Tidal Current Power Research Articles

Tidal Current Energy Resource Distribution in Korea

Korea is a very well-known country for having abundant tidal current energy resources. There are many attractive coastal areas for the tidal current power that have very strong currents due to the high tidal range and the acceleration through the narrow channels between islands in the west and south coasts of the Korean peninsula. Recently, the Korean government announced a plan that aims to increase the portion of electricity generated from renewable energy to 20% by 2030. Korea has abundant tidal current energy resources; however, as reliable resource assessment results of tidal current energy are not sufficient, the portion of tidal current power is very small in the plan. Therefore, a reliable resource assessment should be conducted in order to provide a basis for the development plan. This paper describes the resource assessment of tidal current energy in Korea based on the observational data provided by KHOA (Korean Hydrographic and Oceanographic Agency) and numerical simulation of water circulation. As the observational data were unable to present the detailed distribution of the complicated tidal current between islands, numerical simulation of water circulation was used to describe the detailed distribution of tidal current in Incheon-Gyeonggi and Jeollanam-do, where the tidal energy potentials are abundant. The west and south coastal areas of Korea were divided into seven regions according to the administrative district, and the theoretical tidal current potential was calculated using average power intercepted. The results of this research can provide the insight of the tidal current energy development plan in Korea.

Analysis of Coefficiency According to Blade rpm Change in Tidal Current Power Generation System

Analysis of Coefficiency According to Blade rpm Change in Tidal Current Power Generation System

Preliminary Assessment of Tidal Stream Power Using 3-Dimensional Hydrodynamic Model in the Lembeh Strait

This paper provides a preliminary assessment of potential energy of tidal currents in the Lembeh Strait, North Sulawesi. Using two and three dimensional ocean hydrodynamic model, the assessment was done. A nesting method has been applied in order to simulate tidal currents in the Sulawesi Sea and the Lembeh Straits. Three dimensional simulation results at the Lembeh straits was validated using observation data, which are obtained from filed measurement campaign on 3 to 23 April 2016. Estimation of tidal current or tidal stream power was focused in the Lembeh Straits. The simulation results show power density during a tidal cycle can reach maximum value about 72.346,23 W/m2 at full moon condition. This amount of power is stored in the area between Sarena Island and Sulawesi Island. The result of tidal stream power estimation also reveals strong tidal currents that associated with maximum power occur during flood tide condition.

Review of tidal characteristics of Uldolmok Strait and optimal design of blade shape for horizontal axis tidal current turbines

Ocean energy is a promising renewable energy resource. In particular, South Korea is a country with a large amount of tidal current energy needed for the economically and technically feasible development of a tidal current power plant. In this study, the environmental conditions including the bathymetry and tidal conditions for Uldolmok Strait and previous studies carried out in Uldolmok Strait are first briefly reviewed, and the optimal design of the blade shape and performance of an optimally designed horizontal axis rotor for a 200-kW class tidal current turbine are discussed. For the optimal blade shape design, the design code, the Horizontal Axis Rotor Performance Optimizer developed by the National Renewable Energy Laboratory in the United States, is utilized, and the performance is investigated with respect to the number of blades (two or three) and the pitch control algorithms (variable or fixed). The results indicate that a variable speed fixed pitch turbine with three blades showed the best performance. However, the performances of four alternative cases did not show significant differences. Considering the advantages in terms of maintenance, we also conducted an analysis under various rotor and cut-in speed conditions. Hence, to select the final design, it is necessary to consider the structural integrity related to fatigue, as well as the economic feasibility in manufacturing the blades.

