Parametric resonance has been observed, both numerically and experimentally, in various studies of wave energy converters (WECs). Large heave motions induce a periodic variation in the metacentric height of a WEC body and, consequently, cause a harmonic variation in pitch/roll restoring coefficients, which can parametrically excite the pitch/roll modes. Current studies attempt to determine the onset conditions of parametric resonance, by detecting the boundaries between stable and unstable regions in the parameter space. In the literature, some studies aim to make use of parametric resonance for improving power capture. In contrast, some studies try to suppress the effect of parametric resonance, as it can reduce power capture efficiency in the primary degree of freedom. However, how energy transfers from one mode to another is not fully understood. This study aims to analyse energy transfer between heave and pitch/roll modes when parametric resonance occurs. A generic cylindrical point absorber is studied as a WEC floater to consider non-linear wave-structure interaction, including non-linear Froude-Krylov and viscous forces. A heave-pitch-roll three-degree-of-freedom model is derived for numerical study of the energy transfer between different operational modes.
{"title":"Examination of the virtues of parametric energy coupling in wave energy conversion","authors":"Bingyong Guo, J. Ringwood","doi":"10.36688/imej.5.219-226","DOIUrl":"https://doi.org/10.36688/imej.5.219-226","url":null,"abstract":"Parametric resonance has been observed, both numerically and experimentally, in various studies of wave energy converters (WECs). Large heave motions induce a periodic variation in the metacentric height of a WEC body and, consequently, cause a harmonic variation in pitch/roll restoring coefficients, which can parametrically excite the pitch/roll modes. Current studies attempt to determine the onset conditions of parametric resonance, by detecting the boundaries between stable and unstable regions in the parameter space. In the literature, some studies aim to make use of parametric resonance for improving power capture. In contrast, some studies try to suppress the effect of parametric resonance, as it can reduce power capture efficiency in the primary degree of freedom. However, how energy transfers from one mode to another is not fully understood. This study aims to analyse energy transfer between heave and pitch/roll modes when parametric resonance occurs. A generic cylindrical point absorber is studied as a WEC floater to consider non-linear wave-structure interaction, including non-linear Froude-Krylov and viscous forces. A heave-pitch-roll three-degree-of-freedom model is derived for numerical study of the energy transfer between different operational modes.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42297076","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}
Jonathan Demmer, Matthew Lewis, P. Robins, S. Neill
Worldwide increased demand for offshore renewable energy (ORE) industries and aquaculture requires developing efficient tools to optimize the use of the offshore space, reducing anthropic pressure. The synergetic development of marine renewable energy infrastructure with mariculture has been hypothesized as a way to reduce costs through shared infrastructure. In the Irish Sea, blue mussels (Mytilus edulis L.) represent 40 - 50 % of the total gross turnover of Welsh shellfish industries and the industry has been operating sustainably for over 50 years in North Wales. However, the region is also attractive for tidal energy projects, with strong tidal currents (> 2m/s) occurring, and offshore wind farms, with shallow waters (approx. 50 m) and consistent winds. In this context, it is of scientific and economic interest to study the potential impact of ORE on shellfish larvae recruitment. A numerical approach has been developed using an Eulerian hydrodynamic model coupled with a Lagrangian particle tracking model, which allowed the simulation of tidal currents, wind-driven currents and larval dispersal. Results show: 1) interannual variability of density distribution of larvae; and 2) strong connectivity between commercial shellfish beds and ORE sites. This study shows the importance of ORE site selection in order to: 1) reduce biofouling on ORE infrastructures and 2) develop multi-use platforms at sea to combine needs for ORE and for mariculture.
