Marine Energy

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / i j o m e tidal passes, and comparing species use of neighbouring turbine and non-turbine microhabitats at reasonable distances to the vantage points (<2 km) during favourable sea states (Beaufort Scale < 3). It is hoped that these recommendations lead to the development of standardised shore-based survey methods, providing comparable measurements of spatial overlap across tidal passes earmarked for array deployments: a key step towards estimations of collision risks at population levels.

Electric energy security is essential, yet the high cost and limited sources of fossil fuels, in addition to the need to reduce greenhouse gasses emission, have made renewable resources attractive in world energybased economies. The potential for renewable energy resources is enormous because they can, in principle, exponentially exceed the world's energy demand; therefore, these types of resources will have a significant share in the future global energy portfolio, much of which is now concentrating on advancing their pool of renewable energy resources. Accordingly, this paper presents how renewable energy resources are currently being used, scientific developments to improve their use, their future prospects, and their deployment. Additionally, the paper represents the impact of power electronics and smart grid technologies that can enable the proportionate share of renewable energy resources.

In the span of past few decades, population, urbanization and industrialization have transformed the mankind living standard and dynamics of the nature. Certainly, energy is the basic need for all living organisms. Energy is the route towards the economic growth. The evidence shows that the countries faced with energy crises are left behind in the economic activities; as a result, people are deprived. This study reviewed the available renewable energy resources and potential with positive and negative aspects. This study comprehensively discusses the renewable macro and micro energy resources studied in the past two decades reported in various studies. The paper is divided into two sections; the first section discusses the energy produced in the macro level and the second section discusses the energy produced using different strategies and techniques in the micro level. The potential and positive outcomes of the energy resources were identified. New paradigm of micro energies and importance of reusing the available resource of micro energy using different resources like energy harvesting on the road surface, vibration, airflow, radio frequency and thermal energy etc. were discussed. Lastly, the study focus does not only review but also finds the potential and opportunities for the researchers in the future to utilize the renewable energy resources

It has recently been demonstrated that spectral-domain models of wave energy converters (WECs) can provide an accurate and numerically efficient method for predicting the expected performance of WECs. An oscillating water column (OWC) type WEC has been tested in a wave tank to produce validation data for a spectral-domain model of the OWC. The OWC spectral-domain model consists of linear hydrodynamic coefficients obtained from the commercial boundary-element code WAMIT, together with single-coefficient non-linear terms for the power-take-off (PTO) and the entry/exit losses of the water column. The OWC was tested in a range of representative sea-states with both unimodal and bimodal spectra. The coefficients for the PTO and entry/exit losses were determined using the orifice pressure/flow characteristics and a single calibration sea-state respectively. Comparison of the OWC spectral-domain model with the wave-tank data indicates that the spectral-domain model reproduces the performance of the OWC accurately. The error in spectral-domain model's prediction of power capture is typically less than 5%. The frequency response of the OWC is also well predicted by the spectral-domain model. This demonstrates that a spectral-domain model provides a valid representation of the wave-tank OWC model performance.

Much of the global tidal current energy resource lies in the accelerated flows along narrow channels. These channels have the potential to produce 10s -1000s of MW of electricity. However, realizing 100 MW of a channel's potential is much more complex than installing 100 one MW turbines because large scale power extraction reduces tidal currents throughout the channel, changing the resource. This synthesis and review gives an overview of the issues and compromises in designing the layout of the large tidal turbine arrays required to realize this potential. The paper focuses on macro- and micro-design of arrays. Macro-design relates to the total number of turbines and their gross arrangement into rows, while micro-design adjusts the relative positions of the turbines within a grid and the spacing between rows. Interdependent macro-design compromises balance the total number of turbines, array power output, the power output of each turbine, the loads turbines experience, turbine construction costs, maintaining navigability along the channel and any environmental impacts due to flow reduction. A strong emphasis is placed on providing physical insights about how “channel-scale dynamics” and the “duct-effect” impact on the compromises in array design. This work is relevant to the design of any “large” array which blocks more than 2%-5% of a channel's cross-section, be it 2 turbines in a small channel or 100 turbines in a large channel.

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.