Large Eddy Simulation of Flow around Marine Turbine

Renewable energy usually refers to those natural resources of energy whose availability does not decrease with its usage. Various sources of renewable energy are there such as solar energy, wind energy, marine energy. The Marine Current Turbine (MCT), is an exciting proposition for the extraction of tidal and marine current power. CFD simulation is being widely used in the research on marine current turbines. The present research also represents a step in this direction. Solution of incompressible unsteady Navier-Stokes (N-S) equations is required in the numerical simulation of flow around MCT. Large Eddy Simulation (LES) has been opted which fully resolves the energetic turbulent flow structures and models only the sub-grid scale turbulence. IB method has been used to enforce the boundary conditions on complex geometry. Due to computational limitations we have been able to perform only a coarse grid LES of the marine turbine for specific operating conditions. Nevertheless, the results provide insights into the flow structures around the marine turbine. Analysis shows that the effect of vorticity diminishes after 11R from the turbine rotor blade. However, the velocity deficit region remains until the end of the domain used in our simulations which is 10D distance downstream of the rotor blades.

Estimation of Potential Energy Generated From Tidal Stream in Different Depth Layer at East Flores Waters Measured by ADCP

Tidal works on the currents occur in each layer with significant variations. Variations of types of tidal media are very appropriate to the phase of the tides. Measurement of currents in each layer is necessary to assess the potential that can be used in determining and studying the placement of energy sources as a source of energy to support renewable energy in East Flores.A 15day measurement with the Acoustic Doppler Current Profile (ADCP) instrument can record the speed profile in the study area which has tidal current variabilities and power density variations in the verticalcurrent profiles. The analysis showed that there were two layers of depth with very optimum potential energy: at -3.5 – -5.5 meters with the highests speed of tidal current 3.69m/s and -7.5 – -9.5 meters with the highests speed of tidal current 3.68m/s from the Lowest Astronomical Tide (LAT). Each layers has different character, the upper layer has a maximum-high kinetic power density of 25.71 kW/m2 at layer 10 and 25.43 kW/m2 at layer 9 and the bottom layer had an average kinetic power density of 11.64kW/m2. This bottom layer had the potential with a lower capacity, it shows that this site is also applicable for seabed mounted tidal turbines.

Preliminary Estimation of Tidal Current Energy for Three Straits in the Vicinity of Bali and Lombok Islands

Indonesia is an archipelago country which has a great potential of ocean energy resources including tidal current and wave power. In this present work, tidal power in three different straits, namely Alas strait, Bali strait and Lombok strait will be estimated. In order to achieve our goal, a two-dimensional, depth-integrated Advanced Circulation (ADCIRC-2DDI) model was employed. Eight tidal constituents were imposed along the ocean open boundaries. Two different sources of tidal constituents namely Le Provost and OTIS (OSU Tidal Inversion Software) were used. Tidal elevations have been validated and calibrated against tide gauge data in which at least six tide gauges are available in the study location. We found that, tidal constituents from high resolution database that is OTIS give better results. Open boundary conditions have been improved using Green’s function approach. As a result, significant reduction of the root-mean-square error (RMSE) has been obtained. This indicates that the method is powerful.  Furthermore, tidal current energy was estimated. Since there is no tidal current observation available in the area, tidal velocities were compared with the tidal current obtained from finite element solutions 2014 (FES2014). We found that tidal current obtained from ADCIRC model has a very good agreement with FES2014. Moreover, tidal current speed in the vicinity of Bali and Lombok islands could reach up to 3.8 m/s. As a consequence, tidal current power could exceed 10.98 kW / m 2 with assuming that turbine efficiency is about 0.39.

The effect of uncertain bottom friction on estimates of tidal current power.