{"title":"Evidence of potential synergy between aquaculture and offshore renewable energy","authors":"Jonathan Demmer, Matthew Lewis, P. Robins, S. Neill","doi":"10.36688/imej.5.133-141","DOIUrl":"https://doi.org/10.36688/imej.5.133-141","url":null,"abstract":"Worldwide increased demand for offshore renewable energy (ORE) industries and aquaculture requires developing efficient tools to optimize the use of the offshore space, reducing anthropic pressure. The synergetic development of marine renewable energy infrastructure with mariculture has been hypothesized as a way to reduce costs through shared infrastructure. In the Irish Sea, blue mussels (Mytilus edulis L.) represent 40 - 50 % of the total gross turnover of Welsh shellfish industries and the industry has been operating sustainably for over 50 years in North Wales. However, the region is also attractive for tidal energy projects, with strong tidal currents (> 2m/s) occurring, and offshore wind farms, with shallow waters (approx. 50 m) and consistent winds. In this context, it is of scientific and economic interest to study the potential impact of ORE on shellfish larvae recruitment. A numerical approach has been developed using an Eulerian hydrodynamic model coupled with a Lagrangian particle tracking model, which allowed the simulation of tidal currents, wind-driven currents and larval dispersal. Results show: 1) interannual variability of density distribution of larvae; and 2) strong connectivity between commercial shellfish beds and ORE sites. This study shows the importance of ORE site selection in order to: 1) reduce biofouling on ORE infrastructures and 2) develop multi-use platforms at sea to combine needs for ORE and for mariculture.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45105438","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}
Simon Joßberger, Christain Stadler, Ulf Barkmann, N. Kaufmann, S. Riedelbauch
Up to 6 Schottel Instream Turbines (SIT250) can be mounted on the tidal platform PLAT-I developed by Sustainable Marine Energy. Due to the close proximity of the turbines interactions can occur between them. Two horizontal axis tidal turbines in model scale are investigated experimentally and numerically to analyze these interactions. Experimental data were measured in a towing tank and consist of integral values for torque, thrust and rotational speed. Both a steady state and an unsteady three-dimensional Reynolds Averaged Navier Stokes (RANS) approach are utilized for simulating the turbine flow field. The first part of the paper compares simulation results of a single turbine at different tip speed ratios with measurements to validate the numerical approach and its employed models. The second part analyses the interaction between two turbines. The axial distance in main flow direction between the turbines is half the rotor diameter. The radial distance measured between the hubs of the turbines is varied in steps of 0.2 between 0.0 and 2.0 times the rotor diameter in the experiment and between 0.0 and 1.4 in the simulations. Measurements were conducted for tip speed ratios of 3, 4 and 5. In the simulations the tip speed ratio was fixed at 4. The used simulation domain replicates the actual width and height of the towing tank and a sufficient length up- and downstream of the turbines. The water surface is modeled with a free slip wall. Both thrust and torque are compared between simulation results and experimental data. Furthermore, a detailed analysis of the results and flow field in the numerical simulations is presented and the interaction between the turbines is discussed.
{"title":"Interaction between two horizontal axis tidal turbines in model scale – experiment and simulation","authors":"Simon Joßberger, Christain Stadler, Ulf Barkmann, N. Kaufmann, S. Riedelbauch","doi":"10.36688/imej.5.173-182","DOIUrl":"https://doi.org/10.36688/imej.5.173-182","url":null,"abstract":"Up to 6 Schottel Instream Turbines (SIT250) can be mounted on the tidal platform PLAT-I developed by Sustainable Marine Energy. Due to the close proximity of the turbines interactions can occur between them. Two horizontal axis tidal turbines in model scale are investigated experimentally and numerically to analyze these interactions. Experimental data were measured in a towing tank and consist of integral values for torque, thrust and rotational speed. Both a steady state and an unsteady three-dimensional Reynolds Averaged Navier Stokes (RANS) approach are utilized for simulating the turbine flow field. The first part of the paper compares simulation results of a single turbine at different tip speed ratios with measurements to validate the numerical approach and its employed models. The second part analyses the interaction between two turbines. The axial distance in main flow direction between the turbines is half the rotor diameter. The radial distance measured between the hubs of the turbines is varied in steps of 0.2 between 0.0 and 2.0 times the rotor diameter in the experiment and between 0.0 and 1.4 in the simulations. Measurements were conducted for tip speed ratios of 3, 4 and 5. In the simulations the tip speed ratio was fixed at 4. The used simulation domain replicates the actual width and height of the towing tank and a sufficient length up- and downstream of the turbines. The water surface is modeled with a free slip wall. Both thrust and torque are compared between simulation results and experimental data. Furthermore, a detailed analysis of the results and flow field in the numerical simulations is presented and the interaction between the turbines is discussed.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46786393","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}
A transfer function determination method is proposed in this study to predict the unsteady fluctuations of the performance of a tidal turbine model. This method is derived from the Response Amplitude Operator (RAO) applied in the offshore industry to predict linear wave-induced loads on large structures. It is based on a spectral approach and requires the acquisition of a turbine parameter (e.g. torque, thrust, power or root-blade force) in synchronization with an upstream flow velocity measurement. On the frequency range where the causality between these two signals is proven, the transfer function is established using the ratio between the cross-spectral density and the spectral density of the incoming velocity.The linearity is verified using the coherence function, which shows validity for the turbine power in the lowest frequencies only. This transfer function is then used to reconstruct the power fluctuations which is compared to the recorded one for a particular flow condition with bathymetry generated turbulence. The result shows the dependence on the accurate location of the velocity measurement point used for the reconstruction. This point must exactly correspond to the expected turbine location, i.e. where the turbine response needs to be processed. Bearing in mind its limits, the method can be used to predict the loadings of extreme events on the turbine structure and the performance variations corresponding to the unsteady characteristics of a turbulent flow, for a better grid integration.
