Ocean Energy, Wave Energy, Tidal Current Energy Research Papers (original) (raw)

ABSTRAK Penelitian dilakukan untuk menjawab keingintahuan peneliti untuk mengungkapkan suatu gejala alam atau fenomena alam yaitu terjadinya pasang surut laut yang diakibatkan oleh gaya tarik-menarik antara Bumi-Bulan dan Bimi-Matahari. Kampus Universitas Pancasakti Tegal berada di dekat pantai, pada saat air pasang, beberapa halaman dan jalan yang menuju ke kampus UPS tergenang air laut, kadang-kadang cukup tinggi dan kadang-kadang hanya banjir kecil saja. Hal itulah yang mendorong peneliti ingin mengetahui seberapa besar ketinggian air laut pasang pada saat bulan mati atau bulan baru dan bulan purnama. Metode penelitian yang digunakan adalah metode gaya gravitasi dari hukum Newton tentang gravitasi yaitu gaya tarik-menarik antara dua benda yang bermassa, dalam hal ini antara massa Bumi dan massa Bulan serta massa Bumi dan massa Matahari. Dari pengembangan metode ini, akan didapat ketinggian pasut fungsi dari lintang tempat. Untuk membuktikan kebenaran teori ini, dilakukan pengamatan pasut secara langsung di pantai Kota Tegal. Ketinggian pasut rata-rata, berdasarkan pengamatan selama empat bulan adalah 37,9 cm. Ketinggian rata-rata hasil perhitungan pasang surut air laut secara teori adalah 33,9 cm untuk sistem Bumi-Bulan dan 15,6 cm untuk sistem Bumi-Matahari. Hasil yang diperoleh dari hasil perhitungan pasut dimana gaya pembangkit pasut matahari menggunakan jarak rata-rata bumi-bulan dan jarat rata-rata bumi-matahari. Hasil pengamatan pada bulan Maret, April, Mei dan Juni 2009, ketinggian pasutnya memiliki interval dari 2 cm pada tanggal 23 Maret 2009 sampai dengan 87 cm pada tanggal 1 Juni 2009. Nilai tersebut adalah nilai minimum dan maksimum selama empat bulan pengamatan. Kata Kunci : Pasut, Pasang Surut Air Laut PENDAHULUAN Pasang surut adalah perubahan gerak relatif dari materi suatu planet, bintang dan benda angkasa lainnya yang diakibatkan aksi gravitasi benda-benda angkasa di luar materi itu berada. Pasang surut laut adalah naik turunnya permukaan air laut disertai gerakan horizontal massa air, dan gejala ini mudah dilihat secara visual. Naik turunnya muka air laut biasanya disebut vertical tide dan gerakan horizontal disebut tidal curren (arus pasang surut). Turun-naiknya permukaan air laut ini karena pengaruh gravitasi dari bulan dan matahari. Bila permukaan air laut mengalami kenaikan disebut pasang naik dan sebaliknya bila terjadi penurunan disebut pasang surut. Gaya gravitasi bulan lebih dominan pengaruhnya dibandingkan gaya gravitasi matahari terhadap terjadinya pasang air laut ini, karena posisi bulan lebih dekat ke bumi dibandingkan jarak bumi ke matahari. Pasang besar akan terjadi bila tempat-tempat di bumi mangalami bulan mati dan bulan purnama.

The greatest increase in demand for energy coming from newly industrialized countries where large-scale electricity generation will be required, the environmental requirements for zero or low CO2 emission sources and the need to invest in a sustainable energy mix, involve the development of new energy sources. Wave, tidal and marine current energy could be available as a future energy option and should be able to acquire a significant role in providing a sustainable, secure and safe solution to tackle European and global energy needs. Sun and wind are predictable, but not constant: photovoltaic panels and eolic turbines could barely support alone the peaks of the power request from the grid, and the contribution of hydroelectric seems to have already reached its limits in some European countries. For this reasons, in order to become independent from fossil fuels, it will be fundamental to harvest energy from the largest number of natural phenomena, especially ones that are predictale with high precision, as tides, and ones that are almost constant, as ocean currents.