Uncertainty affects estimates of the power potential of tidal currents, resulting in large ranges in values reported for a given site, such as the Pentland Firth, UK. We examine the role of bottom friction, one of the most important sources of uncertainty. We do so by using perturbation methods to find the leading-order effect of bottom friction uncertainty in theoretical models by Garrett & Cummins (2005 Proc. R. Soc. A 461, 2563–2572. (doi:10.1098/rspa.2005.1494); 2013 J. Fluid Mech. 714, 634–643. (doi:10.1017/jfm.2012.515)) and Vennell (2010 J. Fluid Mech. 671, 587–604. (doi:10.1017/S0022112010006191)), which consider quasi-steady flow in a channel completely spanned by tidal turbines, a similar channel but retaining the inertial term, and a circular turbine farm in laterally unconfined flow. We find that bottom friction uncertainty acts to increase estimates of expected power in a fully spanned channel, but generally has the reverse effect in laterally unconfined farms. The optimal number of turbines, accounting for bottom friction uncertainty, is lower for a fully spanned channel and higher in laterally unconfined farms. We estimate the typical magnitude of bottom friction uncertainty, which suggests that the effect on estimates of expected power lies in the range −5 to +30%, but is probably small for deep channels such as the Pentland Firth (5–10%). In such a channel, the uncertainty in power estimates due to bottom friction uncertainty remains considerable, and we estimate a relative standard deviation of 30%, increasing to 50% for small channels.

Comprehensive Utilization of Seawater Resources Based on Ocean Energy

This study combines the tidal current power generation system with seawater desalination and hydrogen production by concentrated seawater electrolysis, and proposes a comprehensive utilization mode of marine energy and seawater resources. Tidal turbines can provide sufficient power for islands or offshore facilities, while seawater desalination can supply adequate freshwater to islands. However, concentrated seawater, a byproduct of seawater desalination, is usually treated as waste and discharged back to the ocean. It thus becomes a pollution source and meanwhile causes a waste of chemical resources enriched in it, such as hydrogen, chlorine, and sodium. Therefore, this paper further studies the technologies for producing hydrogen and caustic soda by concentrated seawater electrolysis using the tidal current power generation system. By this means, marine energy resources are exploited for marine use, the seawater resource is properly recycled, and the establishment of offshore hydrogen supply stations may become possible.

Dynamic Behavior of Floating Tidal Current Power Device Considering Turbine Specifications

Tidal current power is one of the energy sources of the ocean. Electricity can be generated by converting the flow energy of the current into the rotational energy of a turbine. Unlike tidal barrage, tidal current power does not require dams, which have a severe environmental impact. A floating-type tidal current power device can reduce the expensive support and installation cost, which usually account for approximately 41% of the total cost. It can also be deployed in relatively deep water using tensioned wires. The dynamic behavior of a floater and turbine force are coupled because the thrust and moment of the turbine affect the floater excursion, and the motion of the floater can affect the incoming speed of the flow into the turbine. To maximize the power generation and stabilize the system, the coupled motion of the floater and turbine must be extensively analyzed. However, unlike pile-fixed devices, there have been few studies involving the motion analysis of a moored-type tidal current power device.In this study, the commercial program OrcaFlex 10.1a was used for a time domain motion analysis. In addition, in-house code was used for an iterative calculation to solve the coupled problems. As a result, it was found that the maximum mooring load of 200 kN and the floater excursion of 5.5 m were increased by the turbine effect. The load that occurred on the mooring system satisfied the safety factor of 1.67 suggested by API. The optimum mooring system for the floating tidal current power device was suggested to maximize the power generation and stability of the floater.

A fidelity fluid-structure interaction model for vertical axis tidal turbines in turbulence flows

Tidal energy is now considered as a renewable power source worldwide that can be used to reduce global warming. In order to harvest the tidal current power, horizontal and vertical axis tidal turbines (VATTs) have recently received increasing interests. To implement the detailed design process, the power outputs of 2D and 3D VATTs are simulated by a novel fidelity fluid-structure turbulence model in this work. This model is capable of simulating the fluid dynamics of the turbulent flow, as well as the stress, vibration, deformation, and motion of structures. Most importantly, flow-induced vibration for 3D VATTs is modelled by this model. In order to improve the computational efficiency, a large aspect ratio anisotropic mesh adaptivity is used to speed up simulations. The simulation results of these complex practical test cases are all in good agreement with experimental and numerical data in the literature. The model can be used to accurately predict the power output of VATTs, which can help to choose design configurations with high power output efficiency. More importantly, this model can be used to predict the flow-induced vibration of 3D VATTs, which can help to design VATTs with low vibration. Finally, the comparison between flexible and rigid VATTs shows the advantages of this model which demonstrates its capabilities when analysing the elasticities for realistic VATTs.

