A. Price, David Campos-Gaona, Thomas Davey, David Forehand, Thomas Giles, Peter McCallum, Alasdair McDonald, Matthew Onslow, Brian Sellar, Adam Stock, Reza Yazdanpanah, Seyed Abolfazl Mortazavizadeh
The HAPiGYM is a collection of numerical and experimental modelling environments for testing control of wave energy converters (WECs). It has two applications: rapid prototyping of the control policies themselves, and co-design of control and other WEC subsystems. This collection will grow over time. Initially two environments (‘GYM machines’) will be offered. These will be described in this paper. The HAPiGYM addresses several technical and resourcing challenges surrounding control prototyping and co-design. Time, money, and cross-disciplinary knowledge are common barriers. Tank time can be prohibitively expensive. Hence many control researchers rely on numerical simulations, and many WEC developers use non-representative control models when designing the hydrodynamic absorbers. The state of the art in hydrodynamic models are not suitable for rapid control prototyping: they are either too slow or insufficiently accurate, leading to a ‘Sim2Tank’ gap, where simulation and tank trial results disagree. Hardware-in-the-Loop removes thosemodelling uncertainties associated with the drive train and control hardware. However, uncertainties associated with the hydrodynamic model remain, and unrepresentative artefacts associated with the rig could be added. Two notable schemes that included tank testing for comparative evaluation were WECCCOMP and the Wave Energy Prize (WEP). WECCCOMP allowed participants to compare the performance of their controllers on the same tank test model. The WEP allowed participants to test their own WECs and controllers.Both had metrics that were proxies for levelised cost of energy. The single metric and prescribed methodology focused the efforts and objectives of participants. As a consequence, simplifications inherent in metrics (e.g., the formula for electrical power) and methodology (e.g., spectral parameters of the sea state available as inputs to the control policy) led to control approaches that could not be replicated in real seas, i.e., certain types of control were able to exploit the ‘Tank2Sea’ gap. The HAPiGYM approach acknowledges theissues surrounding Sim2Tank and Tank2Sea gaps. Rather than attempting to eliminate these, participants will be invited to contribute to a discussion of how testing methodology interacts with control. Participants will be able to suggest methods, metrics, and even future GYM machines. The HAPiGYM will offer a selection of settings for each GYM machine, including the resource (waves), type of PTO, and metrics. Participants will be able to rate their controllers against a suite of metrics and experimental set-ups. This will allow a more nuanced comparison between controllers. It will also facilitate more basic research on co-design, e.g. how PTO operational rangeimpacts control and hydrodynamic performance. Stakeholder engagement identified the need for a simple environment to get started on (a small Sim2Tank gap), and a more challenging environment that reflected the control problems o
{"title":"HAPiGYM","authors":"A. Price, David Campos-Gaona, Thomas Davey, David Forehand, Thomas Giles, Peter McCallum, Alasdair McDonald, Matthew Onslow, Brian Sellar, Adam Stock, Reza Yazdanpanah, Seyed Abolfazl Mortazavizadeh","doi":"10.36688/ewtec-2023-499","DOIUrl":"https://doi.org/10.36688/ewtec-2023-499","url":null,"abstract":"The HAPiGYM is a collection of numerical and experimental modelling environments for testing control of wave energy converters (WECs). It has two applications: rapid prototyping of the control policies themselves, and co-design of control and other WEC subsystems. This collection will grow over time. Initially two environments (‘GYM machines’) will be offered. These will be described in this paper. \u0000The HAPiGYM addresses several technical and resourcing challenges surrounding control prototyping and co-design. Time, money, and cross-disciplinary knowledge are common barriers. Tank time can be prohibitively expensive. Hence many control researchers rely on numerical simulations, and many WEC developers use non-representative control models when designing the hydrodynamic absorbers. The state of the art in hydrodynamic models are not suitable for rapid control prototyping: they are either too slow or insufficiently accurate, leading to a ‘Sim2Tank’ gap, where simulation and tank trial results disagree. Hardware-in-the-Loop