Sailing wind turbine ship able to pivot for efficient and resilient energy production and delivery

Abstract

A ship 1 with one or multiple wind turbines 2 installed on it. The ship has a multihull 3 construction with three or more hulls positioned rationally symmetric along the longitudinal axis of the ship,

Description

TITLE Sailing wind turbine ship able to pivot for efficient and resilient energy production and delivery TECHNICAL FIELD AND APPLICATION AREA This invention relates to advancing offshore wind turbine energy production and energy delivery. SUMMARY OF THE INVENTION This invention introduces an unmanned (however not exclusively unmanned) ship (1) on which one or multiple wind turbines (2) are installed. The ship (1) is a monohull or multihull ship that consists of two or more hulls (3). The wind turbines (2) are used in two ways at the same time. Firstly, for electric energy production, whereas the energy is stored on board in the hulls (3) e.g., in batteries or with power-to-x methods for instance using hydrogen. Secondly, the wind turbines (2) are used as sails for ship (1) propulsion. This enables the ship (1) to autonomously sail and navigate to offshore destinations where the wind conditions are beneficial for energy production (stronger and steadier winds) or to destinations where the onboard stored energy is delivered to. Optionally, the ship (1) can have a rationally symmetric multihull (3) construction with three or more hulls along the longitudinal axis. This allows the wind turbine ship (1) to pivot along the longitudinal axis in case the ship capsizes. This provides resilience in sea storms. When the wind turbine ship (1) capsizes this way, it remains its full structural and functional integrity and continues operations. In this case, only some hulls (3) (two in case of a three-hull ship (1)) float on the water and the other(s) are kept in the air. A structural connection between the hulls (3) and the wind turbines (2) is provided with elastically bended mountings (4). Shrouds (5) between the hulls (3) pulling them into the opposite direction versus the outward pushing elastically bended mountings (4) enable stable statics of the overall ship (1) construction. Figure 1 shows a spatial visualization of the sailing wind turbine ship (1) with three wind turbines (2) and three hulls (3) including the mountings (4) that hold the turbines and the shrouds (5) pulling the hulls (3) together. Figure 2 shows a sailing wind turbine ship (1) with three hulls (3) from a crosssection view. Figure 3 shows a sailing wind turbine ship (1) with three wind turbines (2) from a top view. The distance between the wind turbines (2) is large enough to mitigate wake loss effects between the wind turbines (2). In Figure 3, the wind comes from the left-hand side and the ship (1) sails in the indicated direction of movement while producing energy and storing it simultaneously. STATE-OF-THE-ART AND ITS SHORTCOMINGS The dominant state-of-the-art for offshore wind energy production are horizontal offshore wind turbines that generate electric energy that is fed through submarine power cables into the onshore power grid. Using gas pipelines in combination with power-to-x technologies instead of power cables has been also explored and piloted recently1. Offshore wind turbines compared to onshore wind turbines can exploit stronger and steadier wind at sea. Currently, installed offshore wind turbines are predominantly fixed-bottom wind turbines rooted in the seabed by monopile or jacket or similar foundations. These turbines are restricted to coastal waters as far as 80 kilometres from shore and less than 60 meters deep2. Deeper and more distant locations for fixed-bottom wind turbines increase technical difficulties and costs and hence have led to the development of floating platforms for offshore wind turbines, especially relevant for coastal areas without shallow waters. 80% of the world's offshore wind resource potential lies in waters deeper than 60m, which means that floating offshore is needed to further scale offshore wind energy production3. (Bauer, NREL, 2022)4 shows different state-of-the art floating wind turbine concepts with their mooring into the seabed and connection to dynamic and static export power cables. Moored floating offshore provides a huge potential to increase offshore wind energy output in the near-term future and commercially-viability is expected to be reached between 2025-20305. Another key advantage is that moored floating offshore wind has less negative visual impact than onshore and near coast fixed-bottom offshore given floating wind turbines can be installed out of sight in further remote offshore areas. However, moored floating offshore still faces several structural shortcomings: I. LIMITED SCALABILITY - Although moored floating offshore is considered technically viable up to 1,000 m water depth6, the commercial-viability maximum depth is currently considered at around 200-300 m water depth7. Given that the average depth of the ocean is 3,800 m, only a fraction of the offshore wind potential is tapped into with moored floating offshore. 1 https: / / aquaductus-offshore.de 2 National Renewable Energy Laboratory (NREL), Future of wind, Chapter 2.3 Offshore Wind Outlook to 2050,2019 3 Global Wind Energy Council (GWEC), Floating Offshore Wind - A Global Opportunity, 2022 4 Joshua Bauer, NREL, Offshore Wind Energy: Technology Below the Water, 2022 5 DNV, Floating Offshore Wind: The Next Five Years, 2022 6 World Bank Energy Sector Management Assistance Program (ESMAP), Offshore Wind Technical Potential Analysis, Going Global Report, 2019 7 Impacts of water depth increase on offshore floating wind turbine dynamics, Ocean Engineering Volume 224, 2021 Additionally, wind speeds are generally higher and steadier farther from shore8, but these cannot be captured by moored floating offshore due the limitations described above. IL HIGH INSTALLATION COMPLEXITY / COST - Floating platforms, mooring systems, dynamic and static power cables or gas pipelines and grid connections are complex and material intensive. Assembly requires large port infrastructures and installation in the open sea environment leads to high complexity / cost as special installation ships are needed4. III. HIGH MAINTENANCE COMPLEXITY / COST - Material fatigue, corrosion and impact from fishing activity drives additional high maintenance cost / complexity9 as frequently parts need to be repaired and replaced. Given the rough open sea environment, floating platforms and wind turbines cannot be fully maintained offshore. They need to be detached with special installation ships from the moorings and power cables / gas pipelines and towed back to the port (or so-called tow-to-shore) for major component replacements or to avoid high costs or limited availability of heavy lift ships10 that could replace larger components on site. All these complexities / cost increase with water depth and distance from the shore, and hence contribute to the scalability limitations mentioned at the beginning. IV. AERODYNAMICS CHALLENGES - Due to platform and therefore wind turbine movements in the rough open sea along the six degrees of freedom (heave, sway, surge, roll, pitch, and yaw) floating offshore wind faces aerodynamic challenges that can reduce energy output and increase material fatigue11. V. REGULATION COMPLEXITY - Permanent installations in the coastal sea raise siting and environmental permitting challenges12. Power cables and mooring chains effect e.g., fisheries, tourism and wildlife, which can raise public concerns that need to be addressed13. Additionally, lease costs need to be paid for the sea areas that are used. 8 Liu et al, Wind power distribution over the ocean, Geophysical Research Letters, Vol. 35, L13808, 2008 9 Floating Offshore Wind: Market and Technology Review, Carbon Trust, Prepared forthe Scottish Government, 2015 10 Operation and maintenance for floating wind turbines: A review, Renewable and Sustainable Energy Reviews Volume 163, July 2022 11 Daniel Micallef and Abdolrahim Rezaeiha, Floating offshore wind turbine aerodynamics: Trends and future challenges, Renewable and Sustainable Energy Reviews Volume 152, 2021 12 IRENA and GWEC, Enabling frameworks for offshore wind scaleup: Innovations in permitting, International Renewable Energy Agency, Abu Dhabi, 2023 13 Inside the Global Race to Tap Potent Offshore Wind, IEEE Spectrum, 2023 Given these shortcomings, different concepts of unmoored floating offshore wind turbines have been developed. The following tables highlight state-of-the-art references that are relevant in the context of this invention in the unmoored offshore floating wind energy field. The table identifies their disadvantages that are addressed and mitigated by the here presented invention. Reference (Ref.l) System for propulsion of boats by means of winds and streams and for recovery of energy14 Concept Wind turbine installed on a catamaran that mechanically drives a water turbine for propulsion of the catamaran. Illustration see Figure 4 Disadvantages • The system is not designed for energy production. If used for energy production, this concept would be inefficient, as rotational kinetic energy gets used for mechanical propulsion through a water turbine. This would reduce the potential of the wind turbine for energy production. The system to convert wind turbine rotational energy to mechanical water turbine propulsion requires mechanical maintenance and leads to material wear and tear thus further reduces efficiency. • It does not provide any dynamic adjustment to compensate for three degrees of freedom motions (roll, pitch, yaw) caused by sea and wind conditions. Hence, the turbine cannot optimally be positioned into the wind to prevent heeling out of the wind like a sailboat. • The high centre of gravity of the turbine installed at the top leads to a high risk of capsizing in stormy seas. Table 1 Reference (Ref.l) 14 Vidal Jean Pierre, Patent: System for propulsion of boats by means of winds and streams and for recovery of energy US4371346A, 1983 Reference (Ref.2) Dynamically positioned floating offshore wind turbine concept15 Concept Wind turbine is installed on a floating platform. In contrast to a conventional floating offshore wind turbine, it has no moorings. Instead, underwater propellers are used to keep the wind turbine stationary. It may also be equipped with an on-board energy storage system. Illustration see Figure 5 Disadvantages • The underwater propellers consume power to prevent the turbine from drifting in the wind and / or current direction, which reduces overall net power output (see also Xu et al., showing that approx. 