Knowledge of the wave field modification by a wave energy converter (WEC) is important to device and wave farm design. Cylindrical solutions to the linear wave field have long been used to analytically compute wave forces on circularcylindrical geometries and have been the means of an important multi-body interaction theory. The cylindrical solutions are valid for an arbitrary geometry, but previous methods for computing the necessary coefficients were cumbersome. Herein, we present a new method for computing the cylindrical wave-field coefficients for an arbitrary geometry from a known circularcylindrical section of the wave field. The method employs the Fourier transform and the orthogonality property of the depth dependence. The necessary circular-cylindrical section of the wave field is computed with the industry-standard boundaryelement-method solver, WAMIT. Coefficients are computed for the radiated and scattered wave fields of four WECs, a heaving point absorber, a surging point absorber, a terminator, and an attenuator. The resulting cylindrical wave fields are compared over a large domain to wave fields computed completely by WAMIT and are found to be very accurate. The asymptotic representation of the cylindrical wave field is also considered and its range of accuracy is shown to depend the number of partial waves used to accurately represent the cylindrical wave field. Analytical solutions to the WEC wave field enable the use of interaction theories that accelerate WEC array computation and the integration with wave models that include additional physics.

A single-body point absorber system is analysed to improve its power absorption at a finite water depth.  The proposed wave energy converter consists of a single floating body coupled to a direct-drive power take-off system placed on the seabed. The structure of a cylindrical buoy with large draft is changed by a single body composed of three structures rigidly coupled, reducing its volume and improving its frequency-dependent hydrostatic parameters that are obtained through a numerical analysis tool called NEMOH. The undamped natural frequency of the oscillating system is tuned to a specified wave period and the performance of the WEC system is obtained assuming a linear Power Take-Off system. In time domain, the performance of the WEC device is carried-out under a regular (sinusoidal) and irregular incident wave profile. Comparing the performance of the WEC system using the cylindrical and the proposed buoy outcomes that the system with the proposed buoy is able to absorb more ene...

This document describes the Global Positioning System (GPS) and procedures, methods and considerations to be used and observed when using GPS to record location data in the field. Guidance is provided on accuracy requirements for various uses of location data and potential means to obtain the requisite accuracy. This document contains direction developed solely to provide internal guidance to SESD employees.

The purpose of this study was to determine the Diversity Index, Similarity Index, and Dominance Index. The research location in Krukut River along 12 km. The research was conducted in March - June 2017 in 7 sampling points. Macrozoobentos obtained as many as 23 species belonging to the 9 classes are 3 types of Bivalves, 7 types of Arthopoda, 2 types of Molusca, 4 types of insects, 4 types of Oligochaeta, 2 Malacostraca, 1 Crustacea, 1 Diptera, and 1 Nematodes. The highest abundance of macrozoobentos is 10550 Ind/m2, whereas the lowest macrozoobenthic abundance is 850 Ind/m2. The range of Diversity Index (H&amp;#39;) 0.32 - 1.80, Similarity Index (E) 0.58-1.07 and Dominance Index (C) 0.40-0.63. Therefore the result shows that Krukut River is in category medium pollution. Keywords: biology indeks, Krukut river, macrozoobentos, Shannon Wiener

— This paper presents an overview of ocean energy technology as a source of renewable energy. It investigates ocean energy resources and new technologies under development to capture that energy. Ocean energy (also referred as Marine Energy) refers to the energy carried by ocean waves, Tides, temperature difference & salinity. Ocean energy has the potential to play a significant role in the future energy system, whilst contributing to the reduction of carbon emissions and stimulating economic growth in coastal and remote areas where there is a scarce of electricity and cost of transmission of electricity is very high. Ocean energy has attracted increasing interest, particularly in India because India has long sea shore. A number of policy initiatives and mechanisms have been put in place to ensure that ocean energy technologies could become cost-competitive in the short term, in order to exploit the benefits that these technologies to India.

The purpose of this study was to determine the Diversity Index, Similarity Index, and Dominance Index. The research location in Krukut River along 12 km. The research was conducted in March - June 2017 in 7 sampling points. Macrozoobentos obtained as many as 23 species belonging to the 9 classes are 3 types of Bivalves, 7 types of Arthopoda, 2 types of Molusca, 4 types of insects, 4 types of Oligochaeta, 2 Malacostraca, 1 Crustacea, 1 Diptera, and 1 Nematodes. The highest abundance of macrozoobentos is 10550 Ind/m2, whereas the lowest macrozoobenthic abundance is 850 Ind/m2. The range of Diversity Index (H&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) 0.32 - 1.80, Similarity Index (E) 0.58-1.07 and Dominance Index (C) 0.40-0.63. Therefore the result shows that Krukut River is in category medium pollution. Keywords: biology indeks, Krukut river, macrozoobentos, Shannon Wiener