removes thosemodelling uncertainties associated with the drive train and control hardware. However, uncertainties associated with the hydrodynamic model remain, and unrepresentative artefacts associated with the rig could be added. Two notable schemes that included tank testing for comparative evaluation were WECCCOMP and the Wave Energy Prize (WEP). WECCCOMP allowed participants to compare the performance of their controllers on the same tank test model. The WEP allowed participants to test their own WECs and controllers.Both had metrics that were proxies for levelised cost of energy. The single metric and prescribed methodology focused the efforts and objectives of participants. As a consequence, simplifications inherent in metrics (e.g., the formula for electrical power) and methodology (e.g., spectral parameters of the sea state available as inputs to the control policy) led to control approaches that could not be replicated in real seas, i.e., certain types of control were able to exploit the ‘Tank2Sea’ gap. The HAPiGYM approach acknowledges theissues surrounding Sim2Tank and Tank2Sea gaps. Rather than attempting to eliminate these, participants will be invited to contribute to a discussion of how testing methodology interacts with control. Participants will be able to suggest methods, metrics, and even future GYM machines. The HAPiGYM will offer a selection of settings for each GYM machine, including the resource (waves), type of PTO, and metrics. Participants will be able to rate their controllers against a suite of metrics and experimental set-ups. This will allow a more nuanced comparison between controllers. It will also facilitate more basic research on co-design, e.g. how PTO operational rangeimpacts control and hydrodynamic performance. \u0000Stakeholder engagement identified the need for a simple environment to get started on (a small Sim2Tank gap), and a more challenging environment that reflected the control problems o","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130014890","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}
Alina Santa Cruz, Thomas Combret, F. Hadri, Sylvain S. Guillou
Following the development of renewable marine energies, the characterization of areas with strong marine currents has become necessary. The Normandy coasts (France) are among the sites suitable for the installation of tidal turbine parks because they have significant energy potential. Projects to install machines in these sites raise questions about various factors affecting the performance of the turbines that would be placed there. We are currently working on the understanding of the mechanisms leading to the generation of ambient flow turbulence on the seabed. More particularly, we are interested in the impact of the complexity of the bathymetry on the organization of the wake generated. To simplify the modeling of the bathymetry of the seabed, we use generic cylindrical obstacles of rectangular section. The obstacles are placed on the bottom of the study area of the Hydrodynamic Tunnel of the LUSAC laboratory and occupy its entire width. Measurements are made using Particle Image Velocimetry (PIV-2D) for a velocity flow of 3 m/s. In a first time, in a previous contribution, was evaluated the impact of the ratio between the Height and the Width (H/W) of the cross section of the cylinder on the organization of the near wake. Indeed, the average velocity fields obtained for six different obstacles, highlighted the modification of the organization of the flow topology. The variation of this ratio H/W leads to the modification of the length of the average vortex formation zone, implies the presence of two or even three average recirculation zones in the near wake of the cylinder and leads to the possible presence of a recirculation zone average placed upstream of the cylinder. Nevertheless, in the seabed the structures are not isolated. In the contrary, on the seabed we can observe successions of structures anchored on the funds, leading to the interaction of a structure with the wake generated upstream by another one structure. The experimental study with the characterization of the flow around a tandem of “long” cylindrical obstacles of square section (side H). The distance between these two cylinders is equal to 2H. As expected, in the present study, it can be observed the modifications of the topology of the mean flow and the distribution of the turbulent kinetic energy. Indeed, the interaction between the mean recirculation, generated downstream each cylinder, is shown.
