Cost–benefit analysis of a trans-arctic alternative route to the Suez canal: a method based on high-fidelity ship performance, weather, and ice forecast models

Climate change in recent years has produced viable shipping routes in the Arctic. However,\ua0critical uncertainties related to maritime operations in the Arctic make it difficult to predict ship\ua0speeds in ice and, thus, the voyage time and fuel costs. Cost–benefit analysis of alternative Arctic\ua0routes based on accurate environmental condition modeling is required. In this context, this paper\ua0presents a holistic approach that considers the major voyage-related costs of a trans-Arctic route as\ua0an alternative to the conventional routes via the Suez Canal Route (SCR) for existing merchant ships.\ua0This tool is based on high-fidelity models of ship performance, metocean forecasting, and a voyage\ua0optimization algorithm. Case studies are performed based on a general cargo vessel in operation\ua0to quantify realistic expenses inclusive of all the major operational, fuel, and voyage costs of the\ua0specific voyages. A comparison is made between the total costs of the trans-Arctic route and SCR for\ua0different seasons, which proves the economic feasibility of the trans-Arctic route. Overall, this work\ua0can provide valuable insights to help policymakers as well as shipbuilders, owners, and operators\ua0to assess the potential cost-effectiveness and sustainability of future Arctic shipping, thereby better\ua0developing future strategies

Experimental and Numerical Investigation of Speed Loss due to Seakeeping and Maneuvering

Accurate prediction of the real voyaging speed for ocean‐going vessels in the actual weather condition is important for the expanding shipping industry. Ship owners are always aiming at achieving the highest profit, so delivering the goods to the destination within the designed schedule time is of great concern. At the same time, the increasing attention on environmental issues as well as increasing fuel price have put more pressure on optimizing the ship design with respect to energy efficiency. Also, accurate prediction of the real attainable speed will greatly improve the sea margin prediction. From these respects, the research work on speed loss study is important and necessary. Speed loss is usually categorized as voluntary or involuntary. Voluntary speed loss is when the ship master actively reduces the ship speed to avoid slamming, propeller racing, excessive ship motion or other effects that might cause danger or severe discomfort. Voluntary speed loss is subjective and relies on ship master's experience. Different ship masters can have quite different actions to the same circumstance based on their ability to estimate the potential danger. Involuntary speed loss is due to added resistance from waves, wind, current and reduced thrust and efficiency due to waves and other changes in operational conditions. Involuntary speed loss is in focus in this thesis work. In order to investigate the nature of speed reduction in the real environment, integrated knowledge about resistance, propulsion, ship machinery, seakeeping, automatic control and maneuvering are required. This thesis takes advantage of model tests and a numerical simulation tool based on simplified modular concept to investigate the nature of speed reduction in seakeeping and maneuvering conditions. A series of experiments were carried out on a model of 8000 DWT tanker in the large towing tank and ocean basin at Marine Technology Center in Trondheim, Norway. The model was selfpropelled and mainly running in moderate long wave conditions. For speed loss in head sea conditions, three different bow shapes were tested in order to investigate the influence of added wave resistance. Due to the practical difficulty of applying towrope force to balance the frictional resistance coefficient difference between model scale and full scale ship, a method is proposed in this thesis to make compensation for the frictional resistance difference and predict speed loss of the ships when propeller is working at 'ship propulsion point'. Test results show that a conventional bow with bulb and flare gave least calm water resistance, while a bow without bulb and flare gave the least total resistance in the tested wave conditions. That means bulb can have positive influence on calm water resistance and negative effect on added wave resistance. Reduction of speed loss in waves up to order of 10% can be gained by relatively minor changes to the bow shape of a vessel. Another two tests for speed loss in zigzag maneuvering in head waves and speed loss in oblique waves were carried out in the towing tank and ocean basin respectively. Speed loss when doing zigzag maneuvering in waves is due to yawing, added wave resistance and loss of thrust due to steering; while for speed loss in oblique waves is due to added wave resistance and loss of thrust due to steering. For the test of speed loss in oblique waves, towrope force is added by an air fan. Due to limitation of basin length, converged speed is not always achieved during the tests due to the large mass of the model. A converged speed prediction method is proposed which can be used to correct the nonconverged tests results. This method is carefully verified and can give good prediction of attainable speed in waves. However, this method is sensitive to the selection of thrust deduction factor in waves. Also how much speed loss due to added wave resistance and due to steering is pointed out. Speed loss due to added wave resistance and steering is of the same magnitude in head sea and bow sea conditions. While for beam sea, speed loss due to steering is dominating. Numerical simulation work was carried out in order to make comparisons with experimental results. Comparable calculations were performed in the frequency domain tool ShipX and in the time‐domain tool Vessel Simulator. Ship motion is calculated by linear strip theory and added wave resistance in head sea is calculated by the method developed by Gerritsma and Beukelman and the Direct Pressure Integration method. Wave resistance in other than head sea condition in surge, sway and yaw directions is calculated by the method proposed by Loukakis and Sclavounos, which is an extension of the Gerritsma and Beukelman method to other than head sea. For the speed loss in head sea condition, both frequency domain calculations using ShipX and time domain calculations using Vessel Simulator were carried out. It is concluded that both methods can give a good prediction of speed loss in moderate sea conditions. For the cases that steering effect has to be taken into account, time domain simulation is a preferable method. Generally speaking, numerical results can give a good correlation with model test data. Based on the good validation of the numerical tool, further numerical investigations were carried out to compare the speed loss characteristics between conventional propeller‐rudder system and azimuth thrusters. The results showed that conventional propeller‐rudder system has better speed keeping ability than azimuth thrusters. That is because in the conventional propeller‐rudder system propeller force is not decomposed by the rudder angle and also conventional propeller‐rudder system has higher ratio of longitudinal thrust force/transverse thrust force than azimuth thrusters within the working steering angle range. In the end, recommendations to ITTC procedures to predict speed loss and power increase in irregular waves and sea margin were proposed. A method to predict 'ship propulsion point' from the self‐propulsion test carried out at 'model propulsion point' is specified in this thesis. This method will greatly improve the procedures to predict power increase in irregular waves from model tests in regular waves. Also another suggestion is proposed that when evaluating power increase in irregular waves and sea margin prediction, thrust deduction due to ventilation and steering effect should be taken into account in addition to thrust diminution factor

