Daming Wang, D. Conley, M. Hann, K. Collins, S. Jin, D. Greaves
Wave tank model testing has been widely used to assess the performance of Wave Energy Converters (WEC) in different technology readiness levels (TRL). At early stage the use of simple wave conditions such as regular waves and parametric wave spectrum JONSWAP or Pierson-Moskowitz spectrum is acceptable. However at later stages there is a need to use site specific complex wave conditions representative of potential prototype deployment sites. In previous research, 10 different regrouping methods on HF radar measured wave spectrum were tested to find out the most representative sea states for tank testing. It has been shown that by using the K-means clustering technique, the characteristics of wave conditions can be well preserved. In order to assess the power capture performance of a typical WEC in these representative sea states, the RM3 point absorber has been simulated. By analysing how well the average power output predicted from different representative sea-state selection methods compares with the total power output prediction, it is shown that the non-directional wave spectrum K-means clustering method provides the most representative sea states and, for a point absorber, with a very accurate estimation of the total power output, which is not the case by using a traditional binning method. The importance of using the complex site-specific sea states rather than simplified parametric JONSWAP sea states to obtain the accurate total power estimation has also been shown.
{"title":"Power output estimation of WEC with HF radar measured complex representative sea states","authors":"Daming Wang, D. Conley, M. Hann, K. Collins, S. Jin, D. Greaves","doi":"10.36688/imej.5.1-10","DOIUrl":"https://doi.org/10.36688/imej.5.1-10","url":null,"abstract":"Wave tank model testing has been widely used to assess the performance of Wave Energy Converters (WEC) in different technology readiness levels (TRL). At early stage the use of simple wave conditions such as regular waves and parametric wave spectrum JONSWAP or Pierson-Moskowitz spectrum is acceptable. However at later stages there is a need to use site specific complex wave conditions representative of potential prototype deployment sites. In previous research, 10 different regrouping methods on HF radar measured wave spectrum were tested to find out the most representative sea states for tank testing. It has been shown that by using the K-means clustering technique, the characteristics of wave conditions can be well preserved. In order to assess the power capture performance of a typical WEC in these representative sea states, the RM3 point absorber has been simulated. By analysing how well the average power output predicted from different representative sea-state selection methods compares with the total power output prediction, it is shown that the non-directional wave spectrum K-means clustering method provides the most representative sea states and, for a point absorber, with a very accurate estimation of the total power output, which is not the case by using a traditional binning method. The importance of using the complex site-specific sea states rather than simplified parametric JONSWAP sea states to obtain the accurate total power estimation has also been shown.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43529243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ana Julia Lifschitz, D. Coiro, G. Troise, Horacio Giaquinta, Fabio Lazcano, Norma De Cristofaro
This work is a preliminary study to find some sites for the potential use of tidal stream energy and their associated currents in the Chubut coast. In addition, an evaluation of the energy resource of the Chubut Gulfs is made. The possibility of energetic utilization of the tides is achieved by transforming the displacement movement into a rotation movement by means of a hydrokinetic turbine. The energy can be extracted analogously to that of wind energy; therefore, it is not necessary to build a dam, avoiding the environmental and economic disadvantages it represents. Even though the results presented in this paper have significantly improved our understanding of tidal dynamics in this region, the collection of more observations, particularly in the interior and at the mouths of the Gulfs, is necessary to develop and fully shape tidal potential into power generation in the region.