Hybrid Renewable Energy Power System Model Based on Electrification Requirements of One Fathom Bank Malaysia

Renewable energy resources are becoming inexorably in the field of generating electrical power due to the fast development of technology, given to its advantages over non-renewable energy resources. Though the source is available in enormous amount, energy produced from single renewable energy resources such as tidal current may fluctuate with the time and the hour of the day or month, depending on the tides. Thus, by having a hybrid power system consisting two or more renewable energy resources coming into play at the same time would be more reliable to support the targeted area. However, the availability of renewable energies depends on the climate change, therefore having a storage battery or backup power is often essential. In this case, the main purpose of this research is to develop an off-grid hybrid tidal current and solar power system along with backup power to support One Fathom Bank Lighthouse in Malaysia with the intention to reduce the dependency on diesel generators. Having the ability to evaluate economic and technical feasibility of power system, HOMER software is used to run simulation and analyze the best combination of components to form a hybrid power system for the lighthouse. The results are based on the best components and sizing in compliance with the load demand and diesel fuel consumption to provide a reliable and cost-effective system.

Catamaran or semi-submersible for floating platform – selection of a better design

With nonstop advancement in marine engineering, more and more new structures are being designed and explored for tidal current energy. There are three different kinds of support structures for tidal current power station mostly in use, which are sea-bed mounted/gravity based system, pile mounted system and floating moored platform. Comparing all of them, the floating mooring system is most suitable for deep water systems and the application of this arrangement is widely usable. In this paper, a semi-submersible and a catamaran as floating platforms for tidal current power stations are studied are compared on the basis of its economics, efficiency of turbine and stability of the station. Based on basic ship theory and using software MAXSURF, the stability of Catamaran tidal current power station is also calculated. It is found that the catamaran design is optimal choice.

IDENTIFICATION OF POTENTIAL SITES FOR HARVESTING TIDAL CURRENT POWER IN KELIAN CAPE, KELABAT BAY, AND LARANTUKA STRAIT

Harvesting of power from tidal currents is part of an emerging effort to capture energy fromrenewable sources, as non-renewable energy resources are depleted. The Indonesian government plans todevelop tidal energy power generators in several areas and is conducting assessments in Bangka Belitungprovince at two locations in Kelian Cape and Kelabat Bay and in the province of East Nusa Tenggara atLarantuka Strait. Three potential locations namely Kelian Cape, Kelabat Bay, and Larantuka Strait, is assessed.Field measurements, numerical modeling, and potential site analysis are carried out. Both tidal elevation andtidal current validation between field measurement data and numerical modeling results are carried out andshow good agreement. MIKE 3 (licensed) is used for the modeling process The Kelian Cape model presentsthree potential sites at Kelian Cape, with a peak velocity of 1.4 m/s. The Kelabat Bay model gives five potentialsites, located at the bay’s narrowest point, with a peak velocity of 1.15 m/s. The Larantuka Strait model givesfour potential sites in the narrowest area, with a peak velocity of 2.5 m/s. Larantuka Strait is found to have themost potential for the harvesting of tidal current power, as the current velocity at Larantuka Strait is higher,meaning that turbine devices with higher cut-in speeds are suitable. In Kelian Cape and Kelabat Bay, deviceswith low cut-in speed such as the Gorlov Helical Turbine or Sabella Turbine are required.

