The application of newly available technologies in the green maritime sector is difficult due to conflicting requirements and the inter-relation of different ecological, technological and economical parameters. The governments incentivize radical reductions in harmful emissions as an overall priority. If the politics do not change, the continuous implementation of stricter government regulations for reducing emissions will eventually result in the mandatory use of, what we currently consider, alternative fuels. Immediate application of radically different strategies would significantly increase the economic costs of maritime transport, thus jeopardizing its greatest benefit: the transport of massive quantities of freight at the lowest cost. Increased maritime transport costs would immediately disrupt the global economy, as seen recently during the COVID-19 pandemic. For this reason, the industry has shifted towards a gradual decrease in emissions through the implementation of “better” transitional solutions until alternative fuels eventually become low-cost fuels. Since this topic is very broad and interdisciplinary, our systematic overview gives insight into the state-of-the-art available technologies in green maritime transport with a focus on the following subjects: (i) alternative fuels; (ii) hybrid propulsion systems and hydrogen technologies; (iii) the benefits of digitalization in the maritime sector aimed at increasing vessel efficiency; (iv) hull drag reduction technologies; and (v) carbon capture technologies. This paper outlines the challenges, advantages and disadvantages of their implementation. The results of this analysis elucidate the current technologies’ readiness levels and their expected development over the coming years.

In this study, a newly developed zero-dimensional electrochemical model was used for modeling and controlling proton-exchange membrane fuel cell (PEMFC) performance. Calibration of the model was performed with measurements from the fuel cell stack. Subsequently, a compressor and a humidifier on the cathode side were sized and added to the existing model. The aim of this work was to model the PEMFC stack and balance of plant (BoP) components in detail to show the influence of operating parameters such as cathode pressure, stack temperature and cathode stoichiometric ratio on the performance and efficiency of the overall system compared to the original model using a newly developed real-time model. The model managed to predict the profile of essential parameters, such as temperature, pressure, power, voltage, etc. The most important conclusions from this particular case are: the cell power output is only slightly changed with the variations in stoichiometric ratio of the cathode side and adding an external compressor is valid only for high current applications, but in those cases, there is 10–22% power gain. Stack temperature is a very influential parameter. Optimal temperatures were determined through design of experiments (DoE) and for this case are in the 40–60 °C range, where for low current applications lower temperatures are better due lower activation loss (8% difference between 80 °C and 40 °C at 20 A current). For high current applications, due to lower ohmic losses, higher temperatures are desirable.

The latest electronically controlled marine engines have a control system that allows the operator to view all the essential parameters of the engine in real conditions during operation. The system is connected to the electronic control system (ECS) through the control network, thus controlling the engine. The operator has various management and monitoring options. The objective of this paper was to become familiar with the specific factors that affect engine operation and optimize engine operation. A model of a large marine engine was developed and calibrated with measured data. Simulations were performed, and the combustion process was analyzed. The parameter study was performed by varying the fuel injection and the gas exchange timing. Fuel consumption decreases by 6 g/kWh, and NOx emissions decrease by 0.5 g/kWh. The research conducted in this work will be used by engineers to understand the potential of new technologies to optimize combustion in real-world conditions during operation and for the future development of an expert system to continuously monitor, diagnose, and optimize engine health during operation.

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