|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
The notion of reducing our environmental footprint, minimizing leaks and spillages, and identifying operational efficiencies is nothing new. We have been addressing these issues for years. Sustainability, however, has gained a higher profile recently, especially since the 2015 United Nations Framework Convention on Climate Change accord and the evolution of alternative energies. It came, therefore, as a pleasant surprise to review an extraordinary wealth of well-written papers relating not only to this topic, but to all manner of fascinating engineering issues. Let me back up a bit.
While drones have been used on oil and gas facilities for video inspections and other tasks, they have been operated by an on-site pilot or one positioned on a bobbing workboat adjacent to an offshore platform. Now a proof-of-concept study conducted by TechnipFMC has tested the feasibility of a global drone system with drones operated remotely by pilots based anywhere in the world. The study is the subject of a paper (OTC 30241) presented at the Offshore Technology Conference Asia in Kuala Lumpur in November. Construction supervision and health, safety, and environmental (HSE) monitoring were the main drivers of the study. The construction supervision application is part of a larger digitalization ambition to monitor and manage construction activities with data generated from the drone ultimately feeding an internal software dedicated to this business process.
Value methodology has been implemented successfully in new projects to save costs but rarely has been implemented in oil and gas operating facilities to minimize operating costs. The success of value methodology in reducing capital project costs prompted the author to explore its application to operating facilities, specifically toward minimizing operating and maintenance cost. Value methodology is used when value is a concern and requires optimization. Value is defined as the ratio of function to cost.
Whenever I am considering a topic or a theme for the paper selection, I realize that certain topics may generate some instant reaction that is counterproductive. I say counterproductive because it may lead to a decision not to read the synopses, let alone the papers themselves, even though there may be good reasons to read them. The topic for this selection falls in that category: offshore wind energy. Now, if you are tempted to stop reading, please bear with me for a few minutes. I did not select this topic because I want to promote renewable energy or because I believe that oil and gas production will end in the foreseeable future.
The industry requires the ability to test system concepts in a realistic environment on a pilot-scale size. While several units up to 10 MW are being tested onshore, existing electrolyzer technology to convert power to H2 has not yet been applied offshore. However, many suppliers are developing innovative concepts and are scaling up to larger units. It has been estimated that at least 1 MW of electrolyzer capacity can be placed on an offshore platform with existing technology.
For any offshore development, especially an ORE project, a specific site investigation is required to qualify environmental, geophysical, metocean-related, and geopolitical issues. Most ORE developments will cover a significant area of ocean or seabed and will require investigation to ensure that marine life, antiquities, unexploded ordinance, and other ocean users will not be put at risk when installation and operation activities are performed. Obtaining the required permits and approvals from all those potentially affected by an ORE development is a complex and time-consuming operation. All stakeholders connected with a development must be considered because the installation could be in position for 30 or more years. A summary of the types of wind and MHK devices is presented in Table 1 of the complete paper.
Offshore wind is a rapidly maturing sector, increasingly seen as a major contributor to electricity supply in states with coastal demand centers and good wind resources. While an almost 3-decade history exists in European experience, the US only recently is beginning to move forward with grid-scale projects on national and state levels. As floating wind is scaled up, to minimize technical risks experienced in the past, formal processes will help to identify the novel features, novel applications, and highest-risk components. Large offshore wind farms have been built by all countries with coastlines on the southern North Sea, the area with the most favorable conditions: strong, consistent winds; water depths of less than 40 m; sand or clay deeper than 70 m; and close proximity to onshore electrical distribution networks and centers of high demand. Rapid reductions have been realized in the cost of electricity, calculated over the full project lifetime, from well over 200 Euros/MWhr for the first large-scale wind farms to 50/MWhr.
Yua, Songchen (College of Shipbuilding Engineering, Harbin Engineering University) | Li, Peng (College of Shipbuilding Engineering, Harbin Engineering University / Peng Cheng Laboratory) | Qina, Hongde (College of Shipbuilding Engineering, Harbin Engineering University) | Xua, Zhijing (College of Shipbuilding Engineering, Harbin Engineering University)
Marine fishery is gradually developing from the coastal area to the deep sea. The semi-submersible offshore fish farm is one of the most foreseeable aquaculture equipment. However, the vast and abundant deep sea also means that the fish farm will be in a harsh marine environment. A model test of a semi-submersible fish farm was carried out in this paper. In order to obtain the hydrodynamic response characteristics of the fish farm, the accelerations on five different positions and mooring forces of the model under different wave conditions and current were measured, the steady-state amplitudes of the first five harmonics experimental acceleration and mooring tension were obtained. The steady-state amplitudes of non-dimensional first-harmonic acceleration at different positions with different wave periods were compared, and the amplitude trends were analyzed. The influence of higher harmonics acceleration on the first ones was investigated. Besides, the amplitude trend of different harmonics acceleration was analyzed under different conditions. Furthermore, the trend and fluctuation range of mooring tension at front and aft positions under different conditions were compared, and the causes of occurrence of the peak value of the instantaneous amplitude were figured out.