Ice forces acting on towed ship in level ice with straight drift. Part I: Analysis of model test data

A series of tests in an ice tank was carried out using a model-scale ship to investigate the ice loading process. The ship model Uikku was mounted on a rigid carriage and towed through a level ice field in the ice tank of the Marine Technology Group at Aalto University. The carriage speed and ice thickness were varied. In this paper, ice loading process was described and the corresponding ice forces on the horizontal plane were analysed. A new method is proposed to decompose different ice force components from the total ice forces measured in the model tests. This analysis method is beneficial to understanding contributions of each force component and modelling of ice loading on hulls. The analysed experimental results could be used for comparison with further numerical simulations

Ice forces acting on towed ship in level ice with straight drift. Part II: Numerical simulation

A numerical method is proposed to simulate level ice interaction with ship in transverse and longitudinal directions in time domain. A novel method is proposed to simulate non-symmetric transverse force in a stochastic way. On the basis of observations from the model tests, the simulation of longitudinal force combines the ice bending force acting on the waterline, submersion force below the waterline and ice friction forces caused by transverse force and ice floes rotation amidships. In the simulations the ship was fixed and towed through an intact ice sheet at a certain speed. The setup of the numerical simulation is similar to the ice tank setup as much as possible. The simulated results are compared with model tests data and the results show good agreement with the measurement. Keywords: Numerical simulation, Level ice, Ice force, Compariso

Comprehensive Analysis of the Impact of the Icing of Wind Turbine Blades on Power Loss in Cold Regions

Blade icing often occurs on wind turbines in cold climates. Blade icing has many adverse effects on wind turbines, and the loss of output power is one of the most important effects. With the increasing emphasis on clean energy around the world, the design and production of wind turbines tend to be large-scale. So this paper selected the 15 MW wind turbine provided by NREL (American Renewable Energy Laboratory) to study the influence of blade icing on output power. In this paper, a multi-program coupled analysis method named CFD-WTIC-ILM (CFD: Computational fluid dynamics; WTIC: Wind Turbine Integrated Calculation; ILM: Ice loss method) was proposed to analyze the whole machine wind turbine. Firstly, Fensap-ice was used to simulate the icing of the wind turbine blades, and then the icing results were input into WTIC for the integrated calculation and analysis of the wind turbine. Then, the WTIC calculation results were used to simulate SCADA (supervisory control and data acquisition) data and input into ILM to calculate the power loss. Finally, this paper analyzed the comprehensive influence of icing on output power. The calculation results show that the ice mainly accumulates on the windward side of the blade. Icing has a great influence on the aerodynamic characteristics of the airfoil, leading to a significant decrease in the power curve. The rated wind speed is pushed from 10.59 m/s to 13 m/s. The power loss of the wind turbine in the wind speed optimization stage is as high as 37.48%, and the annual power loss rate caused by icing can reach at least 22%