{"title":"Kinetic energy of tidal currents in the province of Chubut, Argentina","authors":"Ana Julia Lifschitz, D. Coiro, G. Troise, Horacio Giaquinta, Fabio Lazcano, Norma De Cristofaro","doi":"10.36688/imej.5.11-22","DOIUrl":"https://doi.org/10.36688/imej.5.11-22","url":null,"abstract":"This work is a preliminary study to find some sites for the potential use of tidal stream energy and their associated currents in the Chubut coast. In addition, an evaluation of the energy resource of the Chubut Gulfs is made. The possibility of energetic utilization of the tides is achieved by transforming the displacement movement into a rotation movement by means of a hydrokinetic turbine. The energy can be extracted analogously to that of wind energy; therefore, it is not necessary to build a dam, avoiding the environmental and economic disadvantages it represents. Even though the results presented in this paper have significantly improved our understanding of tidal dynamics in this region, the collection of more observations, particularly in the interior and at the mouths of the Gulfs, is necessary to develop and fully shape tidal potential into power generation in the region.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41385063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a new analytical model for a horizontal axis cyclorotor-based wave energy converter (WEC). A number of cyclorotor-based WEC concepts and models, with different numbers of hydrofoils, have previously been studied. Our model is derived for a horizontal cyclorotor with 2 hydrofoils. The governing equations are optimised and converted to the polar coordinate system. The mechanical model is based on Newton's second law for rotation. Rotation is considered in two-dimensional potential flow, for both monochromatic and panchromatic waves, including waves generated by the rotating rotor, and viscous losses. The developed model is very convenient for modelling, analysis and control design for a cyclorotor based WEC. The authors of this work have derived new, exact, analytic functions for the free surface perturbation and induced fluid velocity field caused by hydrofoil rotation. These new formulae significantly decrease the model calculation time, compared to previous models, and increase the accuracy of the results. We present the results of free rotation simulations for the rotor in monochromatic and panchromatic waves obtained with the use of the newly derived equations.
{"title":"A validated analytical model for a cyclorotor wave energy device","authors":"Andrei Ermakov, J. Ringwood","doi":"10.36688/imej.5.201-208","DOIUrl":"https://doi.org/10.36688/imej.5.201-208","url":null,"abstract":"We present a new analytical model for a horizontal axis cyclorotor-based wave energy converter (WEC). A number of cyclorotor-based WEC concepts and models, with different numbers of hydrofoils, have previously been studied. Our model is derived for a horizontal cyclorotor with 2 hydrofoils. The governing equations are optimised and converted to the polar coordinate system. The mechanical model is based on Newton's second law for rotation. Rotation is considered in two-dimensional potential flow, for both monochromatic and panchromatic waves, including waves generated by the rotating rotor, and viscous losses. The developed model is very convenient for modelling, analysis and control design for a cyclorotor based WEC. The authors of this work have derived new, exact, analytic functions for the free surface perturbation and induced fluid velocity field caused by hydrofoil rotation. These new formulae significantly decrease the model calculation time, compared to previous models, and increase the accuracy of the results. We present the results of free rotation simulations for the rotor in monochromatic and panchromatic waves obtained with the use of the newly derived equations.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69722236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aldo Ruezga, José M. Cañedo C., M. Verduzco-Zapata, F. Ocampo-Torres
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 energy from incident waves with a wider frequency range, whereas the oscillating system is kept as simple as possible.
{"title":"Performance analysis of a point-absorber wave energy converter with a single buoy composed of three rigidly coupled structures","authors":"Aldo Ruezga, José M. Cañedo C., M. Verduzco-Zapata, F. Ocampo-Torres","doi":"10.36688/imej.4.37-45","DOIUrl":"https://doi.org/10.36688/imej.4.37-45","url":null,"abstract":"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 energy from incident waves with a wider frequency range, whereas the oscillating system is kept as simple as possible.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69722181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Arezoo Hasankhani, James H. VanZwieten, Yu-Shuang Tang, Brock Dunlap, Alexandra De Luera, C. Sultan, N. Xiros
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., normal and hurricane conditions) quantify power statistics and system behavior typical and extreme conditions.
{"title":"Modeling and Numerical Simulation of a Buoyancy Controlled Ocean Current Turbine","authors":"Arezoo Hasankhani, James H. VanZwieten, Yu-Shuang Tang, Brock Dunlap, Alexandra De Luera, C. Sultan, N. Xiros","doi":"10.36688/imej.4.47-58","DOIUrl":"https://doi.org/10.36688/imej.4.47-58","url":null,"abstract":"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., normal and hurricane conditions) quantify power statistics and system behavior typical and extreme conditions.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69722222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Martin Träsch, A. Chambon, Astrid Déporte, J. Drevet, G. Germain, D. Lemosse, G. Pinon
The undulating membrane tidal energy converter is a device that uses the flutter instabilities occurring from the interaction between a slender body and a fluid flow. A new numerical model has been developed using a 2D corotational finite element method to represent the structure and the unsteady point-vortex method to compute the flow. These methods as well as the interaction process are presented. Trajectory and frequency of the undulating motion, hydrodynamic forces on the structure and velocity field in the wake are presented. Comparison shows a good agreement with experimental results obtained from a 1/20th scale prototype without power take off tested in flume tank.
