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 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.

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.

Ammonia fuel has been widely considered as an attractive solution for reducing the green house gas emissions over recent years. Adapting ammonia as fuel on ships would highly reduce the carbon footprint of international shipping and off-shore transportation. Among the different systems currently under development for carbon-free power production in the near future, the combined-cycle gas turbine system stands out for its relatively high system efficiency and a potential for running on pure ammonia fuel while maintaining a low level of NOx emission. This thesis project puts a sight on a special design of this type of COGAS power system and tries to adapt it for maritime usage onboard future ships. Previous researches have pointed out the key design features of the ammonia COGAS power system being running under a high fuel-air ratio with a cooling method based on EGR technology and cracking the additional ammonia fuel into hydrogen in the gas turbine system, then this created hydrogen concentration could be used for re-heating the exhaust before it is used by the combined steam cycle. However, current understanding of this type of COGAS system is still limited under static analysis and designed working points. This thesis project tries to provide a basic view on the off-design performance and dynamic behaviors of this COGAS system, and examines if this system is still able to maintain a low level NOx emission under such working conditions. This thesis project combines a dynamic model of an ammonia gas turbine and a chemical thermodynamic model for simulating the chemical behavior of the work fluid inside the gas turbine system. It is found that the fuel-air equivalence ratio of the gas turbine needs to be designed at a high value to ensure the flammability of the hydrogen consisting exhaust in the re-heating process. A very low NOx emission is observed in the gas turbine exhaust under an assumption of complete chemical reactions. The final NOx emission of the COGAS system is found to be within the EEDI Tier III limitation under both rated and part-load working conditions. The thermal efficiency of the gas turbine is relatively low due to the high equivalence ratio, while a system efficiency comparable with current oil-fueled COGAS power system is able to be expected for the full system of ammonia COGAS. On the phase of dynamic analysis, this project has concluded that traditional fuel control method for controlling gas turbine power generation is not adaptable to gas turbine systems working at fuel-rich conditions. A non-linear behavior is observed due to this high equivalence ratio. This thesis provides a new controlling method with controlling both the fuel injection ratio and the EGR ratio with an additional feedback controlling system attached to the original feed-forward system of the fuel control. Basic tests shows that such method is able to generate a dynamic output with the correct tendency. This thesis project also observes a high sensitivity of NOx emission with the presence of additional oxygen in the exhaust under a complete chemical reaction. In this thesis project it is found that the considered ammonia COGAS system maintains the advantage of traditional COGAS power systems and a is able to take an advantage in comparing with medium-speed diesel systems under an ammonia economy. Power output of the ammonia gas turbine is able to be controlled with a combination of fuel control and EGR control. A low NOx emission within the limit of EEDI Tier III is observed under both rated and part-loading conditions of the power system, but this is achieved with the assumption of a complete chemical reaction. Whether this assumption is adaptable to maritime scaled ammonia gas turbine system requires further kinetic analysis on the combustion process and further research efforts in the designing of the combustor system.