{"title":"EXPERIMENTAL CHARACTERISATION OF THE WAKE OF A BOTTOM-MOUNTED TWO TANDEM OF CYLINDERS PLACED IN A HIGH VELOCITY AREA","authors":"Alina Santa Cruz, Thomas Combret, F. Hadri, Sylvain S. Guillou","doi":"10.36688/ewtec-2023-579","DOIUrl":"https://doi.org/10.36688/ewtec-2023-579","url":null,"abstract":"Following the development of renewable marine energies, the characterization of areas with strong marine currents has become necessary. The Normandy coasts (France) are among the sites suitable for the installation of tidal turbine parks because they have significant energy potential. Projects to install machines in these sites raise questions about various factors affecting the performance of the turbines that would be placed there. \u0000We are currently working on the understanding of the mechanisms leading to the generation of ambient flow turbulence on the seabed. More particularly, we are interested in the impact of the complexity of the bathymetry on the organization of the wake generated. To simplify the modeling of the bathymetry of the seabed, we use generic cylindrical obstacles of rectangular section. The obstacles are placed on the bottom of the study area of the Hydrodynamic Tunnel of the LUSAC laboratory and occupy its entire width. Measurements are made using Particle Image Velocimetry (PIV-2D) for a velocity flow of 3 m/s. \u0000In a first time, in a previous contribution, was evaluated the impact of the ratio between the Height and the Width (H/W) of the cross section of the cylinder on the organization of the near wake. Indeed, the average velocity fields obtained for six different obstacles, highlighted the modification of the organization of the flow topology. The variation of this ratio H/W leads to the modification of the length of the average vortex formation zone, implies the presence of two or even three average recirculation zones in the near wake of the cylinder and leads to the possible presence of a recirculation zone average placed upstream of the cylinder. \u0000Nevertheless, in the seabed the structures are not isolated. In the contrary, on the seabed we can observe successions of structures anchored on the funds, leading to the interaction of a structure with the wake generated upstream by another one structure. The experimental study with the characterization of the flow around a tandem of “long” cylindrical obstacles of square section (side H). The distance between these two cylinders is equal to 2H. \u0000As expected, in the present study, it can be observed the modifications of the topology of the mean flow and the distribution of the turbulent kinetic energy. Indeed, the interaction between the mean recirculation, generated downstream each cylinder, is shown. ","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126344247","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}
Adoption of autonomous underwater vehicle (AUV) technology has recently experienced rapid growth, fueled by possibilities enabled by technological advances. AUVs are particularly useful as unmanned survey platforms, and typically have an array of on-board sensors to collect data for a variety of commercial and military applications. AUVs are autonomous and untethered systems and require a power source, typically batteries, to be carried onboard. An increase in available energy by even a small amount can be game-changing for AUV applications with benefits including longer mission durations, higher sampling rate, more sensing capability, and improved communication capability. This can be accomplished through some self-recharging capability within the AUV, allowing the AUV to extract energy from its surrounding environment, and eliminating the need to recover the vehicle until the mission is complete. This work presents a Wave Power Capture System (WPCS) that can be integrated into an AUV, allowing it to operate for significantly longer periods of time without the need for recovery. This concept utilizes two rotary power take-off (PTO) units that are driven by two independent tendons, located axially along the length of the body. The two tendons are connected to a retractable reaction plate that can be stowed against the body of the AUV when not in use and deployed autonomously when the AUV needs to surface and recharge. This arrangement allows both pitch and heave motion to be primary contributors to relative (power generating) motion. Additional motion in surge, sway and yaw will also result in some secondary power generation. This work focuses on the hydrodynamics and design of the reaction plate so that power capture and quality are enhanced. The geometry of the reaction plate will be constrained to a baseline semicircular shape, allowing the AUV to operate normally when the plate is stowed. Based on previous work, which has indicated that increasing the reaction plate added mass improves WEC power capture, the current work will thus look at different modifications to the reaction plate that effectively enhance its size when deployed, for example, incorporating multiple ‘nested’ reaction plates that mate together when stowed. The light weight of the reaction plate relative to its size means that there may be a tendency for the tendons to go slack and subsequently experience snap loading in cases where the reaction plate does not fall as fast as the AUV body. This work will further investigate the incorporation of dynamically adaptable geometries that reduce the reaction plate’s hydrodynamic resistance in the downward direction, for example, a structure that contains multiple flaps that hinge open during downward travel. A series of experiments will be presented in which the different reaction plate concepts are sinusoidally forced in a quiescent basin to characterize the translational and rotational hydrodynamic coefficients over a range of