50%-80% of energy production is used to maintain the stationary position)16. • The stationary design hinders access to more remote areas with higher wind speeds, which dynamically change due to changing weather conditions. • The design does not consider stability aspects to cope with rough sea environment and adjustment for three degrees of freedom (roll, pitch, yaw) caused by sea and wind conditions. Table 2 Reference (Ref.2) 15 R. Alwan et al, Paper: Investigation of a dynamically positioned floating offshore wind turbine concept, 2018 16 Xu, S., Murai, M., Wang, X., and Takahashi, K.: A novel conceptual design of a dynamically positioned floating wind turbine, Ocean Eng., 221, 108528, https: / / doi.org / 10.1016Zj.oceaneng.2020.108528, 2021 Reference (Ref.3) Unmoored: a free-floating wind turbine invention and autonomous open-ocean wind farm concept17 Concept Free-floating offshore wind turbine for deep waters using one large underwater propeller to maintain its position and move as needed, while two small propellers turn the unit. Illustration see Figure 6 Disadvantages • Same disadvantages as described in Reference (Ref.2). • Proposed advancement of this concept to connect multiple of these free-floating wind turbines in an array as a wind farm does not substantially solve above disadvantages as tugs at each corner of the wind farm are considered to maintain the shape of the array or pull turbines to a desired area which consumes additional energy. Table 3 Reference (Ref.3) 17 Jack H Raisanen et al., Unmoored: a free-floating wind turbine invention and autonomous open-ocean wind farm concept, EERA DeepWind Offshore Wind R&D Conference, 2022 Reference (Ref.4) Autonomous Ship Robot AI System18 Concept Ship capable of continuous autonomous operation at sea using only energy collected from nature. Use of computers, sensors, navigating equipment, terrestrial radio and satellite communications, mechanical, electrical and hydraulic actuators and multi-hull design for course keeping and for navigating the high seas. Illustration no illustration available Disadvantages • Describes only a system for autonomous operation but not a system for energy production. Table 4 Reference (Ref.4) Reference (Ref.5) Innovative Autonomously-Driven Offshore Wind Turbines: a prefeasibility analysis19 Concept Autonomously driven offshore wind turbine ship based on a hydrodynamic floating platform (a catamaran) with an underwater propeller for ship propulsion and an onboard energy storage system. Illustration see Figure 7 Disadvantages • Consumes energy for water propeller propulsion which reduces overall net power output. • High centre of gravity given turbine installed at the top leading to high risk of capsizing in stormy seas. Table 5 Reference (Ref.5) 18 Nelson James Kruschandl, Patent: Autonomous Ship Robot Al System GB251173,2013 19 Xavier Martinez Beseler, Innovative Autonomously-Driven Offshore Wind Turbines: a prefeasibility analysis, DTU Department Electrical Engineering, 2019 Reference (Ref.6) Wind Trawler: operation of a wind energy system in the far offshore environment20 Concept Mobile floating wind-and hydro power producing plant with streamlined substructure with single mounted wind turbine and two mounted submerged hydrokinetic turbines. Combined with hydrogen synthesis and storage system within the substructure. Illustration see Figure 8 Disadvantages • High complexity / cost for installing wind turbines and hydro turbines for energy production and water propellers for propulsion. • Similar to above (Ref.5) consumes energy for water propeller-based propulsion system, which reduces overall net power output. • High centre of gravity, given the turbine is installed at the top, leads to high risk of capsizing in stormy seas. Table 6 Reference (Ref.6) 20 Annan, A. M., Lackner, M. A., and Manwell, J. E: Wind Trawler: operation of a wind energy system in the far offshore environment, J. Phys.-Conf. Ser., 1452,012031,2020 Reference (Ref.7) Exploitation of the far-offshore wind energy resource by fleets of energy ships21 Concept Far-offshore autonomously sailing energy ship using Flettner rotors for wind propulsion, water turbines attached underneath their hull for electricity generation and onboard power-to-X plants for storage of the produced energy. Illustration see Figure 9 Disadvantages • Inefficient energy production as wind energy first needs to be translated into kinetic energy for ship propulsion that then gets translated into electric energy using water turbines. • Requires two-times application of Betz's law instead of one-time. • Maximum power that can be extracted from the wind for energy production needs to apply two-times the Betz's coefficient factor 16 / 27 instead of one-time. Once when energy is extracted from the wind. And a second time when energy is extracted from the relative water flow below the ship with the water turbine. Table 7 Reference (Ref.7) 21 Aurelien Babarit et al, Exploitation of the far-offshore wind energy resource by fleets of energy ships - Part 1: Energy ship design and performance and Part 2 Updated ship design and cost of energy estimate, 2020, 2021 Reference (Ref.8) Multi-objective optimization for an autonomous unmoored offshore wind energy system substructure22 Concept Optimized hull structure for the Wind Trawler concept referenced in (Ref.6). Trimaran substructure (primary hull and two symmetrically spaced equivalent outriggers) optimized with multi-objective optimization (MOO) for bi-modal operation as an energy producer and energy transporter in terms of opposing longitudinal and lateral geometric characteristics Illustration no illustration available Disadvantages • The substructure geometric parameters that influence both power generation performance and capital expenditures (in the form of structural steel mass) are optimized. • However, the fundamental disadvantages mentioned in (Ref.6) remain. Table 8 Reference (Ref.8) Additional relevant references are cited in: • "Counterintuitive Performance of Land and Sea Yachts" by Kirk T. McDonald23, providing an overview and history of wind-powered propeller (turbine) driven yachts • "Comparison of optimal power production and operation of unmoored floating offshore wind turbines and energy ships" by P. Connolly and C. Crawford24 comparing some of the above-mentioned references 22 Annan, A. M., Lackner, M. A., and Manwell, J. E: Multi-objective optimization for an autonomous unmoored offshore wind energy system substructure, J. of Applied Energy, Volume 344,121264, 2023 23 Kirk T. McDonald, Counterintuitive Performance of Land and Sea Yachts Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544, 2021 24 Connolly and C. Crawford, Comparison of optimal power production and operation of unmoored floating offshore wind turbines and energy ships, Wind Energy Science, Articles Volume 8, issue 5 WES, 8, 725-746, 2023 OBJECTIVES OF THE INVENTION The overall goal of the present invention is to overcome the shortcomings of the state-of-the-art for offshore wind energy production and delivery. The goal is to provide a better solution that ultimately improves efficiency, i.e. increases energy output of offshore wind turbines and / or decreases costs. This overall goal can be broken down into the following objectives, that the present sailing wind turbine ship (1) should achieve: I. Increase energy output of offshore wind turbines a) Increase energy output for a given wind capacity b) Scale energy output by increasing addressable wind capacity 11. Decrease costs for offshore wind energy production and delivery a) Decrease cost for building and installing b) Decrease cost during energy production c) Decrease cost for energy delivery The Section ADVANTAGES OF THE INVENTION then refers back to these objectives and describes the extent to which they can be achieved with the here presented sailing wind turbine ship (1) for efficient and resilient energy production and delivery. Resilience is considered as part of decreasing the cost during energy production and cost for rebuilding and reinstallation because resilience reduces damage, repair and replacement costs. DETAILED DESCRIPTION OF THE INVENTION The present invention of a sailing wind turbine ship (1) able to pivot for efficient energy production and delivery. Figures 1, figure 2 and figure 3 show the invention as a whole from different perspectives. This invention comprises the following systems and methods that are described in more detail in the forthcoming sections: 1. Rotationally symmetric multihull ship construction to enable the pivot capability 2. Sailing mechanism with control of wind turbine orientation towards wind and ship hulls 3. Elastic mounting of sailing wind turbines with free rotor space to enable the pivot capability 4. Active ball joint-based control of wind turbines yaw, roll, and pitch 5. Oscillating blade pitch adjustment during rotor revolution for yaw optimization 6. Onboard energy storage with hybrid electro-mechanical energy management system 7. Floodable hulls for deliberate ship pivot and underwater storm shelter 8. Additional hull enhancements 8.1. Fins to reduce drift and improve tacking and sailing close to the wind 8.2. Hull extensions with wind funnel effect 8.3. Hull shapes to enable the pivot capability 1. Rotationally symmetric multihull ship construction to enable the pivot capability The sailing wind turbine ship (1) can be a monohull or a multihull construction such as a classical catamaran or trimaran or other multihull construction with the hulls (3) positioned on the water surface. Alternatively, and focused in this section, the sailing wind turbine ship (1) can also have a multihull construction that comprises three or more hulls (3) positioned rotationally symmetric along the longitudinal axis of the ship (1). Figure 10 shows three options with three to five hulls. Beyond these three options, the multihull rotationally symmetric ship construction can be realized with any number of hulls (3) and any number of hulls (3) can be floating simultaneously on the water. The rotationally symmetric construction allows the ship (1) to pivot along the longitudinal axis if impacted by sea storms through strong winds or heavy seas. Hence, the ship (1) can capsize and it maintains its full structural and functional integrity given the rotationally symmetric construction. The pivot capability allows for a lightweight construction of the ship (1) as it does not need to consider structural counter measures for capsizing in case of sea storms, strong gusts of wind, or so called "monster" waves or other harsh weather conditions. Figure 11 shows the pivot mechanism of the ship (1) in four steps caused by strong wind or wave impact. 