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Tomoaki Utsunomiya - One of the best experts on this subject based on the ideXlab platform.

  • Preliminary design of a 100 MW-net ocean thermal energy conversion (OTEC) power plant study case: Mentawai island, Indonesia
    Journal of Marine Science and Technology, 2019
    Co-Authors: Ristiyanto Adiputra, Jaswar Koto, Takeshi Yasunaga, Tomoaki Utsunomiya, Yasuyuki Ikegami
    Abstract:

    Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce the capital cost, this paper introduces a concept design of the Floating Structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective Floating Structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the ‘typical’ size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2–3 m/s. The general arrangement is also conceptualized in this paper.

  • Preliminary design of a 100 MW-net ocean thermal energy conversion (OTEC) power plant study case: Mentawai island, Indonesia
    Journal of Marine Science and Technology, 2019
    Co-Authors: Ristiyanto Adiputra, Jaswar Koto, Takeshi Yasunaga, Tomoaki Utsunomiya, Yasuyuki Ikegami
    Abstract:

    Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce the capital cost, this paper introduces a concept design of the Floating Structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective Floating Structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the ‘typical’ size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2–3 m/s. The general arrangement is also conceptualized in this paper.

  • Design optimization of Floating Structure for a 100 MW-net ocean thermal energy conversion (OTEC) power plant
    Volume 10: Ocean Renewable Energy, 2018
    Co-Authors: Ristiyanto Adiputra, Tomoaki Utsunomiya
    Abstract:

    This paper presents a design procedure based on optimization to contrive a Floating Structure for a commercial scale of OTEC power plant. In the aim to get a safe yet economical Floating Structure, a commercial oil tanker ship was converted as the plantship. The process was started by defining independent variables, constraints and fix parameters. The independent variables included the velocity of seawater transport and type of oil tanker ship. The next step was breaking down the fix parameters which were kept constant during the iteration process. These parameters were about the general requirements and the necessary equipment to produce 100 MW-net power output. Some constraints were also introduced as permissible borders to determine whether the particular case was acceptable or not. The constraints included the constraint due to provided space, allowed weight, net power output and fluid phenomena on the riser. During the iteration process, a spiral model was developed as analysis guideline. Based on the result of the optimization, it could be concluded that the typical Suez-max oil tanker ship was the best option and the most optimum seawater transport velocity was 3 m/s. Finally, the general arrangements and the base layout design were also conceptualized in this paper.

  • Analysis of the slowly varying drift force on a very large Floating Structure in multidirectional random seas
    Journal of Marine Science and Technology, 2006
    Co-Authors: Shotaro Kida, Tomoaki Utsunomiya
    Abstract:

    In designing the mooring system of a very large Floating Structure (VLFS), it is essential to estimate the slowly varying drift force in random seas. For a small vessel, Hsu's method or Newman's approximation may be used to simulate this slowly varying drift force. However, based on experiments and/or field observations, it was found that the slowly varying drift force acting on a VLFS could be reduced to a great extent from the simulated values based on those methods. Thus, the conventional methods are not applicable for a VLFS. This discovery led to the development of several methods for estimating the slowly varying drift force on a VLFS, e.g., Namba et al. (J Soc Nav Archit Jpn 186:235–242, 1999), and Shimada and Maruyama (J Soc Nav Archit Jpn 190:347–351, 2001). However, Namba's method is only applicable to a pontoon-type VLFS with a shallow draft, and Shimada's method is too simplified to account for the general shape of a VLFS and elastic deformation. These methods have been expanded in this article, and by our proposed method, any shape of VLFS and the effect of elastic deformation of the VLFS can be included. Formulations and several numerical examples are given.

Yasuyuki Ikegami - One of the best experts on this subject based on the ideXlab platform.

  • Preliminary design of a 100 MW-net ocean thermal energy conversion (OTEC) power plant study case: Mentawai island, Indonesia
    Journal of Marine Science and Technology, 2019
    Co-Authors: Ristiyanto Adiputra, Jaswar Koto, Takeshi Yasunaga, Tomoaki Utsunomiya, Yasuyuki Ikegami
    Abstract:

    Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce the capital cost, this paper introduces a concept design of the Floating Structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective Floating Structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the ‘typical’ size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2–3 m/s. The general arrangement is also conceptualized in this paper.

  • Preliminary design of a 100 MW-net ocean thermal energy conversion (OTEC) power plant study case: Mentawai island, Indonesia
    Journal of Marine Science and Technology, 2019
    Co-Authors: Ristiyanto Adiputra, Jaswar Koto, Takeshi Yasunaga, Tomoaki Utsunomiya, Yasuyuki Ikegami
    Abstract:

    Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce the capital cost, this paper introduces a concept design of the Floating Structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective Floating Structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the ‘typical’ size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2–3 m/s. The general arrangement is also conceptualized in this paper.