{"title":"Development & performance enhancement of an AUV wave-charging system","authors":"Brian Rosenberg, Sergiy Taylakov, Timothy Mundon","doi":"10.36688/ewtec-2023-540","DOIUrl":"https://doi.org/10.36688/ewtec-2023-540","url":null,"abstract":"Adoption of autonomous underwater vehicle (AUV) technology has recently experienced rapid growth, fueled by possibilities enabled by technological advances. AUVs are particularly useful as unmanned survey platforms, and typically have an array of on-board sensors to collect data for a variety of commercial and military applications. AUVs are autonomous and untethered systems and require a power source, typically batteries, to be carried onboard. An increase in available energy by even a small amount can be game-changing for AUV applications with benefits including longer mission durations, higher sampling rate, more sensing capability, and improved communication capability. This can be accomplished through some self-recharging capability within the AUV, allowing the AUV to extract energy from its surrounding environment, and eliminating the need to recover the vehicle until the mission is complete. \u0000This work presents a Wave Power Capture System (WPCS) that can be integrated into an AUV, allowing it to operate for significantly longer periods of time without the need for recovery. This concept utilizes two rotary power take-off (PTO) units that are driven by two independent tendons, located axially along the length of the body. The two tendons are connected to a retractable reaction plate that can be stowed against the body of the AUV when not in use and deployed autonomously when the AUV needs to surface and recharge. This arrangement allows both pitch and heave motion to be primary contributors to relative (power generating) motion. Additional motion in surge, sway and yaw will also result in some secondary power generation. \u0000This work focuses on the hydrodynamics and design of the reaction plate so that power capture and quality are enhanced. The geometry of the reaction plate will be constrained to a baseline semicircular shape, allowing the AUV to operate normally when the plate is stowed. Based on previous work, which has indicated that increasing the reaction plate added mass improves WEC power capture, the current work will thus look at different modifications to the reaction plate that effectively enhance its size when deployed, for example, incorporating multiple ‘nested’ reaction plates that mate together when stowed. The light weight of the reaction plate relative to its size means that there may be a tendency for the tendons to go slack and subsequently experience snap loading in cases where the reaction plate does not fall as fast as the AUV body. This work will further investigate the incorporation of dynamically adaptable geometries that reduce the reaction plate’s hydrodynamic resistance in the downward direction, for example, a structure that contains multiple flaps that hinge open during downward travel. \u0000A series of experiments will be presented in which the different reaction plate concepts are sinusoidally forced in a quiescent basin to characterize the translational and rotational hydrodynamic coefficients over a range of ","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122595995","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}
Marine risers such as cables of cylindrical cross-section continuously encounter ocean currents during their service life, causing vortex-induced vibrations (VIV). Such oscillations can last a long period at high frequencies and produce significant damage that accumulates in structural components. The accumulated damage eventually leads to the failure of the structure. The Reynolds number (Re) for marine risers in the ocean can be much higher than the Re of flows that can be solved with the direct numerical simulation (DNS) method. Therefore, turbulence models are necessary for predicting the VIVs [1] at high Re, which are close to the situations in the ocean [2]. In this study, the response of flow around a fixed circular cylinder at Reynolds number 3900 is investigated with DNS and large eddy simulation (LES). This value of the Reynolds number (Re) has often been investigated in previous studies concerning flows past fixed cylinders as a typical case of the early turbulent regime. Despite the DNS method being very accurate, the computational cost increases with the increasing Re while 2D simulations may become inadequate. For 3D simulations, however, a tenfold increase in Re corresponds to 1000 times more computational cost. This makes it virtually impossible to solve engineering application problems with DNS. In order to efficiently simulate VIV in turbulent flows, turbulence modeling constitutes one of the most important aspects of CFD modeling. By investigating the Re 3900 case with both DNS and LES, we can ensure the validity of our turbulence model when comparing our results with literature. With a suitably selected turbulence model, our numerical solution is able to capture most of the real physics of the phenomena, including the Kármán vortex street effects on the lift and drag coefficients. A series of experimental measurements used to validate the simulations are also reported. At Re 3900, the drag coefficient conducted by experiments is 1.01, which is in the range of other researches done before, of around 0.94 - 1.04 [3]. The predicted drag coefficients and Strouhal numbers agree with the experimental data and the values reported in the literature [4]. [1] Liu, Guijie, et al. "A mini review of recent progress on vortex-induced vibrations of marine risers." Ocean Engineering 195 (2020): 106704. [2] Qiu, Wei, et al. "Numerical benchmark studies on drag and lift coefficients of a marine riser at high Reynolds numbers." Applied Ocean Research 69 (2017): 245-251. [3] Wornom, Stephen, et al. "Variational multiscale large-eddy simulations of the flow past a circular cylinder: Reynolds number effects." Computers & Fluids 47.1 (2011): 44-50. [4] Violette, R., Emmanuel De Langre, and J. Szydlowski. "Computation of vortex-induced vibrations of long structures using a wake oscillator model: comparison with DNS and experiments." Computers & structures 85.11-14 (2007): 1134-1141.