2. Sailing mechanism with control of wind turbine orientation towards wind and ship hulls The wind turbine (2) can be flexibly positioned into the wind. The rotary axis can have different yaw angles25 relative to the wind direction, e.g. from y >-90° to y <90° depending on the wind conditions and navigation destination or respective sailing course as shown in Figure 12. The ship hulls (3) direction can also be flexibly turned into or out of the wind, similar to a sailing boat (SB). This combination of wind turbine (2) and hull (3) orientation towards the wind enables the ship (1) to sail different courses including tacking into the wind. The here presented sailing mechanism uses the wind forces generated by aerodynamic characteristics of currently dominant horizontal axis wind turbines (HAWT) with airfoil-shaped blades (6) in combination with suitable yaw angles. Generating lift and drag when the turbine blades move through the air, airfoil-shaped blades play a key role in improving the aerodynamic performance and structural durability of a turbine's blades26. Figure 1327 shows how a lift force (L) generated by the rotating airfoil-shaped blades gets decomposed. 25 To not exclude any potential other use cases there is no restriction fory 26 US Department of Energy, Airfoils, Where the Turbine Meets the Wind, Wind Energy Technologies Office, www.energy.gov, 2023 27 Richard J Crossly, Wind Turbine Blade Design Review, Journal of Wind Engineering, 2012 The lift force (L) gets decomposed into a torque (To) that rotates the rotor and a thrust force (Th). The torque (To) generates electrical energy inside the turbine's (2) generator. The thrust force (Th) is perpendicular to the rotor plane leeward along the rotary axis of the wind turbine (2). In a typical stationary wind turbine, this thrust force (Th) gets absorbed by the wind turbine tower and creates a reaction force R(dr) in Figure 13. In the present invention, this thrust force (Th) is used to push the ship's hulls (3), that are structurally connected to the wind turbine (2), leeward in the water. Consequently, given the drag at the hulls (3) leeward side, this moves the ship (2) forward through a vector force decomposition as described next. The present sailing wind turbine ship (1) uses this wind turbine thrust force (Th) for sailing similar to a lift force (Fls) generated by a curved sail in the wind. This lift force on sails (Fls) of a sailboat (SB) that together with a drift resistance force (Frs) on the keel and lateral line of the sailboat hull results in a forward force (Ffs) of the sailboat (SB) as shown in Figure 14. Figure 15 shows the sailing mechanism of the sailing wind turbine ship (1) that sails the same course as the sailboat (SB) in Figure 14. The thrust force (Th) perpendicular to the rotor plane same as described in Figure 13 gets decomposed into the leeward hull (3) drift resistance force (Frv) at the ship (1) and the resulting forward force (Ffv) of the ship (1) that points into the desired direction of movement. The distance between the wind turbines (2) is large enough to mitigate wake loss effects between the wind turbines (2). Further explanations of this sailing mechanism with control of the sailing wind turbine ship (1) at different sailing courses including sailing close to the wind are described in the Section EXEMPLARY EMBODIMENTS. This sailing mechanism is controlled by two means: Firstly, the wind turbines (2) are flexibly positioned into the wind. The rotary axis can have different yaw angles relative to the wind direction as described in Figure 15. The control of the yaw angles can be realized with a ball joint (8) as presented in Section 4 or alternative means. Secondly, the hulls' (3) orientation can be either controlled with a classical rudder, installed for example at the hulls' (3) stern. Alternatively, to avoid the requirement for a rudder that adds complexities and cost, the here presented sailing mechanism turns the back turbine (2.B) (rear steering) or front turbine (2.F) (front steering) with different yaw angles. Through thrust force (Th) vector decomposition this results in a turn along the vertical axis i.e., a yaw movement of the ship (2). Figure 16 shows both, the steering of a starboard turn, in which the back turbine (2.B) is steered parallel to the longitudinal axis of the ship (1), and the steering of a port turn, in which the front turbine (2.F) is steered parallel to longitudinal axis of the ship (1) instead. Instead of differently steering the yaw angle of the turbines (2), the same effect can be achieved by aerodynamic braking the turbine (2) rotors through rotor pitch angle variations or mechanical braking of the turbine (2) at the rotor shaft. The braked turbines (2) will generate a lower lift force (L), and therefore as well a lower thrust force (Th). Given the relatively lower sidewards force at the rear (port turn) or equally at the front (starboard turn) the hulls (1) turn around the centre point of the ship (1) into the desired direction of movement of the ship (1). The presented invention for sailing wind turbines (2) is derived from the sailing concept of sailboats (SB) but is not a one-to-one application of the same concept. • In the sailboat (SB) sailing mechanism, the conversion of wind energy to kinetic energy that moves the boat (SB) is more direct. The wind flows around the curved sail (step 1) and creates a lift (step 2). This lift force on sails (Fls) together with the drift resistance force (Frs) of the sailboat leads to the forward force (Ffs) (step 3). • In the wind turbine ship (1) sailing mechanism, it is more indirect and requires an additional energy conversion step. The wind flows around the rotor blades (6) (step 1) and creates a lift on the upper side of the airfoil-shaped rotor blade (step 2). This lift force (L) gets decomposed (see Figure 13) into a thrust force (Th) perpendicular to the rotor plane and torque (To) (step 3). The thrust force (Th) pushes the wind turbine (2) into the leeward direction along the rotary axis (see Figure 15). This thrust force (Th) is used similar to the lift force (Fls) at the sail of the sailboat (SB) that gets decomposed and leads to a forward force (Ffv) of the ship (1). This last step relates to (step 3) in the sailboat (SB) sailing mechanism and is (step 4) in the wind turbine ship (1) Hence, one additional step, i.e., one additional force decomposition, is required for the presented sailing mechanism with the control of wind turbine (2) orientation towards wind and hulls (3) as compared in the flow chart in Figure 17. While the wind turbine (2) is used for ship (1) propulsion as described above, the wind turbine (2) generates electric energy at the same time. However, with increasing yaw angle, which is a fundamental feature leveraged in the mechanism above, kinetic wind power conversion to wind turbine (2) electric power output gets reduced. Reduction of rotor area facing the wind and aerodynamic effects such as dynamic stall at the rotor blades impact power output. These effects have been intensively studied for onshore and offshore wind turbines28. The reduction of kinetic wind power conversion into wind turbine (2) output (also called power coefficient CP25) is in the range of 80% to 100% of CPmax (i.e. maximum power coefficient at y =0°) in the yaw angle range of y >-30° to y <3029. This yaw angle range is sufficient for the sailing manoeuvres described above (see also Section Exemplary Embodiments) and only at yaw angles greater than 45°, the power output generated by the wind turbines decreases to half29 as shown in Figure 1829. The x-axis shows the yaw angle. The y-axis the power coefficient (left-hand side) and the power output in watt (right-hand side). 3. Elastic mounting of sailing wind turbines with free rotor space to enable the pivot capability Changing the yaw angle of the wind turbines (2) for the desired sailing course is essential for the sailing mechanism of the ship (1) as described above in Section 2. For the wind turbines (2) to be freely turned at different yaw angles y >-90° to y <90°, it requires a wind turbine mounting (4) that does not block the rotor blades (6) while rotating at any yaw angle. For a typical stationary wind turbine, the wind turbine tower is perpendicular to the rotor axis. In this stationary setup, this type of mounting allows a non-blocking turning of the wind turbine (2) at any yaw angle. However, in case of the rotationally symmetric multihull (3) construction enabling the ship (1) to pivot described in Section 1, requires a different mounting (4). After the pivot around the longitudinal axis of the ship (1), the rotors blades (6) still need to be able to rotate freely at any yaw angle not being blocked by the wind turbine mountings (4). Mounting the wind turbine on a vertical tower (T) or similar structure perpendicular to the rotor axis would block the rotor as shown in Figure 19 (not part of this invention). The mounting (4) needs to provide free space (FS) for the rotor blades (6) to rotate after every pivot of the ship (1). In this free rotor space (FS), no wind turbine mountings (4) can be installed. 