scholarly journals Estimating the stability of a bed protection of a weir-mounted tidal turbine

2020 ◽  
Vol 3 (1) ◽  
pp. 21-24
Author(s):  
Merel C. Verbeek ◽  
Robert J. Labeur ◽  
Wim S. J. Uijttewaal
Keyword(s):  
Tidal Energy ◽  
Potential Effect ◽  
Flow Recirculation ◽  
Tidal Turbines ◽  
Sea Bed ◽  
Tidal Turbine ◽  
The Stability ◽  
Hydrodynamic Data ◽  
Bed Protection ◽  
Horizontal Axis Turbine

Coastal infrastructure, such as bridges and storm surge barriers with weirs, provides an attractive location for harvesting renewable energy using tidal turbines. Often stone layers are applied downstream of coastal infrastructure to protect the sea bed from erosion. However, little is known about the potential effect of tidal energy extraction on the stability of this granular bed protection. This paper describes a study of the flow conditions influencing the stability of the bed protection downstream of a weir-mounted tidal turbine, using hydrodynamic data of an experimental test. The analysis indicates that the flow recirculation zone downstream of a weir may become shorter and flatter due to the presence of a horizontal-axis turbine. As a result, energetic turbulence eddies can transport more horizontal momentum towards the bed – hence the reason a heavier bed protection may be required for granular beds downstream of weirs when a turbine is installed. This information is essential when designing safe bed protections for coastal infrastructure with tidal turbines.

scholarly journals Passive acoustic methods for tracking the 3D movements of small cetaceans around marine structures

2020 ◽  
Author(s):  
Douglas Gillespie ◽  
Laura Palmer ◽  
Jamie Macaulay ◽  
Carol Sparling ◽  
Gordon Hastie
Keyword(s):  
Marine Mammals ◽  
New Technologies ◽  
Three Dimensional ◽  
Tidal Energy ◽  
Time Of Arrival ◽  
Marine Animals ◽  
Tidal Turbines ◽  
Wide Range ◽  
Tidal Turbine ◽  
Passive Acoustic

AbstractA wide range of anthropogenic structures exist in the marine environment with the extent of these set to increase as the global offshore renewable energy industry grows. Many of these pose acute risks to marine wildlife; for example, tidal energy generators have the potential to injure or kill seals and small cetaceans through collisions with moving turbine parts. Information on fine scale behaviour of animals close to operational turbines is required to understand the likely impact of these new technologies. There are inherent challenges associated with measuring the underwater movements of marine animals which have, so far, limited data collection. Here, we describe the development and application of a system for monitoring the three-dimensional movements of cetaceans in the immediate vicinity of a subsea structure. The system comprises twelve hydrophones and software for the detection and localisation of vocal marine mammals. We present data demonstrating the systems practical performance during a deployment on an operational tidal turbine between October 2017 and October 2019. Three-dimensional locations of cetaceans were derived from the passive acoustic data using time of arrival differences on each hydrophone. Localisation accuracy was assessed with an artificial sound source at known locations and a refined method of error estimation is presented. Calibration trials show that the system can accurately localise sounds to 2m accuracy within 20m of the turbine but that localisations become highly inaccurate at distances greater than 35m. The system is currently being used to provide data on rates of encounters between cetaceans and the turbine and to provide high resolution tracking data for animals close to the turbine. These data can be used to inform stakeholders and regulators on the likely impact of tidal turbines on cetaceans.

Assessment of Zooplankton Injury and Mortality Associated With Underwater Turbines for Tidal Energy Production

2013 ◽  
Vol 47 (4) ◽  
pp. 142-150 ◽  
Author(s):  
David R. Schlezinger ◽  
Craig D. Taylor ◽  
Brian L. Howes
Keyword(s):  
Size Distribution ◽  
Particle Density ◽  
Collaborative Work ◽  
Tidal Energy ◽  
Energy Potential ◽  
Marine Renewable Energy ◽  
Tidal Turbines ◽  
Video Images ◽  
Significant Difference ◽  
Tidal Turbine