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

The Banda Sea region which includes the Moluccas and Nusa Tenggara consists of 3,478 small islands separated from each other by deep seas. This region can be regarded as the most complex energy supply chain in Indonesia due to geographic condition and lacking of energy infrastructure. The newly issued Indonesian general plan of energy aims to establish a strategy for planning the region's energy mix until 2050. By then, national primary energy should not be dominantly supported by oil and gas, and renewable energy should contribute 31%. In addition, government has committed to attain near 100% electricity ratio by 2020. Recent hydrocarbon discoveries and ocean energy mapping indicate that the Banda Sea region is an attractive area where the country's primary energy needs may partly be fulfilled. However, the region's sustainability in energy production still has to be established with greater efforts. Hydrocarbon search has been discouraged by the geologically risky nature of the region. The implementation of renewable energy, particularly ocean energy, is hampered by technology immaturity and constraining operational rules and policies.

In this paper, a novel approach for simulating Oscillating Water Column (OWC) using lattice Boltzmann method (LBM) is presented. A direct comparison between a real wave flume and a 3D-Large Eddy Simulation (LES) numerical lattice Boltzmann (LB) wave flume is developed through the analysis of an OWC energy converter in order to validate the LBM approach for simulating OWCs. The numerical model uses a Volume-of-Fluid (VOF) approach and handles the water-air coupling into the OWC air chamber. The experimental and numerical setup are described. Comparisons for water level during free oscillation test, water level and air pressure under regular wave attacks are given and show that the LB model is accurate. We also discuss the efficiency of the simulated OWC. The 3D numerical model offers a powerful tool in order to study the 3D phenomena occurring into OWCs.

Motions in nature, for example ocean waves, can play a significant role in tomorrow's electricity production, but the constructions require adaptations to its media. Engineers planning hydropower plants have always taken natural conditions, such as fall height, speed of flow, and geometry, as basic design parameters and constraints in the design. The present paper describes a novel approach for electric power conversion of the vast ocean wave energy. The suggested linear electric energy converter is adapted to the natural wave motion using straightforward technology. Extensive simulations of the wave energy concept are presented, along with results from the experimental setup of a multisided permanent magnet linear generator. The prototype is designed through systematic electromagnetic field calculations. The experimental results are used for the verification of measurements in the design process of future full-scale direct wave energy converters. The present paper, describes the energy conversion concept from a system perspective, and also discusses the economical and some environmental considerations for the project. q

As advances in numerical modelling techniques support the increased confidence in predictions from computer simulations, the need remains to have experimental verification built into the design process. This paper outlines the experimental investigation carried out on a shielded vertical axis turbine in a marine environment. The experiments consist of performance measurements and the use of particle image velocimetry on a small scale device in a marine current flume. The results demonstrate that the performance of the device can be modelled numerically; in particular, the results show that the numerical model used can correctly predict the increase in performance with Reynolds number. Highlights ► Identification of the energy conversion mechanisms in a vertical axis turbine. ► Validation of a CFD model with experimental performance data and PIV. ► Turbine performance increases with Reynolds number due to changes in flow regime.

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

MARINET (Marine Renewables Infrastructure Network for emerging Energy Technologies) is an EC-funded network of research centres and organisations that are working together to accelerate the development of marine renewable energy -wave, tidal & offshore-wind. The initiative is funded through the EC's Seventh Framework Programme (FP7) and runs for four years until 2015. The network of 29 partners with 42 specialist marine research facilities is spread across 11 EU countries and 1 International Cooperation Partner Country (Brazil).

This paper investigates the accuracy of the Computational Fluid Dynamics (CFD) based Immersed Body Force (IBF) turbine modelling method for predicting the flow characteristics of a Momentum-Reversal-Lift type of tidal turbine. This empirically-based CFD model has been developed based on the actuator disc method enhanced with additional features to mimic the effect of the complex blade motion on the downstream wake, without the high computational costs of explicitly modelling the dynamic blade motion. The model has been calibrated against the flow characteristics data obtained from experiment and found to perform well, although there are few inconsistencies in the flow patterns which show some of the limitations of the IBF model compared to a full dynamic blade motion simulation. However, given the complexity and computational cost of modelling the detailed blade motion the limitations of the IBF model are acceptable and will be useful especially for optimisation of arrays of devices where there is a significant computational demand.