Structural Parametric Optimization of the VolturnUS-S Semi-Submersible Foundation for a 15 MW Floating Offshore Wind Turbine

The full exploitation of offshore wind resources can essentially satisfy the massive energy demand. The realization and application of ultra-high-power offshore wind turbines are crucial to achieving full use of deep-sea wind energy and reducing the cost of wind power. For the VolturnUS-S semi-submersible floating foundation of a 15 megawatt (MW) offshore wind turbine, the effect of structural parameters on hydrodynamic performance was investigated by controlling the variables described in this paper. Accordingly, the floating foundation was optimized and coupled to the 15 MW offshore wind turbine. The dynamic performance of the integrated 15 MW offshore wind turbine was analyzed under different operating conditions, by applying the aero-hydro-servo-elastic coupled method. The results show that for a wave in a 0-degree direction, a 5% increase of column spacing will reduce the peak value of the pitch transfer function by 33.61%, and that a 5% decrease of the outer column diameter will further reduce the peak value by 26.27%. The standard deviation of the time-domain surge responses was reduced by 19.78% for the optimized offshore wind turbine, and the maximum value of the mooring line tension was reduced by 13.55% under normal operating conditions

Numerical analysis of blade icing influence on the dynamic response of an integrated offshore wind turbine

When a wind turbine is working in a cold and humid environment, icing may occur which lead to its performance reduction or even blades fracture. In this paper, a CFD-WTIA (Wind Turbine Integrated Analysis) coupled method is established to analyze the blade icing process and its influence on the overall dynamic performance of an integrated jacket-support offshore wind turbine. Firstly, motions of the blades are calculated by the WTIA method and used as input into CFD. Then, dispersed multi-phase model and melting-solidification model are used to simulate the icing growth phenomenon of three-dimensional blades. The k-ε turbulence model is used to calculate the aerodynamic performance before and after icing. Finally, the aerodynamic results after blade icing are returned to WTIA for integrated dynamic response acquisition. At the same time, the dynamic response of the wind turbine under the combined influence of ice and sea ice is analyzed. Results show that the blade ice-accretion increases linearly along the blade span-wise direction and is mainly concentrated on the leading edge of the blade. Lift and drag coefficients are seen deceased and increased respectively after icing. Power production, generator torque, rotor speed, as well as blade vibration are quantitatively studied. The methodology and findings of this paper can provide a good reference for the safety performance evaluation of an icing offshore wind turbine

Structural Parametric Optimization of the VolturnUS-S Semi-Submersible Foundation for a 15 MW Floating Offshore Wind Turbine

The full exploitation of offshore wind resources can essentially satisfy the massive energy demand. The realization and application of ultra-high-power offshore wind turbines are crucial to achieving full use of deep-sea wind energy and reducing the cost of wind power. For the VolturnUS-S semi-submersible floating foundation of a 15 megawatt (MW) offshore wind turbine, the effect of structural parameters on hydrodynamic performance was investigated by controlling the variables described in this paper. Accordingly, the floating foundation was optimized and coupled to the 15 MW offshore wind turbine. The dynamic performance of the integrated 15 MW offshore wind turbine was analyzed under different operating conditions, by applying the aero-hydro-servo-elastic coupled method. The results show that for a wave in a 0-degree direction, a 5% increase of column spacing will reduce the peak value of the pitch transfer function by 33.61%, and that a 5% decrease of the outer column diameter will further reduce the peak value by 26.27%. The standard deviation of the time-domain surge responses was reduced by 19.78% for the optimized offshore wind turbine, and the maximum value of the mooring line tension was reduced by 13.55% under normal operating conditions

Research on Mooring System Design for Kulluk Platform in Arctic Region

Mooring system design of a floating offshore structure in the arctic region is considered to be extremely important. This paper aims at investigating an optimal mooring system for the Kulluk platform operating in the Beaufort Sea, which has ice-free and ice-covered conditions during the whole year time. In order to complete the layout design of the mooring system to satisfy the year-round operation, both the effect of wave loads and ice loads should be considered. The research establishes a coupled numerical production system composed of the Kulluk platform and mooring system. Wave load is solved by potential flow theory. The slender finite element method is used to compute the tension of the mooring system. The nonlinear finite element method, discrete element method, and empirical formula are compared to analyze ice load. Finally, the discrete element method is selected for the analysis of the Kulluk, and the simulated results are compared reasonably with the field data. When studying the mooring line configurations, quantitative time-domain analysis is carried out, including tension of mooring lines and the motions of the platform under different working conditions. The research work in this paper will provide a reference for the optimal design of the mooring system of the platform operating in the Arctic Sea