AbstractCollaborative work between the UMASS-Marine Renewable Energy Center, the Town of Edgartown, and the Coastal Systems Program is focused on developing the tidal energy potential of Muskeget Channel. We have undertaken detailed oceanographic and environmental surveys to optimize in-stream turbine power generation and to quantify potential environmental effects. In 2011 and 2012, tidal turbine demonstration projects were conducted in Muskeget Channel to determine the combined effects of blade strikes, shear stress, turbulence, and cavitation on zooplankton. Single turbines may minimally impact zooplankton populations; however, full-scale projects may potentially alter zooplankton populations forming the base of coastal food webs. Static plankton tows were performed up- and downstream of the operating turbine axis. Integral flow meters allowed adjustment of tow duration to optimize zooplankton density in the concentrate. Samples were held at in situ temperatures, and sequential photomicrographs and video images were taken to determine particle density, size distribution, and the number of live organisms in samples taken up and down gradient of the operating tidal turbines within 3 h of collection. Statistical analysis showed no significant difference in the total number or size distribution of motile zooplankters, indicating tidal turbine operation did not cause significant mortality and suggested that impacts of commercial size tidal energy projects upon zooplankton populations in Muskeget Channel may be negligible.

scholarly journals Accuracy of the actuator disc-RANS approach for predicting the performance and wake of tidal turbines

2013 ◽  
Vol 371 (1985) ◽  
pp. 20120293 ◽  
Author(s):  
W. M. J. Batten ◽  
M. E. Harrison ◽  
A. S. Bahaj
Keyword(s):  
Large Scale ◽  
Scale Effects ◽  
Tidal Energy ◽  
Rans Model ◽  
Tidal Turbines ◽  
Actuator Disc ◽  
Element Approach ◽  
Tidal Stream ◽  
Turbine Wake ◽  
Horizontal Axis Turbine

The actuator disc-RANS model has widely been used in wind and tidal energy to predict the wake of a horizontal axis turbine. The model is appropriate where large-scale effects of the turbine on a flow are of interest, for example, when considering environmental impacts, or arrays of devices. The accuracy of the model for modelling the wake of tidal stream turbines has not been demonstrated, and flow predictions presented in the literature for similar modelled scenarios vary significantly. This paper compares the results of the actuator disc-RANS model, where the turbine forces have been derived using a blade-element approach, to experimental data measured in the wake of a scaled turbine. It also compares the results with those of a simpler uniform actuator disc model. The comparisons show that the model is accurate and can predict up to 94 per cent of the variation in the experimental velocity data measured on the centreline of the wake, therefore demonstrating that the actuator disc-RANS model is an accurate approach for modelling a turbine wake, and a conservative approach to predict performance and loads. It can therefore be applied to similar scenarios with confidence.

Experimental study of the duct-effects of the tidal current turbines in multi-row-staggered layout

2020 ◽  
Author(s):  
Yaling Chen ◽  
Binliang Lin ◽  
Jinxi Guo
Keyword(s):  
Tidal Current ◽  
Turbine Rotor ◽  
Power Performance ◽  
Tidal Current Energy ◽  
Tidal Turbines ◽  
Initial Stage ◽  
Tidal Turbine ◽  
Wake Zone ◽  
The Stability ◽  
Current Energy

<p>Tidal turbine array was optimized to increase the power production in order to improve the commercial competitivity of tidal current energy with other forms of energy generation. Due to duct-effects, the power performance of turbines in the staggered layout was better than that of the aligned layout. However, shear layer with enhanced turbulence occurred between the duct zone and isolated wake zone downstream, which had influence on the performance stability and increased the fatigue failure of tidal turbines. The study conducted a series of laboratory experiments to investigate the duct-effects of tidal turbines located in multi-row array with staggered layout. The turbine rotor was represented by porous disc. The flow thrust and time-varying velocity were measured using micro strain gauge and acoustic doppler velometer, respectively. Results showed that the flow was accelerated between turbines with the increment around 20% behind the first row, while the duct-effects were weakened as distance increased downstream. The shear-induced turbulence was enlarged by the duct-effect when it diffused mainly towards individual wake zone at the initial stage. As the turbulence filled the whole individual wake zones, it diffused rapidly to lateral sides and jointed together, and the turbulence intensity across the array wake was significantly higher than that of the free flow. Correspondingly, the performance of turbine rotor located downstream was improved limitedly by the duct-effects, and the stability was reduced clearly. It indicated that the advantage of the duct-effect induced in the staggered layout was limited in the near wake as the lateral interval between two turbine centres was 2 times of rotor diameter.</p><p>Keywords<strong>:</strong> Turbine rotor array; Staggered layout; Duct-effects; Turbine performance; Shear-induced turbulence</p>

Exploring the Effect of Length and Angle on NACA 0010 for Diffuser Design in Tidal Current Turbines