Toshifumi Fujiwara - One of the best experts on this subject based on the ideXlab platform.

  • VIM simulation on a cylindrical Floating Structure
    Journal of Marine Science and Technology, 2018
    Co-Authors: Toshifumi Fujiwara
    Abstract:

    Vortex-induced motion (VIM) on a cylindrical Floating Structure can be easily found in ocean strong current. Since the VIM on the Structure with long-term low-frequency motion causes fatigue damage of the Structure’s mooring lines and risers, precise VIM assessment is needed for the safe evaluation of them. In the standard of the International Organization for Standardization ISO19901-7, ‘Specific requirements on stationkeeping systems for Floating offshore Structures and mobile offshore units’, for instance, a concrete method of assessing VIM displacement is not represented in the standard document, though the requirement on the VIM demands for an assessment on the basis of a proper way. In this paper, a VIM time-domain simulation method on a Floating Structure with circular cylinder form, that is, for example a Spar, an MPSO (mono-column type Floating production storage and off-loading) and so on, is shown using the wake oscillator model. Transverse and in-line VIM are treated for the floater’s motion. The assessment quality of the simulation on the VIM amplitudes of floaters in current is confirmed by model test data.

  • VIM Simulation Method on a Cylindrical Floating Structure
    Volume 1: Offshore Technology; Offshore Geotechnics, 2016
    Co-Authors: Toshifumi Fujiwara
    Abstract:

    A cylindrical Floating Structure can basically experience Vortex-induced Motion (VIM) in strong current. Since the VIM on the Structure with long term low-frequency motion causes fatigue damage of the Structure’s mooring lines and risers, precise VIM assessment is needed for the safety evaluation of them. In the standard of the International Organization for Standardization ISO19901-7, ‘Specific requirements on stationkeeping systems for Floating offshore Structures and mobile offshore units’, for instance, a concrete method of assessing VIM displacement is not represented in the standard document, though the requirement on the VIM demands to do the assessment on the basis of proper ways.Then in this paper, a VIM simulation method on a Floating Structure with circular cylinder form, that is, for example a Spar, a MPSO (Mono-column type Floating Production Storage and Offloading) and so on, is shown using the wake-oscillator model. Transverse VIM is only treated since it is dominant factor on the fatigue damage of the mooring lines and risers. The assessment quality of the simulation method on the transverse VIM of floaters in current is confirmed by model test data.Copyright © 2016 by ASME

Ristiyanto Adiputra - One of the best experts on this subject based on the ideXlab platform.

  • Preliminary design of a 100 MW-net ocean thermal energy conversion (OTEC) power plant study case: Mentawai island, Indonesia
    Journal of Marine Science and Technology, 2019
    Co-Authors: Ristiyanto Adiputra, Jaswar Koto, Takeshi Yasunaga, Tomoaki Utsunomiya, Yasuyuki Ikegami
    Abstract:

    Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce the capital cost, this paper introduces a concept design of the Floating Structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective Floating Structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the ‘typical’ size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2–3 m/s. The general arrangement is also conceptualized in this paper.

  • Preliminary design of a 100 MW-net ocean thermal energy conversion (OTEC) power plant study case: Mentawai island, Indonesia
    Journal of Marine Science and Technology, 2019
    Co-Authors: Ristiyanto Adiputra, Jaswar Koto, Takeshi Yasunaga, Tomoaki Utsunomiya, Yasuyuki Ikegami
    Abstract:

    Ocean thermal energy conversion is one of the promising renewable energy resources yet relatively unexplored due to its high capital cost for being utilized in commercial scale. In the aim to reduce the capital cost, this paper introduces a concept design of the Floating Structure from a converted oil tanker ship. To propose the design process, the general principles of designing a converted tanker FPSO is adapted and then modified to deal with ocean thermal energy conversion (OTEC) characteristic. In the design process, the arrangement of the OTEC layout is carried out by constraint satisfaction method and the prospective Floating Structure size is varied using Monte Carlo simulation. The variables in the design process consist of the velocities of cold water and warm water transport, the size of the plantship, and the location of the OTEC equipment to the seawater tank. Constraints are introduced as allowable border to determine the acceptability for particular case including the provided space and buoyancy, and the net power output estimation. The results show that the ‘typical’ size of a Suezmax oil tanker ship is the optimum one for the plantship with the velocity of the water transport of 2–3 m/s. The general arrangement is also conceptualized in this paper.