{"title":"Determination of the Response Amplitude Operator of a tidal turbine as a spectral transfer function","authors":"B. Gaurier, G. Germain, J. Facq","doi":"10.36688/imej.5.151-160","DOIUrl":"https://doi.org/10.36688/imej.5.151-160","url":null,"abstract":"A transfer function determination method is proposed in this study to predict the unsteady fluctuations of the performance of a tidal turbine model. This method is derived from the Response Amplitude Operator (RAO) applied in the offshore industry to predict linear wave-induced loads on large structures. It is based on a spectral approach and requires the acquisition of a turbine parameter (e.g. torque, thrust, power or root-blade force) in synchronization with an upstream flow velocity measurement. On the frequency range where the causality between these two signals is proven, the transfer function is established using the ratio between the cross-spectral density and the spectral density of the incoming velocity.The linearity is verified using the coherence function, which shows validity for the turbine power in the lowest frequencies only. This transfer function is then used to reconstruct the power fluctuations which is compared to the recorded one for a particular flow condition with bathymetry generated turbulence. The result shows the dependence on the accurate location of the velocity measurement point used for the reconstruction. This point must exactly correspond to the expected turbine location, i.e. where the turbine response needs to be processed. Bearing in mind its limits, the method can be used to predict the loadings of extreme events on the turbine structure and the performance variations corresponding to the unsteady characteristics of a turbulent flow, for a better grid integration.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47559379","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}
I. M. Viola, G. Pisetta, W. Dai, A. Arredondo-Galeana, A. Young, A. Smyth
Tidal turbines experience large load fluctuations due to the unsteady environment and the shear in the tidal flow. Mitigating these fluctuations without affecting the mean load would result in lower capital and operational costs. In this paper we discuss how this could be achieved through blades that passively and elastically adapt their camber and angle of attack to counteract unsteady flow conditions. Firstly, we discuss the underlying principles of unsteady thrust mitigation. We show that complete cancellation of the thrust fluctuations would be possible if every blade section could pitch passively and independently of neighbouring sections. Secondly, we provide proof of principle for two practical implementations through physical experiments and computational fluid dynamics simulations. We consider a blade that is rigid near the leading edge and flexible near the trailing edge. We show that the unsteady load mitigation is proportional to the ratio between the length of the flexible and rigid parts of the blade. For example, for a blade section where the flexibility is concentrated in a hinge at 3/4 of the chord, the amplitude of the fluctuations is 3/4 of the original amplitude. Secondly, we consider a solid, rigid blade with a passive pitch mechanism. We show that, for a 1 MW turbine operating in shear flow, more than 80% of the unsteady loading is mitigated. These results demonstrate the potential effectiveness of morphing blades for mitigating thrust fluctuations on tidal turbines.
