Electro-fuels (E-fuels) are a potential zero-carbon fuel option, that are able to reduce emissions from the marine sector. However, e-fuels still face several challenges, as currently, their production costs are high, and the implementation
of e-fuels in the marine sector is still in a research and development phase. Therefore, this study focuses on the impact that implementing an e-fuel has for both the vessel and vessel owner, from a techno-economic perspective. Since this research is performed at Heerema Marine Contractors (HMC), the focus is on large offshore construction vessels.
Through findings obtained from literature research and a case study, a general indication is obtained regarding the impact of implementing an e-fuel on a large offshore vessel. Several KPIs are defined to quantify and evaluate this impact by
comparing them to a fossil base case.

Environmental and operational challenges associated with an excessive fuel consumption have led to the need for future naval vessels to be less dependent on fossil fuels. The chosen configuration is combined diesel-electric and diesel (CODLAD). However, there is a performance gap regarding the manoeuvrability between the previously implemented gas-turbine propulsion and the diesel-electric hybrid propulsion. In order to reduce this performance gap between a gas-turbine propulsion system and a diesel-eclectic propulsion system a new optimized control system needs to be developed.
Adaptive pitch control avoids the angle of attack peak, reducing the torque peak that can potentially overload the diesel engine. Adaptive pitch control is the only control strategy that operates at a low angle of attack, and therefore is less perceptible for cavitation. However this peak in angle of attack is responsible for the peak in thrust. Adaptive pitch control therefore needs large shaft speed fluctuations to be able to create a large thrust. Adaptive pitch control is therefore either slow or forces the diesel engine to rapidly make large changes in its shaft speed. The rapid changes in shaft speed could increase the amount of wear inside the engine, reducing the time between maintenance.
During the simulations torque control for the diesel engine performs extremely well during acceleration. Using torque control for the diesel engine the static power distribution of the propeller load was varied. During these variations it was concluded that a large acceleration can be achieved with a heavy loading on the diesel engine in steady state, supported by a large torque production during acceleration by the induction machine. A heavy matching of the diesel engine was possible because the diesel engine only produced the power needed for the steady state propeller power as matched via the combinator. The induction machine is made responsible for keeping the speed and coping with disturbances. The induction machine is inherently more suited than the diesel engine, due to its fast response as well as it being able to produce full torque or maximum power without any negative adverse effects. However torque control is not available from manufacturers.
This research includes a novel implementation of a dynamic power split, which produced very promising results. The dynamic power split uses the diesel engine with speed control parallel with the electric drive in dynamic torque control. The dynamic torque control for the induction machine allow for optimal usage of the inherent characteristics of the electrical machine. Using dynamic torque control the induction machine is responsible for the high frequency load changes such as disturbances as well as the first part of the acceleration. The diesel engine governed by a slower integral dominated PI controller accounts for the low frequency load changes, including the higher load at a new steady sate. The diesel engine with speed control parallel with the electric drive in dynamic torque control produces excellent acceleration characteristics, making it a viable option to improve the acceleration characteristics of a diesel-electric hybrid system.

The swift reduction of human’s carbon footprint is essential to prevent irreversible damage to the climate and to meet climate policy targets. Designing flexible and reliable future energy systems is a big contributor to meeting these goals. While energy system models have improved in the last few decades, they remain vulnerable against parametric and structural uncertainty due to the varying characteristics of parameters and the hardship of modelling all constraints and drivers accurately. This thesis proposes a method that addresses both uncertainty types in energy system modelling by applying SPORES cost optimisation and Monte Carlo scenario modelling simultaneously.

The main case study uses 27 input scenarios with varying outcomes for grid electricity price, solar yield and energy consumption to provide insight in a 100 household neighbourhood energy system with heating, cooling, electricity and hydrogen as energy carriers. With 1377 (near-)optimal solutions, a novel approach in analysis and post processing is used to provide 52 useful configuration options that each have their strengths and weaknesses to different political, economical, social and technical drivers. These configurations are tested for cost, security of supply, CO2 emissions and grid dependency. Those results are visualised through ridge plots and statistical tables to provide a clear overview between each configuration’s trade-offs. An example is included to show how those results can be used for improving energy system design in practice.

This thesis shows that two methods can successfully be combined into one universal one, while providing valuable design insights for energy systems under uncertainty. Furthermore, this method can be applied to a wide variety of energy systems, as long as its possible components, their technical aspects and their allowed interactions are known beforehand. As many future energy system aspects are uncertain, it should be seen as a vital tool to help speed up the decarbonization.

The Autonomous Low Energy Replenishment Dredger (ALERD) strives to revolutionize the dredging world. The ALERD operates autonomously underwater, which saves energy during the dredging process and transit. Autonomous underwater operation drives the need of alternative energy facilities. However, due to the energy savings of dredging, alternative energy supplies are possible. A wish of C-Job is that the ALERD operates with zero emissions, and therefore the system should comply with it as well. This introduces the research goal: Devising a sustainable electrical energy supply for ALERD. An additional challenge to the research goal is that the dimensions are not yet established and are still an open question in the research.
The simulation model uses the calculated electric load balance of the Autonomous Underwater Maintenance Dredger (AUMD) and scaling to determine the power balance of the ALERD over various hopper volumes. Furthermore, the operational area has been studied to determine charging/bunker locations and distances. The project requires an annual sedimentation of 12 million m³, including foreshore and coastal replenishment.
To determine the best system, a literature review was done towards the systems. Two key systems came out as the best systems for autonomous and sustainable operation: The Li-ion battery and the Proton Exchange Membrane Fuel Cell (PEMFC). The systems have very different characteristics. Typically, batteries have high costs for the energy storage and fuel cells costs are determined by the nominal power output.
The abovementioned systems were both used in a simulated operational profile of the ALERD. Results from the simulation, suggests that the battery has the optimal performance at 2-3 times dredging per energy cycle, where 4-9 times are the optima for the Hybrid solution. When both systems have charging/bunker stations near the operational area, a dredging cost of €*** per m³ can be achieved for both systems. However, when the ship is charging/bunkering in the port, the costs per m³ increase with €*** for the hybrid and €*** for the battery powered ALERD. This results in a maximal investment of €** million for a local charging/bunker station, to be economically feasible. By making these stations accessible for other purposes, profit can be taken to recoup the investment. It is however expected, that these local stations will not be feasible for the first generation of ALERDs.
When cost development is taken into account, the Total Cost of Ownership (TCO) prefers the hybrid system. Which is a result from the sharply decreasing hydrogen and fuel cell costs. The system also achieves a lower TCO than a conventional dredger, in a manageable time.
A (near) future orientated system has also been considered, the direct-fed ammonia Solid Oxide Fuel Cell (SOFC). It has comparable costs per cubic metre for port bunkering as the other systems, when they are locally charging/bunkering. Furthermore, there are a lot of practical advantages by the use of ammonia instead of hydrogen as fuel. This consists of better fuel handling and easier storage.
Together with the benefits of taking more energy inside the ALERD, it is believed that the hybrid types of ALERD have the best characteristics for coastal maintenance. It depends on the developments of the ammonia SOFC, if it is ready to supply energy to the ALERD, or that the hydrogen PEMFC is the best solution in a hybrid design. Furthermore, the decision depends on the results of the weight and stability study, which is still ongoing. The results could eliminate a systems by its volume or weight. Due to the reserved space and freedom in the ship design, this is however not expected.