- by Riccardo Novo
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- Renewable Energy, Wave Energy, Tidal Stream Energy, Green Energy

The purpose of this paper is to create a reasonable model for the AquaBuOY, a wave energy converter technology developed by AquaEnergy Development UK Limited (a subsidiary of Finavera Renewables). The AquaBuOY, as stated in “Mathematical and Numerical Modeling of the AquaBuOY Wave Energy Converter” [1], is modeled as a two-body system of linear second order differential equations corresponding to the vertical motion of the two bodies. As the system is difficult to solve by hand, even given a number of assumptions and an expected outcome, it was vital that we could create a model of the system in Simulink. Once created, the Simulink model allowed us to quickly change any individual parameter, such as size and mass of components or location of the buoy, as reflected in changes in amplitude and wave frequency, and model its effect on the efficiency of the approximated system. The goal of the project, in addition to calculating the output efficiency of the system, was to demonstrate proficiency in the course material.

Researchers have shown growing interest in the development of traditional Savonius turbine due to their numerous benefits such as structural simplicity, self-start ability, relatively low operating speed, bi-directional rotational ability and lower environmental impact. However, Savonius turbines exhibits lower efficiency as compared to other similar marine current turbines. This paper proposes a novel design concept for the Savonius turbine. In addition, this work investigates flow and pressure distribution around the buckets of novel rotor with a two-dimensional unsteady numerical model. The proposed marine current turbine with novel design is named as Reza Turbine. Numerical model employed the Dynamic Mesh Method (DMM) for modelling mesh movement around the blades of rotor for different position with respect to computational domain. Developed numerical model solves the unsteady Reynolds averaged Navier-Stokes equations by using SIMPLE algorithm. In addition, we conducted an experiment in a low speed wind tunnel to obtain important performance parameters namely torque, power and performance for the proposed turbine. A set of flow speed were used as inlet boundary condition for both numerical and experimental model. A comparison between numerical and experimental results shows that the SST k-u turbulence model gives satisfactory results for the developed novel turbine. The developed ReT is showed 52% improvement in efficiency as compared conventional Savonious turbine. Since the peak of power coefficient obtained was 0.321 for ReT, while 0.21 was reported for conventional Savonius turbine.

With the diminishing supply of fossil-based energy, new renewableenergy sources including marine tidal current are being explored.In vertical axis marine current turbine applications, Savonius-type rotorhas been shown as suitable for low current speeds normally associatedwith Malaysia seas. However, the efficiency of the rotor is low and assuch efforts are being made to optimise the rotor in variousmanners. This paper describes a validation procedure preparation for aparametric study to obtain an optimised Savonius turbine rotor. Theresearch work results have been validated by comparison with theexisting published experiment data. The study was based on conductingtwo and three dimensional analyses using Computational FluidDynamics (CFD) RANSE code. Some parametric analysis has beensuggested to obtain an optimal configuration for the turbine

This paper presents results obtained from a series of experiments conducted in wave flume to assess the influence of the offshore low-crested breakwater as a defence structure in reducing the wave forces on vertical seawall. The main aim of the tests was to know the effect of crest elevation of the offshore low-crested breakwater as a rehabilitation structure for the existing damaged shore protection structures. In this study five relative breakwater heights are used and associated flow evolution was analyzed. With the sections proposed in this study, it is possible to achieve considerable reduction of wave force on the seawall. Modification factor is proposed to estimate the shoreward force on the seawall defenced by low-crested breakwater. q

Oceanic surface gravity waves have a mean Lagrangian motion, the Stokes drift. The dynamics of winddriven, basin-scale oceanic currents in the presence of Stokes drift are modified by the addition of so-called vortex forces and wave-induced material advection, as well by wave-averaged effects in the surface boundary conditions for the dynamic pressure, sea level, and vertical velocity. Some theoretical analyses previously have been made for the gravity wave influences on boundary-layer motions, including the Ekman currents. The present paper extends this theory to the basin-scale, depth-integrated circulation in a bounded domain. It is shown that the Sverdrup circulation relation, with the meridional transport proportional to the curl of the surface wind stress, applies to Lagrangian transport, while the associated Eulerian transport is shown to have a component opposite to the Stokes-drift transport. A wave-induced correction to the relation between sea level and surface dynamic pressure is also derived. Preliminary assessments are made of the relative importance of these influences using a global wind climatology and an empirical relationship between the wind and wave fields. Recommendations are made for further development and testing of this theory and for its inclusion in general circulation models.