The purpose of this study was to determine the Diversity Index, Similarity Index, and Dominance Index. The research location in Krukut River along 12 km. The research was conducted in March - June 2017 in 7 sampling points. Macrozoobentos obtained as many as 23 species belonging to the 9 classes are 3 types of Bivalves, 7 types of Arthopoda, 2 types of Molusca, 4 types of insects, 4 types of Oligochaeta, 2 Malacostraca, 1 Crustacea, 1 Diptera, and 1 Nematodes. The highest abundance of macrozoobentos is 10550 Ind/m2, whereas the lowest macrozoobenthic abundance is 850 Ind/m2. The range of Diversity Index (H&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) 0.32 - 1.80, Similarity Index (E) 0.58-1.07 and Dominance Index (C) 0.40-0.63. Therefore the result shows that Krukut River is in category medium pollution. Keywords: biology indeks, Krukut river, macrozoobentos, Shannon Wiener

The purpose of this study was to determine the Diversity Index, Similarity Index, and Dominance Index. The research location in Krukut River along 12 km. The research was conducted in March - June 2017 in 7 sampling points. Macrozoobentos obtained as many as 23 species belonging to the 9 classes are 3 types of Bivalves, 7 types of Arthopoda, 2 types of Molusca, 4 types of insects, 4 types of Oligochaeta, 2 Malacostraca, 1 Crustacea, 1 Diptera, and 1 Nematodes. The highest abundance of macrozoobentos is 10550 Ind/m2, whereas the lowest macrozoobenthic abundance is 850 Ind/m2. The range of Diversity Index (H&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) 0.32 - 1.80, Similarity Index (E) 0.58-1.07 and Dominance Index (C) 0.40-0.63. Therefore the result shows that Krukut River is in category medium pollution. Keywords: biology indeks, Krukut river, macrozoobentos, Shannon Wiener

One key step of the industrial development of a tidal energy device is the testing of scale prototype devices within a controlled laboratory environment. At present, there is no available experimental protocol which addresses in a quantitative manner the differences which can be expected between results obtained from the different types of facilities currently employed for this type of testing. As a consequence, where differences between results are found it has been difficult to confirm the extent to which these differences relate to the device performance or to the test facility type. In the present study, a comparative "Round Robin" testing programme has been conducted as part of the EC FP VII MaRINET program in order to evaluate the impact of different experimental facilities on the test results. The aim of the trials was to test the same model tidal turbine in four different test facilities to explore the sensitivity of the results to the choice of facility. The facilities comprised two towing tanks, of very different size, and two circulating water channels. Performance assessments in terms of torque, drag and inflow speed showed very similar results in all facilities. However, expected differences between the different tank types (circulating and towing) were observed in the fluctuations of torque and drag measurements. The main facility parameters which can influence the behaviour of the turbine were identified; in particular the effect of blockage was shown to be significant in cases yielding for high thrust coefficients, even at relatively small blockage ratios.

Increased global renewable power demands and the high energy density of ocean currents have motivated the development of ocean current turbines (OCTs). These compliantly mooring systems will maintain desired near-surface operating depths using variable buoyancy, lifting surface, sub-sea winches, and/or surface buoys. This paper presents a complete numerical simulation of a 700 kW variable buoyancy controlled OCT that includes detailed turbine system, inflow, actuator (i.e., generator and variable buoyancy), sensor, and fault models. Simulation predictions of OCT performance are made for normal, hurricane, and fault scenarios. Results suggest this OCT can operate between depths of 38 m to 329 m for all homogeneous flow speeds between 1.0-2.5 m/s. Fault scenarios show that rotor braking results in a rapid vertical OCT system assent and that blade pitch faults create power fluctuations apparent in the frequency domain. Finally, simulated OCT operations in measured ocean currents (i.e.,...

It has been established that Wave Energy Converters efficiency can be improved by control. One of the main challenges of reactive control is the non-causality of the optimal controller. This study presents a methodology to solve the non-causality issue by providing a deterministic forecast of the controlled body velocities. This forecast is achieved by using the measurements of the states of the most up wave device of the array. The reactive control approach also implies strong instabilities due to the extreme dynamics of the controlled devices. The proposed method suggests to mitigate this behavior by applying a window function on the optimal controller impedance. In order to maximize the efficiency of the resulting control and ensure the robustness of the system, a stability analysis is conducted. Optimal sets of parameters are determined and applied to a time domain simulation of an array of 10 cylindrical floating WECs. The results obtained show an average efficiency of the arra...

