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This work is focused on the performance of one of the offshore floating concepts: the OC4-DeepCwind semisubmersible wind turbine, because of its minimal dynamic coupling between wave-induced and turbine-induced motion and its easier and lower-cost offshore installation. To asses this issue, a 1/80th scale model is designed, assembled and tested und...
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This paper describes work performed during the first half of Phase I of the Offshore Code Comparison Collaboration Continuation, with Correlation project (OC5). OC5 is a project run under the International
Energy Agency Wind Research Task 30, and is focused on validating the tools used for modeling offshore wind systems. In this first phase, simula...
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... One of the most available and environmentally friendly renewable energy sources to meet this prediction is wind power [2]. A decade ago, wind power was seen as a minor supplement to hydropower rather than a main source of energy, however, this perception is changing [5].On top of that, among offshore renewable energy sources, offshore wind energy appears to be the most promising for the upcoming years and decades due to higher and steadier wind speeds in open seas [6], [7]. The first offshore wind turbine, with a capacity of 220 kW and located 250 meters offshore beyond the beach, was installed in Sweden in 1990. ...
... 6 shows a diagram of wind turbines supported by a large-diameter column deeply sunk into the earth, known as a monopile. This sort of foundation is commonly used in the offshore wind sector due to its simplicity[45]. ...
... 6 Hywind Tampen FOWF transportation summary ...
To address climate change and energy security issues associated with fossil fuels, new power generation methods such as renewable energy sources as a sustainable alternative for electricity generation are introduced. One of the most available and environmentally friendly renewable energy sources is wind power. Wind energy is expected to grow ninefold by 2050, accounting for 11% of total primary energy consumption worldwide. Within the domain of wind energy, offshore wind energy appears to be the most promising in the years ahead due to higher and steadier wind speeds in open seas. However, despite producing clean electricity during operation, offshore wind turbines have environmental impacts throughout upstream and downstream life cycle stages such as manufacturing, installation, and decommissioning. Offshore wind technology's environmental impact and energy performance can be measured, and the most commonly used assessment method is life cycle assessment (LCA). Nevertheless, after performing a scoping literature review method, it was observed that comprehensive assessments of the environmental impacts of different offshore wind technologies are limited. This study aims to bridge this gap by conducting a comprehensive cradle-to-grave LCA of two real case scenarios: floating (FOWF) and bottom fixed offshore wind farms (BFOWF), specifically Hywind Tampen and Dogger Bank. It encompasses all stages from manufacturing, transportation, installation, operation, and maintenance (O&M), and decommissioning. The methodology employed utilizes openLCA® software and ecoinvent 3.9 databases, with the ReCiPe 2016 v1.03 midpoint (H) impact assessment method. Key findings indicate that the environmental impact of Hywind Tampen FOWF is higher compared to Dogger Bank BFOWF, with sensitivity analysis revealing significant influences of capacity factor and lifetime of the wind farm. Among the life cycle stages analyzed, manufacturing emerges as the primary contributor to total emissions, with the O&M stage following closely behind. Consequently, this study underscores the critical need for the implementation of more sustainable manufacturing methods. One solution could be designing turbines with greater generation capacity to minimize material usage. Maintaining material usage at current levels for larger wind turbines could result in a significant decrease in emissions. Finally, the reliability of wind turbines needs to increase to reduce the share of O&M. Having said that this study also compares the emissions from the two studied offshore wind farms with other renewable and non-renewable energy sources, and although there are some environmental impacts associated with the offshore wind farms, they still could be one of the best alternatives for fossil fuels and some other renewable energy sources.
... Types of stabilizing mechanisms include buoyancy, ballast and mooring lines. Semi-submersible, tension leg platforms, barges and spars rely on the above-mentioned mechanisms [7,8]. Spars are ballast-stabilized structures that have a large amount of ballast, which places the centre of mass below the centre of buoyancy. ...
... Floating offshore wind turbine platforms are mainly based on existing structures in oil and gas industries [10]. The advantage of offshore wind turbines is that their capacity is higher and steadier than onshore wind turbines since the sea emplacement allows larger rotor diameters, and the speed of the wind is stronger and steadier [7]. In addition, wind farms can be located near high-demand coastal cities, which is cost-effective in terms of electricity transmission lines. ...