- by Juan M Restrepo and +1
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- Ocean Waves, Ocean Energy, Wave Energy, Tidal Current Energy, Shallow Water Equation (SWE)
- by Shijo Jose
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- Renewable Energy, Tidal Stream Energy, Renewable energy resources, Geothermal Energy

The unsteady flow field in the vicinity of a NACA 63-215 hydrofoil in a closed-loop water channel at Reynolds number of Re ≈ 29103 is investigated experimentally. A Tomographic Particle Image Velocimetry (TomoPIV) is used to determine the velocity field in the near-wake region of the studied hydrofoil. The manufactured hydrofoil was mounted on the 3D traverse and installed vertically in the water tunnel test section. The TomoPIV measurement volume was performed in a voxel with the volume of 164 × 168 × 82 mm3 (X, Y, Z). Vortex identification techniques including Q-criterion and λci criterion, together with helicity of flow are evaluated in the wake of the hydrofoil. Vorticity and swirling strength are used to further understand the location and behavior of the dynamic pattern of the vortex shedding in the trailing edge of the hydrofoil. The vorticity magnitudes as they transport downstream is explored to dissipate their energy in the wake. The flow pattern reflects a turbulent behavior required for higher efficiency of the designed hydrofoil. The results are compared with literature. This work obtains a validated model for the wind farm case and will be a basis of the ocean current turbine arrays wake structure analysis.

The challenge in the hydrodynamic modelling of tidal and marine turbine farms is to take into account the interaction of flow events across a wide range of scales, such as as the blade scale, turbine scale, array scale and regional scale. Whilst the interaction of the blade and turbine scales can be studied using the classical Blade- Element-Momentum (BEM) theory, no basic theory was available until recently to describe the interaction of the turbine and larger scales. The two-scale actuator disc theory (ADT), first proposed in 2012 by Nishino and Willden, explain the interaction of the turbine and array scales at a fundamental level; however, its validity or applicability to real problems has only partially been confirmed. Hence in this study we perform 3D RANS simulations of single and double rows of porous discs (8 discs for each row) in the middle of a shallow open channel with a vertically sheared flow. The simulation results are shown to agree qualitatively with the two-scale with the two-scale ADT and importantly, the optimal intra-disc spacing predicted by the simulations (to maximise the total power) agrees well with the theory, for both single-row and double-row cases

The aim of this study was to develop a model of ocean wave energy converter based on water mass gravity force (WEC-WGF) to overcome the flaws of existing wave energy converter that rely on water buoyancy force. This paper presented physical model experiment result of wave energy converter based on water mass gravity force. The harvested energy were compared with calculated theoretical energy based on linear wave theory. The physical model investigation was carried out at wave simulator (flume) in Hydraulics Laboratory Department of Civil Engineering, Hasanuddin University Indonesia on February-March 2016. The physical model consists of a series of one-way gear connected with plastic container as an interface between converter and regular generated wave. Investigation was carried out to observe the influence of gravity weight mass and wave height variations on converters harvested power. The experiment result indicated that the amount of converter Power Take Off (PTO) were strongly influenced by variation of gravity weight mass (M gw), followed by wave height (H) and wave period (T) respectively. These results outperform the calculated power by means of linear wave theory. The result of this experiment could be used as a reference to develop theoretical or analytical model of wave energy converter based on water mass gravity force. Keywords— Wave, Gravity Force, Renewable Energy, Wave Energy Converter I. INTRODUCTION Energy, water and food are essential needs to support the continuation of human activities. In the last few decades, the main source of energy depends on the burning of fossil fuel. Since the depletion of oil resources, most countries in the world started to realize the importance of environmental conservation and efficient use of fossil fuel reserves. Moreover, the reduction of fossil fuel as a main source of energy hopefully could reduce the level of CO2 emissions which are considered as a main source of global air pollution. The total global CO2 emissions in 2013, comprised of; power plants contribute 42%, transportation 23%, industrial activities 19%, households 6%, services and other sectors produced 3% to 7%. The amount of CO2 released into the atmosphere in the last 42 years increased by approximately 230% from 13.995 million tons in 1971 increased to 32.190 million tons in 2013 [1] [2]. Efforts to reduce CO2 emissions has been carried out through the utilization of renewable energy sources such as wind energy (wind), hydropower plants, solar power, ocean currents and wave energies. In term of energy density, wave energy poses the greatest energy content that is available for 24 hours. However it has not been fully utilize due to the cost per kWh did not economically feasible due to the flaws of existing wave energy converter technologies [3].