  • Design optimization of Floating Structure for a 100 MW-net ocean thermal energy conversion (OTEC) power plant
    Volume 10: Ocean Renewable Energy, 2018
    Co-Authors: Ristiyanto Adiputra, Tomoaki Utsunomiya
    Abstract:

    This paper presents a design procedure based on optimization to contrive a Floating Structure for a commercial scale of OTEC power plant. In the aim to get a safe yet economical Floating Structure, a commercial oil tanker ship was converted as the plantship. The process was started by defining independent variables, constraints and fix parameters. The independent variables included the velocity of seawater transport and type of oil tanker ship. The next step was breaking down the fix parameters which were kept constant during the iteration process. These parameters were about the general requirements and the necessary equipment to produce 100 MW-net power output. Some constraints were also introduced as permissible borders to determine whether the particular case was acceptable or not. The constraints included the constraint due to provided space, allowed weight, net power output and fluid phenomena on the riser. During the iteration process, a spiral model was developed as analysis guideline. Based on the result of the optimization, it could be concluded that the typical Suez-max oil tanker ship was the best option and the most optimum seawater transport velocity was 3 m/s. Finally, the general arrangements and the base layout design were also conceptualized in this paper.

Hideyuki Suzuki - One of the best experts on this subject based on the ideXlab platform.

  • Beating vibration phenomenon of a very large Floating Structure
    Journal of Marine Science and Technology, 2018
    Co-Authors: Hisayoshi Endo, Hideyuki Suzuki
    Abstract:

    When a very large Floating Structure (VLFS) is subjected to successive regular waves, it may sometimes suffer from “beating vibration”. This phenomenon occurs when the wave period approaches the natural periods of the Structure. The beating action occurs with the period far longer than the incident wave period and sometimes has a conspicuous ups and downs. The vibration amplitude due to regular wave will be alternatively increased and decreased as the synergistic effect caused by the beating. The mechanism of the beating vibration has been investigated through FEM simulation based on the time-domain analysis then the example cases of beating phenomena are demonstrated focusing on the VLFS which was preliminarily designed as a supply base for a deep ocean. It has turned out that the fundamental characteristics of the beating action are mainly contributed by the magnitude of period gap between the incident wave and the natural period of the Structure, and also by the magnitude of the damping force.

  • Progressive Collapse of Mooring System of Semisubmersible Type Floating Structure
    Journal of the Society of Naval Architects of Japan, 1999
    Co-Authors: Taro Ide, Hideyuki Suzuki, Noriaki Oka, Koichiro Yoshida
    Abstract:

    This paper deals with progressive collapse behavior of mooring system of very large Floating Structure. We have studied progressive collapse behavior of mooring system of barge type Floating Structure which is installed in calm sea, moored by dolphin mooring, and protected by break water. In this report, Floating Structure installed in open sea is considered. The wave condition may be so strong that semisubmersible type is reasonable rather than barge type. The water depth may be so large that it should be moored by inclined tension legs.Time series program which models in-plane elastic response as a beam and anti-plane elastic response based on the theory of plates is made and progressive collapse behavior is simulated.An experiment was made on collapse behavior under regular and irregular wave using 1/333 scale model of semisubmersible type Floating Structure moored by inclined tension legs. Mooring rope is set to be cut off from Floating Structure when the load on the rope is over preset value.

  • A consideration of the structural design of a large-scale Floating Structure
    Journal of Marine Science and Technology, 1996
    Co-Authors: Hideyuki Suzuki, Koichiro Yoshida, Kazuhiro Iijima
    Abstract:

    The land area of Japan, especially flat land, is very small compared with its economic size. Large-scale Floating Structures are one solution to satisfy the demand for space by utilizing the ocean. This paper presents a general view of the dynamic response characteristics of large-scale Floating Structures, pontoons and semi-submersibles. For example, it is shown that the natural frequencies of eigenmodes are higher than the natural frequency of heaving motion. The response of the outer framework of a Structure is shown to be generally larger than the response of the central part. Within the limits of our present understanding of the general dynamic response characteristics of such Structures, the design and analysis of semi-submersible, large-scale Floating Structures is discussed. For a pontoon-type large-scale Floating Structure, a type whose perimeter Structure has been modified to become lighter and more rigid is proposed. With this modification, the dynamic response of the whole Structure is imporved.

  • A Consideration on the Dynamic Behavior and the Structural Design of Large Scale Floating Structure
    Journal of the Society of Naval Architects of Japan, 1995
    Co-Authors: Hideyuki Suzuki, Koichiro Yoshida
    Abstract:

    This paper presents two topics related to the design of large Floating Structure. One is a proposal of a new type of large Floating Structure in which the dynamic response characteristics of the edge Structure is modified from the other remaining uniform part. According to the understanding on the general response of the uniform large Floating Structure clarified in the previous report, the response of the edge Structure becomes significant. This response will not be acceptable when the Structure is used for runway of an airport from the view point of noraml function and structural strength. The dynamic response of the whole Structure is improved by this modification.Another topics is stability of the large Floating Structure considering elastic deformation of the Structure. When some buildings and other Structures are built on the Floating Structure, local elastic deformation must be considered. By using analytical solutions of continuous plate on elastic foundation, the deflection and inclination of the large Floating Structure under concentarted force and moment are calculated.