Floating offshore wind turbine foundations are based on platforms operated by the oil and gas industry. However, they are designed and optimized to meet the wind turbines’ operating criteria. Although Malaysia is considered a low-wind-speed country, there are some locations facing the South China Sea that are found to be feasible for wind energy harnessing. The average daily wind speed may reach up to 15 m/s. Therefore, designing a cost-effective platform that can operate in Malaysian waters which has less severe environmental conditions compared to the North Sea would be a prudent undertaking. In this study, a new design of a multi-purpose floating offshore wind turbine platform (Mocha-TLP) is presented. In addition, the dynamic response of the platform to wave loads was investigated using the Navier–Stokes code STAR CCM+ developed by CD-adapco. Moreover, free-oscillation tests were performed to determine the natural periods of the platform. Three approaching wave cases and two wave conditions (WC) were considered. The results show that the natural periods of the platforms were within the recommended range for pitch, roll, yaw, heave, sway and surge motions. The platform was stable in rotational motion within the three cases. However, it experienced a noticeable surge motion which was more critical with wave condition one (WC1) since the wavelength equalled the length of the structure. The dynamic response of the platform to wave loads wase minimal and within the operational requirements for wind turbines.
... Offshore wind farms are given special attention due to the higher and steadier wind speed. Moreover, it is possible to locate wind farms near coastal cities where the energy demand is high and saves the cost of electrical transmission lines [9]. The technology of offshore wind turbines started in the 1990s, where the first offshore wind turbine was installed in 1990 in Sweden with a 220 kW capacity and 250 m far from the shoreline [10]. ...
The Government of Malaysia has set a striving target to achieve a higher usage of renewable energy (RE) in the energy mix which is currently around 2% of the country’s electricity. Yet, the government intends to increase this ratio up to 20% by the year 2025. Most of the renewable energy in Malaysia comes from hydropower and biomass sources. Meanwhile, numerous studies have been conducted to determine the feasibility of wind energy in Malaysia. Several locations were reported to be economically viable for wind energy development such as Kudat, Mersing, and Kuala Terengganu. This study presents and discusses the whole life cycle cost analysis of an offshore wind farm in Kudat, Malaysia and determines the cost drivers of offshore wind energy developments. It covers the wind data collection and analysis, breakdown of whole life cycle cost structure, and calculation of the levelized cost of energy (LCOE). Results showed that almost 67% of the total cost was incurred by the capital expenditure (CAPEX), and around 26% by operation and maintenance costs (OPEX), while decommissioning costs (DECOM) reached up to 7% of the whole life cycle costs. The LCOE was calculated and determined to be USD 127.58/MWh.
... They have reached 509 GW and 592 GW by the 2018 for solar and wind energy respectively and are expected to reach 126 GW and 903 by the year 2023 [3]. The offshore wind farms have several advantages as it allows to install high capacity of wind turbines and the wind speed at offshore sites is stronger and steadier [4]. Besides that, it is possible to locate the wind farms near the coastal cities with high energy demand and this is cost-effective for electricity transmission lines. ...
Renewable energy generation is given a priority in sustainable development worldwide to decrease the dependency of fossil fuel-based power generation. Wind energy is one of the fast-developing sources of clean energy in the last decades due to the speedy development of wind turbines’ capacity and the possibility of installing them at offshore sites. Malaysia has set-up a promising plan for renewable energy development to reduce GHG emissions by 45% by the year 2030. To date, Malaysia is depending on conventional methods for power generation such as natural gas coal and hydro. This paper discusses the future of wind power in Malaysia in terms of defining the most suitable places and their energy density and the techno-economical aspect of wind energy. It was found that Terengganu, Borneo, and Sabah are the most suitable places with an average annual wind power density greater than 500 kWh/m2.