New types of aquaculture equipment are gradually put into the ocean to relieve the environmental pressure in coastal area. As a typical new type of aquaculture equipment, semi-submersible fish farm is in a harsher marine environment than the traditional offshore cage. In order to ensure the normal operation of semi-submersible fish farm and the normal survival of aquaculture products, the hydrodynamic performance of which will be the focus of attention. The hydrodynamic analysis of semisubmersible fish farm is similar to that of traditional cage, but there are also differences.
For traditional net cage, Lader et al. (2005, 2007) carried out a series of experiments on different solid ratio of net, and the hydrodynamic forces induced by different current velocity were compared. Fredriksson et al. (2007) compared the experimental data and numerical results of static deformation of a floating collar. By numerical simulation, Huang et al. (2008) studied the hydrodynamic performance of gravity cages induced by wave and current. Taking rigid and flexible floating collars as the object of study, Li and Faltinsen (2016, 2018) carried out model tests of single floating collar under different wave steepness. By comparing the results with that of numerical simulation by WAMIT, the importance of 3D flow, hydroelasticity and strong hydrodynamic frequency dependency was demonstrated; the changes of additional mass and damping coefficients were emphatically analyzed. Xu et al. (2020) studied the drag and wake of an individual long-line mussel dropper using computational fluid dynamics approaches. They found that surface roughness and sharp crowns on the rough cylinder resulted in larger drag coefficients and Strouhal numbers. By numerical simulation, Qin et al. (2020) addressed the probability distribution of the heave motion under irregular waves and extended the conditions of the most probable maximum normalized bending stress distribution of the floating collar. Qin et al. (2020) devised an experimental study of an offshore aquaculture cage induced by wave-structure interactions. The relationship between the first-, second-harmonics acceleration and wave amplitude were analyzed, and the effects of mooring loads were assessed. Concerning the safety and economic efficiency, Liu et al. (2019) conducted a series experiments to obtain the optimum submergence depth of a fish cage. By model test and numerical simulation, Yang et al. (2020) studied the hydrodynamic responses and optimize mooring design factors of a floating rope enclosure. Li et al. (2012) studied the deformation of the floating collar, and they found the flexible effects on the dynamic responses. Kristiansen and Faltinsen (2015) conducted an experiment of a net cage. Results with only waves as well as combined waves and current were obtained.
TAN, Lei (College of Science and Technology, Nihon University.) | Ikoma, Tomoki (College of Science and Technology, Nihon University.) | Fujishima, Katsuhide (College of Science and Technology, Nihon University.) | Aida, Yasuhiro (College of Science and Technology, Nihon University.) | Masuda, Koichi (College of Science and Technology, Nihon University.)
In this paper the motions of a barge-type floating foundation installed with four moonpools and a VAWT are investigated through physical model tests and numerical calculations. The characteristics of motion responses and mooring tether tensions under various wave conditions are examined. The gyroscopic effects of turbine rotations are studied by varying the mass and the rotational speed of wind turbine. Linear potential calculations are carried out using WAMIT. It is found that the gyroscopic effect due to turbine rotations can be significant. The firstorder motions of the floating system are substantially reduced by the gyroscopic effect, while the second-order motions and tether tensions may be significantly increased. The viscous damping of water motions in moonpools is found not negligible to produce reasonable predictions.
To exploit ocean wind energy, varied types of FOWTs (Floating Offshore Wind Turbines) have been proposed over the past decades. In terms of floating foundation, there are mainly Spar, semi-submersible, TLP (Tension Leg Platform), and pontoon (or barge) types of FOWTs. Among these types, the pontoon type of FOWTs are simple to design, construct and install, and they are generally placed in shallow water. With regard to wind turbines, there are mainly two types: HAWTs (Horizontal Axis Wind Turbines) and VAWTs (Vertical Axis Wind Turbines). When multiple HAWTs are installed on a floater, it is necessary to consider the wake effects of air flow and the motions of the floating foundation due to the turbulence around the turbines. The distance between two HAWTs should be no less than one third of the diameter of a turbine rotor. Hence a large area is usually required for the floating systems installed with an array of HAWTs. So far, the concept of floating systems installed with multiple HAWTs has not been commercialized
By contrast, VAWTs have advantages over HAWTs in multi-turbine installed floating systems. For example, VAWT has no requirement for wind direction and its installation and maintenance costs are relatively low. The concept of VAWTs installed on a floating barge may go back to the report of Shigeo (2002). So far, various floating VAWT concepts have been proposed (e.g., Akimoto et al., 2011; Collu et al., 2012; Shires, 2013; Paulsen et al., 2015). The floating systems installed with multiple wind turbines have several advantages, such as reducing mooring tethers, causing less disturbance to sailing and fishery activities, improving the maintainability and workability of the facilities, and potentially enhancing power extraction (Jin et al., 2020). In addition to these advantages, for the development of the floating systems, it is necessary to consider the performance of floating systems in safety and stability.