Ocean waves are a huge, largely untapped energy resource, and the potential for Extracting energy from waves is considerable. Research in this area is driven by the need to meet renewable energy targets, with this efforts a huge number of devise are designed for converting wave energy in to useful energy, but is relatively immature compared to other renewable energy technologies. This report introduces the general status of wave energy and evaluates the device types that represent current wave energy converter (WEC) technology.

Due to the low current speeds associated with Malaysian tidal currents, Savonius turbine was
chosen as a device in extracting this energy. However, this turbine suffers from poor efficiency. The present paper describes some works carried out to improve the turbine. The effect of speeds on performance was found to be minimal while the use of deflectors improved flow into the rotor and contributes significantly to the coefficient of performance improvement. The use of ducts was also studied, indicating improved flow characteristics.

Renewable energy resources need to be explored to maintain and meet energy demand andreplace the slowly depleting fossil fuels. The ocean is a huge reservoir of renewable energyresources such as wind, wave and tide/current. Malaysia, surrounded by sea with longcoastline, is poised to exploit the potential of this energy. Universiti Teknologi Malaysia(UTM) has embarked on research work in renewable energy to find a suitable ocean energydevice for Malaysian sea conditions. This paper presents current progress on development of devices to extract two potential sources of ocean energy in Malaysia viz. wave and currentenergy. The ocean wave energy is being explored using the Oscillating Water Column(OWC ) concept. A small scale model of the OWC was constructed and tested in MarineTechnology Laboratory. A reflector was attached underneath the air chamber at threeangular positions. Tests were carried out to determine the best angular position giving the best air pressure to drive the turbine. The other work involves the development of the MarineCurrent Turbine (MCT). The project incorporates the characteristic of Malaysia’s ocean of shallow water and low speed current in developing the turbines. Preliminary characteristicsand experimental results of the vertical axis turbines being developed will be presented

Marine currents may represent a renewable energy source characterized by a limited environmental impact. In Italy, the Strait of Messina seems to be suited for exploitation of this energy source. A vertical axis turbine, with blades oscillating about the pivotal axis according to the Voith–Schneider system, has been considered. This paper presents a preliminary theoretical investigation of the performance of this kind of turbine that may be employed to tap marine currents energy sources. The investigation is conducted by means of a simple momentum model based on the “single-disk single-streamtube” approach. The theoretical results are compared with experimental measurements. The adequate agreement between experimental and theoretical results shows that such a simple model may be able to predict the power coefficient and the operating range of the turbine.

The world is heavily dependent on fossil fuels since most of its energy requirements are fulfilled by conventional methods of burning these fuels. The energy demand is increasing by day with growing population. The energy production by fossil fuels is devastating the environment and survival of life on globe is endangered. The renewal energy technologies are vital to ensure future energy sustenance and environmental issues. Ocean is a vast resource of renewable energy. The technology today makes it possible to extract energy from tides. The growing interest in exploring tidal current technologies has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The purpose of this study is to present a comprehensive review of tidal current technologies to harness ocean energy. The ocean energy resources are presented. The author discusses tidal energy technologies. The tidal current turbines are discussed in detail. The author reviews today’s popular tidal current technologies. The present status of ocean energy development is also reported.

