No abstract

The shipping industry has been facing great pressure to become more sustainable, emanating from the increasingly stringent environmental regulations, fuel prices volatility and societal needs. As a result, a variety of established technologies have been developed aiming to improve the environmental and economic performance of the modern ship energy systems, however leading to additional challenges for the technology selection during the design process. This study introduces an innovative method that integrates the economic and environmental aspects of sustainability to support decisions on the synthesis of the modern ship energy systems. The method includes a simulation model for predicting the energy systems performance during the ship lifetime. A genetic algorithm, NSGA-II, is employed to solve the multi-objective combinatorial optimisation problem of selecting the integrated ship energy systems configuration. The derived results are visualised to reveal the Pareto front and the trade-offs among the objectives. The method is novel in supporting the synthesis of the integrated ship energy systems, as it includes both environmental and economic objectives, as well as evaluates the performance of the systems over an expected operational profile. The developed method is implemented for the case study of an Aframax oil tanker and the derived results analysis indicates that the ship energy systems sustainability can be improved by adopting LNG fuel and dual fuel engines technology, as well as by introducing other emerging technologies like fuel cells and carbon capture, although the latter are associated with a high cost. It is concluded that the inclusion of both environmental and economic objectives highlights the trade-offs between more environmentally friendly or cost efficient configurations, thus supporting the multi-objective decision-making process.

In April 2018, the International Maritime Organisation adopted an ambitious plan to contribute to the global efforts to reduce the Greenhouse Gas emissions, as set by the Paris Agreement, by targeting a 50% reduction in shipping’s Green House Gas emissions by 2050, benchmarked to 2008 levels. To meet these challenging goals, the maritime industry must introduce environmentally friendly fuels with negligible, or low SOX, NOX and CO2 emissions. Ammonia use in maritime applications is considered promising, due to its high energy density, low flammability, easy storage and low production cost. Moreover, ammonia can be used as fuel in a variety of propulsors such as fuel cells and can be produced from renewable sources. As a result, ammonia can be used as a versatile marine fuel, exploiting the existing infrastructure, and having zero SOX and CO2 emissions. However, there are several challenges to overcome for ammonia to become a compelling fuel towards the decarbonisation of shipping. Such factors include the selection of the appropriate ammonia-fuelled power generator, the selection of the appropriate system safety assessment tool, and mitigating measures to address the hazards of ammonia. This paper discusses the state-of-the-art of ammonia fuelled fuel cells for marine applications and presents their potential, and challenges.

The shipping industry has been facing increasing challenges due to the stringent regulations for anthropogenic emissions limits, the new targets for carbon emissions reduction and the potential carbon pricing introduction. These have led to an upsurge of activities towards improving the environmental footprint of cruise ships. This study investigates the impact of carbon pricing on the cruise ships optimal power plant configuration. Mathematical models are used to estimate the performance of the cruise ship energy systems. A novel bi-objective optimisation method for the cruise ship energy systems synthesis is developed, which employs the Non-Sorting Genetic Algorithm II optimisation algorithm and uses as objectives the Life Cycle Cost and the lifetime carbon emissions. Cruise ship configurations that perform optimally under carbon pricing scenarios while complying with the air emissions regulations are identified. The results show that the baseline configuration does not belong to the optimal solutions. Solutions including carbon capture, waste heat recovery and dual fuel generator sets that operate with natural gas or methanol can reduce drastically the carbon emissions. The optimisation identified solutions that reduce the Life Cycle Cost by 40% compared to the baseline configuration despite increasing their capital cost, whilst reducing of the carbon emissions more than 37%.

The stringent regulatory framework for the emissions and safety from shipping operations as well as the market pressure to reduce the operational costs has led the cruise ship industry to pursue and investigate alternative solutions for both the new-built and the existing ships by using multi-objective optimisation methods. This study aims at investigating and comparatively analysing the optimal power plant solutions for different fuel types for an existing cruise ship by employing cost, emissions and safety objectives in a lifecycle basis. For this purpose, a bi-objective optimisation method is employed to identify optimal power plant configurations of a modern cruise ship considering the actual ship operational profile and several energy system design parameters. In subsequence, availability and the blackout event frequency were estimated using availability formulas and the Combinatorial Approach for Safety Assessment. The results demonstrate that the cruise ship power plant optimal configurations with dual fuel engines operating with natural gas exhibit lower lifecycle cost and lifetime emissions, whilst demonstrating a level of the systems safety comparable to the baseline power plant configuration. Furthermore, it is concluded that an increase in the generator sets redundancy does not necessary result in a considerable improvement of the power plant safety performance.