Chul-Hee Jo

Wake Effect on HAT Tidal Current Power Device Performance

The rotor that initially converts the flow energy into rotational energy is a very important component that affects the efficiency of the entire tidal current power system. Rotor performance is determined by various design variables. Power generation is strongly dependent on the incoming flow velocity and the size of the rotor. To extract a large quantity of power, a tidal current farm is necessary with a multi-arrangement of devices in the ocean. However, the interactions between devices also contribute significantly to the total power capacity. Therefore, rotor performance, considering the interaction problems, needs to be investigated to maximize the power generation in a limited available area. The downstream rotor efficiency is affected by the wake produced from the upstream rotor. This paper introduces the performance of a downstream rotor affected by wakes from an upstream rotor, demonstrating the interference affecting various gabs between devices.

Design and Performance Test of Savonius Tidal Current Turbine with CWC

*Inha University, Incheon, Korea**Hyundai Engineering and Construction, Yongin, KoreaKEY WORDS: TCP (Tidal current power) 조류발전, Renewable energy 신재생 에너지, VAT (Vertical axis turbine) 수직축 터빈, CWC (Circulating water channel) 회류수조, Savonius turbine 사보니우스 터빈, CFD (Computational fluid dynamics) 전산유체역학ABSTRACT: Due to global warming, the need to secure alternative resources has become more important nationally. Because of the very stro ng current on the west coast, with a tidal range of up to 10 m, th ere are many suitable sites for the application of TCP (tidal c urrent power) in Korea. In the southwest region, a strong current is created in the narrow channels between the numerous islands. A rotor is an essential com-ponent that can convert tidal cu rrent energy into rotational energy to generate electricity. The design optimization of a roto r is very important to maximize the power production. The performance of a rotor can b e determined using various parameters, including the number of blades, shape, sectional size, diameter, etc. There are many offshore jetties and piers with high current velocities. Thus, a VAT (vertical a xis turbine) system, which can generate power regardless of flow direction changes, could be effectively applied to cylindrical structures. A VAT system could give an advan-tage to a caisson-type breakwater because it allows water to ci rculate well. This paper introduces a multi-layer vertical axis tidal current power system. A Savonius turbine was designed, and a performance anal ysis was carried out using CFD. A physical model was also demon strated in CWC, and the results are compared with CFD.교신저자 이강희: 인천광역시 남구 용현4동, 032-860-8849, kanghee@inha.edu

Performance analysis of 200kW tidal current power turbine with pre-deformed blades

The importance and understanding of renewable energy has increased even more after the nuclear power plant accident in Japan four years ago. Among the various renewable energy sources, tidal current power is recognized as the most promising energy source in terms of predictability and reliability. In general, a tidal current power turbine has two or three blades that are subjected to hydrodynamic loads during operation. The blades are continuously deformed by various incoming flow velocities. Depending on the flow velocity, blade size, and material properties, the deformation rates can be different, which could affect the performance of the turbine and its power rate. Since deformed blades can decrease the performance of the turbine, the power generation could be affected accordingly. We examined design criteria of a tidal current turbine, and the results of a fluid-structure interaction (FSI) analysis conducted using computational fluid dynamics (CFD) and the finite element method (FEM). Since pre-deformed blades can be used to optimize the blade geometry for operating conditions, this concept could contribute to the performance enhancement and commercialization of tidal turbines.

Preliminary Design and Performance Analysis of Ducted Tidal Turbine

Recently, focus has been placed on ocean energy resources because environmental concerns regarding the exploitation of hydrocarbons are increasing. Tidal current power, one of the ocean energy resources, has great potential worldwide due to its high energy density. The flow velocity is the most crucial factor for the power estimation of TCP(Tidal Current Power) system since the kinetic energy of the flow is proportional to the cube of the flow speed. So sufficient inflow speed to generate electricity from the tidal current power is necessary. A duct system can accelerate the flow velocity, which could expand the applicable area of TCP systems to relatively lower velocity sites. The shapes of the inlet and outlet could affect the flow rate inside the duct. To investigate the performance of the duct, various ducts were preliminary designed considering the entire system that is single-point moored TCP system and a series of simulations were carried out using ANSYS-CFX v13.0 CFD software. This study introduces a ducted turbine system that can be moored to a seabed. A performance estimation and comparison of results with conventional tidal converters were summarized in this paper.