Researchers and engineers around the globe are striving to improve green energy technologies. Among green energy technologies, diffuser augmented tidal turbines are attracting focus due to enormous potential for producing energy. The power output by a tidal turbine is directly proportional to the cube of velocity of incoming fluid flow. Thus, even a minor increase in velocity considerably increases the power output. The diffuser helps accelerate the velocity of incoming fluid flow. Hence, the efficiency of the turbine is significantly increased by using a diffuser. It is challenging to accelerate the incoming flow by a diffuser due to its shape, geometry and fabrication limitations. The diffuser design requires great deal of innovation and time investment. The research community is investing considerable time and financial resources in this arena. However, limited research results are available for diffuser augmented tidal turbines due to their emerging nature, large and costly research & development setup, startup cost and proprietary issues. The purpose of this paper is to present the numerical simulation of 2D model of diffuser for tidal turbine. Numerical simulation results of velocity profile for fifteen models with different mesh sizes is presented in detail. The effect of mesh density on coefficient of velocity is discussed. Predicted results are then compared to experimental results and found in reasonable agreement. The research is essential for utilizing CFD tools for diffuser design for tidal turbine.

The dependence on fossil fuels for energy production has come to an alarming stage. Energy demand continues to increase with growing population. Consequently fossil fuel reserves are continuously draining and the world is confronted with their extinction in near future. Burning fossil fuels has also put our environment on the edge of destruction. Energy resource depletion and devastation of environment has compelled researchers to explore renewable and green resources of energy. Tidal current technologies have salient advantages such as cleaner than fossil fuels, intermittent but predictable, security and diversity of supply, and limited social and environmental impacts. Tidal current technologies continue to develop and expand, yet needs time to prove their full potential. This paper presents the background for shift towards renewable energy, especially tidal energy. It outlines classification of ocean energy resources and tidal energy. This paper also documents today’s popular tidal current devices and reports on the present status of ocean energy development.

This paper presents the results of a pilot experiment with an existing tidal energy converter (TEC), Evopod 1 kW floatable prototype, in a real test case scenario (Faro Channel, Ria Formosa, Portugal). Operational results related to the description of power generation capacity, energy capture area and proportion of energy flux are presented and discussed. The data is now available to the scientific community and to TEC industry developers, enhancing the operational knowledge of TEC technology concerning efficiency, environmental effects, and interactions (i.e. device/environment).

As long as it is economical, Turkey, which is encircled on three sides by the seas, should have the utmost benefit of using her existing potential of the wave motion. This paper presents our assessment on whether it is feasible to integrate the wave energy systems into the current Turkish Energy Program. The data required for calculating the approximate wave energy densities at many sites along the Turkish coasts have been derived from “Wind and Deep Water Wave Atlas of the Turkish Coast”, MEDCOAST Publications, have been used in a wave energy project analysis, which has been conducted by using RETScreen® International, “Small Hydro” in order to find out the cost effectiveness of a wave power converter system to harness the sea power from Turkish waters having a mild climate. The technically available resource has been estimated approximately 10 TWh/year with an annual wave power between 4 and 17 kW/m. This is 7.8 % of the economically feasible potential of current Turkish hydroelectrical energy. The regions in the west of the Black Sea in the north of Istanbul Straits and off the southwestern coasts of Aegean Sea between Marmaris and Finike have been suggested as the best sites to harness the wave energy.

- by Egemen SULUKAN and +1
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- Wave Energy, Ocean Energy, Wave Energy, Tidal Current Energy, Ocean wave energy, Wave Energy Converters

Dalam kehidupan sehari-hari, manusia pasti membutuhkan energi. Energi yang digunakan pun bermacam-macam jenisnya, seperti energi listrik, panas, dan lain-lain. Karena keberadaannya yang selalu dicari, sumber energi konvensional lambat laun akan habis dan manusia harus mencari sumber energi alternatif untuk memenuhi kebutuhan energinya. Penting untuk mengetahui jumlah konsumsi energi sebelum menentukan kriteria sumber energi alternatif yang sesuai dengan kebutuhan.

Today, the world is heavily dependent on fossil fuels, as most of the energy requirements are being met through conventional methods of burning these fuels. The energy demand is increasing day with growing population. Consequently, fossil fuel reserves are depleting continuously and will soon run out in coming years. Therefore, renewable energy resources have gained enormous attention in recent years. The growing interest in exploring tidal current technologies has many compelling reasons such as its renewable nature, tidal energy is cleaner than fossil fuels, intermittent but predictable, security and diversity of supply, and limited social and environmental impacts. Tidal current technologies are still in development phase, yet need some time to mature to prove their full potential. Tidal current turbine is an important tidal current technology. The purpose of this paper is to present a comprehensive review of tidal current turbine, its potential and associated challenges. The paper discusses general theoretical background of fluid flow in a tidal stream and forces governing the flow behavior. The author will also discuss the core issues and challenges faced in research and development such as unforgiving marine environment, corrosion, cavitation phenomena and extreme structural loads.