An Oscillating Water Column (OWC) is a wave energy converter consisting of a partially submerged chamber with an air column over the water column. The work done by the air column under excitation by the incident waves is used to generate electrical energy through a power takeoff (PTO) device. The air column is under pressure due to the damping from the PTO device and this pressure is essential for the extraction of wave energy using the OWC. The relationship between the PTO damping and the hydrodynamic efficiency of the OWC provides more insight into the wave energy extraction using an OWC. In this paper, two-dimensional Computational Fluid Dynamics (CFD) simulations are used to investigate the response of the OWC under different values of damping from the PTO device. The PTO damping on the chamber is represented using a linear pressure drop law with the permeability coefficient derived from Darcy's equation for flow through porous media. The model is validated by comparing the numerical results to experimental data. The influence of the PTO damping on the chamber pressure, the free surface motion, the velocity of the vertical motion of the free surface and the hydrodynamic efficiency of the OWC is studied. The hydrodynamic efficiency is calculated as the ratio of the power delivered at the vent of the OWC to the incident wave power. It is found that the PTO damping needed to attain the maximum OWC hydrody

Aspiring to build GW arrays of turbines is essential if tidal stream energy is to make a significant contribution to meeting the demand for renewable power. Many channels have the potential to produce several GW. Realizing one GW of this potential is much more complex than installing 1000 one MW turbines because large scale power extraction reduces tidal currents throughout a channel, changing the resource. This work uses a 1D model to estimate the minimum number of turbines required to produce 1 GW in two example channels loosely based on the Pentland Firth and the Minas Passage. The minimum number of 400 m 2 turbines is 350-800, depending on how they are arranged into rows. For some arrays adding turbines increases the total output of the array, while simultaneously reducing the output of every turbine within it. For other arrays adding turbines increases both the array output and the output of every turbine within it, despite a reduction in tidal currents. Thus turbines in large ...

Abstract: In view of the depleting non-renewable energy resources, renewable energy resources technologies
are being developed. In wave energy areas, the focus is on the Oscillating Water Column (OWC) concept. The
main objective of this research work was to design and build a system to convert the wave energy from
Malaysian sea areas into useful power. In this study, the designed OWC chamber has been subjected to
various modifications and tests to improve its performance. To simplify assessment of performance, the effect
of modifications to the air pressure generated in the chamber was measured. In addition, a two-stage Savoniustype
air turbine was designed and attached to the OWC chamberfor generating energy. The final system was
tested in a wave tank. The experimental results show clearly that the wave energy can be harnessed into useful
work to drive an air turbine.

Barrier-islands are common landforms and biodiverse habitats, yet they received scarce neoichnological attention. This gap is tackled by studying the Mula di Muggia barrier-island system (Grado lagoon, Italy), focusing on morphology, ecology and ethology of individual traces. The following incipient ichnotaxa are identified: Archaeonassa, Arenicolites, Bergaueria, 'diverging shafts', Helminthoidichnites, Lockeia, Macanopsis, Monocraterion, Nereites, Parmaichnus, Polykladichnus, Skolithos, Thalassinoides and 'squat burrows'. Vertebrate (Avipeda-/Ardeipeda-like, Canipeda) and invertebrate tracks ('parallel furrows') are also described. For each ichnotaxon, tracemaker and behavior are discussed, together with their position with respect to sediment barriers. Results suggest that sediment barriers impose a sharp contrast in terms of ichnological composition. Back-barrier is dominated by branched burrows (i.e. Thalassinoides, Parmaichnus), while the fore-barrier presents vertical and U-shaped burrows (Arenicolites, Skolithos). The environmental conditions of the back-barrier show that low-oxygen substrates favor intense bioturbation, provided that the water column is sufficiently oxygenated.