{"title":"Numerical modelling of an undulating membrane tidal energy converter","authors":"Martin Träsch, A. Chambon, Astrid Déporte, J. Drevet, G. Germain, D. Lemosse, G. Pinon","doi":"10.36688/imej.3.119-126","DOIUrl":"https://doi.org/10.36688/imej.3.119-126","url":null,"abstract":"The undulating membrane tidal energy converter is a device that uses the flutter instabilities occurring from the interaction between a slender body and a fluid flow. A new numerical model has been developed using a 2D corotational finite element method to represent the structure and the unsteady point-vortex method to compute the flow. These methods as well as the interaction process are presented. Trajectory and frequency of the undulating motion, hydrodynamic forces on the structure and velocity field in the wake are presented. Comparison shows a good agreement with experimental results obtained from a 1/20th scale prototype without power take off tested in flume tank.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42156314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Niall D. McLean, Matthew A. Holland, R. MacIver, E. Bannon
Many wave energy converter developers opt to carry out scaled prototype open water testing of their device as part of their technology development. Developers who have done this recently include Sea Power (1/5 scale, Galway Bay, 2017), CorPower (1/4 scale, EMEC, 2018) and Marine Power Systems (1/4 scale, FaBTest, ongoing). Scaled open water testing offers several benefits, including more representative realisations of sub-systems, identification and resolution of technological issues associated with scaling-up, and de-risking the manufacturing and marine operational procedures ahead of commercial-scale testing. In preparation for testing in Stage 3 of the Novel Wave Energy Converter programme, Wave Energy Scotland has considered requirements of a suitable scaled open water site and the methods for selection. In common with commercial site identification, this must consider operational infrastructure, time and funding constraints, and the appropriateness of site characteristics. This appropriateness is further complicated by the need to find a site of comparable scaled water depth and where the sea-states of interest (when scaled to full-scale) are likely to occur with sufficient frequency over the duration of the intended testing campaign. This paper presents an approach, and its associated assumptions, to identify locations which have the potential to satisfy the scaled open water site considerations, before discussing the challenges to satisfy the critical testing outcomes, and the pragmatism required to meet all requirements.
作为技术开发的一部分，许多波浪能转换器开发商选择对其设备进行规模原型开放水域测试。最近这样做的开发商包括Sea Power(1/5规模，Galway Bay, 2017)， CorPower(1/4规模，EMEC, 2018)和Marine Power Systems(1/4规模，FaBTest，正在进行中)。大规模的开放水域测试提供了几个好处，包括更有代表性的子系统实现，与扩大规模相关的技术问题的识别和解决，以及在商业规模测试之前降低制造和海上操作程序的风险。在为新型波浪能转换器计划第三阶段的测试做准备时，苏格兰波浪能源公司考虑了合适的开阔水域场地的要求和选择方法。与商业地点识别一样，这必须考虑操作基础设施、时间和资金限制以及地点特征的适当性。由于需要找到一个具有可比的比例水深的地点，并且在预期的测试活动期间，感兴趣的海况(当按比例缩放到全尺寸时)可能会以足够的频率出现，因此这种适当性进一步复杂化。本文提出了一种方法及其相关假设，在讨论满足关键测试结果的挑战和满足所有要求所需的实用主义之前，确定有可能满足规模开阔水域考虑的位置。
{"title":"Site selection for scaled open water testing of a wave energy converter","authors":"Niall D. McLean, Matthew A. Holland, R. MacIver, E. Bannon","doi":"10.36688/imej.3.101-110","DOIUrl":"https://doi.org/10.36688/imej.3.101-110","url":null,"abstract":"Many wave energy converter developers opt to carry out scaled prototype open water testing of their device as part of their technology development. Developers who have done this recently include Sea Power (1/5 scale, Galway Bay, 2017), CorPower (1/4 scale, EMEC, 2018) and Marine Power Systems (1/4 scale, FaBTest, ongoing). Scaled open water testing offers several benefits, including more representative realisations of sub-systems, identification and resolution of technological issues associated with scaling-up, and de-risking the manufacturing and marine operational procedures ahead of commercial-scale testing. In preparation for testing in Stage 3 of the Novel Wave Energy Converter programme, Wave Energy Scotland has considered requirements of a suitable scaled open water site and the methods for selection. In common with commercial site identification, this must consider operational infrastructure, time and funding constraints, and the appropriateness of site characteristics. This appropriateness is further complicated by the need to find a site of comparable scaled water depth and where the sea-states of interest (when scaled to full-scale) are likely to occur with sufficient frequency over the duration of the intended testing campaign. This paper presents an approach, and its associated assumptions, to identify locations which have the potential to satisfy the scaled open water site considerations, before discussing the challenges to satisfy the critical testing outcomes, and the pragmatism required to meet all requirements.