2012 ◽  
Vol 201-202 ◽  
pp. 438-441 ◽  
Author(s):  
Nasir Mehmood ◽  
Liang Zhang ◽  
Jawad Khan
Keyword(s):  
Kinetic Energy ◽  
Tidal Current ◽  
Current Flow ◽  
Tidal Energy ◽  
Research Community ◽  
Financial Resources ◽  
Considerable Time ◽  
Tidal Turbines ◽  
Tidal Turbine

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 menas 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 increasedby using adiffuser. The research community is investing considerable time and financial resources in thisgrowingdomain. The diffuser augmented tidal turbinesresearch datais rather scarce due to their emerging nature, large and costly research & development setup, startup cost and proprietary issues. The purpose of this paper is to study the effect of length and angle on NACA 0010airfoil 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.

Tidal Turbine Blade Selection for Optimal Performance in an Array

2011 ◽  
Author(s):  
Rachel F. Nicholls-Lee ◽  
Stephen R. Turnock ◽  
Stephen W. Boyd
Keyword(s):  
Tidal Cycle ◽  
Free Stream ◽  
Stokes Equations ◽  
Tidal Energy ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Energy Capture ◽  
Tidal Turbines ◽  
Outer Domain ◽  
Tidal Turbine

In order to maximize tidal energy capture from a specific site free stream devices are situated in arrays. In an array the downstream evolution of the wake generated by a rotating tidal energy conversion device influences the performance of the device itself, the bypass flow to either side as well as the performance of any downstream device. As such it is important to design a turbine that can perform efficiently and effectively in these circumstances. Use of passively adaptive composite blades for horizontal axis tidal turbines has been shown to improve performance in fluctuating inflows. Active adaptation and/or bi-directional hydrofoil sections could be implemented in order to optimize performance throughout the tidal cycle. This paper considers the performance in an array of four free stream turbines implementing standard rigid blades, wholly bidirectional blades, passively adaptive blades and actively adaptive blades. The method used to evaluate the performance of tidal current turbines in arrays couples an inner domain solution of the blade element momentum theory with an outer domain solution of the Reynolds averaged Navier Stokes equations. The annual energy capture of four devices with each blade type in a staggered array is then calculated for a single tidal cycle and compared.

scholarly journals 3D Simulation with Flow-Induced Rotation for Non-Deformable Tidal Turbines

2021 ◽  
Vol 9 (3) ◽  
pp. 250
Author(s):  
Ilan Robin ◽  
Anne-Claire Bennis ◽  
Jean-Claude Dauvin
Keyword(s):  
Vertical Axis ◽  
Tidal Energy ◽  
Fluid Structure Interactions ◽  
Good Correspondence ◽  
Tidal Turbines ◽  
Tidal Turbine ◽  
Correct Direction ◽  
Convergence Study ◽  
Vertical Axis Tidal Turbine ◽  
Mesh Convergence

The overall potential for recoverable tidal energy depends partly on the tidal turbine technologies used. One of problematic points is the minimum flow velocity required to set the rotor into motion. The novelty of the paper is the setup of an innovative method to model the fluid–structure interactions on tidal turbines. The first part of this work aimed at validating the numerical model for classical cases of rotation (forced rotation), in particular, with the help of a mesh convergence study. Once the model was independent from the mesh, the numerical results were tested against experimental data for both vertical and horizontal tidal turbines. The results show that a good correspondence for power and drag coefficients was observed. In the wake, the vortexes were well captured. Then, the fluid drive code was implemented. The results correspond to the expected physical behavior. Both turbines rotated in the correct direction with a coherent acceleration. This study shows the fundamental operating differences between a horizontal and a vertical axis tidal turbine. The lack of experiments with the free rotation speed of the tidal turbines is a limitation, and a digital brake could be implemented to overcome this difficulty.

scholarly journals Study of Hydrodynamic Interference of Vertical-Axis Tidal Turbine Array

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1228
Author(s):  
Guangnian Li ◽  
Qingren Chen ◽  
Hanbin Gu
Keyword(s):  
Vertical Axis ◽  
Tidal Energy ◽  
Element Model ◽  
Hydrodynamic Performance ◽  
Maximum Efficiency ◽  
Hydrodynamic Characteristics ◽  
Tidal Turbines ◽  
Tidal Turbine ◽  
Vertical Axis Turbine ◽  
Vertical Axis Tidal Turbine

