Semi-Submersible Crane Vessel (SSCV). The method facilitates a comprehensive comparison of energy supply options using multiple criteria. It also integrates decision-makers’ preferences with the characteristics of alternative energy supplies, providing insights into the most suitable choice. This research features a case study centered on Heerema Marine Contractors’ SSCV Sleipnir.
To create this method, a literature review on Multi-Criteria Decision Making (MCDM) methods was conducted. The Analytic Hierarchy Process (AHP) model was chosen as the foundational framework for the decision-making tool. During the research key limitations and requirements for designing an energy supply for a SSCV were identified. Furthermore, the research contains an examination of various fossil and sustainable fuels, including Marine Gas Oil (MGO), (E-)Liquefied Natural Gas ((E-)LNG), EHydrogen, E-Methanol, E-Ammonia, Uranium, and Thorium. Additionally, the study considers diverse energy conversion systems including Internal Combustion Engines (ICE), Proton Exchange Membrane Fuel Cells (PEMFC), Solid Oxide Fuel Cells (SOFC), Direct Methanol Fuel Cells (DMFC), Molten Salt Reactors (MSR), and Very High-Temperature Reactors (VHTR). A set of significant criteria are identified and the accompanying characteristics of the energy supplies regarding these criteria are gathered. The literature research is followed by a financial assessment. This assessment shows that the financial impact of fossil- and e-fuel energy supplies is highly dominated by Operational Expenditure (OPEX), while the nuclear energy supplies are highly dominated by its Capital Expenditures (CAPEX).
The preferences of Heerema’s decision-makers are collected via a survey, revealing that the Technological Readiness Level (TRL) of the system, health risk, emissions, Levelized Cost Of Energy (LCOE), maintenance requirements, and efficiency of the conversion system are found to be the most important criteria according to the survey results. The preference weights assigned to the criteria are integrated with the energy supply characteristics, providing a score that indicates the suitability of each energy supply considering the SSCV’s limits and requirements, aligned with the preferences of the decision-maker. Hence, the optimal energy supply choice can be deduced from this data.
Although the fossil fuel MGO is included to act as a base-case scenario during this case study, the results of the method show that MGO used in an ICE would be the best-suiting energy supply according to the preferences of the decision-makers. Since MGO energy supplies are assumed to be non-compliant with the EU-emission goals they are excluded. When excluding MGO from the results, methanol used in an ICE is identified as the best-suiting alternative. This can be attributed to its relatively high TRL, favorable overall characteristics, and absence of significantly low scores regarding the criteria assigned high priority by the decision-makers, in comparison to other energy supplies.
However, the validity of the presented results is reduced due to several factors. These include the reliance on assumptions about alternative energy supplies, a limited number of interviewees, and the sensitivity to uncertainties about future developments. Nevertheless, this study shows that the use of this method can provide insights into complex decision problems regarding future energy supply choices. Also, the study identifies a range of attractive energy supplies, with methanol used in an ICE ranked as the most suitable option. These high-ranking energy supplies can be an interesting subject for further studies.