The ocean is full of untapped energy, however it is a wild place where harsh conditions can occur that can damage wave energy converters (WEC’s). During high load conditions, many WEC’s must go into survival mode to prevent damage or are overdesigned to continue operating in high sea states, which can increase capital costs. The authors propose a different approach, where geometry control is used to change to an absorber shape that experiences minimal hydrodynamic loads during high sea states. This could allow for a decrease in capital costs while increasing the operating range of WEC’s. This paper seeks an optimal geometry of a submerged planar pressure differential WEC that minimizes heave excitation force or motion magnitudes without using the power take-off system. Simple elliptical and circular absorbers as well as optimized absorbers are compared to quantify heave load reductions. Optimized absorbers are generated using a summation of Fourier terms with controllable weights and phases that are optimized with a genetic algorithm for two regular wave conditions. Heave load reductions are found to depend on wave frequency, orientation angle, and elongation. It is shown that peak loads can be reduced by up to 60% when comparing to a circular absorber.
{"title":"Shape Optimization of a Submerged Pressure Differential Wave Energy Converter for Load Reductions","authors":"Michael Kelly, Mohammad-Reza Alam","doi":"10.1115/omae2019-96390","DOIUrl":"https://doi.org/10.1115/omae2019-96390","url":null,"abstract":"\u0000 The ocean is full of untapped energy, however it is a wild place where harsh conditions can occur that can damage wave energy converters (WEC’s). During high load conditions, many WEC’s must go into survival mode to prevent damage or are overdesigned to continue operating in high sea states, which can increase capital costs. The authors propose a different approach, where geometry control is used to change to an absorber shape that experiences minimal hydrodynamic loads during high sea states. This could allow for a decrease in capital costs while increasing the operating range of WEC’s. This paper seeks an optimal geometry of a submerged planar pressure differential WEC that minimizes heave excitation force or motion magnitudes without using the power take-off system. Simple elliptical and circular absorbers as well as optimized absorbers are compared to quantify heave load reductions. Optimized absorbers are generated using a summation of Fourier terms with controllable weights and phases that are optimized with a genetic algorithm for two regular wave conditions. Heave load reductions are found to depend on wave frequency, orientation angle, and elongation. It is shown that peak loads can be reduced by up to 60% when comparing to a circular absorber.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116389178","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}
In this paper, idealised analytical and numerical models are used to explore the potential for local blockage effects to enhance the performance of turbines in tidal channels. Arrays of turbines modelled using the volume-flux-constrained actuator disc and blade element momentum theories are embedded within one-dimensional analytical and two-dimensional numerical channel domains. The effects of local blockage on the performance of arrays comprising one and five rows of actuator discs and tidal rotors operating in steady and oscillatory channel flow are then examined. In the case of steady flow, numerical results are found to agree very well with the two-scale actuator disc theory of Nishino & Willden [1]. In the case of oscillatory flow, however, numerical results show that the shorter and more highly blocked arrays produce considerably more power than predicted by the one-dimensional two-scale theory. These results support the findings of Bonar et al. [2], who showed that under certain oscillatory flow conditions, the power produced by a partial-width tidal turbine array can be much greater than predicted by two-scale theory. The departure from theory is most noticeable in the case of five turbine rows, where the two-scale theory predicts that the maximum available power should decrease with increasing local blockage but the numerical model shows the maximum available power to increase. The effects of local blockage are found to be less pronounced for the more realistic tidal rotor than for the highly idealised actuator disc but for both models, the results show that in oscillatory flow, considerably more power is available to the shorter and more highly blocked turbine arrays.