{"title":"Morphing Blades","authors":"I. M. Viola, G. Pisetta, W. Dai, A. Arredondo-Galeana, A. Young, A. Smyth","doi":"10.36688/imej.5.183-193","DOIUrl":"https://doi.org/10.36688/imej.5.183-193","url":null,"abstract":"Tidal turbines experience large load fluctuations due to the unsteady environment and the shear in the tidal flow. Mitigating these fluctuations without affecting the mean load would result in lower capital and operational costs. In this paper we discuss how this could be achieved through blades that passively and elastically adapt their camber and angle of attack to counteract unsteady flow conditions. Firstly, we discuss the underlying principles of unsteady thrust mitigation. We show that complete cancellation of the thrust fluctuations would be possible if every blade section could pitch passively and independently of neighbouring sections. Secondly, we provide proof of principle for two practical implementations through physical experiments and computational fluid dynamics simulations. We consider a blade that is rigid near the leading edge and flexible near the trailing edge. We show that the unsteady load mitigation is proportional to the ratio between the length of the flexible and rigid parts of the blade. For example, for a blade section where the flexibility is concentrated in a hinge at 3/4 of the chord, the amplitude of the fluctuations is 3/4 of the original amplitude. Secondly, we consider a solid, rigid blade with a passive pitch mechanism. We show that, for a 1 MW turbine operating in shear flow, more than 80% of the unsteady loading is mitigated. These results demonstrate the potential effectiveness of morphing blades for mitigating thrust fluctuations on tidal turbines.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48010566","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}
Sarah Newman, Dhruv Bhatnagar, R. O'Neil, A. Reiman, Danielle Preziuso, B. Robertson
Marine energy resources could promote clean energy and resilience of coastal and island microgrids, and thus, these applications are a key future market for marine energy development. To demonstrate these benefits, this paper illustrates how inclusion of wave resources into energy resilience solutions can improve overall grid efficiency and sustainability, as well as maintain electricity supply during grid outages. The paper describes a case study evaluation of the potential to add wave energy to the Moloka'i grid as Hawaii strives to meet a 100% clean energy target. The Microgrid Component Optimization for Resilience tool is used to simulate operation in off-grid conditions and size different combinations of wave, solar photovoltaic (PV), wind, storage, and fuel resources required to meet resilience objectives. This research investigates how including wave resources in a microgrid contributes to reducing or eliminating biofuel generation, producing a zero-greenhouse gas emission profile in the latter case, and avoiding the over-sizing of PV and battery systems to accommodate periods of unavailability or high demand. Insight from this paper supports the value proposition of wave resources for future markets and informs the relationship between marine generators and microgrids or isolated grids.
{"title":"Evaluating the resilience benefits of marine energy in microgrids","authors":"Sarah Newman, Dhruv Bhatnagar, R. O'Neil, A. Reiman, Danielle Preziuso, B. Robertson","doi":"10.36688/imej.5.143-150","DOIUrl":"https://doi.org/10.36688/imej.5.143-150","url":null,"abstract":"Marine energy resources could promote clean energy and resilience of coastal and island microgrids, and thus, these applications are a key future market for marine energy development. To demonstrate these benefits, this paper illustrates how inclusion of wave resources into energy resilience solutions can improve overall grid efficiency and sustainability, as well as maintain electricity supply during grid outages. The paper describes a case study evaluation of the potential to add wave energy to the Moloka'i grid as Hawaii strives to meet a 100% clean energy target. The Microgrid Component Optimization for Resilience tool is used to simulate operation in off-grid conditions and size different combinations of wave, solar photovoltaic (PV), wind, storage, and fuel resources required to meet resilience objectives. This research investigates how including wave resources in a microgrid contributes to reducing or eliminating biofuel generation, producing a zero-greenhouse gas emission profile in the latter case, and avoiding the over-sizing of PV and battery systems to accommodate periods of unavailability or high demand. Insight from this paper supports the value proposition of wave resources for future markets and informs the relationship between marine generators and microgrids or isolated grids.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42920961","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}
Carwyn Frost, M. Togneri, P. Jeffcoate, Thomas Lake, C. Boake, R. Starzmann, A. Williams
Tidal resource assessment for the characterisation of turbine performance or Annual Energy Prediction currently uses the method of bins as recommended by international standards. An alternative method is proposed in this paper and applied to the Sustainable Marine Energy PLAT-I deployment in Connel Sound, Scotland. This method may be suitable for tidal turbines which operate from the surface. Three instrumentation types are used in this work, a bed-mounted Acoustic Doppler Profiler (ADP), and platform-mounted Acoustic Doppler Velocimeter (ADV) and Electromagnetic Current Meter (ECM). By comparing the resource characteristics from these three sources, a comparison of their velocity magnitudes and turbulence characteristics is made, demonstrating the difference between methodologies. It was found that the ADP evaluated using the method of bins produced a more conservative velocity distribution, in comparison to the ADV and ECM. Consequently, a representative AEP showed a difference of 3.8kWh (50% of ADP total) for the month of data collected. When comparing the Turbulence Intensity between devices, the ADP and ECM had similar metrics whilst the ADV had up to 14% higher values. The significance of these differences requires further work comparing them to the SME PLAT-I turbines power output to ascertain which best represents the onset flow experienced by the turbine and if there is a correlation between power performance and turbulence intensity.
