In the competitive offshore wind installation market, contractors like DEME strive to optimize operations. This thesis centers on the optimization of the support vessel fleet composition, which consist of a num- ber of walk to work vessels, and are a crucial part of inter-array cable installation. By fine-tuning this composition, operational expenses can be reduced by 10-20% to current industry practices.
The cable installation process involves a complex set of operations, each necessitating a crew to be present on the foundations. Support vessels play a central role in routing of these crews and their equip- ment to these foundations.This thesis introduces an innovative approach that integrates operational scheduling and crew routing into a single formulation for optimizing the fleet of walk-to-work vessels. This hybrid model combines elements of a continuous-time rich multi-visit multi-period Vehicle Routing Problem with a time-varying Resource Constrained Project Scheduling Problem. It also factors in the substantial impact of weather conditions on offshore operations by accounting for variable weather win- dows in each scheduling period.
The formulated model is rigorously verified and validated to ensure it closely mirrors real-world sup- port vessel behavior. Although it slightly underestimates fuel consumption, this discrepancy is deemed acceptable given its minor role in the overall objective. Sensitivity analyses highlight the critical impor- tance of accurate performance data for the cable laying vessel, which significantly influences the model’s outcomes. However, the model is found to be most effective for modeling a single cable string compris- ing 6-8 turbines, with scalability issues arising when attempting to expand beyond this scope.
A focused case study delves into the impact of various weather conditions and inter-array distances on the optimal vessel composition. The study evaluates two types of walk-to-work vessels, individually and in combination. Results reveal that, under the assumption of zero downtime, the industry norm of chartering cheaper vessels is cost-effective, while the pricier vessel results in a 10% costlier solu- tion. As weather conditions worsen, a composition of costlier vessels proves more cost-effective over the scheduling horizon. Such conditions are to be expected in far offshore locations, especially on the cheaper vessels, which have lower workability limits. The study identifies potential cost reductions of up to 25%, with even marginal downtime conditions yielding 10-20% reductions to the industry standard. Moreover, delays imposed on the cable laying vessel are significantly reduced when utilizing a compo- sition that includes at least as one of the more expensive vessels.
In summary, this thesis establishes a foundation for optimizing support vessels in offshore wind installa- tion. The presented model introduces a novel framework, combining multi-visit routing with time-varying resource scheduling, while considering shared vehicles and coupled routing and scheduling over a multi- period horizon. For regions prone to harsh weather conditions, such as those further offshore and during winter months, it is advised to utilize more expensive vessels that have higher workability limits and bet- ter performance figures. Additionally, there appears to be limited justification for simultaneous use of multiple vessels during the cable installation, as the added costs do not seem to outweigh the marginal improvements in installation duration. Future research should focus on refining solution methods for the proposed formulation and incorporating crew transfer vessels into the fleet composition.

The maritime industry is preparing for a future where human presence is no longer required on board of ships. This will revolutionize the global execution of maritime operations and consequentially introduce unprecedented challenges to the corresponding logistics. This paper presents a non-standard facility location problem (FLP) that arises in the maritime survey industry. The goal is to determine a number of uncapacitated facilities and assign a heterogeneous fleet of both remotely operated vessels and traditional vessels to the located facilities in order to serve the inspection demand of offshore infrastructures such as oil platforms and wind parks. The facilities serve as sites where vessels can refuel and accommodate crew changes. Both current traditional vessels and future uncrewed surface vessels (USVs) are considered in the heterogeneous fleet that respectively combines the distinctive routing behavior of centroid-like hubs and drone-like \textit{one-to-one} trips simultaneously. A mixed-integer linear programming (MILP) model is constructed to determine the optimal harbor locations and the associated vessel fleet size \& mix to perform the inspection demand of North-Sea assets over a multi-period time interval. The simulation results are reported for a real case study commissioned by geo-data company Fugro. The results of the model suggest that the effective establishment of facility locations and corresponding fleet allocation can reduce the total costs and environmental footprint of the survey operations in the North-Sea. This research provides a first piece of reflection regarding MIP problems for remote and autonomous operations in the maritime industry. The research pointed out that the complexity of USV operations in combination with traditional vessels is difficult to capture within an acceptably sparse facility location problem. Finally, this study identifies the stochasticity of inspection operations to be the most promising future contribution to automation research in the maritime industry.