{"title":"Local Blockage Effects for Idealised Turbines in Tidal Channels","authors":"Lei Chen, P. A. J. Bonar, C. Vogel, T. Adcock","doi":"10.1115/omae2019-95347","DOIUrl":"https://doi.org/10.1115/omae2019-95347","url":null,"abstract":"\u0000 In this paper, idealised analytical and numerical models are used to explore the potential for local blockage effects to enhance the performance of turbines in tidal channels. Arrays of turbines modelled using the volume-flux-constrained actuator disc and blade element momentum theories are embedded within one-dimensional analytical and two-dimensional numerical channel domains. The effects of local blockage on the performance of arrays comprising one and five rows of actuator discs and tidal rotors operating in steady and oscillatory channel flow are then examined. In the case of steady flow, numerical results are found to agree very well with the two-scale actuator disc theory of Nishino & Willden [1]. In the case of oscillatory flow, however, numerical results show that the shorter and more highly blocked arrays produce considerably more power than predicted by the one-dimensional two-scale theory. These results support the findings of Bonar et al. [2], who showed that under certain oscillatory flow conditions, the power produced by a partial-width tidal turbine array can be much greater than predicted by two-scale theory. The departure from theory is most noticeable in the case of five turbine rows, where the two-scale theory predicts that the maximum available power should decrease with increasing local blockage but the numerical model shows the maximum available power to increase. The effects of local blockage are found to be less pronounced for the more realistic tidal rotor than for the highly idealised actuator disc but for both models, the results show that in oscillatory flow, considerably more power is available to the shorter and more highly blocked turbine arrays.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122496232","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}
As a part of the assessment of foundation resistance for monopiles, several offshore wind standards prescribe symmetric 35-hour (or 42-hour) storm sequences in terms of wind speed and significant wave height. The temporal evolution of the peak period is not specified explicitly in the standards, despite the fact that large monopile wind turbines are sensitive to the wave period. In the present work, the storm sequences according to the standards are first compared to hindcast data for intermediate water depth locations in the North Sea. An alternative storm sequence is proposed based on the hindcast data, and possible values of the peak period evolution are proposed for the standard models. The responses of a 10 MW monopile wind turbine are then computed for both the standard and proposed sequences using a time domain aero-hydro-servo-elastic code coupled to a macro element model for the soil-structure interaction. The resulting mudline load cycles are then compared for the different storm sequences.
{"title":"Dynamic Response of a Large-Diameter Monopile Considering 35-Hour Storm Conditions","authors":"E. Bachynski, A. Page, G. Katsikogiannis","doi":"10.1115/omae2019-95170","DOIUrl":"https://doi.org/10.1115/omae2019-95170","url":null,"abstract":"\u0000 As a part of the assessment of foundation resistance for monopiles, several offshore wind standards prescribe symmetric 35-hour (or 42-hour) storm sequences in terms of wind speed and significant wave height. The temporal evolution of the peak period is not specified explicitly in the standards, despite the fact that large monopile wind turbines are sensitive to the wave period. In the present work, the storm sequences according to the standards are first compared to hindcast data for intermediate water depth locations in the North Sea. An alternative storm sequence is proposed based on the hindcast data, and possible values of the peak period evolution are proposed for the standard models. The responses of a 10 MW monopile wind turbine are then computed for both the standard and proposed sequences using a time domain aero-hydro-servo-elastic code coupled to a macro element model for the soil-structure interaction. The resulting mudline load cycles are then compared for the different storm sequences.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123215662","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}
Bradley A. Ling, T. Lettenmaier, M. Fowler, M. Cameron, A. Viselli
The design of a 1/15th geometrically scaled wave tank model of the Azura™ commercial-scale wave energy device is presented. The objectives of the wave tank tests, conducted at the University of Maine Harlod Alfond Wind/Wave Ocean Engineering Lab (W2), included verification of the Azura’s energy capture in irregular waves, evaluation of performance in survival wave conditions, and testing of two advanced control algorithms. Due to the difficulty in properly Froude Scaling a hydraulic system, the model used a direct-drive rotary motor/generator power takeoff (PTO), with the dynamics of the hydraulic PTO included via a hardware-in-the-loop simulation. This PTO implementation led to additional design requirements being imposed on the model drivetrain. In addition to the model PTO design, the instrumentation design, structural design, and test plans are presented. The resulting model and PTO achieved a high level of controllability, and accurately emulated the dynamics of the hydraulic PTO of the full-scale Azura prototype.
{"title":"Design and Construction of a 1/15th Scale Wave Tank Model of the Azura Commercial Wave Energy Converter","authors":"Bradley A. Ling, T. Lettenmaier, M. Fowler, M. Cameron, A. Viselli","doi":"10.1115/omae2019-95538","DOIUrl":"https://doi.org/10.1115/omae2019-95538","url":null,"abstract":"\u0000 The design of a 1/15th geometrically scaled wave tank model of the Azura™ commercial-scale wave energy device is presented. The objectives of the wave tank tests, conducted at the University of Maine Harlod Alfond Wind/Wave Ocean Engineering Lab (W2), included verification of the Azura’s energy capture in irregular waves, evaluation of performance in survival wave conditions, and testing of two advanced control algorithms. Due to the difficulty in properly Froude Scaling a hydraulic system, the model used a direct-drive rotary motor/generator power takeoff (PTO), with the dynamics of the hydraulic PTO included via a hardware-in-the-loop simulation. This PTO implementation led to additional design requirements being imposed on the model drivetrain. In addition to the model PTO design, the instrumentation design, structural design, and test plans are presented. The resulting model and PTO achieved a high level of controllability, and accurately emulated the dynamics of the hydraulic PTO of the full-scale Azura prototype.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124819521","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}
The aim of the current work is to find out the effects of tubercles on the blade and wake of the turbine, which could be used in situations, where interaction among the array turbines is inevitable. Steady simulations are performed on a linear cascade setup of modified and unmodified infinite span NACA 63421 section blade, at Reynolds numbers 5 × 105 and 106 at inboard (low radial location) spacing. The tubercles used are at the scale of the boundary layer. The study showed that the boundary layer scale tubercles are advantageous only at higher Re and deeper stall regimes.