{"title":"comparison of platform and sea-bed mounted flow measurement instrumentation for SME PLAT-I","authors":"Carwyn Frost, M. Togneri, P. Jeffcoate, Thomas Lake, C. Boake, R. Starzmann, A. Williams","doi":"10.36688/imej.5.195-200","DOIUrl":"https://doi.org/10.36688/imej.5.195-200","url":null,"abstract":"Tidal resource assessment for the characterisation of turbine performance or Annual Energy Prediction currently uses the method of bins as recommended by international standards. An alternative method is proposed in this paper and applied to the Sustainable Marine Energy PLAT-I deployment in Connel Sound, Scotland. This method may be suitable for tidal turbines which operate from the surface. Three instrumentation types are used in this work, a bed-mounted Acoustic Doppler Profiler (ADP), and platform-mounted Acoustic Doppler Velocimeter (ADV) and Electromagnetic Current Meter (ECM). By comparing the resource characteristics from these three sources, a comparison of their velocity magnitudes and turbulence characteristics is made, demonstrating the difference between methodologies. It was found that the ADP evaluated using the method of bins produced a more conservative velocity distribution, in comparison to the ADV and ECM. Consequently, a representative AEP showed a difference of 3.8kWh (50% of ADP total) for the month of data collected. When comparing the Turbulence Intensity between devices, the ADP and ECM had similar metrics whilst the ADV had up to 14% higher values. The significance of these differences requires further work comparing them to the SME PLAT-I turbines power output to ascertain which best represents the onset flow experienced by the turbine and if there is a correlation between power performance and turbulence intensity.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45307326","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}
Transverse Axis Crossflow Turbines (TACTs) are a niche subset of tidal turbines. TACTs are not as well understood as the more traditional horizontal axis turbine and associated flow theory which leans heavily on advances in wind energy and marine propulsion. This paper reviews laboratory and field based experimental fluid dynamics work from the perspective of turbine performance. The available literature deviates significantly in perspective and scope since it is found that not all papers declare a full complement of parameters, thereby making it difficult to check or validate the respective results. Therefore, identifying trends amongst the variable and sparse datasets is difficult. None of the papers reviewed cite adherence to the recommended tank testing guidelines. The work reviewed analyses aspects such as mounting supports, solidity, blockage and blade support locations in isolation, but the cumulative impact of these variables is unknown. Arising from the analyses carried out as part of this review, blade loading, solidity and blockage were identified as key parameters and are the subject of planned research. Trends between solidity and blockage with tip speed ratio were identified. This paper contributes to the understanding of TACT performance through the tidal turbine performance curve and highlights the need for comprehensive physical testing and model validation.