The purpose of this study was to determine the Diversity Index, Similarity Index, and Dominance Index. The research location in Krukut River along 12 km. The research was conducted in March - June 2017 in 7 sampling points. Macrozoobentos obtained as many as 23 species belonging to the 9 classes are 3 types of Bivalves, 7 types of Arthopoda, 2 types of Molusca, 4 types of insects, 4 types of Oligochaeta, 2 Malacostraca, 1 Crustacea, 1 Diptera, and 1 Nematodes. The highest abundance of macrozoobentos is 10550 Ind/m2, whereas the lowest macrozoobenthic abundance is 850 Ind/m2. The range of Diversity Index (H&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) 0.32 - 1.80, Similarity Index (E) 0.58-1.07 and Dominance Index (C) 0.40-0.63. Therefore the result shows that Krukut River is in category medium pollution. Keywords: biology indeks, Krukut river, macrozoobentos, Shannon Wiener

ABSTRACT Much of the global tidal current energy resource lies in the accelerated flows along narrow channels. These channels have the potential to produce 10s -1000s of MW of electricity. However, realizing 100 MW of a channel’s potential is much more complex than installing 100 one MW turbines because large scale power extraction reduces tidal currents throughout the channel, changing the resource. This synthesis and review gives an overview of the issues and compromises in designing the layout of the large tidal turbine arrays required to realize this potential. The paper focuses on macro- and micro-design of arrays. Macro-design relates to the total number of turbines and their gross arrangement into rows, while micro-design adjusts the relative positions of the turbines within a grid and the spacing between rows. Interdependent macro-design compromises balance the total number of turbines, array power output, the power output of each turbine, the loads turbines experience, turbine construction costs, maintaining navigability along the channel and any environmental impacts due to flow reduction. A strong emphasis is placed on providing physical insights about how channel-scale dynamics” and the “duct-effect” impact on the compromises in array design. This work is relevant to the design of any “large” array which blocks more than 2%-5% of a channel’s cross-section, be it 2 turbines in a small channel or 100 turbines in a large channel.

The Reference Model Project, supported by the U.S. Department of Energy, was developed to provide publically available technical and economic benchmarks for a variety of marine energy converters. The methodology to achieve these benchmarks is to develop public domain designs that incorporate power performance estimates, structural models, anchor and mooring designs, power conversion chain designs, and estimates of the operations and maintenance, installation, and environmental permitting required. The reference model designs are intended to be conservative, robust, and experimentally verified. The Backward Bent Duct Buoy (BBDB) presented in this paper is one of three wave energy conversion devices studied within the Reference Model Project. Comprehensive modeling of the BBDB in a Northern California climate has enabled a full levelized cost of energy (LCOE) analysis to be completed on this device.

This article describes a 2D CFD simulation implementation of a crossflow tidal turbine, the blades of which have their pitch modified during revolution. Unsteady flow around the turbine is computed with an URANSE method, using the solver ANSYS-CFX. Spatial and temporal discretizations have been studied. The pitch motion of the blades is obtained through mesh deformation, and the main rotation is implemented through sliding boundaries, with general grid interface model. The turbulence model used is kω SST. Langtry Menter transition model was tried but showed high discrepancies with experimental results. Five experimental cases were used to assess the accuracy of the simulation. It provided accurate computed forces for a wide range of tip speed ratios, and proved to be suitable for exploratory simulations. Harmonic pitch control was thus implemented for a tip speed ratio of 5, close to an operational value for a crossflow turbine. First, second and third harmonics pitch function were tested. It was shown that an improvement of more than 50% could be achieved with the second harmonics, with a large reduction in thrust. The flow inside the turbine and close to the blade was examined so that the case of performance improvement due to pitch control could be clearly understood. It was observed that turbine efficiency improvement requires a very slight recirculation and an angle of attack decrease on the upstream part of the turbine, and an angle of attack increase on the downstream part. The flow deceleration through the turbine was found to be a primary factor in pitch function as well. Moreover the hydrodynamic torque and thus the energy required to control the pitch were found to be insignificant.

This paper concerns the numerical shape optimization of the diffuser of a horizontal axis hydro turbine. The turbine is part of the tethered system GEM developed for harnessing ocean current energy. The methodology consists of: a first phase in which axial symmetric analysis has been performed CFD simulating the turbine with pressure jump across actuator disk; a second phase where 3D CFD computations have been performed and compared with experiments. Results from both CFD axisymmetric model and experimental data show a significant increase for the power coefficient, while the 3D model not fully confirms this advantage.

Blog post written for the European Marine Energy Centre website (see url to read in full).

"Just a few weeks ago the UK National Infrastructure Commission released its report on how the national electricity grid needs to change in order to keep the lights on, and meet the 2050 target to reduce carbon emissions by 80%. ‘Smart Power’ is its solution, combining three new infrastructure technologies: increased interconnection with other countries; localised, flexible production and consumption; and grid battery storage. ‘All change’ is its mantra. The report imagines a timescale around fifteen years from now. This is future-making work, it would appear...."