Tidal energy is one of the most predictable forms of renewable energy. Tides posses both potential and kinetic energy. Tidal energy can be utilized by capturing potential energy i.e. by means of tidal barrage and tidal fence or by capturing kinetic energy i.e. by means of tidal current technologies. This study is focused on diffuser augmented tidal turbines that capture the kinetic energy. The power generated by a tidal turbine is directly proportional to the cube of velocity of current flow. The role of the diffuser in diffuser augmented tidal turbines is to help accelerate the incoming current velocity. Consequently, the efficiency of the turbine is significantly increased by using a diffuser. The research community is investing considerable time and financial resources in this growing domain. The diffuser augmented tidal turbines research data is rather scarce due to their emerging nature, large and costly research & development setup, start up cost and proprietary issues. The purpose of this paper is to study the effect of length and angle on NACA 0010 airfoil for diffuser design. Numerical simulation is carried out to investigate velocity and mass flow rate at the throat. The drag force due to diffuser installation is also calculated.

A procedure for the optimisation of hydrokinetic turbine array layout through surrogate modelling is introduced. The method comprises design of experiments, computational fluid dynamics simulations, surrogate model construction, and constrained optimisation. Design of experiments are used to build polynomial and Radial Basis Function surrogates as functions of two design parameters: inter-turbine longitudinal and lateral spacing, with a view to approximating the capacity factor of turbine arrays with inline and staggered layouts, each of which having a fixed number of turbines. For this purpose, two scenarios have been used as case studies, considering uniform and non-uniform free-stream flows. The major advantage of this method in comparison to those reported in the literature is its capability to analyse different design parameter combinations that satisfy optimality criteria in reasonable computational time, while taking into account complex floweturbine interactions and different turbine types.

- by Eduardo González-Gorbeña and +1
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- Hydrodynamics (Physics), Computational Fluid Dynamics, Renewable Energy, Marine Renewable Energy

As marine and hydrokinetic (MHK) technologies which convert the flow of fluid into useful electrical power are developed, it is desirable to simulate drivetrain performance and refine control strategies in a laboratory prior to field installation. This paper presents and evaluates a technique developed to operate the prime mover of a dynamometer so that it drives a machine under test like an MHK turbine's rotor. The approach utilizes environmental and rotor numerical models to calculate hydrodynamic torque. Relationships between shaft torque, shaft speed, and variable frequency drive native torque reference were used to modify torque reference settings to achieve actual emulated torque values. The accuracy at which physical shaft torque matches theoretical hydrodynamic torque was then evaluated for three basic operating states: locked rotor, spin up/down, and variable flow operation. Percent-error of averaged measured and theoretical shaft torque during simulation of these states was 9.7%, 5.5%, and 5.2%, respectively, demonstrating the success of applying the proposed technique.

- by William Laing and +1
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- Ocean Engineering, Ocean Energy, Ocean Energy, Wave Energy, Tidal Current Energy, Ocean Renewable Energy
- by Friðgeir Grímsson
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- Paleobiology, Paleontology, Plant Ecology, Climate Change

Tidal energy is the most foreseeable form of renewable energy. Tidal energy can be harnessed by tidal barrage, tidal fence and tidal current technologies. Present efforts are focused on diffuser augmented tidal turbines that exploit the kinetic energy of the tidal currents. Power generated by a tidal current turbine is due to the cubic relationship between power and flow velocity. A minor increase in flow velocity can significantly increase the power output. A diffuser is a device that can help in stimulating flow velocity. Incorporating a diffuser around a turbine can increase the efficiency of the tidal turbine. Many research groups are investing considerable time and financial resources in this emerging domain. Limited results are available for diffuser augmented tidal turbines due to their emerging nature, large and costly research and development setup, startup cost and proprietary issues. The purpose of this paper is to study a NACA 0015 airfoil for diffuser design for tidal current turbines. Numerical simulation of the diffuser is carried out to check the velocity and mass flow rate at throat. The drag, for various NACA 0015 diffuser models is also calculated on the diffuser.

