Marine Energy Research Open Access

Icing Models and Mitigation Methods for Offshore Wind in Cold Climate Regions: A Review

Offshore wind turbines (OWTs) in cold climate regions have become increasingly significant due to the abundant wind resources with the development of renewable energy. These areas offer considerable potential for the development of OWTs. Generating energy for communities in cold climate regions involves overcoming significant challenges posed by the remote and harsh environmental conditions. This review presents the state-of-the-art research regarding prediction models for ice accretion on wind turbine components. Furthermore, this review summarizes advanced mitigation solutions, such as cold-weather packages and ice protection systems, designed to address icing issues. The present study identifies critical knowledge gaps in OWT deployment in cold climate regions and proposes future research directions.

Strategic Deployment of Service Vessels for Improved Offshore Wind Farm Maintenance and Availability

This research explores the optimization of Operations and Maintenance (O&M) strategies for offshore wind farms using a sophisticated O&M simulator built on the Markov Chain Monte Carlo method. By integrating real-world constraints such as vessel availability and weather conditions, the study assesses O&M logistics’ impacts on wind farm availability, energy production, and overall costs across different scenarios in the Celtic Sea. Through comparative analysis of eight case studies involving various combinations of Crew Transfer Vessels (CTV) and Service Operation Vessels (SOV), the research highlights the critical role of strategic vessel deployment and the potential of permanent SOV stationing to enhance operational efficiency, reduce downtime, and lower O&M costs. In this study, the permanent SOV can increase up to 20% availability of the whole wind farm. The findings underscore the importance of adaptive O&M planning in improving the sustainability and financial viability of offshore wind energy projects.

Marine Energy, the Future Practical Route to Carbon Neutrality—Foreword: Navigating the Voyage of Marine Energy Research

Energy Harness and Wake Structure of “Cir-Tri-Att” Oscillators for Flow-Induced Motion Tidal Energy Conversion System

The research focuses on the flow-induced motion (FIM) and energy harness of “Cir-Tri-Att” oscillators (CTAO). The wake was photographed by particle image velocimetry (PIV) to explore wake structures. With the increase of the aspect ratios: the ability of oscillators to galloping under self-excitation or external excitation is enhanced. When ζ = 0.033, U_r = 12.5, the maximum amplitude ratio A* = 2.408 for oscillators with α = 1:1. Moreover, oscillators with higher aspect ratios can bear larger loads, which is conducive to energy utilization and conversion. The maximum power output P_harn = 16.588 W and the optimal efficiency η_harn = 24.706% appear in oscillators with α = 1.5:1. Additionally, In the soft galloping (SG), the wake mode is 4P or 3P. The wake vortex is more broken and its scale increases, but the force effect of the oscillators is better and the oscillation is more stable. The pressure difference makes for a longer oscillation period. This paper summarizes the FIM, energy harness and wake structures of the CTAO under different working conditions, which provides theoretical and data support for the optimization oscillators of flow-induced motion tidal energy conversion system.

Numerical Investigation of a Point Absorber Wave Energy Converter Integrated with Vertical Wall and Latching Control for Enhanced Power Extraction

This study presents a numerical investigation of a point absorber wave energy converter (WEC) with a focus on improving its performance through the utilization of a vertical wall and latching control in the power take-off (PTO) system. Prior to numerical evaluations, experimental data incorporating PTO considerations and numerical simulation results were examined to validate the accuracy of the numerical methodology employed in this research. This study introduces a numerical PTO model and latching control for a further investigation. Comparative analyses were carried out on the displacement, velocity, and force of the PTO, absorbed power, and capture width ratio (CWR), considering the incorporation of a vertical wall and latching control. The results confirm that the introduction of both vertical wall and latching control significantly improves the CWR of the WEC, showing the effectiveness of incorporating a vertical wall and latching control in enhancing power extraction.

Offshore Renewable Energy Advance

Offshore renewable energy generation has become an important means to address the energy crisis and climate change, which has gained widespread attention in recent years. This article presents classic domestic and international cases that introduce the development and industrial transformation of generation technologies for offshore wind, offshore photovoltaics, ocean wave energy, tidal energy and temperature difference energy. Offshore power generation projects face challenges in design, safety, long-term operation and economic feasibility. Offshore renewable energy generation is gradually moving towards industrialization, and is expected to become a key component of global energy supply in the future with technological advancements and policy support, providing strong support for tackling climate change and achieving sustainable development goals.