{"title":"Review of experimental studies on Transverse Axis Crossflow Turbines","authors":"R. Gallagher, Carwyn Frost, P. Schmitt, C. Young","doi":"10.36688/imej.5.161-171","DOIUrl":"https://doi.org/10.36688/imej.5.161-171","url":null,"abstract":"Transverse Axis Crossflow Turbines (TACTs) are a niche subset of tidal turbines. TACTs are not as well understood as the more traditional horizontal axis turbine and associated flow theory which leans heavily on advances in wind energy and marine propulsion. This paper reviews laboratory and field based experimental fluid dynamics work from the perspective of turbine performance. The available literature deviates significantly in perspective and scope since it is found that not all papers declare a full complement of parameters, thereby making it difficult to check or validate the respective results. Therefore, identifying trends amongst the variable and sparse datasets is difficult. None of the papers reviewed cite adherence to the recommended tank testing guidelines. The work reviewed analyses aspects such as mounting supports, solidity, blockage and blade support locations in isolation, but the cumulative impact of these variables is unknown. Arising from the analyses carried out as part of this review, blade loading, solidity and blockage were identified as key parameters and are the subject of planned research. Trends between solidity and blockage with tip speed ratio were identified. This paper contributes to the understanding of TACT performance through the tidal turbine performance curve and highlights the need for comprehensive physical testing and model validation.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42314963","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 Energy Converter (WEC) performance is generally sensitive to the wave direction. So, it is important to include the effect of multi-directional waves in numerical modelling. A realistic representation of ocean waves should account for wave height and directional spreading parameters specific to the WEC deployment location. A high quality generalised directional distribution is dependent on the wave direction and frequency. Here we compare the power produced, the wave field, and the motion of the WaveSub device for different frequency-directional distribution cases. Directional spreading has been modelled using different model distributions such as the uniform cosine fourth, Mitsuyasu, Hasselman and Donelan-Banner. The hydrodynamic coefficients are computed for all wave directions using Nemoh. Then, the WEC-Sim code has been extended to add the capability to simulate different user selected frequency-directional spreading. The excitation force applied to each hydrodynamic body is updated to account for the effect of the directional spectrum. Results show that power produced is generally 10-20% lower than a single direction case. The motion of the device demonstrates the introduction of sway, roll, and yaw for the directional spreading simulations while the resultant wavefield is more uniform compared to the non-directional case. Computational time is significantly lower than comparable CFD approaches and this makes this method particularly effective.
{"title":"Influence of directional wave spreading on a WEC device","authors":"E. Faraggiana, J. Chapman, I. Masters","doi":"10.36688/imej.5.227-242","DOIUrl":"https://doi.org/10.36688/imej.5.227-242","url":null,"abstract":"Wave Energy Converter (WEC) performance is generally sensitive to the wave direction. So, it is important to include the effect of multi-directional waves in numerical modelling. A realistic representation of ocean waves should account for wave height and directional spreading parameters specific to the WEC deployment location. A high quality generalised directional distribution is dependent on the wave direction and frequency. Here we compare the power produced, the wave field, and the motion of the WaveSub device for different frequency-directional distribution cases. Directional spreading has been modelled using different model distributions such as the uniform cosine fourth, Mitsuyasu, Hasselman and Donelan-Banner. The hydrodynamic coefficients are computed for all wave directions using Nemoh. Then, the WEC-Sim code has been extended to add the capability to simulate different user selected frequency-directional spreading. The excitation force applied to each hydrodynamic body is updated to account for the effect of the directional spectrum. Results show that power produced is generally 10-20% lower than a single direction case. The motion of the device demonstrates the introduction of sway, roll, and yaw for the directional spreading simulations while the resultant wavefield is more uniform compared to the non-directional case. Computational time is significantly lower than comparable CFD approaches and this makes this method particularly effective.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49589811","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}
14th European Wave and Tidal Energy Conference (EWTEC 2021) was organized by the University of Plymouth, UK from 5th – 9th September 2021. It was the first time the conference had been hosted in the South West of the UK, and with the impact of COVID-19, it was also the first time the event was held in a full hybrid format with presenters and audience both in person and online.
{"title":"Preface to the special issues of the Fourteenth European Wave and Tidal Energy Conference (EWTEC 2021)","authors":"D. Greaves","doi":"10.36688/imej.5.i","DOIUrl":"https://doi.org/10.36688/imej.5.i","url":null,"abstract":"14th European Wave and Tidal Energy Conference (EWTEC 2021) was organized by the University of Plymouth, UK from 5th – 9th September 2021. It was the first time the conference had been hosted in the South West of the UK, and with the impact of COVID-19, it was also the first time the event was held in a full hybrid format with presenters and audience both in person and online.","PeriodicalId":36111,"journal":{"name":"International Marine Energy Journal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45526207","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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