OTEC 라이저 거동 최적화를 위한 단면 설계

Abstract

10MW OTEC (Ocean Thermal Energy Conversion) system in the pre-commercial class inevitably needs a long riser with the 4m diameter in order to intake amount of cold water. The OTEC system in commercial scale is impossible without the development of a riser with a large diameter and new material due to no commercial pipe in 4m diameter. In order to produce the electricity with the OTEC system in the Pacific Ocean near the equator, the length of a large diameter riser must be longer than 1,000m to intake cold water. A long riser with a large diameter exposed to the harsh wave, current, and top excitation by a floating structure has to keep its safety for continuous operation of an OTEC. In this study, the optimal design for a cross-section of a 10MW OTEC riser is performed. A FRP-based composite material is considered to adjust the density and stiffness. The dynamic structure analysis for the designed composite riser is performed to check the riser safety with the numerical method of FEM. Stresses along the riser length loaded by wave, current, and top excitation of a floating structure are analyzed. The cross-section of a riser consists of FRP in the inner and outer layers along the thickness and foam between two FRP layers. Stress distribution of a riser is analyzed according to the density and stiffness determined with the component ratio of FRP and foam materials. The effect of a lumped weight in the end of a riser ment of a riser with a large diameter and new material due to no commercial pipe in 4m diameter. In order to produce the electricity with the OTEC system in the Pacific Ocean near the equator, the length of a large diameter riser must be longer than 1,000m to intake cold water. A long riser with a large diameter exposed to the harsh wave, current, and top excitation by a floating structure has to keep its safety for continuous operation of an OTEC. In this study, the optimal design for a cross-section of a 10MW OTEC riser is performed. A FRP-based composite material is considered to adjust the density and stiffness. The dynamic structure analysis for the designed composite riser is performed to check the riser safety with the numerical method of FEM. Stresses along the riser length loaded by wave, current, and top excitation of a floating structure are analyzed. The cross-section of a riser consists of FRP in the inner and outer layers along the thickness and foam between two FRP layers. Stress distribution of a riser is analyzed according to the density and stiffness determined with the component ratio of FRP and foam materials. The effect of a lumped weight in the end of a riser