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成果報告書詳細
管理番号20170000000105
タイトル*平成27年度中間年報 風力等自然エネルギー技術研究開発 海洋エネルギー技術研究開発 海洋エネルギー発電システム実証研究(機械式波力発電)
公開日2017/6/2
報告書年度2015 - 2015
委託先名三井造船株式会社
プロジェクト番号P07015
部署名新エネルギー部
和文要約
英文要約Title: An experimental study of wave-power generation system (Mechanical method)
(FY2011-FY2016) FY2015 Annual Report
Prime contractor: Mitsui Engineering & Shipbuilding Co., Ltd. (MES)
Subcontractor: Tokyo University, Penta-Ocean Construction CO.LTD

1. Changing structural type for durability in actual field
Tension Leg Platform (TLP) is one of the mooring systems that can support an upper structure tightly with additional buoyancy chamber. The characteristic of TLP is that motions of upper structure by waves are too small. Although a fatigue analysis was conducted by using designed structure with TLP in FY2014 based on actual wave condition data at Kozu-island, a lack of fatigue strength for TLP was found out and the increase of weight for reinforcement of structure was required.
Therefore, the mooring system was modified to a slack mooring in FY2015. The characteristics of the slack mooring are that an acting force on a structure is reduced on the one hand and increasing motions on the other. Since efficiency for a power generation may be influenced by motion, a simulation with the slack mooring was conducted in FY2015 with Resonance Control that we will introduce, or with Standard Control. And analyses of structure and mooring system at the slack mooring were carried out in FY2015.

2. Estimation of power generation
In order to estimate in advance high efficiency for power generation with Resonance Control, simulation with the slack mooring model was conducted by using irregular wave input data based on marine conditions at Kozu-island. Simulation model is founded on equation of motion about 2 degree of freedom between float and spar. As results of simulation, the relative velocity of float to spar with Resonance Control got bigger than that of Standard Control. The improvement of power generation 30% as compared with Standard Control was confirmed under Resonance Control, since generated power is proportional to the squares of the relative velocity.

3. Survival analysis
Unsteady analysis for survival conditions with the slack mooring was conducted by using OrcaFlex. OrcaFlex is one of the most popular simulation packages in the world for design of offshore marine systems. Survival condition of wave is 100-year return period, significant wave height and averaged period are 10m and 12.4s, respectively. As a preliminary examination, survival analyses with changing buoyancy at sub-surface float and direction of an ocean current were conducted, maximum mooring load, declination angle of mooring, and pull-out strength on a gravity based anchor were estimated. Base on results, the final specification of the mooring system will be determined going through Water Tank Test that will be held in FY2016.
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