{"title":"Effects of Tubercles on Blade and Wake of HAMCT in Post Stall Regimes: Linear Cascade Study","authors":"Varun Raj Dondapati, M. Kantharaj","doi":"10.1115/omae2019-96287","DOIUrl":"https://doi.org/10.1115/omae2019-96287","url":null,"abstract":"\u0000 The aim of the current work is to find out the effects of tubercles on the blade and wake of the turbine, which could be used in situations, where interaction among the array turbines is inevitable. Steady simulations are performed on a linear cascade setup of modified and unmodified infinite span NACA 63421 section blade, at Reynolds numbers 5 × 105 and 106 at inboard (low radial location) spacing. The tubercles used are at the scale of the boundary layer. The study showed that the boundary layer scale tubercles are advantageous only at higher Re and deeper stall regimes.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124052498","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}
Casey M. Fontana, S. Arwade, D. DeGroot, Spencer T Hallowell, C. Aubeny, B. Diaz, Melissa E. Landon, S. Ozmutlu, A. Myers
While the offshore wind industry has shown a steady trend towards floating turbines, costs of these systems remain high. A multiline anchor concept may significantly reduce the high cost of floating wind, in which floating turbines share anchors. This work investigates the potential cost benefit of implementing a multiline anchor system relative to the conventional single-line anchor system over a range of spatial parameters. The OC4 DeepCwind semisubmersible platform is used to design catenary mooring systems for different water depths and turbine spacings. In all cases, the maximum anchor force in the 3-line anchor system is less than or equal to that of the single-line anchor system. Cost models for the mooring lines, anchors, installation and geotechnical site investigation are presented and discussed. In a 100-turbine farm, the multiline anchor system results in a 9–19% reduction in stationkeeping costs, with high and low estimates for the cost models additionally included. Larger reductions in the combined line and anchor cost result from mooring system configurations with smaller ratios of water depth to turbine spacing. Due to perimeter effects in the multiline configuration, larger cost reductions can be achieved for larger farm sizes.
{"title":"Force Dynamics and Stationkeeping Costs for Multiline Anchor Systems in Floating Wind Farms With Different Spatial Parameters","authors":"Casey M. Fontana, S. Arwade, D. DeGroot, Spencer T Hallowell, C. Aubeny, B. Diaz, Melissa E. Landon, S. Ozmutlu, A. Myers","doi":"10.1115/omae2019-96395","DOIUrl":"https://doi.org/10.1115/omae2019-96395","url":null,"abstract":"\u0000 While the offshore wind industry has shown a steady trend towards floating turbines, costs of these systems remain high. A multiline anchor concept may significantly reduce the high cost of floating wind, in which floating turbines share anchors. This work investigates the potential cost benefit of implementing a multiline anchor system relative to the conventional single-line anchor system over a range of spatial parameters. The OC4 DeepCwind semisubmersible platform is used to design catenary mooring systems for different water depths and turbine spacings. In all cases, the maximum anchor force in the 3-line anchor system is less than or equal to that of the single-line anchor system. Cost models for the mooring lines, anchors, installation and geotechnical site investigation are presented and discussed. In a 100-turbine farm, the multiline anchor system results in a 9–19% reduction in stationkeeping costs, with high and low estimates for the cost models additionally included. Larger reductions in the combined line and anchor cost result from mooring system configurations with smaller ratios of water depth to turbine spacing. Due to perimeter effects in the multiline configuration, larger cost reductions can be achieved for larger farm sizes.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127624029","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}
S. Shi, R. Patton, Mustafa Abdelrahman, Yanhua Liu
This article presents a data-efficient learning approach for the complex-conjugate control of a wave energy point absorber. Particularly, the Bayesian Optimization algorithm is adopted for maximizing the extracted energy from sea waves subject to physical constraints. The algorithm learns the optimal coefficients of the causal controller. The simulation model of a Wavestar Wave Energy Converter (WEC) is selected to validate the control strategy for both the regular and irregular waves. The results indicate the efficiency and feasibility of the proposed control system. Less than 20 function evaluations are required to converge towards the optimal performance of each sea state. Additionally, this model-free controller can adapt to variations in the real sea state and be insensitive and robust to the WEC modeling bias.