Motion Control of Floating Wind-Wave Energy Platforms

Mitigating wave-induced motions in floating multi-body systems is a critical challenge in ocean engineering. For single floating structures, such as floating platforms or vessels, applying active control requires considerable energy. It is also a common solution to add auxiliary structures and a power take-off (PTO) device, thereby forming a multi-body system that utilises passive control. However, the effectiveness of this method is limited due to varying phase differences between control forces and motions, which change across different wave frequencies. The present work proposes a novel semi-active structural control method, which can effectively provide optimised control force to the main body within a multi-body system. The key point of this method is tuning the phases between the forces and motions of floating bodies. Proper tuning can neutralise the main floating body’s wave-induced motion by utilising the wave-induced motion of the auxiliary structure. The controller is developed under an optimal declutching control framework, adjusting the damping coefficients of the PTO system to provide discrete resistance to the target body. A floating semi-submersible (SS) platform equipped with a heave ring as an auxiliary structure is selected and analysed as the case study. The results demonstrate the method’s efficacy in reducing motion for floating wind turbine (FWT) platforms and its applicability to various types of multiple floating bodies. Interestingly, our optimal declutching control can “kill two birds with one stone”. It can simultaneously enhance motion reduction and increase power capture. In the current study, the proposed controller achieved a maximum motion reduction of 30% for the platform.

Hydrodynamic Performance of a Hybrid Floating Power Dock Combining Multi-Cantilever Type Buoys

This paper proposes a novel three-dimensional oscillating pendulum wave energy converter (WEC) that integrates an oscillating float dock station. The device captures wave energy by utilizing both the pitch and roll motions of its primary float and the pendular motion of a buoy. A time-domain analysis method is used to numerically evaluate the hydrodynamic behavior and energy conversion efficiency of the WEC. In ANSYS AQWA, a multi-cantilever WEC model is employed to address the fluid-solid coupling, calculating the device’s motion response and capturing the width ratio under various environmental conditions. Additionally, by modifying key geometric parameters including float radius, length, and cantilever angle, the study examines the rotation at the articulation point and the capture width ratio variation for different device configurations. Results indicate that the device achieves a maximum capture width ratio at a float radius of approximately 120 mm under T = 1.4 s, and a 130 mm for wave periods of 1.5 s and 1.6 s. The highest average capture width ratio is reached at a power take-off (PTO) damping coefficient of 400 N·s/m. The study further investigates the effect of cantilever angle and float length, aiding in the optimization of these geometric parameters.

State of the Art in Wave Energy Conversion Technologies in China

This paper reviews the advancements in wave energy converter technologies in China, covering device design, performance evaluation, and system control techniques. It highlights power control technologies in wave energy conversion, including adaptive control, model predictive control, clutch control, clamp control, resistive load control, approximate optimal speed control, nonlinear control, and intelligent control methods. Through an analysis of these technologies, the study outlines the future directions and challenges in wave energy development in China, while also proposing potential pathways for optimizing the performance of wave energy conversion devices.

Research Status and Development Trend of Floating Photovoltaic Structure System

Under the guidance of the dual carbon goals, the development and utilization scale of new energy in China, including photovoltaics and wind power, has steadily increased. Particularly, the floating photovoltaic technology in inland waters has been developing quickly over the past decade because it could compensate for certain shortcomings of traditional terrestrial photovoltaics. The offshore floating photovoltaic (FPV) pilot projects are also continuously emerging due to the advantages of longer daylight hours, higher radiation levels, and enhanced efficiency of light utilization in marine environments compared to terrestrial settings under identical solar irradiance conditions. To comprehensively understand the development prospects of offshore FPV systems, the development progress of FPV systems was traced, and an analysis was conducted on the forms of various types of floating structures, their technical characteristics, and their applicability in the marine environment. Summarization was carried out on the floating photovoltaic mooring system in terms of the classification of the mooring, the chain deployment mode, the form of the mooring foundation, etc., and a few new types of mooring systems were put forward. Finally, the development trend of the offshore FPV system was predicted.