A metamodel simulation based optimisation approach for the tidal turbine location problem is introduced. The method comprises design of experiments, computational simulations, metamodel construction and formulation of a mathematical optimisation model. Sample plans with different number of data points are used to fit 2nd and 3rd order polynomial as a function of two design parameters: longitudinal and lateral spacing, with a view to approximating the power output of tidal turbine farms with inline and staggered layouts, each Aquatic Science and Technology ISSN 2168-9148 2015 34 of them with a fixed number of turbines. The major advantage this method has, in comparison to those reported in the literature, is the capability to analyse different design parameter combinations that satisfy optimality criteria in reasonable computational time, while taking into account complex flow-turbine interactions.

""Abstract
Renewable energy resources need to be explored to maintain and meet energy demand and replace the slowly depleting fossil fuels.  Malaysia, surrounded by sea with long coastlines, is poised to exploit the potential of this energy. This research work aims at designing a suitable device to extract energy from Malaysian sea current.  Malaysia’s ocean has a low current velocity averaging 0.56 m/s, which is below the working velocity of presently available current energy devices.  To overcome this velocity limitation, a Savonius-type Vertical Axis Marine Current Turbine (VAMCT) design was proposed.  The experiment to measure the torque of a Savonius-type turbine, which hitherto has been used for wind energy application, is presented in this paper.  The laboratory experiment was carried out in the towing tank facility in Marine Technology Laboratory at Universiti Teknologi Malaysia.  The Savonius model was attached to the towing carriage and current flow was simulated by moving the carriage in still water. The results show that turbine with double stacking rotors each with two paddles and overlap ratio of 0.21 give the best performance.
Keywords  ocean energy, renewable energy, marine current energy
""

The purpose of this study was to determine the Diversity Index, Similarity Index, and Dominance Index. The research location in Krukut River along 12 km. The research was conducted in March - June 2017 in 7 sampling points. Macrozoobentos obtained as many as 23 species belonging to the 9 classes are 3 types of Bivalves, 7 types of Arthopoda, 2 types of Molusca, 4 types of insects, 4 types of Oligochaeta, 2 Malacostraca, 1 Crustacea, 1 Diptera, and 1 Nematodes. The highest abundance of macrozoobentos is 10550 Ind/m2, whereas the lowest macrozoobenthic abundance is 850 Ind/m2. The range of Diversity Index (H&amp;#39;) 0.32 - 1.80, Similarity Index (E) 0.58-1.07 and Dominance Index (C) 0.40-0.63. Therefore the result shows that Krukut River is in category medium pollution. Keywords: biology indeks, Krukut river, macrozoobentos, Shannon Wiener

The purpose of this study was to determine the Diversity Index, Similarity Index, and Dominance Index. The research location in Krukut River along 12 km. The research was conducted in March - June 2017 in 7 sampling points. Macrozoobentos obtained as many as 23 species belonging to the 9 classes are 3 types of Bivalves, 7 types of Arthopoda, 2 types of Molusca, 4 types of insects, 4 types of Oligochaeta, 2 Malacostraca, 1 Crustacea, 1 Diptera, and 1 Nematodes. The highest abundance of macrozoobentos is 10550 Ind/m2, whereas the lowest macrozoobenthic abundance is 850 Ind/m2. The range of Diversity Index (H&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) 0.32 - 1.80, Similarity Index (E) 0.58-1.07 and Dominance Index (C) 0.40-0.63. Therefore the result shows that Krukut River is in category medium pollution. Keywords: biology indeks, Krukut river, macrozoobentos, Shannon Wiener

This paper presents an integrated model for an offshore wind turbine taking into consideration a contribution for the marine wave and wind speed with perturbations influences on the power quality of current injected into the electric grid. The paper deals with the simulation of one floating offshore wind turbine equipped with a permanent magnet synchronous generator, and a two-level converter connected to an onshore electric grid. The use of discrete mass modeling is accessed in order to reveal by computing the total harmonic distortion on how the perturbations of the captured energy are attenuated at the electric grid injection point. Two torque actions are considered for the three-mass modeling, the aerodynamic on the flexible part and on the rigid part of the blades. Also, a torque due to the influence of marine waves in deep water is considered. Proportional integral fractional-order control supports the control strategy. A comparison between the drive train models is presented.