... The interference effects between multiple FOWTs and the impacts of second-order sum-frequency wave excitations on the coupled dynamic performance were also investigated. Besides, the experimental tests in wave basin facilities using various scale models were carried out to verify the numerical simulation results and study the coupled aero-hydrodynamic performance of different FOWT designs [32][33][34][35][36]. Several intermediatescale FOWT models were also deployed on the ocean coast to meet the requirement of full-sized construction of commercial-scale projects [37]. ...
In order to further understand the coupled aero-hydrodynamic performance of the floating offshore wind turbine (FOWT) in realistic ocean environment, it is necessary to investigate the interference effects between the unsteady aerodynamics of the wind turbine and different degree-of-freedom (DOF) platform motions under combined wind-wave excitation. In this paper, a validated CFD analysis tool FOWT-UALM-SJTU with modified actuator line model is applied for the coupled aero-hydrodynamic simulations of a spar-type FOWT system. The aero-hydrodynamic characteristics of the FOWT with various platform motion modes and different wind turbine states are compared and analyzed to explore the influence of the interference effects between the wind turbine and the floating platform on the performance of the FOWT. The dynamic responses of local relative wind speed and local attack angle at the blade section and wind-wave forces acting on the floating platform are discussed in detail to reveal the interaction mechanism between the aerodynamic loads and different DOF platform motions. It is shown that the surge motion and the pitch motion of the floating platform both significantly alter the local attack angle, while only the platform pitch motion have significant impacts on the local relative wind speed experienced by the rotating blades. Besides, the shaft tilt and the pro-cone angle of the wind turbine and the height-dependent wind speed all contribute to the variation of the local attack angle. The coupling between the platform motions along different DOFs is obviously amplified by the aerodynamic forces derived from the wind turbine. In addition, the wake deflection phenomenon is clearly observed in the near wake region when platform pitch motion is considered. The dynamic pitch motion of the floating platform also contributes to the severe wake velocity deficit and the increased wake width.
... Therefore, a wave basin test for a scaled-down FOWT model is desirable to reduce the risk and cost, which allows the dynamic characteristics of a floating system to be accurately evaluated. The scaled-down FOWT model tests in wave basins have been initiatively conducted by research groups utilizing different concepts, such as the WindFloat concept by Principle Power, Inc., U.S. [5,6], GustoMSC Tri-Floater concept by GustoMSC [7], TLPWT concept by CEHINAV-UPM [8], HYWIND concept by Hydro Oil & Energy, Norway [9], SPAR-type FOWT concept by Yokohama National University [10], three DeepCWind concepts by the University of Maine [11,12], TLP and SPAR concept by Worcester Polytechnic Institute [13], and the semi-submersible concept by University of Strathclyde [14], etc. These experiments aimed to validate and investigate the global dynamic characteristics of various FOWT types. ...
... Overall, good agreements were observed with each other [67]. However, there were slight differences regarding the phases of the free-decay dynamic responses, which can be caused by the existence of nonlinear wave loads [14]. This led to the somewhat different predictions of natural periods, as presented in Table 3. Slight discrepancies of the damping ratios of the free-decay motions among the different numerical simulations were also observed. ...
In the design phase of a floating offshore wind turbine, the influence of aero-hydro-structure dynamic coupling needs to be fully considered to yield reliable analysis results. In this study, a highly elaborated computational model based on a dynamic fluid body interaction method with a superimposed motion and catenary mooring solver is applied and compared with common engineering approaches. An overset-based technique is also utilized to effectively handle large movements of a full floating wind turbine body due to the coupled influence of wind-wave loads. The DeepCwind semi-submersible floating platform mounted by the NREL 5-MW baseline wind turbine is used to obtain validation and verification of the new computational model with the experimental test data and the NREL FAST code. Various computational results for unsteady aerodynamics, hydrodynamics, and fully coupled aero-hydrodynamics including mooring line loads are compared stage by stage with the test data and numerical results calculated by the NREL FAST code. Overall, the predicted results of the aerodynamic performances, platform dynamic responses, and mooring line tensions show good agreements with the presented numerical solutions and the FAST solutions. In addition, multi-phase unsteady flow fields with complex inference effects in the blade-tip vortices, shedding vortices, and turbulent wakes are numerically visualized and investigated in detail.