The maritime industry is progressively transitioning towards sustainable practices, with a significant focus on integrating zero-emission power generation systems. However alternative fuels and technologies implementation on large scale is still pending.
Ships and especially yachts today are designed just for their immediate needs with no future consideration taken into account. This thesis addresses the need for adaptable power room designs in superyachts, facilitating the integration of zero-emission power generation systems as technology evolves. The primary aim is to develop a design method enabling easy retrofitting and future-proofing of yacht power rooms.
The research identifies the current design methods limitation where power rooms are designed for specific scenarios without considering future adaptability. To address this gap, the thesis proposes a three-step design method: layout concepts, design rationale, and a layout evaluation model. This model evaluates power room layouts based on Connection Costs and Retrofit Costs, offering indicators to assess future-proofing capabilities of power rooms arrangements.
A future-proof road-map based on four different scenarios was identified. By applying the design method to these scenarios, various layout concepts were developed, refined based on expert opinions and then evaluated with the model. The results highlight key practices for future-proofing power rooms, such as prioritizing connections between zero emissions power generation systems and auxiliary systems, pre-arranging transport equipment, and designing access openings to facilitate easy retrofitting.
This research underscores the need for a flexible approach to power room design, ensuring superyachts can transition smoothly to zero-emission operations in the coming years.

For many shipbuilders, the majority of a vessel's lifecycle greenhouse gas emissions occurs during its operational phase, commonly referred to as downstream emissions. For Feadship, this challenge is particularly pronounced, with downstream emissions accounting for 94% of a superyacht’s carbon footprint. Addressing this majority requires accurate and efficient methods to predict propulsion energy use during the design stage - a task hindered by the limitations of existing prediction methods, which are either time-intensive or prone to significant errors. This is affecting the design process in two ways: an increased risk of incorrectly proportioned energy and power systems, and limited exploration of design space. Data-driven methods, based on machine learning algorithms, have been proposed in the literature. However, these methods expose two key gaps in the literature: their performance under extrapolation conditions and their limitations when applied to small datasets.

This thesis addresses these challenges by developing hybrid modeling approaches that combine physical insights through a physical model with data-driven techniques, enabling improved predictive accuracy under extrapolation scenarios and with small datasets. Three modeling approaches are tested - physical models (PMs), data-driven models (DDMs), and a combination of the two that forms hybrid models (HMs) - with a shared prediction target, namely calm-water ship resistance. Four datasets were assessed: Dataset 1 (CFD resistance), Dataset 2 (CFD power), Dataset 3 (towing tank tests), and Dataset 4 (speed-power trials), resulting in the selection of computational fluid dynamics (CFD) resistance data as the basis for training the models.

Instead of directly learning from the CFD resistance data, it appears more effective when the data-driven model learns to apply corrections to the output of a PM. Where traditionally these corrections were based on the naval architect's experience, they are now driven by data, offering fast and accurate alternative to existing methods. This philosophy is embodied in this study through a newly developed parallel HM, which achieves superior performance by learning how to apply these corrections to the PM's output automatically. During interpolation, the new HM demonstrates a mean average percentage error (MAPE) of 3.8%, outperforming the best available PM (6.7%) and the best DDM (8.9%). For extrapolation, standalone DDMs, including the best interpolator, failed dramatically, with MAPE values exceeding 180% in some cases. The new HM maintains average errors within 12% across scenarios. And with less data, the new HM consistently outperformed the best DDM, with its competitive edge most pronounced at low data availability (10% of CFD observations). By advancing these methodologies, the study not only enhances early-stage design confidence but also contributes to future steps towards automated design optimization.

In the yachting decarbonisation by 2030, multiple fuels usage provides flexibility to ocean-crossing superyachts in a scenario where alternative fuels become progressively available worldwide. Hydrotreated vegetable oil (HVO) and methanol (MeOH) are selected among all sustainable fuels. The desired flexibility can be achieved with a multi-fuel system. To make optimal use of the tanks' capacity, HVO and methanol are alternately stored in all tanks, yielding mutual fuels’ contamination. The lack of standards and research on accepted fuels impurity makes full fuels separation relevant to be explored to avoid performance degradation of dual-fuel engines. Identified technologies for separating HVO-methanol mixtures are gravity-settling tanks and disc-bowl centrifuges. Shake tests were conducted on HVO-MeOH mixtures to quantify the separation time and relative concentrations to obtain complete gravity separation. The fuels were poured into a beaker with methanol at 1, 5, 10-70% v/v. Visual and microscopic examinations identified MeOH traces in HVO. The tests revealed that full separation was not achieved in the 1 hour-3 days observation time, due to the low-density difference between the fuels. Hence, as the experimental outcomes evidenced incomplete HVO-methanol separation, centrifuges were studied to achieve this goal. A mathematical model was developed for disc-bowl centrifuges to assess the separator performance and separation time. Integration with a multi-fuel system helped size the centrifuge by providing the separator working conditions for varying engine modes. Complete separation is theoretically possible with a separator larger than the existing disc-bowl designs, due to the low-density difference between methanol and HVO. The maximum separation time ranges 5-10 minutes for MeOH droplets ranging 12-16 µm in diameter. Droplets with a diameter outside this range coalesce quasi-instantaneously. Lastly, when integrating the centrifuge within the multi-fuel system, HVO and MeOH buffer tanks are needed onboard, respectively with about 1/3 and 1/20 of the storage tanks' capacity.