Offshore Renewable Energy Advance

Offshore renewable energy generation has become an important means to address the energy crisis and climate change, which has gained widespread attention in recent years. This article presents classic domestic and international cases that introduce the development and industrial transformation of generation technologies for offshore wind, offshore photovoltaics, ocean wave energy, tidal energy and temperature difference energy. Offshore power generation projects face challenges in design, safety, long-term operation and economic feasibility. Offshore renewable energy generation is gradually moving towards industrialization, and is expected to become a key component of global energy supply in the future with technological advancements and policy support, providing strong support for tackling climate change and achieving sustainable development goals.utf-8

Icing Models and Mitigation Methods for Offshore Wind in Cold Climate Regions: A Review

Offshore wind turbines (OWTs) in cold climate regions have become increasingly significant due to the abundant wind resources with the development of renewable energy. These areas offer considerable potential for the development of OWTs. Generating energy for communities in cold climate regions involves overcoming significant challenges posed by the remote and harsh environmental conditions. This review presents the state-of-the-art research regarding prediction models for ice accretion on wind turbine components. Furthermore, this review summarizes advanced mitigation solutions, such as cold-weather packages and ice protection systems, designed to address icing issues. The present study identifies critical knowledge gaps in OWT deployment in cold climate regions and proposes future research directions.utf-8

Strategic Deployment of Service Vessels for Improved Offshore Wind Farm Maintenance and Availability

This research explores the optimization of Operations and Maintenance (O&M) strategies for offshore wind farms using a sophisticated O&M simulator built on the Markov Chain Monte Carlo method. By integrating real-world constraints such as vessel availability and weather conditions, the study assesses O&M logistics’ impacts on wind farm availability, energy production, and overall costs across different scenarios in the Celtic Sea. Through comparative analysis of eight case studies involving various combinations of Crew Transfer Vessels (CTV) and Service Operation Vessels (SOV), the research highlights the critical role of strategic vessel deployment and the potential of permanent SOV stationing to enhance operational efficiency, reduce downtime, and lower O&M costs. In this study, the permanent SOV can increase up to 20% availability of the whole wind farm. The findings underscore the importance of adaptive O&M planning in improving the sustainability and financial viability of offshore wind energy projects.utf-8

Numerical Investigation of a Point Absorber Wave Energy Converter Integrated with Vertical Wall and Latching Control for Enhanced Power Extraction

This study presents a numerical investigation of a point absorber wave energy converter (WEC) with a focus on improving its performance through the utilization of a vertical wall and latching control in the power take-off (PTO) system. Prior to numerical evaluations, experimental data incorporating PTO considerations and numerical simulation results were examined to validate the accuracy of the numerical methodology employed in this research. This study introduces a numerical PTO model and latching control for a further investigation. Comparative analyses were carried out on the displacement, velocity, and force of the PTO, absorbed power, and capture width ratio (CWR), considering the incorporation of a vertical wall and latching control. The results confirm that the introduction of both vertical wall and latching control significantly improves the CWR of the WEC, showing the effectiveness of incorporating a vertical wall and latching control in enhancing power extraction.utf-8

Hydrodynamic Performance of a Hybrid Floating Power Dock Combining Multi-Cantilever Type Buoys

This paper proposes a novel three-dimensional oscillating pendulum wave energy converter (WEC) that integrates an oscillating float dock station. The device captures wave energy by utilizing both the pitch and roll motions of its primary float and the pendular motion of a buoy. A time-domain analysis method is used to numerically evaluate the hydrodynamic behavior and energy conversion efficiency of the WEC. In ANSYS AQWA, a multi-cantilever WEC model is employed to address the fluid-solid coupling, calculating the device’s motion response and capturing the width ratio under various environmental conditions. Additionally, by modifying key geometric parameters including float radius, length, and cantilever angle, the study examines the rotation at the articulation point and the capture width ratio variation for different device configurations. Results indicate that the device achieves a maximum capture width ratio at a float radius of approximately 120 mm under T = 1.4 s, and a 130 mm for wave periods of 1.5 s and 1.6 s. The highest average capture width ratio is reached at a power take-off (PTO) damping coefficient of 400 N·s/m. The study further investigates the effect of cantilever angle and float length, aiding in the optimization of these geometric parameters.utf-8

