Houlder’s Approach to Sustainable Offshore Wind Installation

Offshore wind energy is a solution to the energy crisis that we face today. It capitalizes on strong offshore winds to promote a cleaner and more environmentally sustainable future. In 2023, the global offshore wind capacity was approximately 75 gigawatts (GW), with forecasts suggesting growth beyond 200 GW by 2030. This rapid expansion highlights the sector’s potential to combat climate change and its ability to deliver cost-competitive electricity, with generation costs as low as $40 per megawatt-hour (MWh) — lower than many traditional energy sources.

Despite its promise, the industry grapples with multifaceted installation, operations, and maintenance challenges. Leveraging advanced computer-aided engineering (CAE) tools, including finite element analysis (FEA) and computational fluid dynamics (CFD), can alleviate these hurdles, expediting the adoption of offshore wind as a primary energy source. This article explores Houlder's comprehensive approach to addressing a few challenges using Fidelity Fine Marine within the Fidelity CFD platform, showcasing their expertise through a case study on monopile durability against sea wave forces.

About Houlder

Houlder is a multidisciplinary firm with a maritime history that dates back to the 1800s. The company is renowned for its expertise in engineering, design, and innovation in marine technology. Houlder aims to be the preferred partner in global maritime decarbonization.

The vessel analysis team is a key part of Houlder's core operations. This team utilizes advanced techniques, such as instrumented sea trials and computer simulations, to develop and optimize marine vessels. Their work supports conceptual designs and performance assessments for solutions like energy-saving devices and wind-assist technologies, contributing to advancements in maritime sustainability.

Current Challenges with Offshore Wind Installation

Designing and installing offshore wind turbines presents numerous challenges, primarily concerning their structural integrity. These turbines must be engineered to endure extreme weather conditions. A crucial aspect of this engineering is foundation design, which requires a careful selection of foundation types, like monopiles, gravity bases, tripods, etc., based on seabed conditions and water depth to ensure stability against lateral forces and sediment movement.

Additionally, understanding hydrodynamic forces such as wave action and ocean currents is essential for maintaining the integrity of the foundations. Addressing saltwater corrosion is also vital; corrosion analysis helps identify vulnerabilities and implement protective measures to prolong the lifespan of construction materials.

Another complexity lies in the installation and management of subsea cables. Proper handling and burying of cables are critical to prevent damage during installation while accessing turbines for maintenance under adverse weather conditions can pose significant operational challenges. Effectively coordinating these elements is key to the successful deployment and operation of offshore turbines.

CFD And FEA Tools to Address Offshore Wind Installation Challenges

CFD and FEA tools are increasingly used to address challenges associated with offshore wind installations. FEA is particularly useful for simulating stress and deformation in foundation designs, such as monopiles and jackets. It allows engineers to assess the effects of wave action and currents, identify stress concentrations, and make informed decisions on material selection and protective coatings.

In parallel, CFD tools are important in understanding cable performance under varying ocean conditions. This insight aids in installation planning and vessel design necessary for turbine maintenance. Furthermore, the CFD tool helps in modeling sediment dispersion and changes in water quality, which is essential for developing strategies to mitigate environmental impacts.

By effectively utilizing both CFD and FEA tools, the offshore wind industry can significantly enhance installation safety and efficiency, ensuring a more sustainable approach to harnessing wind energy.

Houlder’s Approach to Offshore Wind Installation

Houlder undertook a project to evaluate the response of a free-standing monopile that lacked cured grout when subjected to a vibrating wave protection and installation device mounted on a jack-up barge. The absence of cured grout in the monopile required a thorough analysis of its response to sea wave forces, which was conducted using a CFD tool. Fidelity Fine Marine was used as the CFD tool in this case study.

A monopile without a cured grout

Fidelity Fine Marine is a specialized virtual naval architecture and marine design tool that offers exceptional free surface modeling and highly automated optimization processes. This tool allows users to solve and optimize design aspects such as propulsion, resistance, seakeeping, wind studies, and maneuvering through dedicated workflows supported by a knowledgeable team. By using Fidelity Fine Marine, you can achieve maximum accuracy and efficiency in your marine projects.

Objectives and Methodology

Methodology of the study

The study involved simulating diverse scenarios, requiring approximately 360 hours of simulations across different wave heights, wave periods, water depths, and system configurations. The inputs to this study included a detailed CAD model, borehole dimensions, rock properties, mass and inertial properties of the monopile, and motion data from potential flow simulations. FEA was employed to determine the essential pin joint rotational stiffness necessary for the simulation.

A twang test was conducted to assess the monopile’s natural period in various conditions, with the results compared to potential flow simulations to provide some numerical validation. Sensitivity studies on parameters like timestep, mesh quality, frequency of added mass estimation, etc., enhanced the robustness of the findings. Houlder’s methodology was to understand the system's response to regular inputs, allowing for the creation of a transfer function for each case studied. These transfer functions were then used to predict the systems’ motion in an irregular sea state.

Transfer function for each case

Results and Insights

The simulations generated valuable data regarding the monopile’s performance and insights into its response under different conditions. By actively benchmarking against competitor work, Houlder enhanced its methodologies and took the opportunity to compare two methods: machine learning and linear superposition techniques.

Comparison of results from transfer function and CFD simulation

The monopile installation is currently ongoing, and Houlder’s customer is comparing the predictions produced from this study to reality. The initial findings revealed a strong correlation between the real-life data and the predicted simulations, validating the accuracy and reliability of their modeling approach. With a strong commitment to decarbonization, Houlder continuously improves its processes and technologies, leveraging multidisciplinary teams to focus on innovation and lead the way in sustainable practices within the maritime sector.

As we forge into a new era of sustainability and environmental consciousness, Houlder’s dedication and innovative spirit exemplify the maritime industry's potential to adapt and thrive. The challenges may be complex, but with expertise and a commitment to excellence, Houlder is steering towards a greener, more sustainable future at sea.

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