Development and the environmental impact analysis of tidal current energy turbines in China

Chinese government pays more attentions to renewable energies (RE) in the context of increasing energy demand and climate change problems. As a promising RE, the utilization of marine renewable energy (MRE) is engaging in the world, including the wave energy and tidal current energy mainly. At the same time, the tidal current energy resources in China are abundant. Thus, the utilization of tidal current energy becomes an inevitable choice for China to meet the challenge of global climate change. The Renewable Energy Law (amendment) and “Twelfth Five-Year” Plan of Renewable Energy Development (2011-2015) were released in recent years in China, the tidal current energy are successfully implemented in China, including the R&D and pilot projects. After the summary of the status of tidal current energy converters in recent years in China, especially the devices being in the open sea test. The environmental impact study in China is also introduced in order to offer reference for the environmental impact assessment of tidal current power generation.

2015S-GS10-2 五島におけるデバイス設置を考慮した潮流発電のフィージビリティスタディ

2015S-GS10-2 五島におけるデバイス設置を考慮した潮流発電のフィージビリティスタディ

A review of the current status for environmental impact assessment of tidal and oceanic current power generation

A review of the current status for environmental impact assessment of tidal and oceanic current power generation

수중체 형상에 따른 수중 조류발전장치 운동성능

수중체 형상에 따른 수중 조류발전장치 운동성능

Application of an Airfoil to the Tidal Turbine Design by Analyzing Two-dimensional Performance in the Water

The tidal turbine, the first device converting the in-line flow energy into rotational motion, is one of the crucial components that affects the performance of the tidal current power system. The tidal turbine is designed by using BEMT (Blade Element Momentum Theory) developed for wind turbine that has large similarities. But the differences exist in range of Reynolds number and in working fluid that should be considered for tidal turbine design. Since the airfoil profile has been developed for wind turbine, it might contain essential errors in 2-dimensional characteristics. In this study, using validated CFD (Computational Fluid Dynamics) analysis method with experimental data obtained from flume tank, the 2-dimensional airfoil performance was evaluated considering operating conditions of the tidal turbine for design optimization. Based on the obtained characteristics of the airfoil, the horizontal axis tidal turbine of 10m diameter was designed. Performance of the designed turbine has been analyzed, and the results are summarized in this paper.

Tidal Current Power Resources and Influence of Sea-Level Rise in the Coastal Waters of Kinmen Island, Taiwan

The tidal current power (TCP) resource, the impact of TCP extraction on hydrodynamics and the influence of sea-level rise (SLR) on TCP output in the coastal waters of Kinmen Island (Taiwan) are investigated using a state-of-the-art unstructured-grid depth-integrated numerical model. The model was driven by eight tidal constituents extracted from a global tidal prediction model and verified with time series of measured data for tide level and depth-averaged current. The simulations showed reasonable agreement with the observations; the skill index was in the excellent (0.71–0.93) range with regard to simulating tide level and currents. Model predictions indicated that the channel between Kinmen and Lieyu serves as an appropriate site for deploying the tidal turbines because of its higher tidal current and deeper water depth. The bottom friction approach was utilized to compute the average TCP over a spring-neap cycle (i.e., 15 days). Mean TCP reached its maximum to 45.51 kW for a coverage area of 0.036 km2 when an additional turbine friction coefficient (Ct) increased to 0.08, and a cut-in speed of 0.5 m/s was used. The annual TCP output was estimated to be 1.08 MW. The impact of TCP extraction on the change in current is significant, with a maximum reduction rate of instant current exceeding 60%, and the extent of influence for the average current is 1.26 km in length and 0.30 km in width for the −0.05 m/s contour line. However, the impact of TCP extraction on the change in tide level is insignificant; the maximum change in amplitude is only 0.73 cm for the K2 tide. The influence of SLR on the TCP output in Kinmen waters was also estimated. Modeling assessments showed that due to SLR produces faster tidal current, the annual TCP output increased to 1.52 MW, 2.01 MW, 2.48 MW and 2.97 MW under the same cut-in speed and coverage area conditions when SLR 0.25 m, SLR 0.5 m, SLR 0.75 m and SLR 1.0 m were imposed on the model.