28 Daniel Micallef and Tonio Sant, Wind Turbines, - Design, Control and Applications, Chapter 2: Review of Wind Turbine Yaw Aerodynamics, Intech Open, 2016 29 Husaru et al, Effect of yaw angle on the global performances of Horizontal Axis Wind Turbine - Q Blade simulation, 2019 IO P Conf. Ser.: Mater. Sci. Eng. 595 012047 Figure 20 shows this free rotor space (FS) marked as a hatched area in a two-dimensional view from above. The free rotor space (FS) is defined by the maximum yaw angles. As the ship (1) pivots around the longitudinal axis the cross-section area of (FS) as shown in Figure 20, forms a solid of revolution that is a sphere hollowed out by two embedded cones (EC) on two sides (see right hand side in Figure 20). To preserve the free rotor space (FS), the mountings (4) first need to follow the direction along the rotor axis at yaw angle = 0°, in this situation the same as the longitudinal axis of the ship (1), before the mountings (4) can go into any direction perpendicular to the rotor axis. In the latter direction, the mountings (4) finally need to connect structurally with the hulls (3) to provide functional statics of the ship (1) holding the wind turbines (2). Figure 21 shows different options persevering the free rotor space (FS) by following first the direction along the rotor axis and only behind the free rotor space (FS) the mountings (4) are connected perpendicular to the rotor axis with the hulls (3). The present invention focuses on elastically bended mountings (4). Elastically bended or deformed materials such as metals deform when pushed, pulled, and twisted and can return to its original shape after external forces and pressures that caused the deformation stop30. Most materials have an amount of force or pressure for which they deform elastically. If more force or pressure is applied, then they have plastic deformation31. The in this invention presented mountings (4) are for this reason elastically bended or deformed so they function additionally as a spring that stores elastic potential energy. This energy is also referred to as elastic free energy, that produces a restoring force (Fr) against the distortion32. Figure 22 shows different elastically bended mounting (4) options. The here presented invention includes these options and any elastically bended mountings (4) of wind turbines (2) that restoring force (Fr) acts perpendicular away from the longitudinal axis of the ship (1) not restricted to the options shown in Figure 22. The curved form of the mountings (4) can also be a combination of plastic and elastic deformation or already the result of the melting process. Nevertheless, a certain elasticity will be given and is utilized for the described purpose. 30 R. D. Knight, "Elasticity," in Physics for Scientists and Engineers: A Strategic Approach, 2nd ed. San Francisco, U.S.A.: Pearson Addison-Wesley, 2008,pp. 278 31 Hawkes et al, "Deformation and Elasticity," in Physics for Scientists and Engineers, 1 st ed. Toronto: Cengage, 2014, pp. 265-268. 32 P. M. Chaikin and T. C. Lubensky, Principles of Condensed Matter Physics, Chapter 6: Generalized Elasticity pp. 288-352, Cambridge University Press, 1995 The restoring forces (Fr) act perpendicular away from the longitudinal axis, so it pushes the hulls (3) outwards, i.e., the restoring force (FR) acts as an expanding force on the ship's (1) hull (3) construction. Conversely, the contractive forces (Fc) of the shrouds pull the hulls (3) together. Overall, the two forces (Fc) and (Fr) act in opposite directions. In the equilibrium, the contractive force (Fc) and restoring forces (Fr) hold the wind turbine (2) and provide stable statics. At the same time, they provide an elastic wind turbine mounting (4) that contributes to the stability and resilience of the sailing wind turbine ship (1) as both the wind turbines (2) and as well the hulls (3) are suspended. How the wind turbines (2) are connected to the above-described mountings (4) is described in the next Section 4. 4. Active ball joint-based control of wind turbine yaw, roll, and pitch Figure 23 shows the wind turbine (2) roll motion around the longitudinal x-axis of the ship (1), the pitch motion around the transverse y-axis and the yaw motion around the vertical z-axis. The yaw motion of the wind turbine (2) is already described in Section 2 and how the yaw motion is controlled for the sailing mechanism of the wind turbine ship (1). Additionally, the yaw motion of the wind turbine (2) is also impacted by the yaw motion of the ship (1), which in turn is influenced by the sea and wind conditions such as waves, currents, gusts of wind or differences of wind force at different heights (so called wind shear). Similarly, the wind turbine (2) roll and pitch motions get also impacted by the roll and pitch motions of the ship (1) influenced by the sea conditions. This includes also heeling of the ship (1), a the less temporary roll motion of the ship (1) caused by the wind force on the sails or here the wind turbines (2). This can have a negative impact on the wind flow through the rotor plane of the wind turbine (2) and consequently on the performance of the power generation. Uncontrolled roll, pitch, and yaw motions of the wind turbine (2) reduce the rotor area that is facing the wind and changes the wind flows at the airfoil-shaped rotor blades. This reduces the wind power that can be extracted as described already with Figure 18 regarding the yaw angle and the analogue effect has to be considered as well regarding the roll and pitch motions. For this reason, the present invention includes a control of wind turbine (2) roll, pitch and yaw based on an active ball joint (8). On the one hand, the ball joint (8) is used to control the yaw motion of the wind turbine (2) for the ship's (1) sailing capability. And on the other hand, the ball joint (8) is used to counteract and hence to neutralize the sea condition driven roll, pitch and yaw motions of the wind turbine (2). Figure 24 shows the active ball joint (8) three-axis control including roll, pitch and yaw Figure 25 shows one horizontal and two vertical active ball joint (8) installation options and how they are structurally connected to the wind turbine (2). The horizontal active ball joint (8) installation provides an axisymmetric lightweight solution. However, it requires a powerful active ball joint torque to hold heavy weight wind turbines (2). The vertical active ball joint installation provides more favourable statics. However, an additional element, a rotary motor (7) is required. The rotary motor (7) (e.g. electric or hydraulic or otherwise) rotates the active ball joint (8) together with the installed wind turbine (2) around the longitudinal axis of the ship (1). This enables to reset the wind turbine (2) into this hanging position after ship (1) pivots. This option benefits from favourable statics as the wind turbine (2) can be fixed at its centre of mass which balances the forces that act on active ball joint (8). If technically more beneficial for the active ball joint (8) way of working, the wind turbine (2) can be also installed on top of the active ball joint in the same way. I.e. applying a 180° rotation of the vertical active ball joint (8) installation, so that the gravity pushes the ball head into the ball joint housing see right-hand side of Figure 25. The active ball joint can be built and steered electro-mechanically as described in IEEE transactions on robotics33. Another gimbal-based implementation of the active ball joint (8) or here called spherical parallel is described in (Skyentific, 2 0 2 3)34. Other alternative technical embodiments are active magnetic ball joints. Active magnetic ball joints work frictionless and maintenance free35. However, their energy consumption for active electromagnetic field generation needs to be considered compared to the enhanced wind turbine power output achieved by the neutralization of externally caused roll, pitch and yaw motions. Other possible technical embodiments to control the three-axis motions include: three-axis gimbal with mechanical bearings or active magnetic bearings, combined pan and tilt units, Stewart platforms 33 K. Abe, K. Tadakuma and R. Tadakuma, "ABENICS: Active Ball Joint Mechanism with Three-DoF Based on Spherical Gear Meshings," in IEEE Transactions on Robotics, vol. 37, no. 5, pp. 1806-1825, 2021 and patent application JP2023038119A filled in 2021 34 www.skyentific.com, Spherical Parallel Joint (stepper motors, 3DoF), 2023 35 Fang Zhang et al., Electromagnetic Driving Modal and Control of Magnetic Levitation Spherical Active Joint, 3rd Annual International Conference on Mechanics and Mechanical, 2017 or so-called hexapods on a rotational table, or artificial muscle-based ball joints36 or any functional equivalent thee-axis control. 5. Oscillating blade pitch adjustment during rotor revolution for yaw optimization As described in Section 2, the yaw manipulation of the wind turbine (2) is fundamental for the wind turbine (2) sailing mechanism. However, as described the wind turbine (2) torque and consequently power output gets reduced with increasing yaw angle (see Figure 18). For this reason, this invention includes a mechanism for oscillating blade (6) pitch adjustment during rotor revolution to optimize the wind flow angle at the airfoil blades (6) when the turbine (2) is in yaw. It is state-of-the-art to adjust the blade (6) pitch based on wind conditions. The novelty and key element of this part of the invention is, that the blade (6) pitch is adjusted in an oscillating motion back and forth, not only occasionally when the environmental wind conditions change, but continuously during each rotor revolution. This optimizes the wind flow around the rotor blades (6) as the yaw angle impacts the blades (6) differently depending on their rotation position when the wind turbine (2) is yawed. Figure 26 shows the wind turbine (2) in yaw at y and its rotors blades (6) at different rotation positions. The left-hand side shows the view from above with the true wind coming from the side at the yaw angle of y. The right-hand side shows one rotor blade (6) at four rotation positions (0°, 90°, 180°, 270°). Here, the true wind direction comes from the viewer perspective perpendicular into the drawing plane (here as well the rotor plane) with a yaw deviation to the right from the rotary axis. Four cross-sections CSo°, CSgo°, CSibo°, and CS27o° are marked. The following Figures 27 to 30 show the wind triangle vector diagrams at these cross-sections. It is shown that the optimal pitch angle P is different at each rotation position to optimize the streamlined wind flow around the airfoilshaped rotor blades (6). This enhances airfoil lift and, torque and thrust generation. The angle of attack a stays the same as its determined by the construction design of the airfoil shape. These different adjustments for the blade (6) pitch angles Po°, Pgo°, Pibo°, and P27o° for the rotor blade (6) rotation cases (0°, 90°, 180°, 270°) and corresponding pitch angles for all rotor positions in between define the oscillating blade pitch adjustment mechanism during rotor revolution for yaw optimization. 