Superyachts are large emitters of greenhouse gases, as well as other emissions such as NO_x, SO_x and PM. In order to meet the climate goals set by the IMO, to reduce GHG emissions by 50% in 2050, alternative fuels are being investigated. Methanol is an alternative fuels with great potential. Methanol can be produced completely carbon neutral from biomass or captured CO₂, contains no sulphur, can be stored in liquid form at atmospheric pressure and temperature and can be used in both fuel cells and combustion engines. There are currently no yachts sailing on methanol but methanol has already been implemented in several other ships. Both yacht builders and owners show interest in the implementation of methanol. Since it is unclear which alternative fuel will become the standard on the long term in the yachting industry, it is of interest to also investigate the impact over a longer period of time or of several pathways. Previous research is limited to emissions and costs related to alternative fuels on a limited range of ship types which do not include yachts. The impact of methanol on the design, emissions and costs is still largely unknown for yachts. In order to determine this impact, the properties of methanol, rules & regulations regarding methanol, design impact of the storage of methanol, environmental impact of using methanol and the impact on costs are investigated. To determine this impact for several yachts, a tool has been developed which can be used from the early design stages. The tool uses the properties of a yacht to determine power and fuel volume requirements for the implementation of methanol. It also determines the available volume in the yacht for methanol storage in a basic tank arrangement. Together these form the properties of the yacht with the implementation of methanol. From these properties, the emissions and costs are determined and then combined in a pathway analysis to determine differences in impact of several future pathways. The results show that using methanol generally has a positive impact on emissions, compared to a diesel yacht. Methanol offers SO_x free emissions, a reduction of PM emissions and NO_x emissions equal to that of diesel without the necessity of after treatment. CO₂ emissions slightly increase with fossil methanol but can be net zero with renewable methanol. The impact of methanol on converter and storage costs is considered negligible compared to a diesel yacht. Fuel costs of fossil methanol are slightly higher than fossil diesel, renewable methanol fuel costs are lower than renewable diesel and 5 times higher than fossil methanol. The impact of methanol on the design is relatively large. Compared to diesel, approximately 2.3 times the amount of fuel is required for an equal range. The double bottom is not a feasible location for methanol tanks. A significant amount of interior area is occupied by the fuel tanks and the surrounding cofferdams. Therefore retrofitting existing yachts with methanol is not considered feasible. For new designs, methanol is considered a feasible option.

Two important trends can be witnessed in the world of superyachts. Firstly, the luxury landscape is shifting from collecting tangible assets to pursuing exclusive tailor-made experiences. The second trend is the electrification and the use of batteries on superyachts. Due to the increase of emission restrictions, there is more interest towards battery-powered yachts.

During the Monaco Yacht Show of 2016, Feadship presented their answer to these trends: a unique multibody superyacht concept by the name of Choice. A multibody superyacht is a combination of multiple yachts, including at least one superyacht, and designed around positive involving interaction. In the case of Choice, this interaction enables a combination of three bodies, of which one solely propulsed by batteries, to sail long distances. By the means of interaction, the weight of the batteries are kept within reasonable amounts. Besides the previous features, the multibody creates significant more flexibility and possibilities for its use. On the contrary, sailing with three interacting bodies instead of a conventional yacht could use more energy.

At the moment of writing, there is no such multibody concept sailing the seas. Therefore this thesis analyses a range of multibody superyacht concepts by comparison of total energy consumption. To gain more understanding of the multibody superyacht usage, a fictive itinerary is designed. This also functions as a business case for the concept design boundaries and the energy consumption comparison.

Different multibody superyacht concepts are created within the boundaries of the design space. By splitting the design space into two parts, i.e. the multibody design space and single body design space, the process is kept comprehensible. All concepts have an equal overall functionality, measured by the available luxury area. The difference between the concepts is found in the way of distributing the area over the three bodies within each multibody concept. The battery propulsion could be fitted in either, or multiple, of the three bodies. Different possibilities concerning the location of the batteries are assessed too.

When designing the single bodies within the multibody concepts, a challenge arises. Due to the weight of the required batteries, the single bodies within the multibody are heavier than their conventional fuel powered counterparts. To compensate for this weight, the bodies size is increased, while maintaining the predefined functionality. Due to the size increase, more engine power is required. Consequently, the battery capacity should increase, resulting in more weight. This thesis proposes a design tool for the single body to solve this iterative process. If the designer provides information on the functionality and usage of a yacht, the design tool calculates the main dimensions of a single body concept. The functionality of a single body is predefined by six yacht types and functions as design tool input. Other input is derived from the business case. Through this input, the design tool generates single body solutions.

By combining the solutions of the multibody design space and single body design space, three multibody concepts are established. To compare the multibody superyacht concepts with the conventional way of yachting, a benchmark concept is created. The benchmark concept consists of two fuel powered bodies, with an equal amount of luxury area as the multibody concepts. These four concepts are then compared to each other on total energy consumption in the fictive itinerary. The comparison is based on equal activity time for the guests throughout all concepts.

All three multibody concept designs have a lower total energy consumption than the conventional benchmark. One of the multibody concepts saves up to 33.2% of energy compared to the benchmark. This reduction is mainly due to slow steaming of the largest body within the multibody. Note that the energy consumption reduction does not jeopardise the amount of activity time for the guests.