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46555534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Enabling Future Arrays in Tidal (EnFAIT) is an EU Horizon 2020 flagship tidal energy project. It aims to demonstrate the development, operation and decommissioning of the world’s largest tidal array (six turbines), over a five-year period, to prove a cost reduction pathway for tidal energy and confirm that it can be cost competitive with other forms of renewable energy. To determine the optimal site layout and spacing between turbines within a tidal array, it is essential to accurately characterise tidal turbine wakes and their effects. This paper presents a state-of-the-art review of tidal turbine wake modelling methods, with an overview of the relevant fundamental theories. Numerical and physical modelling research completed by both academia and industry are considered to provide an overview of the contemporary understanding in this area. The scalability of single device modelling techniques to an array situation is discussed, particularly with respect to wake interactions.
{"title":"Review of tidal turbine wake modelling methods","authors":"E. Jump, A. Macleod, Tom Wills","doi":"10.36688/imej.3.91-100","DOIUrl":"https://doi.org/10.36688/imej.3.91-100","url":null,"abstract":"Enabling Future Arrays in Tidal (EnFAIT) is an EU Horizon 2020 flagship tidal energy project. It aims to demonstrate the development, operation and decommissioning of the world’s largest tidal array (six turbines), over a five-year period, to prove a cost reduction pathway for tidal energy and confirm that it can be cost competitive with other forms of renewable energy. To determine the optimal site layout and spacing between turbines within a tidal array, it is essential to accurately characterise tidal turbine wakes and their effects. This paper presents a state-of-the-art review of tidal turbine wake modelling methods, with an overview of the relevant fundamental theories. Numerical and physical modelling research completed by both academia and industry are considered to provide an overview of the contemporary understanding in this area. The scalability of single device modelling techniques to an array situation is discussed, particularly with respect to wake interactions.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43614765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wave induced motions due to actual sea state conditions will impact the performance of floating horizontal axis tidal turbine systems. This paper presents the results from numerical simulations of a 3-bladed horizontal axis tidal turbine oscillating in surge motion in a moving reference frame. The optimum tip-speed ratio, λ = 4.4 and k-ω SST turbulence model were used in the present study. The Navier-Stokes equation was modified by adding an inertial term to the equation and the Dirichlet boundary condition was also modified in order to simulate in the moving reference frame. The surge oscillations were parameterised in terms of the ratio of surge amplitude to rotor radius, A*, and the ratio of oscillation frequency to the rotational frequency of the rotor, ω*. A series of tests were conducted to study the effect of each parameter on the hydrodynamic performance of the tidal turbine. The results show that stall can occur on the blade when the velocity relative to the rotor is sufficiently high. In certain cases, negative thrust and power coefficients were observed when the velocity relative to the rotor is low. The fluctuation in blade loading increases together with the amplitude and frequency of oscillation, which will contribute to the fatigue of the rotor.