36 L. Grunert, Patent Offenlegungsschrift: Steuerbares Kugelgelenk, DE 10 2008 037 930 A1, DPMA, 2010 Figure 27 shows the wind triangle vector diagram at the rotor blade (6) cross-section CSo° at 0° rotation. The difference to a classical wind triangle diagram of a horizontal wind turbine with airfoil blades (as e.g. shown in textbooks37) is, that the true wind direction comes from an angle y and thus the turbine (2) is in yaw The vector decomposition derives an apparent wind velocity wo" that leads to a smaller pitch angle Po° than in an equivalent scenario with wind from zero yaw Bo"Can be calculated as follows with equation Elo°: Bno= cos1 f “° ^°°+ — a k|u| ■ |v0» + u|7 Elo" is based on E2o°, E3o° and E4o° as per below: Equation E20°: a + Po° = Xo° Po° = Xo° _ a Equation E30°: y0»= cos1 ( ^0° J k|u| ■ |w0»|7 Equation E4o°: w0«= v0« + u Figure 28 shows the wind triangle at the rotor blade (6) cross-section CSgo° at 90° rotation. Figure 28 includes a 3D-orientation that visualizes the direction of the true wind at this 90° rotor blade (6) rotation position. To derive the apparent wind velocity w9o° impacting the optimal blade (6) pitch angle Pgo°, a projection of the true wind velocity vgo° on the rotor axis is required. Only this projected component has an impact on the pitch angle Pgo°, as the remaining component is parallel to the longitudinal axis of the rotor blade (6) and thus does not impact the blade pitch whatever the length of this component. i ii i r n ■! ■ n-i o 1 / U ° ( era • COS(v) • I Vano I + u) \ P9o°can be calculated as follows with equation EI900: PQn°= cos1 —■—— — a v|u|■|era- cos(y)- Ivgod +u|7 Elgo° is based on E2go°, E3go°, E4go° and E5go° as per below: Equation E2go°: a + p90» = X900 <=> P900 = X900 - a Equation E390-: y90»= cos'1 (,^°^90°.) \|U| ■ |Wgo»|7 Equation E4go°: w90o= p90o + u Equation E5go°: p90» = era • cos(y) • |v90o|, era = unit vector parallel to rotor axis38 37 Erich Hau, Windkraftanlagen: Grundlagen, Technik, Einsatz, Wirtschaftlichkeit, p. 93ff, 4th Edition, Springer, 2008 38 In the direction of the reference wind at zero yaw Figure 29 shows the wind triangle vector diagram at the rotor blade cross-section CSiso° at 180° rotation. Already visually it can be noticed that Piso° is larger than Po°. Section EXEMPLARY EMBODIMENTS shows corresponding calculations and confirms this. Pi8o°can be calculated as follows with equation Eliso°: Pian»= cos1 f"” _ a \|u| ■ |v180»+ u|7 Eli8o° is based on E2iso°, E3iso° and E4iso° as per below: Equation E2iso°: a + Pi8o° = Xiso» <=> Piso» = Xiso» - a Equation E3iso°: Xi80°= cos'1 ° ^,180° J k|u| ■ |w180»|7 Equation E4iso°: w180o= v180o + u Figure 30 shows the wind triangle vector diagram at the rotor blade cross-section CS27o° at 270° rotation. Again, a projection, here p27o°, is needed to derive the wind vector that impacts the optimal blade (6) pitch. n i ii i r 11 ■! ■ n-i o 1 / U ° ( era • COS(v) • I Vo 79° I + 11) \ P27o°can be calculated as follows with equation EI2700: p?7n°= cos1 —■—— — a V|u|■|era- cos(y)- |v27o°I +u|7 E127o° is based on E227o°, E327o°, E427o° and E527o° as per below: Equation E227o°: a + p27o» = X27o» <=> p27o» = X27o» - a Equation E327o°: X270»= cos'1 \|u| • |W270°| / Equation E427o°: w270o= P2700 + u Equation E527o°: P270o=Cra ’ cos(y) • |v270o|, era = unit vector parallel to rotor axis39 The generalized calculation equation at any rotor blade (6) rotation angle p for pe, is defined by projecting the true wind velocity ve on the one hand onto the rotor axis39 to obtain pe, and on the other hand onto any parallel to the rotational wind velocity u to obtain an extension of the rotational wind velocity u+. Vector addition of pe + u + u+ provides apparent wind velocity vector we. The angle between u and we provides ye and then pe by deducting angle of attack a. Additionally, the apparent wind is impacted by the relative wind caused by the ship (1) forward 39 In the direction of the reference wind at zero yaw movement. This relative wind vector can be additionally included to calculate the adjustment of the pitch angle p. Calculations for pitch angle pe at different rotation angles g are provided in Section EXEMPLARY EMBODIMENTS. One finds that Po° = Pm™, and Pibo° = PMax. with Po° <Pgo° <Pibo° >P27o° >Po° and accordingly for all rotation angles in between the described four cases. The following Figure 31 shows this pattern in a qualitative oscillation diagram with the rotor blade (6) rotation angle on the horizontal x-axis and the adjusted pitch angle p on the vertical y-axis. Typically, aerodynamic engineering of wind turbines tries to eliminate and avoid any kinds of oscillation movements as typically they increase vibration forces and thus material fatigue. However here, it is a counter measure to neutralize or at least reduce an otherwise oscillating effect caused by the changing wind flow conditions during rotor revolution when the wind turbine (2) is in yaw. Above describes the adjustment of optimal blade (6) pitch for wind speeds up to the rated wind speed, for which a specific wind turbine (2) is designed. For higher wind speeds, it is state-of-the-art that the pitch angle is changed to control (reduce) the power transferred from the wind to the generator at above rated wind speeds. The same mechanism can be also applied accordingly to the here presented oscillating blade (6) pitch adjustment during rotor revolution for yaw optimization. For technical realization, state-of-the-art wind sensors can be used and the pitch angle of a blade (6) can be changed by a motor, called pitch actuator. An extension of the above-described mechanism of oscillating blade (6) pitch adjustment is to also adjust the rotor blades (6) twist dynamically in an oscillation during rotor revolution. The exact dynamic twist angle can be calculated in the same way as above for the rotor blade (6) pitch angle. Technically, this extension can be implemented, for instance, using flexible rotor blades (6) and adjusting the twist angle at individual cross-sections with electric servos or any other actuators. 6. Onboard energy storage with hybrid electro-mechanical energy management system The generated energy from the wind turbines (2) is stored onboard the ship (1). The energy storage is placed inside the hulls (3). The energy storage technology can be electric batteries or any liquid-, gas-, or solid-based energy storage system using e.g. fuels such as hydrogen, methanol or ammonia. For the energy storage system, the key element of this part of the invention is to make direct use of the mechanical energy available at the wind turbine's (2) drive train (9) for certain process steps of the electro-mechanical energy management system. Instead of using a portion of the electric energy produced by the wind turbines (2) for certain process steps of the energy management system requiring mechanical energy, the mechanical energy is directly used from the mechanical energy that the wind turbine (2) provides at the drive train (9). This has the advantage of bypassing inefficiencies caused by the conversion from wind turbine (2) rotational energy i.e. mechanical energy into electrical energy and back to mechanical energy For the case of hydrogen energy storage, this can be applied for example for desalination of seawater or for compression of hydrogen to increase energy storage density. The process for desalination of seawater requires operating pressure from 800 to 1000 psi to pressure seawater against a saltrejecting membrane through reverse osmosis40. The process of hydrogen compression is required as typically hydrogen is produced by fuel cells at low pressure (20-30 bar) and must be compressed to increase energy storage density by using for example reciprocating or rotary i.e. mechanical compressors41. Figure 32 shows how the hybrid electro-mechanical energy management system is integrated into the wind turbine (2) by installing one or more compressors or any other mechanical device directly at the drive train (9). The compressors or any other mechanical devices are connected with pipes or hoses or sub-drive trains or any other ways of connection with other devices such as fuel cells, desalination devices, etc. The produced electrical energy or the produced hydrogen, methanol or any other fuel is then transferred through electric cables, gas pipes or hoses or any other means into the hulls (3) where the energy storage e.g. batteries or fuel tanks are placed. Furthermore, discharge interfaces are integrated into the hulls (3) to get outside access to the energy storage. 7. Floodable hulls for deliberate ship pivot and underwater storm shelter The here presented sailing wind turbine ship (1) is able to pivot along the longitudinal axis if impacted by harsh weather and sea conditions while maintaining its full structural and functional integrity (see Section 1). The in this section presented mechanism provides additionally the capability for the ship (1) to deliberately pivot without any external impact. This can be useful for maintenance operations to easier access upper parts of the ship (1) or to make use of redundant systems (e.g. rudders or engines installed at the hulls' ends) that can be made use of in a different pivot position. Further, the mechanism to deliberately pivot can be used to resiliently cope with heavy sea storms. The ship (1) is able to pivot under water. With that, it can seek shelter underwater from stormy sea, in order to be less exposed to stormy wind speeds and stormy 40 David M. Warsinger, Emily W. Tow, Kishor G. Nayar, Laith A. Maswadeh, John H. Lienhard V, Energy efficiency of batch and semi-batch (CCRO) reverse osmosis desalination, Water Research, Volume 106, 2016 41 www.energy.gov / eere / fuelcells / gaseous-hydrogen-compression waves. Figure 33 shows the deliberate pivot mechanism in five steps. Step 2 is applied in the underwater shelter use case. The hulls (3) have a floodable compartment separated from a not floodable compartment for the energy storage system e.g. batteries or fuel tanks. If the floodable compartments are not flooded, they create buoyancy that enable to ship to float. Step 1 of the deliberate pivot mechanism starts with flooding hull (A) (see Figure 33) by opening one or more valves to let water flow in and one or more additional valves from where the air or other gas inside the hull (A) can flow out. The floodable compartment of hull (A) gets filled with water and consequently sinks. Additionally, hull (B) gets pulled down. Step 2 completes this movement and the ship (1) floats upside-down on hull (B) and (C) with hull (A) under water. In this position the ship (1) can seek shelter below the water surface in case of heavy storms and critical winds or waves that could impact the structural integrity of the ship (l).The wind turbine (2) therefore is constructed in a waterproof way to support this manoeuvre. Step 3 starts the ship (1) to float up by partly flooding hull (B) and then slightly later, partly inflating hull (A) and at the same time. This creates a downside movement of hull (B) and an upside movement of hull (A). The inflation can be done by pumping air through pipes or hoses from ship (1) parts that are above the water surface. Alternatively, in case the energy storage system is based on a gas lighter than air such as hydrogen, this gas can be used for the inflation. The gas will be released from the storage tanks into the floodable compartment through respective valves. The gas inflates the floodable compartment and the water inside gets pushed out. Step 4 stops the partial flooding of hull (B) once hull (B) and hull (A) are on the same level. Then both hull (B) and (A) are fully inflated and thus lift the ship (1) up. Step 5 completes the uplift movement and the ship (1) floats with two hulls (B) and (A) on the water surface while hull (C) is up in the air. This way the ship (1) can make a complete deliberate pivot. 