For the shared mobility service providers, it is essential to have an economic operation and therefore, it is necessary to maximise their fleet utilisation. Of influence on the latter is the availability of the spare parts. The topics for which spare part forecasting research is already performed are different in several ways compared to the field of free-floating shared vehicles. The many different users with each different driving skill, wear and tear by operation, events as vandalism and traffic accidents and constantly standing out on the street result in sudden failures of parts. Three different forecast models are presented in this paper. The effect of including demand generating factors in the forecast approach is analysed. The methods show that a better forecast performance can be achieved while including demand generating factors into the analysis. The forecast accuracy can be further improved and some suggestions for improvement are given in the paper.

The demand for renewable energy is growing, due to a growing awareness among people about the effect of burning fossil fuels on the environment. Governments have signed climate agreements and are obliged to decrease their level of exhaust gasses. This change in attitude regarding the environment led to an upcoming market for renewables. A significant part of the demand for renewable energy is covered by the wind industry, both on- and offshore. Especially the offshore wind market holds huge potential, due to stable wind conditions and growth opportunities. A side effect of the evolving industry is that turbines are increasing in size and are being installed in deeper water depths. It is expected that the methods of installation, currently used in the offshore wind market, will no longer be suitable for the installation of new generation turbines. In this research, installation of offshore wind turbine towers using a heavy lift vessel (HLV) is opted as an alternative to the current installation methods (jack-up installation). The major benefits of floating installation, when compared to jack-up installation, are the independency on both soil conditions and jacking operations. A challenge of floating installation, however, is the introduction of vessel motions resulting in excitation of the tower. The main objective of this research is to find the most efficient way to control the motions of the tower during installation using a HLV. To fulfill this objective, first, a conceptual design study has been conducted, which focused on developing concepts for the safe installation of offshore wind turbine towers using a HLV. Safe installation was assumed if the displacements of the tower bottom maintain within limits, as specified in a list of design requirements and criteria. Before examining any concept in more detail, the response of the tower and the effect of applying a form of motion compensation has been examined in a general way. To test the response of the tower in the crane in a general way, with and without motion compensation, the tower in the crane has been represented by a double pendulum system with a moving support point. Then, using the numeric model, the response of the tower in the crane has been computed for certain sea-states in both frequency- and time domain and for both the free hanging- and the motion compensated case. The motion compensation system has been represented by a virtual spring damper system, of which, by changing the simulation parameters, the optimal configuration (position, stiffness and damping) has been determined that minimizes the tower response. From the results, it can be concluded that a significant reduction of the tower bottom displacements can be achieved under the application of an active motion compensation system, the requirements for safe installation, however, are not yet fulfilled.