{"title":"The effects of surge motion on floating horizontal axis tidal turbines","authors":"M. Osman, R. Willden, C. Vogel","doi":"10.36688/imej.3.45-54","DOIUrl":"https://doi.org/10.36688/imej.3.45-54","url":null,"abstract":"Wave induced motions due to actual sea state conditions will impact the performance of floating horizontal axis tidal turbine systems. This paper presents the results from numerical simulations of a 3-bladed horizontal axis tidal turbine oscillating in surge motion in a moving reference frame. The optimum tip-speed ratio, λ = 4.4 and k-ω SST turbulence model were used in the present study. The Navier-Stokes equation was modified by adding an inertial term to the equation and the Dirichlet boundary condition was also modified in order to simulate in the moving reference frame. The surge oscillations were parameterised in terms of the ratio of surge amplitude to rotor radius, A*, and the ratio of oscillation frequency to the rotational frequency of the rotor, ω*. A series of tests were conducted to study the effect of each parameter on the hydrodynamic performance of the tidal turbine. The results show that stall can occur on the blade when the velocity relative to the rotor is sufficiently high. In certain cases, negative thrust and power coefficients were observed when the velocity relative to the rotor is low. The fluctuation in blade loading increases together with the amplitude and frequency of oscillation, which will contribute to the fatigue of the rotor.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41779417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Constantin Scherelis, I. Penesis, P. Marsh, R. Cossu, M. Hemer, Jeffrey T. Wright
With the tidal energy industry moving towards commercial-scale developments, it is important to consider potential interactions between tidal energy converters (TECs) and the marine environment prior to the instalment of large-scale TEC arrays. The Banks Strait, a tidal channel located in the northeast of Tasmania, Australia, was identified as a promising candidate site for tidal energy by the Australian Tidal Energy (AUSTEn) project. To gain an understanding about potential overlap between TEC arrays and fish usage of the Banks Strait tidal channel, fish density distributions were estimated from hydroacoustic surveys during the tidal resource characterization campaign. Differences in fish density were examined according to bottom–depth, bottom – type, current speed, temperature and vertical distribution. Fish densities were significantly higher at night and displayed preferences for depths between 20 – 40 m and current speeds between 1.75 – 2 m/s. Fish density was generally highest in the bottom 10 m from the sea floor at all depths sampled. Variation by temperature and bottom–type sampled was not significant. Future studies involving long-term, stationary surveys of fish densities along with repeated surveys across different seasons would provide a more wholistic picture of fish distributions in the Banks Strait to inform developers about potential device encounter probabilities.
{"title":"Relating fish distributions to physical characteristics of a tidal energy candidate site in the Banks Strait, Australia","authors":"Constantin Scherelis, I. Penesis, P. Marsh, R. Cossu, M. Hemer, Jeffrey T. Wright","doi":"10.36688/IMEJ.3.111-118","DOIUrl":"https://doi.org/10.36688/IMEJ.3.111-118","url":null,"abstract":"With the tidal energy industry moving towards commercial-scale developments, it is important to consider potential interactions between tidal energy converters (TECs) and the marine environment prior to the instalment of large-scale TEC arrays. The Banks Strait, a tidal channel located in the northeast of Tasmania, Australia, was identified as a promising candidate site for tidal energy by the Australian Tidal Energy (AUSTEn) project. To gain an understanding about potential overlap between TEC arrays and fish usage of the Banks Strait tidal channel, fish density distributions were estimated from hydroacoustic surveys during the tidal resource characterization campaign. Differences in fish density were examined according to bottom–depth, bottom – type, current speed, temperature and vertical distribution. Fish densities were significantly higher at night and displayed preferences for depths between 20 – 40 m and current speeds between 1.75 – 2 m/s. Fish density was generally highest in the bottom 10 m from the sea floor at all depths sampled. Variation by temperature and bottom–type sampled was not significant. Future studies involving long-term, stationary surveys of fish densities along with repeated surveys across different seasons would provide a more wholistic picture of fish distributions in the Banks Strait to inform developers about potential device encounter probabilities.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43321573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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