8. Additional hull enhancements This section presents different hull (3) enhancements in addition the presented above: 8.1. Fins to reduce drift and improve tacking and sailing close to the wind 8.2. Hull extensions with wind funnel effect 8.3. Hull shapes to enable the pivot capability 8.1. Fins to reduce drift and improve tacking and sailing close to the wind Important for the sailing mechanism presented in Section 2, is the drift resistance force (Frv) to ensure that the ship (1) does not drift too much away leeward and hence cannot keep the desired sailing course (see Figure 15). To improve the hull (3) shape to provide more drift resistance force (Frv) compared to the simplistic cylinder tube shape as presented so far, fins (10) that act as a keel are added to the hulls (3). Figure 39 shows the fins from a back or front cross-sectional view of the ship (1) on the left-hand side and from a side view on the right-hand side. One or more fins (10) are built foldable with a flexible material. Figure 35 describes the folding mechanism based on an active joint (11) at the front of the fin (10), a luff (12) that holds the frontside of the fin (10) and a flexible material (13) that contracts when the fin is folded. When the active joint (11) is turned up, the fin (10) unfolds. If the active joint (11) turns down, the fin (10) folds. At the hulls (3) that float on the water, the fins (10) are fully unfolded under water, to provide additional drift resistance. On the top hull (3), the fins (10) act as sails if the ship (1) sails close reach courses upwind. If the ship (1) sails other courses, then the fins (10) are folded to not provide drag. 8.2. Hull extensions with wind funnel effect Figure 36 shows an alternative hull (3) enhancement. A hull extension (13) that provides a wind tunnel effect that increases the wind turbines (2) capacity factors as it funnels additional wind flow from above the ship (1) into the wind turbines (2) rotor areas. Additionally, it creates a low-pressure region behind the wind turbine (2), due to a strong vortex formation that draws more wind flow into the wind turbine (2). And consequently, this additional wind flow increases power output42. This wind funnel effect is maximized at half wind course as shown in Figure 41 cross-sectional view and side view of the ship (1). 42 Yuji Ohya and Takashi Karasudani, A Shrouded Wind Turbine Generating High Output Power with Wind-lens Technology, MDPI Energies Journal, 2010 In addition to the wind funnel effect, this hull extension also provides a keel effect under water below the hulls (3) that float on the water surface. Therefore, it increases drift resistance and hence reduces the ship (1) drift similar to the enhancement presented in Section 8.1. above. 8.3. Hull shapes to enable the pivot capability Various hull shapes for multihull ships are known in prior art that all have been optimized for different characteristics. For example: • Vertically oval hull shapes provide more drift resistance than circular hull shapes. • Flat hull shapes have a shallow draft. • V-shaped hulls cut through the water and waves and therefore providing more stability in rough waters. Moreover, they create a wave that lifts the ship up and out of the water, reducing drag. • Hydrofoil hull extensions lift the ship above the water surface and reduce forward drag. • SWATH (Small Waterplane Area Twin Hull) shapes have a relatively high forward drag, therefore are slower but have a fraction of the motion in heavy seas43. • Asymmetrical hull shapes reduce interference drag between the hulls44. Figure 37 shows some of the aforementioned multihull shapes in a cross-sectional view on their wetted surface area, i.e. total surface area of the hull and appendages below the waterline. The here presented invention takes any multihull ship hull shape (not restricted to the selection presented above) and duplicates the wetted surface area in a rotationally symmetric reflection to enable the pivot capability of the ship (1) and thus forms a novel hull (3) shape for the ship (1). Each hull (3) of the ship (1) has two wetted surface areas of the selected hull shape. According to the number of hulls (3) of the ship (1) (see again Figure 10 in Section 1) the degree for the rotationally symmetric reflection is: 360° divided by the number of hulls (3) of the ship (1). This way the wetted surface area of the hull (3) shape is always properly aligned to the water plane in any pivot position. 43 Stenger Jacob Johannes, Patent: Surface ship, US3279407A, 1964 ^Yanuar et al., Drag reduction of X-pentamaran ship model with asymmetric-hull outrigger configurations and hull separation, Energy Reports of 6th International Conference on Power and Energy Systems Engineering (CPESE) Japan, 2019 Figure 38 shows a combination of the oval and V-shaped hull (3) option for ship (1) with three hulls before and after a 120° pivot. The in Figure 38 presented combination of an oval and V-shaped hull (3) provides a keel effect reducing drift as presented in Section 8.1 and a wind funnel effect increasing wind turbine (2) power output as also presented in Section 8.2. ADVANTAGES OF THE INVENTION The present invention provides several advantages regarding the goal to improve efficiency of offshore wind energy production and delivery, i.e. to increase energy output and / or decrease costs. These advantages are linked back to the declared objectives of the invention as per the following: I. Increase energy output of offshore wind turbines a) Increase energy output for a given wind capacity i) Direct conversion of wind power into electrical energy: The here presented invention directly converts the kinetic energy of the wind into electrical energy without inefficient indirections such as first moving the ship with the wind power to then generate electrical energy with hydro turbines under the hull of the ship as presented in the state-of-the-art, for example (Ref.6), (Ref.7), and (Ref.8). These approaches first convert the wind power partly into kinetic energy for ship propulsion that then gets converted into electric energy using water turbines. This requires two-times the application of Betz's law instead of onetime. I.e. the Betz's coefficient 16 / 27 needs to be factored in two-times instead of onetime for the maximum power that can be extracted from the wind (see also disadvantages of (Ref.7) for further explanation). ii) Exploiting wind power directly for ship (1) propulsion instead of separate propulsion engine: The here presented invention uses the wind turbines (2) in two ways at the same time. Firstly, for electric energy production that will be stored on board in the ship hulls (3). Secondly, the wind turbines (2) are used as sails for ship (1) propulsion. Compared to other approaches presented in the state-of-the art, for example (Ref.2), (Ref.3), (Ref.5), (Ref.6), and (Ref.8), the here presented invention does not consume previously produced electrical energy or any other stored energy for a separate propulsion system. Additional efficiency losses caused by the conversion from one form of energy into another. Hence, the net energy balance gets improved compared to the above-mentioned state-of-the-art. iii) Leveraging increased wind speeds from ship (1) forward movement: Additionally, to the two advantages described above, the here presented invention also leverages the increased speed of the apparent wind caused by the combination of true wind and relative wind from the forward movement of the ship (1). Depending on the sailing course of the ship (1) the apparent wind speed can be slower or faster than the original true wind. In the beam reach course when assuming an already high ship speed the apparent wind significantly increases compared to the true wind. Despite the reduction factor caused by the yaw angle between the wind turbine (2) and this faster apparent wind, the cubic influence of wind speed on power output can increase the net power output up to a factor of approx. 1.57 compared to a non-moving stationary wind turbines as e.g. presented in the state-of-the-art about moored floating offshore wind turbines. Hence, this beam reach course effect provides a significant energy output increase potential for a given wind capacity. iv) Reduction of wake losses in wind farms: Wake losses are a key factor in large-scale wind farms. For specific wind directions and wind speeds, wake losses in wind farms can approach and even exceed 30%. For a typical offshore wind farm, they are kept in the range of 10% or lower on an annual energy production level by the optimization of the layout45. The present invention has the advantage, that there are no wake losses in a fleet of wind turbine ships (1). Thanks to their mobility, the wind turbine ships (1) can position themselves in relation to the wind in such a way that wake losses are avoided and thus up to 10% more power output can be achieved compared to stationary wind turbine farms. v) Tackling three-degrees of freedom movements directly at the wind turbine (2): Three-degrees of freedom movements (roll, pitch and yaw motions) of the wind turbine caused by sea and wind conditions negatively affect the wind turbine power output and increase material fatigue. In the field of moored floating offshore wind turbines (see IV. AERODYNAMIC CHALLENGES in Section STATE-OF-THE-ART) different solutions have been presented46 and implemented47 or are still under research48. However, the 45 Dr. Martin Dorenkamper, Large-Scale Wind Farm Effects - A Key Contributor for Economic Wind Farm Operation, Blog Fraunhofer-Institut fur Windenergiesysteme, 2022 46e.g. D. Roddierand C. Cermelli, Patent: Floating wind turbine platform with ballast control and mooring system, US9139266B2 47 e.g. www.principlepower.com / windfloat / advantage / performance 48 e.g. B. Wen et al, Power performance of an offshore floating wind turbine in