Motion Control of Floating Wind-Wave Energy Platforms

Mitigating wave-induced motions in floating multi-body systems is a critical challenge in ocean engineering. For single floating structures, such as floating platforms or vessels, applying active control requires considerable energy. It is also a common solution to add auxiliary structures and a power take-off (PTO) device, thereby forming a multi-body system that utilises passive control. However, the effectiveness of this method is limited due to varying phase differences between control forces and motions, which change across different wave frequencies. The present work proposes a novel semi-active structural control method, which can effectively provide optimised control force to the main body within a multi-body system. The key point of this method is tuning the phases between the forces and motions of floating bodies. Proper tuning can neutralise the main floating body’s wave-induced motion by utilising the wave-induced motion of the auxiliary structure. The controller is developed under an optimal declutching control framework, adjusting the damping coefficients of the PTO system to provide discrete resistance to the target body. A floating semi-submersible (SS) platform equipped with a heave ring as an auxiliary structure is selected and analysed as the case study. The results demonstrate the method’s efficacy in reducing motion for floating wind turbine (FWT) platforms and its applicability to various types of multiple floating bodies. Interestingly, our optimal declutching control can “kill two birds with one stone”. It can simultaneously enhance motion reduction and increase power capture. In the current study, the proposed controller achieved a maximum motion reduction of 30% for the platform.utf-8

Energy Harness and Wake Structure of “Cir-Tri-Att” Oscillators for Flow-Induced Motion Tidal Energy Conversion System

The research focuses on the flow-induced motion (FIM) and energy harness of “Cir-Tri-Att” oscillators (CTAO). The wake was photographed by particle image velocimetry (PIV) to explore wake structures. With the increase of the aspect ratios: the ability of oscillators to galloping under self-excitation or external excitation is enhanced. When ζ = 0.033, U_r = 12.5, the maximum amplitude ratio A* = 2.408 for oscillators with α = 1:1. Moreover, oscillators with higher aspect ratios can bear larger loads, which is conducive to energy utilization and conversion. The maximum power output P_harn = 16.588 W and the optimal efficiency η_harn = 24.706% appear in oscillators with α = 1.5:1. Additionally, In the soft galloping (SG), the wake mode is 4P or 3P. The wake vortex is more broken and its scale increases, but the force effect of the oscillators is better and the oscillation is more stable. The pressure difference makes for a longer oscillation period. This paper summarizes the FIM, energy harness and wake structures of the CTAO under different working conditions, which provides theoretical and data support for the optimization oscillators of flow-induced motion tidal energy conversion system.utf-8

Influence of Soil Damping and Aerodynamic Damping on the Dynamic Response of Monopile Wind Turbines under Earthquake and Wind Loads

Vibration damping is essential for predicting the responses of wind turbines, and contributions mainly come from structural, soil, and aerodynamic damping. In engineering design, it is difficult to precisely account for the individual contributions of each damping source. As a result, a simplified approach is commonly used, where a total damping factor is applied that combines the effects of structural, soil, aerodynamic, and other damping sources. However, the accuracy of this simplified approach in predicting the dynamic response of turbines has not been thoroughly evaluated. This study primarily focuses on the applicability of vibration-damping simplification methods, particularly in analyzing the dynamic response of turbines under earthquake and wind loads.utf-8

State of the Art in Wave Energy Conversion Technologies in China

This paper reviews the advancements in wave energy converter technologies in China, covering device design, performance evaluation, and system control techniques. It highlights power control technologies in wave energy conversion, including adaptive control, model predictive control, clutch control, clamp control, resistive load control, approximate optimal speed control, nonlinear control, and intelligent control methods. Through an analysis of these technologies, the study outlines the future directions and challenges in wave energy development in China, while also proposing potential pathways for optimizing the performance of wave energy conversion devices.utf-8

Research Status and Development Trend of Floating Photovoltaic Structure System

Under the guidance of the dual carbon goals, the development and utilization scale of new energy in China, including photovoltaics and wind power, has steadily increased. Particularly, the floating photovoltaic technology in inland waters has been developing quickly over the past decade because it could compensate for certain shortcomings of traditional terrestrial photovoltaics. The offshore floating photovoltaic (FPV) pilot projects are also continuously emerging due to the advantages of longer daylight hours, higher radiation levels, and enhanced efficiency of light utilization in marine environments compared to terrestrial settings under identical solar irradiance conditions. To comprehensively understand the development prospects of offshore FPV systems, the development progress of FPV systems was traced, and an analysis was conducted on the forms of various types of floating structures, their technical characteristics, and their applicability in the marine environment. Summarization was carried out on the floating photovoltaic mooring system in terms of the classification of the mooring, the chain deployment mode, the form of the mooring foundation, etc., and a few new types of mooring systems were put forward. Finally, the development trend of the offshore FPV system was predicted.utf-8