Due to the global climate change there is a increasing demand for transportation on renewable fuels. An increasing trend in electric propulsion can already be seen in the automotive industry and this is now also gaining popularity in the maritime sector. Due to limited capacity if the onboard battery, especially electric ferries are becoming more popular, because of the relative short sailing distances. The first electric ferry became operational in 2015 in Norway and since than a hand full of electric vessels was developed. An electric vessel requires a charging mechanism to charge while unloading and loading passengers in the port. Besides, generally also a mooring mechanism is necessary. This enables the vessel to turn off the propeller while charging which limits the energy demand while charging. Various systems have been developed already. However, these are not standardized solutions but all one of a kind systems designed for a specific vessel or fleet. Which of these is the best solution is not easy to determine and strongly depends on the vessel characteristics and the operating environment. To supply the expected increasing demand for electric vessels, a guideline is developed which will help the engineer to find a suitable charging and mooring mechanism and to decrease the selection time for this system. The will provide Damen a strategic advantage towards other shipyards in vessel tenders since both the development costs and delivery time is lower.
This guideline is developed based on the knowledge gained during a case study for a 81m Ropax ferry, sailing in the surroundings of Vancouver Island. For the case study an engineering design method was selected from literature and applied to this case, for which Damen had a hard time finding a charging and mooring mechanism. First thought was to combine both into one mechanism, but this is difficult due to conflicting functionalities of both systems. Due to the limited time available for the research, the design of the mooring mechanism is not taken into account for the case study. Setting the requirements for the charging mechanism is complex due to the range of different fields of interest that should be taken into account. However, the requirements of these various aspects are often related in some way to one another. This makes it easy to lose sight of the structure of all requirements. Comparing the functions that the charging mechanism should fulfill within these requirements and the existing charging mechanisms, it can be concluded that no suitable system is available yet. The gap between these is defined as a set of three functions; to compensate the tidal difference, deal with misalignments between the vessel and the shore and to provide flexibility for vessel motions. A new design was made which covers this gap. Additional research was done to ensure sufficient flexibility from the power cable, since this proved to be critical in the state of the art systems.
From the knowledge gained during this case study, the guideline is developed. The guideline provides insight in the influential factors while selecting an mechanism. This should offer the engineer a structure to set the requirements and ensures that no aspect is left out of the requirements. An overview with the already existing mechanisms is provided which should be consulted multiple times during the process, to check whether a suitable systems exist, if the requirements should are too tight or if the project is not profitable at all. The structure of the requirements is designed such, that the relative easy requirements are set first. This prevents from doing demanding calculations or going on expensive business trips, while it could have been seen earlier that a project is not feasible or profitable at least. The guideline is validated while selecting a charging mechanism for a different type of vessel. This validation proved to decrease the selection time for a charging mechanism significantly compared to previous projects within Damen. After the test, a charging system was found which is preferred for the vessel. This charger is now further discussed with the supplier of the system.

Wind power is the fastest-growing energy source and the offshore wind industry is expected to grow by over 80 GW through 2024. There is a need to reduce all associated costs to be competitive in a market that might be fully subsidy-free soon. Adapting a predictive or condition-based maintenance strategy can help in reducing O&M costs, as it accounts for more than 30% of the lifetime costs in offshore turbines.This master thesis focuses on developing a novel gearbox condition monitoring technique using raw Supervisory Control And Data Acquisition (SCADA) data from an offshore wind farm. The developed approach attempts to leverage the use of physics of failure technique and artificial neural network models for continuous monitoring of gearbox condition. Utilizing SCADA data for monitoring and fault detection can help in eliminating retrofitting additional expensive sensors such as an online oil monitoring system, vibration monitoring systems and so on for the same purpose.Firstly, a physics of failure methodology is implemented to monitor turbines on a farm level. Using Failure Mode, Effects Analysis (FMEA), the operating regimes under which gears and bearings can potentially get damaged are ascertained. A correlation between the damage operating conditions and the root cause of failure is analyzed using boxplots. In particular, a correlation between operating conditions and, the unusual and unexplained White Etching Cracks or axial cracking failure that occur frequently in the high-speed shaft bearings is studied. Additionally, this methodology is also used to complement the Artificial Neural Network model developed for anomaly detection.Finally, an Artificial Neural Network (ANN) based on a Recurrent Neural Network (RNN) is developed for fault detection. The model is trained on data when the turbine was operating normally, to predict gear bearing and gearbox lubrication oil temperatures. A stacked Gated Recurrent Unit (GRU), a type of RNN model with two hidden layers resulted in predictions with the lowest mean squared error (0.14640퐶) and with good generalization. The difference/residual between the measured and ANN predicted temperatures are used to flag anomalies. The ANN-based condition monitoring method is validated through case studies using real data from wind turbines. The results from the case studies indicate that the RNNbased fault detection method can detect a failure in the wind turbine gearbox components as early as 3-6 months before it fails.