platform pitching motion, Energy journal, volume 154,2018 or www.floatech-project.com challenge of roll, pitch and yaw motions is addressed on the floating platform level instead of addressing it at the turbine level. The whole floating platform needs to be moved for the counter-motions which requires inherently more energy than applying the counter motions directly at the turbine level. The here presented invention applies the countermotions in a more energy efficient method directly at the wind turbine (2) with an active ball joint (8)-based control of wind turbine (2) yaw, roll and pitch (see Section 4). In contrast, the mobile unmoored floating offshore wind turbines presented in the state-of-the-art (Ref.l) to (Ref.7) do not mention nor address this challenge at all. Only (Ref.8) partly addresses roll motions by considering different heeling angles (5°, 10°, 15°) and minimizing it for improved wind turbine output by enlarging the distance of the trimaran outriggers from the main hull. But the problem is addressed at the platform level and not directly at the wind turbine. vi) Oscillating blade pitch adjustment during rotor revolution for yaw optimization: As described in Section 2, the yaw manipulation of the wind turbine (2) is fundamental for the wind turbine ship's (1) sailing mechanism. However, as described the wind turbine (2) torque and consequently power output gets reduced with increasing yaw angle (see Figure 18). For this reason, this invention includes a mechanism for oscillating blade pitch adjustment during rotor revolution to optimize the wind flow angle at the airfoil blades when the wind turbine (2) is in yaw so that the reduction of power output for the wind turbine (2) in yaw can be reduced. It is state-of-the-art to adjust the blade pitch based on wind conditions. The novelty and key element of this part of the invention is, that the blade pitch is adjusted in an oscillating motion back and forth, not only occasionally when the environmental wind conditions change, but continuously during each rotor revolution. This optimizes the wind flow around the rotor blades (6) as described in Section 5. The state-of-the-art does not consider sailing with wind turbines in yaw positions. Therefore, no comparable optimizations are described. vii) Increased power output through wind funnel effect of the hulls (3): The wind funnel effect for increasing wind turbine's power output is described in prior art. However, it has not yet been considered for mobile unmoored sailing wind turbines (2) as presented in Section 8. b) Scale energy output by increasing accessible wind capacity i) Access far offshore regions with stronger and steadier winds: Stationary moored floating offshore wind turbines still face limitation in scalability with regard to water depth and distance from shore as presented in the state-of-the-art. The here presented invention of sailing wind turbine ships (1) shares the advantage of the unmoored mobile wind turbine concepts (Ref.l) to (Ref.8) of the presented STATE-OF-THE-ART that it is not limited by these scalability constraints and can increase the access to far offshore regions with stronger and steadier winds. ii) Less limitations through regulation, protracted permitting processes and approval procedures: The non-stationary unmoored mobile concept of the here presented invention has the advantage of accessing offshore regions for wind power generation beyond the territorial waters, i.e. the 12 nautical miles zones and the 200 nautical miles exclusive economic zones (EEZ). This helps to alleviate environmental and socioeconomic concerns linked to coastal regions e.g. from an environmental protection or fishing and tourism perspective. Therefore, it also reduces the regulation complexity as described in V. REGULATION COMPLEXITY in section STATE-OF-THE-ART as no protracted permitting processes and approval procedures for fixed installations are required. II. Decrease costs for offshore wind energy production and delivery a) Decrease cost for building and installing i) Pivot capability and underwater shelter enable lightweight construction: Typically, any platform or ship for offshore wind energy needs to be constructed in a very strong and robust construction to cope with the rough wind and sea offshore conditions. By design, it is tried to prevent massive roll, pitch, and yaw motions of the platform or ship. E.g. moored floating offshore wind platforms use heavy weight semi-submersible structures to reduce wave impact. An extreme case of roll, that is capsizing, is prevented by mooring anchors. Or for mobile unmoored floating offshore wind e.g. by expanding the distance between the trimaran outriggers of (Ref.8), therefore adding structural mass to cope with the rough offshore conditions. The here presented invention has the advantage that is built by design not to prevent these impacts of rough wind and sea conditions but to cope resiliently with them. On the one hand, roll, pitch and yaw motions are counteracted on and neutralized with the active ball joint (8)-based control (see Section 4). On the other hand, capsizing of the ship (1) in heavy seas and storms is coped with the pivot capability (see Section 1). In very strong storms, the ship can leverage the floodable hulls (3) and seek shelter underwater through the deliberate pivot mechanism (see Section 7) Hence, the here presented sailing wind turbine ship (1) can be built with a much lighter construction which decreases built and material cost. ii) Lightweight elastic mountings (4) and shrouds (5) instead of heavy wind turbine towers: Typical state-of-the start horizontal wind turbines are mounted on vertical towers. These are heavy and strong structures as they need to carry the whole turbine and rotor weight and cope with the aerodynamic wind forces and loads. Especially, the thrust force along the rotary axis into the leeward direction requires very stable and strong statics of the wind tower. For floating offshore, be it moored or unmoored stationary or mobile, this concept is inherently disadvantageous as the centre of gravity is at the top and thus the length of the tower contributes to the multiplication of the roll, pitch and yaw motions. The here presented invention has the advantage to use a lightweight mounting (4). The elastically bended mountings (4) together with the shrouds (5) hold the wind turbine (2) within the ship (1) structure and not at the top of it (see Section 3), which improves the positioning of the centre of gravity. iii) No special offshore heavy lift ships needed for installations: The here presented invention is an autonomous sailing wind turbine ship (1), that by design requires no support of special offshore heavy lift ships. The ship (1) is built in a shipyard and then navigates independently to the place of use. This is an advantage to the state-of-the-art of moored floating offshore wind, where special and costly ships are required for towing the wind turbine to the target site and for installing the anchors and power cables or gas pipelines as described in the state-of-the-art. b) Decrease cost during energy production i) No special offshore heavy lift ships needed for maintenance: Offshore maintenance and support is complex / costly as maintenance staff and material deployment offshore is more challenging than onshore. On top of this, given the rough sea environment, moored floating wind turbine platforms cannot be fully maintained offshore but need to be detached with special offshore installation ships from the moorings and cables or pipelines and towed back to the port for major component replacements or to avoid high costs or limited availability of even more expensive and scarce heavy lift ships49 that could technically do the major component replace at the offshore site. All these complexities / cost increase with water depth and distance from the shore, and hence contribute to scalability limitations. In contrast, the here presented invention operates fully mobile and returns to port or near-shore or offshore sub-station autonomously and regularly as part of the integrated energy delivery process for unloading the stored energy where in parallel also regular maintenance can be conducted synergistically. Additionally, major component replacements can benefit from the mobile operating model and can be conducted when the ship (1) returns autonomously back to port. This is enabled by multiple redundancy options e.g. able to continue operations with two out of three hulls (3), applying a deliberate pivot or by installing three wind turbines on one ship (1), so that if one fails two can be still utilized for the sailing and energy production. In case the sailing wind turbine ship (1) still is out of operations, it can be towed back to the port without detaching any moorings or power cable installations. ii) Less damage during offshore operations through storms: Damage of the ship (1) in extreme weather conditions such as in hurricanes and typhoons or through so called "monster" waves is reduced by leveraging the underwater shelter capability provided by the floodable hulls (3) as presented in Section 7. c) Decrease cost for energy delivery i) Flexible mobile energy delivery without grid connection: Dynamic power cabling and export cabling or gas pipelines, electricity sub-stations and grid connections put a high complexity / cost burden on state-of-the-art floating offshore wind solutions. The here presented sailing wind turbine ship (1) has the advantage of operating fully mobile with onboard energy storage. This enables to provide the energy when and where it is needed based on forward looking optimized dynamic route planning and navigation considering wind conditions at the dynamically planned route and schedule for energy delivery at desired destinations as presented in Section 6. 