{"title":"Vortex induced vibrations of marine risers: validating turbulence models","authors":"Chang, A. Vakis, Arthur Veldman, Eize","doi":"10.36688/ewtec-2023-342","DOIUrl":"https://doi.org/10.36688/ewtec-2023-342","url":null,"abstract":"Marine risers such as cables of cylindrical cross-section continuously encounter ocean currents during their service life, causing vortex-induced vibrations (VIV). Such oscillations can last a long period at high frequencies and produce significant damage that accumulates in structural components. The accumulated damage eventually leads to the failure of the structure. \u0000The Reynolds number (Re) for marine risers in the ocean can be much higher than the Re of flows that can be solved with the direct numerical simulation (DNS) method. Therefore, turbulence models are necessary for predicting the VIVs [1] at high Re, which are close to the situations in the ocean [2]. \u0000In this study, the response of flow around a fixed circular cylinder at Reynolds number 3900 is investigated with DNS and large eddy simulation (LES). This value of the Reynolds number (Re) has often been investigated in previous studies concerning flows past fixed cylinders as a typical case of the early turbulent regime. Despite the DNS method being very accurate, the computational cost increases with the increasing Re while 2D simulations may become inadequate. For 3D simulations, however, a tenfold increase in Re corresponds to 1000 times more computational cost. This makes it virtually impossible to solve engineering application problems with DNS. In order to efficiently simulate VIV in turbulent flows, turbulence modeling constitutes one of the most important aspects of CFD modeling. \u0000 \u0000By investigating the Re 3900 case with both DNS and LES, we can ensure the validity of our turbulence model when comparing our results with literature. With a suitably selected turbulence model, our numerical solution is able to capture most of the real physics of the phenomena, including the Kármán vortex street effects on the lift and drag coefficients. A series of experimental measurements used to validate the simulations are also reported. At Re 3900, the drag coefficient conducted by experiments is 1.01, which is in the range of other researches done before, of around 0.94 - 1.04 [3]. The predicted drag coefficients and Strouhal numbers agree with the experimental data and the values reported in the literature [4]. \u0000 \u0000[1] Liu, Guijie, et al. \"A mini review of recent progress on vortex-induced vibrations of marine risers.\" Ocean Engineering 195 (2020): 106704. \u0000[2] Qiu, Wei, et al. \"Numerical benchmark studies on drag and lift coefficients of a marine riser at high Reynolds numbers.\" Applied Ocean Research 69 (2017): 245-251. \u0000[3] Wornom, Stephen, et al. \"Variational multiscale large-eddy simulations of the flow past a circular cylinder: Reynolds number effects.\" Computers & Fluids 47.1 (2011): 44-50. \u0000[4] Violette, R., Emmanuel De Langre, and J. Szydlowski. \"Computation of vortex-induced vibrations of long structures using a wake oscillator model: comparison with DNS and experiments.\" Computers & structures 85.11-14 (2007): 1134-1141.","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134113212","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 paper presents the study of multi-PTO interaction in single-air chamber oscillating-water-column (OWC) wave energy converters (WECs). This strategy seeks: i) tunning system's performance to sea states, ii) increasing reliability through modular designs that are easier to install and replace, and iii) increasing conversion efficiency through better matching between available power and electric conversion equipment. The strategy was assessed through a novel non-linear time-domain model for OWC WECs implemented in the multi-physics object-oriented language Modelica. The model considers multiple degrees of freedom associated with the various PTOs. Different case studies are presented to show the proposed approach's versatility, some of the constraints expected in real implementations, and potential pathways to overcome them. The wave-to-wire model considers air compressibility and non-linear power take-off systems, which is fundamental to assessing the damping level variation required for each sea state considered. The cases presented are for a fixed-structure coaxial-duct OWC WEC, but the results are generalisable for floating structures. Results show a significant increase in mean annual power, and control strategies are proposed for power maximisation. Furthermore, some critical points are shown in the operational conditions' envelop for the system under a selected Portuguese wave climate. The identification of these critical values is important for the control of the OWC WECs. This study represents an advance in the control strategies considering multiple PTOs for a single OWC air chamber to foster innovation actions.