- by Nasir Mehmood
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- Tidal Stream Energy, Tidal Stream Turbine Modelling, Tidal turbine, Ocean Energy

This study is focused on diffuser augmented tidal current turbines that capture the kinetic energy in a tidal stream. The energy that can be extracted from tides is proportional to the cube of the current velocity. The role of the diffuser in diffuser augmented tidal turbines is to help accelerate the incoming current velocity. Consequently, the efficiency of the turbine can be significantly increased by using a diffuser. The research community is investing considerable time and financial resources in this growing domain. The diffuser augmented tidal turbines research data is rather scarce due to their emerging nature, large and costly research and development setup, start up cost and proprietary issues. The purpose of this study is to investigate the effect of length and angle on NACA 0018 airfoil for diffuser design. CFD simulation is carried out to investigate velocity and mass flow rate at the throat. The drag force due to diffuser installation is also calculated. Velocity inside the diffuser increases with diffuser length and angle of attack. Velocity increases up to stall angle and then drops due to flow separation. The drag force is also dominant compared to lift coefficient near stall angle region.

The renewal energy technologies are increasingly popular to ensure future energy sustenance and address environmental issues. The tides are enormous and consistent untapped resource of renewable energy. The growing interest in exploring tidal energy has compelling reasons such as security and diversity of supply, intermittent but predictable and limited social and environmental impacts. The tidal energy industry is undergoing an increasing shift towards diffuser augmented turbines. The reason is the higher power output of diffuser augmented turbines compared to conventional open turbines. The purpose of this study is to present a comprehensive review of diffuser augmented horizontal axis tidal current turbines. The components, relative advantages, limitations and design parameters of diffuser augmented horizontal axis tidal current turbines are presented in detail. CFD simulation of NACA 0016 airfoil is carried out to explore its potential for designing a diffuser. The core issues associated with diffuser augmented horizontal axis tidal current turbines are also discussed.

Electrical power cables in tidal turbine farms contribute a significant share to capital expenditure (CAPEX). As a result, the routing of electrical power cables connecting turbines to cable collector hubs must be designed so as to obtain the least cost configuration. This is referred to as a tidal cable routing problem. This problem possesses several variants depending on the number of cable collector hubs. In this paper, these variants are modeled by employing the approach of the single depot multiple traveling salesman problem (mTSP) and the multiple depot mTSP of operational research for the single and multiple cable collector variants, respectively. The developed optimization models are computationally implemented using MATLAB. In the triple cable collector cable hub variant, an optimal solution is obtained, while good-quality suboptimal solutions are obtained in the double and single cable collector hub variants. In practice, multiple cable collector hubs are expected to be employed as the multiple hub configurations tend to be more economic than the single hub configurations. This has been confirmed by this paper for an optimal tidal turbine layout obtained with OpenTidalFarm. Suggestions are presented for future research studies comprising a number of heuristics.

Diffuser augmented tidal turbines are getting enormous attention due to their immense potential to increase the generated power output. Researchers around the globe are investing considerable time and financial resources in this domain. Limited research results are available for diffuser augmented tidal turbines due to their emerging nature, large and costly research and development setup, start up cost and proprietary issues. Turbine enclosed in a diffuser is based on the principle that the generated power output by a tidal turbine is directly proportional to the cube of velocity of incoming fluid flow. Thus, even a minor increase in velocity considerably increases the generated power output. The diffuser helps accelerate the incoming fluid flow. Hence, the efficiency of the turbine is significantly increased by using a diffuser. It is challenging to accelerate the incoming flow by using a diffuser due to its shape, geometry and fabrication limitations. The diffuser design requires great deal of innovation and time investment. The purpose of this paper is to present the study of 2D model of diffuser for tidal current turbine. The study involves developing a 2D CFD model of diffuser, acquiring simulation results and comparison with experimental results. The mesh is generated in ICEM followed by simulation in CFX. The simulation results are compared to experimental results and found in reasonable agreement. The research is essential to utilize CFD tools for diffuser design used for tidal current turbine.