49 J. McMorland, Operation and maintenance for floating wind turbines: A review, Renewable and Sustainable Energy Reviews Volume 163, July 2022 EXEMPLARY EMBODIMENTS i. Four sailing courses examples (using common sailing course terminology50) a) Running downwind course Figure 39 shows the ship (1) running downwind course. The wind turbine (2) generates a thrust force (Th) parallel to the rotor axis in the leeward direction. The drift resistance force (Frv) is relatively low compared to the other courses, as in this course it is the same as the hull (3) forward drag (the water resistance force opposing forward movement), that is by design low. Hence, the forward force (Ffv) equals the thrust force (Th) minus the drift resistance force (Frv) as shown in the vector diagram on the right-hand side of Figure 44. Compared with the other sailing course examples, the running downwind course for the ship (1) is less suitable for efficient energy production especially for ships (1) with more than one wind turbine (2) as a) the wind turbines (2) are lined up in a row causing significant wake loss effects and b) the relative wind (headwind) from the movement of the ship (2) is directly opposing the wind direction which reduces the apparent wind at the wind turbine (2) substantially. b) Broad reach course Figure 40 shows the ship (1) sailing broad reach course. As explained in Section 2, the thrust force (Th) gets decomposed into the drift resistance force (Frv) and the forward force (Ffv) (see vector decomposition diagram on the right-hand side of Figure 40). The wind turbines (2) rotary axes point directly into the wind. With enough distance between the wind turbines (2) no (or at least significantly less than in previous downwind example) wake loss effect reduces the energy output and thrust generated. Additionally, no yaw deviation from the wind direction of the true wind (that would otherwise reduce power output see Figure 18) further contributes to a relatively high forward force (Ffv) and energy output. However, here too the relative wind from the movement of the ship (1) reduces the apparent wind and leads to an actual yaw deviation of the wind turbine (2) from the apparent wind direction depending on the ship's (1) movement velocity. 50 Zeke Quezada, Understanding Points of Sail, https: / / asa.com / news / 2022 / 12 / 06 / points-of-sail, American Sailing Association, 2022 c) Beam reach course Figure 41 shows the ship (1) sailing a beam reach course perpendicular to the wind direction. The wind turbines (2) are in 30° yaw. Therefore, the energy output and thrust force (Th) is reduced to 80% (see Figure 18). Given the thrust force (Th) is reduced, the forward force (Ffv) is reduced, too. The relative wind from the movement of the ship (1) increases on the one side the apparent wind and on the other hand further increases the actual yaw angle to the apparent wind as well depending on the ship's (1) movement velocity. At a very high movement velocity of the ship (1) combined with a low yaw angle (significantly lower than the in Figure 41 shown 30°), this beam reach course enables the wind turbines (2) to generate up to approx. 1.57 times the energy output compared to non-moving stationary wind turbines, (see Section ADVANTAGES OF THE INVENTION). d) Close reach courses Figure 42 shows the sailing wind turbine ship (1) sailing close reach course. This course enables the ship (1) to gradually tack against the wind so that together with leveraging changing wind directions the ship (1) has full control to navigate to any destination. The ship hulls (3) are slightly turned into the wind e.g. 18° windwards from beam reach course. The wind turbines (2) are still in 30° yaw. The resulting angle between thrust force (Th) and drift resistance force (Frv) is then: 30° -18° = 12°. Consequently, the forward force (Ffv) gets lower and with that also the movement velocity of the ship (1). Thus, the effect of the relative wind from the movement of the ship (1) on the increase of the yaw angle and on the apparent wind as well gets lower. Additionally, to the four described sailing courses any course in between can be sailed by the sailing wind turbine ship (1), excluding the no-go zone directly against the wind as typical for sailing. The implications on wind turbine (2) energy output and forward force (Ffv) and consequently ship (1) forward velocity are then as well a combination of the ones described above for the four courses. ii. Four oscillating blade pitch angle calculations The following sections show calculations of the blade (6) pitch angle p adjustment and its oscillating nature for four scenarios of rotor rotation at 0°, 90°, 180° and 270° for a wind turbine (2). The wind turbine (2) has the following parameters across all four scenarios: • diameter d: 100 m • tip speed ratio X: 7 • blade angle of attack a: 10° • yaw y: 30° • undisturbed wind velocity at wind turbine site vu: 12 m / s • true wind speed at the rotor plane v: 8 m / s (typically 2 / 3 of the actual wind velocity vu) • tip speed vt: 84 m / s (with tip speed ratio X = 7 and vu= 12 m / s) The four scenarios look each at the cross-section at the middle of the blade (6), where the rotational wind velocity u = 42 m / s (half of tip speed vt) a) Blade pitch angle at 0° rotor position Under the given scenario the blade (6) pitch angle at 0° rotor rotation is Po° = -1.6° calculated with the corresponding wind velocity vectors: • u = 42 m / s, with vector notation y : u = 42 see vector dimensions in Figure 43 \ 0 / / 8 cos(30°)\ • Vo" = 8 m / s, with vector notation: v0° = 8 sin(30°) \ 0 / / 8cos(30°) \ / 6.9\ • wo- = 46.5 m / s, with: iv0o = 42 + 8 sin(30°) = 46 , see Section 5 equation (E4o°) \ 0 / \ 0 / With Section 5 equation (E3o°) and (E2o°) one gets (Elo°): Po° = cos - 10° = cos1 ( 1932 ) - 10° = 8.4° - 10° = -1.6° .42 ■ 46.5 / Figure 43 shows the calculation results in their geometrical context. The vector space dimensions are shown for both, the frontal view and the view from above for orientation. b) Blade pitch angle at 90° rotor position Under the given scenario the blade (6) pitch that provides the optimal apparent wind w9o° angle at 90° rotor rotation is p9o° = -0.4° calculated with the wind velocity vectors: / X\ / 0 \ • u = 42 m / s, with vector notation I y j: u= 0 see vector dimensions in Figure 44 W \42 / • V9o° = 8m / s / 8 cos(30°)\ p9o° = 0 , see Section 5 Equation (E59o°) \ 0 / / 8cos(30°)\ [6-9\ • W9o° = 42.6 m / s, with: w90o = 0 = 0 , see Section 5 equation (E49o°) \ 42 / \42 / With Section 5 equation (E39o°) and (E29o°) one gets (El9o°): p90o = cos - 10° = cos1 ( 1764 ) - 10° = 9.6° - 10° = -0.4° .42 ■ 42.67 Figure 44 shows the calculation results in their geometrical context. The vector space dimensions are shown for both, the frontal view and the view from above for orientation. c) Blade pitch angle at 180° rotor position Under the given scenario the blade (6) pitch that provides the optimal apparent wind wiso° angle at 180° rotor rotation is Piso° = 0.1° calculated with the corresponding wind velocity vectors: • u = 42 m / s, with vector notation y : u = —42 see vector dimensions in Figure 45 \ 0 / / 8 cos(30°)\ • Vi8o° = 8 m / s, with vector notation: v180o = I 8 sin(30°) I \ 0 / / 8cos(30°) \ / 6.9 \ • Wi8o° = 38.6 m / s, with: w180» = I -42 + 8 sin(30°) I = I -38 I, see equation (E4iso°) \ 0 / \ 0 / With Section 5 equation (E3iso°) and (E2iso°) one gets (Eliso°): • p180o= cos1 - 10° = cos-1 (4215^6) - 10° = 10.1° - 10° = 0.1° ■38 0 Figure 45 shows the calculation results in their geometrical context. The vector space dimensions are shown for both, the frontal view and the view from above for orientation. d) Blade pitch angle at 270° rotor position Under the given scenario the blade (6) pitch that provides the optimal apparent wind W27o° angle at 270° rotor rotation is P27o° = -0.4° calculated with the wind velocity vectors: / X\ / 0 \ • u = 42 m / s, with vector notation I y j: u = 0 see vector dimensions in Figure 46 W \—42 / • v27o° = 8m / s / 8 cos(30°)\ P2700 = 0 , see Section 5 equation (E527o°) \ 0 / / 8 cos(30°)\ / 6.9 \ • W27o°= 42.6 m / s, with: w27o° = 0 = 0 , see Section 5 equation (E427o°) \ -42 / \—42 / With Section 5 equation (E327o°) and (E227o°) one gets (E127o°): / / 0 \ / 6.9 \ \ P270° — COS - 10° = cos”1 ( 1764 ) - 10° = 9.6° - 10° = -0.4° .42 ■ 42.67 Figure 46 shows the calculation results in their geometrical context. The vector space dimensions are shown for both, the frontal view and the view from above for orientation. With the same method as presented in Section 5 and exemplarily applied in above calculations any other scenario of wind turbine (2) setup, wind conditions and rotor positions can be calculated. The above method for oscillating adjustment of blade (6) pitch angle and the corresponding calculations can be further extended to consider an additional wind vector caused by the relative wind of the moving ship (1). However, the movement velocity of the moving ship (1) is relatively slow compared to the offshore wind speeds and the rotational wind velocity at the blades (6) resulting from rotor rotation. Therefore, the impact of the relative wind of the moving ship (1) is less significant on the overall blade (6) pitch angle calculation and hence is neglected in the above calculations. The relative wind of the moving ship (1) can be added to further add accuracy. Independently of that, it can be noticed that a clockwise rotating wind turbine (2) provides aerodynamic advantages in a yawed wind turbine (2) sailing course (see e.g. beam reach and close reach courses above) when the wind comes from the port side of the sailing wind turbine ship (1). This is the opposite situation as in the above section ii. Shown example calculations a) - d), where the wind is coming from starboard side. The apparent wind velocity in a) - d) is the highest at the top (i.e. at 0° rotor blade (6) rotation) and the lowest at the bottom (i.e. at 180° rotor blade (6) rotation) given the yawed wind turbine (2). Though much less offshore than onshore, the wind blows typically relatively stronger at a higher distance from the ground than close to the surface, which is called wind shear. Hence, if the wind comes from the port side of the ship (1) instead of from the starboard side as shown in a) - d), the apparent wind at the rotor blade (6) bottom position (i.e. at 180° rotor blade (6) rotation) is relatively stronger and relatively weaker at the top position (i.e. at 0° rotor blade (6) rotation). This the oscillating blade (6) pitch angle adjustment can balance out or at least counteract the wind shear effect and thus provide a more balanced load on the wind turbine (2) which is beneficial e.g. regarding reduced material fatigue. Another aspect to consider is that the oscillating blade (6) pitch angle adjustment also consumes energy. In the case that this does not provide a net benefit for the energy output under given environmental conditions (e.g. frequent changes of wind direction, gusts of wind, wake loss or other aerodynamical effects) or in case of relatively high energy consumption for the pitch control, the presented adjustment method can be still used to calculate the optimal average blade (6) pitch angle for a given yaw angle of the wind turbine (2) when sailing a specific course to the wind.

Images