{"title":"Control of multiple PTOs in single OWC air chambers","authors":"J. Portillo, L. Gato, J. Henriques","doi":"10.36688/ewtec-2023-394","DOIUrl":"https://doi.org/10.36688/ewtec-2023-394","url":null,"abstract":"The paper presents the study of multi-PTO interaction in single-air chamber oscillating-water-column (OWC) wave energy converters (WECs). This strategy seeks: i) tunning system's performance to sea states, ii) increasing reliability through modular designs that are easier to install and replace, and iii) increasing conversion efficiency through better matching between available power and electric conversion equipment. The strategy was assessed through a novel non-linear time-domain model for OWC WECs implemented in the multi-physics object-oriented language Modelica. The model considers multiple degrees of freedom associated with the various PTOs. Different case studies are presented to show the proposed approach's versatility, some of the constraints expected in real implementations, and potential pathways to overcome them. The wave-to-wire model considers air compressibility and non-linear power take-off systems, which is fundamental to assessing the damping level variation required for each sea state considered. The cases presented are for a fixed-structure coaxial-duct OWC WEC, but the results are generalisable for floating structures. Results show a significant increase in mean annual power, and control strategies are proposed for power maximisation. Furthermore, some critical points are shown in the operational conditions' envelop for the system under a selected Portuguese wave climate. The identification of these critical values is important for the control of the OWC WECs. This study represents an advance in the control strategies considering multiple PTOs for a single OWC air chamber to foster innovation actions.","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"57 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115773294","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 present study considers the design optimisation of an Oscillating Water Column (OWC) incorporated into a pile-supported breakwater structure. This has been achieved by performing a substantial number of scaled physical model tests and a methodical variation of key device parameters within multiple configurations. The key aspects that have been investigated include: (a) the geometric characteristics of the breakwater structure, (b) the pneumatic efficiency of the OWC, (c) the geometry of the OWC chamber and (d) the relative position of the OWC chamber within the breakwater. The present work considers (monochromatic) regular waves of varying steepness and effective water depth as incident wave conditions. The efficiency of the designed structure in terms of shore protection capacity and wave energy extraction was assessed by quantifying relevant transmission coefficients and the power output metrics. This has been achieved by using a combination of collocated and complementary measuring devices, such as arrays of wave gauges, pressure transducers and a high-definition video camera. The study concluded that systematic refinement of the geometrical parameters can substantially enhance the overall hydrodynamic efficiency of a pile-supported OWC breakwater. Additionally, it was found that a configuration featuring a chamber positioned in front of the breakwater, with a relative chamber breadth of 0.67, outperforms wider breadth configurations in terms of both energy extraction efficiency and reduction of the transmission coefficient. Taken together, the present study provides an in-depth analysis of the effects of key design parameters of a breakwater-integrated OWC, its efficiency and shore protection potential.
{"title":"Experimental investigation on the hydrodynamic performance of a pile-supported OWC-type breakwater","authors":"Yusuf Almalki, I. Karmpadakis, Chris Swan","doi":"10.36688/ewtec-2023-549","DOIUrl":"https://doi.org/10.36688/ewtec-2023-549","url":null,"abstract":" The present study considers the design optimisation of an Oscillating Water Column (OWC) incorporated into a pile-supported breakwater structure. This has been achieved by performing a substantial number of scaled physical model tests and a methodical variation of key device parameters within multiple configurations. The key aspects that have been investigated include: (a) the geometric characteristics of the breakwater structure, (b) the pneumatic efficiency of the OWC, (c) the geometry of the OWC chamber and (d) the relative position of the OWC chamber within the breakwater. The present work considers (monochromatic) regular waves of varying steepness and effective water depth as incident wave conditions. The efficiency of the designed structure in terms of shore protection capacity and wave energy extraction was assessed by quantifying relevant transmission coefficients and the power output metrics. This has been achieved by using a combination of collocated and complementary measuring devices, such as arrays of wave gauges, pressure transducers and a high-definition video camera. The study concluded that systematic refinement of the geometrical parameters can substantially enhance the overall hydrodynamic efficiency of a pile-supported OWC breakwater. Additionally, it was found that a configuration featuring a chamber positioned in front of the breakwater, with a relative chamber breadth of 0.67, outperforms wider breadth configurations in terms of both energy extraction efficiency and reduction of the transmission coefficient. Taken together, the present study provides an in-depth analysis of the effects of key design parameters of a breakwater-integrated OWC, its efficiency and shore protection potential.","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117259584","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}
Christine Lynggard Hansen, H. Wolgamot, P. Taylor, J. Orszaghova, Adi Kurniawan, H. Bredmose
We present physical results for a Design Wave analysis of the M4 wave energy converter (WEC), whichis currently being developed for a kW scale deployment in King George Sound, off the coast of Albany, Western Australia. The M4 wave energy converter is a hinged multifloat device utilising relative pitch as the power-producing mode of motion. We have conducted wave basin experiments at the Australian Maritime College in Launceston, TAS Australia, at a scale of 1:15 compared to the ocean trial. We present an experimental analysis of the hinge rotation in a severe sea state identified for the King George Sound location. We identify the most extreme response of the hinge rotation and the wave that causes it – the so-called Design Wave. By averaging the largest structural responses measured in long irregular wave realisations of the extreme sea states, we identify the most likely extreme response.The Design Wave is found to be the average of the surface elevation signals occurring simultaneously with instances of the largest response. The Design Wave thus identified is then produced in the basin and the M4 response measured.