Performance Estimation of a Tidal Turbine with Blade Deformation Using Fluid-Structure Interaction Method

The turbine is one of the most important components in the tidal current power device which can convert current flow to rotational energy. Generally, a tidal turbine has two or three blades that are subjected to hydrodynamic loads. The blades are continuously deformed by various incoming flow velocities. Depending on the velocities, blade size, and material, the deformation rates would be different that could affect the power production rate as well as turbine performance. Surely deformed blades would decrease the performance of the turbine. However, most studies of turbine performance have been carried out without considerations on the blade deformation. The power estimation and analysis should consider the deformed blade shape for accurate output power. This paper describes a fluid-structure interaction (FSI) analysis conducted using computational fluid dynamics (CFD) and the finite element method (FEM) to estimate practical turbine performance. The loss of turbine efficiency was calculated for a deformed blade that decreased by 2.2% with maximum deformation of 216mm at the blade tip. As a result of the study, principal causes of power loss induced by blade deformation were analysed and summarised in this paper.

Performance and Mooring Analysis of 10 KW Floating Duct-Type Tidal Current Power System

Recently, focus has been placed on ocean energy resources because environmental concerns regarding the exploitation of hydrocarbons are increasing. Among the various ocean energy sources, tidal current power (TCP) is recognized as the most promising energy source in terms of predictability and reliability. The enormous energy potential in TCP fields has been exploited by installing TCP systems. The flow speed is the most important factor for power estimation of a tidal current power system. The kinetic energy of the flow is proportional to the cube of the flow’s velocity, and velocity is a critical variable in the performance of the system. Since the duct can accelerate the flow speed, its use could expand the applicable areas of tidal devices to relatively low velocity sites. The inclined angle of the duct and the shapes of inlet and outlet affect the acceleration rates of the flow inside the duct. To investigate the effects of parameters that increase the flow speed, a series of simulations are performed using the commercial computational fluid dynamics (CFD) code ANSYS-CFX. Experimental investigations were conducted using a circulation water channel (CWC). Also, mooring system concepts are investigated using the commercial mooring analysis software WADAM and OrcaFlex. Due to other floating structures operating within a limited area, station-keeping is needed in order to keep the motions of the floating duct structures within permissible limits. In this study, methods for optimizing the mooring system of a floating duct-type tidal current power system in shallow water are investigated. Based on the performance and mooring analysis results of the 10 kW floating duct-type TCP system, a new design for a small capacity floating TCP system is introduced.Copyright

A comparison of coupled and uncoupled dynamic analysis for the flexible riser in shallow water

Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system

OPTIMIZATION OF MOORING SYSTEM FOR MULTI-ARRAYED TIDAL TURBINES IN A STRONG CURRENT AREA

Recently, focus has been placed on ocean energy resources as environmental concerns regarding the exploitation of hydrocarbons are increasing. The enormous energy potential in tidal current power fields has been exploited by installing floating tidal current power turbines. Due to other floating structures operating within a limited area, stationkeeping is needed in order to keep the motions of the floating structures within permissible limits. In this study, methods for selecting and optimizing the mooring system for floating tidal current power systems in shallow water are investigated. The mooring system provides restoring forces and moments on a floating structure, pulling the structure back toward its equilibrium position. Typically, the mooring lines are segmented in order to optimize the force and displacement characteristics known as the mooring line characteristics. The mooring system concepts investigated in this study include the distributed mass, clump weight, and buoyancy element mooring systems.© 2014 ASME

Numerical Analysis of Offshore Pile Structure for Tidal Current Devise Using FSI Method

Recently, large scale tidal devices have been deployed with a maximum rotor diameter of 20m. These devices impose significant loading on supporting structures. The supporting structure for tidal current power device is under dynamic loadings caused by environmental loadings. Not only the environmental loadings but also the rotating turbine creates dynamic loading as well. The rotating turbine is obviously and continuously deformed for various incoming flow velocities. In many cases, a pile fixed foundation is used to secure the structure. In this study, the commonly used pile fixed type is applied with three blade turbine. A numerical analysis of the hydro-forces from a rotating tidal current turbine to a tower was conducted to determine the deformation distribution along the pile tower. The FSI analysis technique is used in the study.Copyright

Interference Effects on the Performance of Multi-arrayed HAT TCP Devices

Tidal current power system is the energy converter which converts the kinetic energy of tidal stream into electric energy. The performance of the rotor which initially converts the energy is determined by various design factors and it should be optimized by the ocean environment of the field. Flow direction changes due to rise and fall of the tides, but horizontal axis turbine is very sensitive to direction of flow. To investigate the rotor performance considering the interaction problems with incidence angle of flow, series of experiments have been conducted. The results and findings are summarized in the paper.