The hydrodynamic interference between tidal turbines must be considered when predicting their overall hydrodynamic performance and optimizing the layout of the turbine array. These factors are of great significance to the development and application of tidal energy. In this paper, the phenomenon of hydrodynamic interference of the tidal turbine array is studied by the hydrodynamic performance forecast program based on an unsteady boundary element model for the vertical-axis turbine array. By changing the relative positions of two turbines in the double turbine array to simulate the arrangement of different turbines, the hydrodynamic interference law between the turbines in the array and the influence of relative positions on the hydrodynamic characteristics in the turbine array are explored. The manner in which the turbines impact each other, the degree of influence, and rules for turbine array arrangement for maximum efficiency of the array will be discussed. The results of this study will provide technical insights to relevant researchers.

scholarly journals Hydrodynamics and Tidal Turbine Generator Stability Analysis in Several Wave Variations

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Muhammad Ikhwan ◽  
Syamsul Rizal ◽  
Marwan Ramli ◽  
Zainal A. Muchlisin ◽  
Said Munzir
Keyword(s):  
Angular Velocity ◽  
Equilibrium Point ◽  
Phase Plane ◽  
Synchronous Generator ◽  
Turbine Generator ◽  
Permanent Magnet Synchronous Generator ◽  
Tidal Turbines ◽  
Tidal Turbine ◽  
The Stability ◽  
Lower Limits

The development of tidal turbines continues to be carried out by many researchers, including the incorporation of a control system for optimization purposes. This paper attempts to assess the stability of two mechanical systems in a tidal turbine: a propeller harvesting kinetic energy and a d-q diagram system on a permanent-magnet synchronous generator (PMSG). The method employed is the representation of a phase plane profile with a stable eigenvalue. The critical value of the turbine’s rotations per minute provides some points of equilibrium. The effect of the angular velocity singular on the modified system was also investigated. There is no cutoff control for the generator rotational speed in the case of weak currents, according to the results. The combination of the three tidal turbine components results in a shift in the equilibrium point. Although PMSG has an infinite equilibrium point along the line Id = 0, the effect of the rotor angular velocity prevents all of these points from being in equilibrium. Finally, in this study, the rotor angular velocity caused by the speed and type of ocean currents are only the upper and lower limits. The stability of the various wave variations is within this range.

The Development of a Risk-Based Guideline for the Design of Current and Tidal Turbines

2015 ◽  
Author(s):  
Laura-Mae Macadré ◽  
Stéphane Paboeuf ◽  
Nicolas Dietenbeck ◽  
Stéphane le Diraison
Keyword(s):  
Wind Energy ◽  
New Technology ◽  
Tidal Energy ◽  
Certification Process ◽  
Guidance Note ◽  
Tidal Turbines ◽  
Wide Range ◽  
Tidal Turbine ◽  
Certification Type ◽  
Offshore Oil

Tidal turbines are emerging technologies offering a great potential by the harnessing of a renewable and predictable resource. However, exploitation at sea comes with significant design, installation, grid connection, and maintenance operations challenges. Consequently, guidelines and standards are required to ensure safety, reliability and quality for these innovative technologies, to support designers and to accelerate the development and commercialisation of the tidal technology. As tidal energy concepts are only at the demonstration stage, only few standards have been published about tidal and current turbines and no dedicated certification procedures have been developed so far. The aim of this paper is to present a risk-based certification process developed by Bureau Veritas for tidal turbines and published in the Guidance Note NI603 Current and Tidal Turbines. Based on experience accumulated over the past years with tidal turbines technology developers, typical challenges related to the design and installation of tidal devices at sea will be highlighted in this paper. To support tidal turbines designers to take up these challenges, Bureau Veritas provides a decision-making guide gathering 1) recommendations from the existing experience at sea of tidal devices, 2) best practices from related sectors, such as shipping, wind energy or offshore oil & gas, 3) a risk-based approach to consider for the particular requirements of each tidal turbine installation. In particular for tidal turbines, projects are highly site specific with huge impacts on farm layouts and foundation designs, to name but a few of the issues to be addressed. Paradoxically, the aim of certification societies is to develop rules and tools that can be applicable to a wide range of designs. Consequently, trying not to be design-specific, a proposal of a generic certification process is made in this paper. Existing certification principles from more mature sectors such as wind energy, offshore oil & gas or shipping have been adapted to the specificities of tidal turbines. This paper addresses different certification procedures such as prototype certification, component certification, type certification and project certification. Their respective application and interactions are developed, with a focus on prototype and type certification. In addition, particular attention is paid to the novelty induced by tidal turbines. Consequently, a risk-based guidance is provided to use qualification of new technology for the most innovative parts of the tidal device.

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