{"title":"Design Wave analysis of the M4 wave energy converter device","authors":"Christine Lynggard Hansen, H. Wolgamot, P. Taylor, J. Orszaghova, Adi Kurniawan, H. Bredmose","doi":"10.36688/ewtec-2023-476","DOIUrl":"https://doi.org/10.36688/ewtec-2023-476","url":null,"abstract":"We present physical results for a Design Wave analysis of the M4 wave energy converter (WEC), whichis currently being developed for a kW scale deployment in King George Sound, off the coast of Albany, Western Australia. The M4 wave energy converter is a hinged multifloat device utilising relative pitch as the power-producing mode of motion. We have conducted wave basin experiments at the Australian Maritime College in Launceston, TAS Australia, at a scale of 1:15 compared to the ocean trial. We present an experimental analysis of the hinge rotation in a severe sea state identified for the King George Sound location. We identify the most extreme response of the hinge rotation and the wave that causes it – the so-called Design Wave. By averaging the largest structural responses measured in long irregular wave realisations of the extreme sea states, we identify the most likely extreme response.The Design Wave is found to be the average of the surface elevation signals occurring simultaneously with instances of the largest response. The Design Wave thus identified is then produced in the basin and the M4 response measured.","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127233868","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}
N. Faedo, Y. Peña-Sanchez, E. Pasta, G. Papini, F. Mosquera, Francesco Ferri
It is already well-known that the vast energy available in ocean waves can provide a massive contribution towards effective decarbonisation. Nonetheless, due to the irregular reciprocating motion of ocean waves, convergence towards a single type of technology becomes rather difficult, and tailored research, aiming at ultimately providing reliable WEC systems, is still required to achieve commercialisation. Once a given concept is established, numerical models become almost automatically required for a (very) large variety of tasks, including e.g. dynamical and performance assessment, control technology, geometry optimisation, and mooring design, among others. Depending on the requirements associated with a specific task, different types of models are used, with very different levels of complexity (both computational and analytical) and fidelity. For instance, a fully nonlinear estimation of the hydrodynamic response of a WEC would often require high-fidelity numerical modelling techniques, based on e.g. computational fluid-dynamics (CFD), while control applications prefer analytical expressions able to capture the main underlying dynamics in a simplified form. Regardless of the associated complexity, validation is always required for the reliable utilisation of a specific model for a given application, with experimental validation being the most valuable tool to secure this objective. In recent years, different initiatives were put in place, aiming at the identification of numerical model accuracy through a set of widely available case studies. For instance, the OES-Task 10 has been running a number of experiments followed by blind numerical model validations for several single-body wave energy converters. While the proposed methodologies proved to be efficient, the cases under study are all focused on single-body devices. Since the sector is slowly approaching a pre-commercial stage, it is important to prove the capabilities of numerical models also for farm configurations which are, ultimately, the way in which WEC systems will be effectively deployed. Motivated by this, we present, in this paper, an overview of an experimental campaign performed at Aalborg University during the period of September-October 2021, where 8 different array layouts of up to 5 devices have been tested, using a 1:20 prototype of the Wavestar WEC system as a baseline device (see PDF file for reference). Data has been collected systematically for regular and irregular wave conditions, including e.g. free-surface elevation at different points in the wave tank (with 19 wave probes in place), effective wave excitation forces acting on each device and layout, and associated motion variables. Furthermore, each different layout has been also tested under (reactive) controlled conditions, providing experimental data on PTO forces and associated motion (i.e. under controlled conditions). The results of this experimental campaign will be available as part of an Open-Access da