{"title":"Learning a Predictionless Resonating Controller for Wave Energy Converters","authors":"S. Shi, R. Patton, Mustafa Abdelrahman, Yanhua Liu","doi":"10.1115/omae2019-95619","DOIUrl":"https://doi.org/10.1115/omae2019-95619","url":null,"abstract":"\u0000 This article presents a data-efficient learning approach for the complex-conjugate control of a wave energy point absorber. Particularly, the Bayesian Optimization algorithm is adopted for maximizing the extracted energy from sea waves subject to physical constraints. The algorithm learns the optimal coefficients of the causal controller. The simulation model of a Wavestar Wave Energy Converter (WEC) is selected to validate the control strategy for both the regular and irregular waves. The results indicate the efficiency and feasibility of the proposed control system. Less than 20 function evaluations are required to converge towards the optimal performance of each sea state. Additionally, this model-free controller can adapt to variations in the real sea state and be insensitive and robust to the WEC modeling bias.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114624896","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}
The reliability of offshore wind turbines is a key factor when estimating maintanence costs, downtime due to component failure and overall efficiency during operational life. Offshore wind turbines have limited accessibility and operate in harsh environments and, as a result, it is difficult to perform frequent checks on electrical and mechanical component. Drivetrain test rigs (DTR) are crucial to the task of: validating the design of new components to avoid early life failure, observe the behaviour of components under load over long periods of time in a controlled environment and produce a maintanence plan that minimize costs and frequency of intervention. In this paper, after a brief introduction on the state of the art in DTR technology, is described a methodology that can be used to create an effective conceptual design for a drivetrain test rig, focusing also on the possible downscaling. The paper starts by analyzing the benefits of the drivetrain use in the wind power industry, bringing examples of real test rigs used in industrial and academical world. Once the topic is mastered it is possible to proceed with a description of the various phases needed to obtain the conceptual design, from the definition of layout to the preliminary 3D modeling. The test rig that is here designed, while inspired from full scale dynamometers used in the industry, is thought as a laboratory tool for academical use that can be used by students to investigate fault detection methods and health monitoring systems of wind turbines. It is also included a section dedicated to the possible techniques for downscaling the test rig, based on simple considerations of the drivetrain mechanical behaviour. Downscaling becomes a key factor when facing the need to test turbine components of ever increasing dimensions in laboratories with limited space and budget. The definition of a procedure to create a scaled version will allow laboratories to build test rigs of smaller dimension but with a damage model for the various components still closely linked to the one in real scale. Downscaling is also a necessity when working with limited power sources, not able to recreate the conditions that the real scale turbine encounters. The ultimate goal is to define a solid base to allow further development in the detailed design phase.
{"title":"On Design and Analysis of a Drivetrain Test Rig for Wind Turbine Health Monitoring","authors":"Lorenzo Balestra, A. Nejad, G. Naldi","doi":"10.1115/omae2019-96721","DOIUrl":"https://doi.org/10.1115/omae2019-96721","url":null,"abstract":"\u0000 The reliability of offshore wind turbines is a key factor when estimating maintanence costs, downtime due to component failure and overall efficiency during operational life. Offshore wind turbines have limited accessibility and operate in harsh environments and, as a result, it is difficult to perform frequent checks on electrical and mechanical component. Drivetrain test rigs (DTR) are crucial to the task of: validating the design of new components to avoid early life failure, observe the behaviour of components under load over long periods of time in a controlled environment and produce a maintanence plan that minimize costs and frequency of intervention.\u0000 In this paper, after a brief introduction on the state of the art in DTR technology, is described a methodology that can be used to create an effective conceptual design for a drivetrain test rig, focusing also on the possible downscaling.\u0000 The paper starts by analyzing the benefits of the drivetrain use in the wind power industry, bringing examples of real test rigs used in industrial and academical world. Once the topic is mastered it is possible to proceed with a description of the various phases needed to obtain the conceptual design, from the definition of layout to the preliminary 3D modeling.\u0000 The test rig that is here designed, while inspired from full scale dynamometers used in the industry, is thought as a laboratory tool for academical use that can be used by students to investigate fault detection methods and health monitoring systems of wind turbines. It is also included a section dedicated to the possible techniques for downscaling the test rig, based on simple considerations of the drivetrain mechanical behaviour. Downscaling becomes a key factor when facing the need to test turbine components of ever increasing dimensions in laboratories with limited space and budget. The definition of a procedure to create a scaled version will allow laboratories to build test rigs of smaller dimension but with a damage model for the various components still closely linked to the one in real scale. Downscaling is also a necessity when working with limited power sources, not able to recreate the conditions that the real scale turbine encounters.\u0000 The ultimate goal is to define a solid base to allow further development in the detailed design phase.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114288086","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}
The study presents analyses of key parameters that affect the performance of the point absorbing wave energy converter (WEC). Performance is assessed by running hydrodynamic and structural response simulations and calculating the power absorption of the WEC and fatigue damage in the mooring lines from the output data. The baseline model of the WEC input to the simulation is modelled after the WaveEL 3.0 device, designed by Waves4Power and installed in Runde, Norway. Simulations are run for single buoy and small array configurations, varying environmental conditions, mooring system, and WEC buoy shaft length. Environmental conditions are chosen to reflect locations studied as potential future installation sites. Select configurations are further analyzed through an analysis of LCOE and LCA. The results show that optimal mooring line geometry depends on water depth, and that optimal shaft length depends on the average sea conditions at the location. The array simulations show that small WEC separating distances will limit the mooring line length, which will result in lower power absorption and lower fatigue lives in the mooring lines. The LCOE shows that the four-buoy array configuration is the most profitable, and both the LCOE and LCA show that the main process contribution to climate change and the total product cost is the manufacturing of the WEC buoy itself. The research in this study demonstrates the importance of using simulations to make effective WEC design choices for a given environment.
{"title":"Making Effective WEC Design Choices Based on Simulation and Analysis","authors":"C. Vance, J. Ringsberg, Shun-Han Yang","doi":"10.1115/OMAE2019-95138","DOIUrl":"https://doi.org/10.1115/OMAE2019-95138","url":null,"abstract":"\u0000 The study presents analyses of key parameters that affect the performance of the point absorbing wave energy converter (WEC). Performance is assessed by running hydrodynamic and structural response simulations and calculating the power absorption of the WEC and fatigue damage in the mooring lines from the output data. The baseline model of the WEC input to the simulation is modelled after the WaveEL 3.0 device, designed by Waves4Power and installed in Runde, Norway. Simulations are run for single buoy and small array configurations, varying environmental conditions, mooring system, and WEC buoy shaft length. Environmental conditions are chosen to reflect locations studied as potential future installation sites. Select configurations are further analyzed through an analysis of LCOE and LCA. The results show that optimal mooring line geometry depends on water depth, and that optimal shaft length depends on the average sea conditions at the location. The array simulations show that small WEC separating distances will limit the mooring line length, which will result in lower power absorption and lower fatigue lives in the mooring lines. The LCOE shows that the four-buoy array configuration is the most profitable, and both the LCOE and LCA show that the main process contribution to climate change and the total product cost is the manufacturing of the WEC buoy itself. The research in this study demonstrates the importance of using simulations to make effective WEC design choices for a given environment.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123637928","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}
H. E. Sheshtawy, O. E. Moctar, T. Schellin, S. Natarajan
A tidal stream turbine was designed using one of the optimised hydrofoils, whose lift-to-drag ratio at an angle of attack of 5.2 degrees was 4.5% higher than that of the reference hydrofoil. The incompressible Reynolds-averaged Navier Stokes equations in steady state were solved using k-ω (SST) turbulence model for the reference and optimised tidal stream turbines. The discretisation errors and the effect of different y+ values on the solution were analysed. Thrust and power coefficients of the modelled reference turbine were validated against experimental measurements. Output power and thrust of the reference and the optimised tidal turbines were compared. For a tip speed ratio of 3.0, the output power of the optimised tidal turbine was 8.27% higher than that of the reference turbine of the same thrust.
{"title":"Numerical Investigation of an Optimised Horizontal Axis Tidal Stream Turbine","authors":"H. E. Sheshtawy, O. E. Moctar, T. Schellin, S. Natarajan","doi":"10.1115/omae2019-95722","DOIUrl":"https://doi.org/10.1115/omae2019-95722","url":null,"abstract":"\u0000 A tidal stream turbine was designed using one of the optimised hydrofoils, whose lift-to-drag ratio at an angle of attack of 5.2 degrees was 4.5% higher than that of the reference hydrofoil. The incompressible Reynolds-averaged Navier Stokes equations in steady state were solved using k-ω (SST) turbulence model for the reference and optimised tidal stream turbines. The discretisation errors and the effect of different y+ values on the solution were analysed. Thrust and power coefficients of the modelled reference turbine were validated against experimental measurements. Output power and thrust of the reference and the optimised tidal turbines were compared. For a tip speed ratio of 3.0, the output power of the optimised tidal turbine was 8.27% higher than that of the reference turbine of the same thrust.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127838909","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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