{"title":"Overview of an experimental campaign for arrays of wave energy conversion systems","authors":"N. Faedo, Y. Peña-Sanchez, E. Pasta, G. Papini, F. Mosquera, Francesco Ferri","doi":"10.36688/ewtec-2023-379","DOIUrl":"https://doi.org/10.36688/ewtec-2023-379","url":null,"abstract":"It is already well-known that the vast energy available in ocean waves can provide a massive contribution towards effective decarbonisation. Nonetheless, due to the irregular reciprocating motion of ocean waves, convergence towards a single type of technology becomes rather difficult, and tailored research, aiming at ultimately providing reliable WEC systems, is still required to achieve commercialisation. \u0000Once a given concept is established, numerical models become almost automatically required for a (very) large variety of tasks, including e.g. dynamical and performance assessment, control technology, geometry optimisation, and mooring design, among others. Depending on the requirements associated with a specific task, different types of models are used, with very different levels of complexity (both computational and analytical) and fidelity. For instance, a fully nonlinear estimation of the hydrodynamic response of a WEC would often require high-fidelity numerical modelling techniques, based on e.g. computational fluid-dynamics (CFD), while control applications prefer analytical expressions able to capture the main underlying dynamics in a simplified form. \u0000Regardless of the associated complexity, validation is always required for the reliable utilisation of a specific model for a given application, with experimental validation being the most valuable tool to secure this objective. In recent years, different initiatives were put in place, aiming at the identification of numerical model accuracy through a set of widely available case studies. For instance, the OES-Task 10 has been running a number of experiments followed by blind numerical model validations for several single-body wave energy converters. While the proposed methodologies proved to be efficient, the cases under study are all focused on single-body devices. \u0000Since the sector is slowly approaching a pre-commercial stage, it is important to prove the capabilities of numerical models also for farm configurations which are, ultimately, the way in which WEC systems will be effectively deployed. Motivated by this, we present, in this paper, an overview of an experimental campaign performed at Aalborg University during the period of September-October 2021, where 8 different array layouts of up to 5 devices have been tested, using a 1:20 prototype of the Wavestar WEC system as a baseline device (see PDF file for reference). Data has been collected systematically for regular and irregular wave conditions, including e.g. free-surface elevation at different points in the wave tank (with 19 wave probes in place), effective wave excitation forces acting on each device and layout, and associated motion variables. Furthermore, each different layout has been also tested under (reactive) controlled conditions, providing experimental data on PTO forces and associated motion (i.e. under controlled conditions). The results of this experimental campaign will be available as part of an Open-Access da","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125945567","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}
Md Imran Ullah, Irina Temiz, Johan Forslund, Jessica Santos Döhler
Wave energy has been an immense area of interest in research and industry in our move towards a sustainable energy production society due to its high energy density and surface area. However, the grid connection of wave energy converters is still one of the major challenges due to the complexity of varying wave resources (amplitude and frequency). Wave energy converters grid integration can lead to several potential challenges, such as voltage fluctuations, harmonics and flicker. Using an energy storage system can help to mitigate few challenges by balancing the grid demand with the wave energy converter power supply. Hence, improving the power quality. This study assesses the power quality of wave energy converters equipped with energy storage against the scenario without any energy storage at different power levels. The power quality in this paper is investigated using total harmonic distortion (THD) of the grid current, dc-link voltage ripple and battery current ripple. The study shows that the addition of a hybrid energy storage system lowers the grid current THD at the point of common coupling (PCC), stabilizes the dc-link voltage ripple and reduces the stress of the battery.
{"title":"Power quality assessment of a wave energy converter using energy storage","authors":"Md Imran Ullah, Irina Temiz, Johan Forslund, Jessica Santos Döhler","doi":"10.36688/ewtec-2023-315","DOIUrl":"https://doi.org/10.36688/ewtec-2023-315","url":null,"abstract":"Wave energy has been an immense area of interest in research and industry in our move towards a sustainable energy production society due to its high energy density and surface area. However, the grid connection of wave energy converters is still one of the major challenges due to the complexity of varying wave resources (amplitude and frequency). Wave energy converters grid integration can lead to several potential challenges, such as voltage fluctuations, harmonics and flicker. Using an energy storage system can help to mitigate few challenges by balancing the grid demand with the wave energy converter power supply. Hence, improving the power quality. This study assesses the power quality of wave energy converters equipped with energy storage against the scenario without any energy storage at different power levels. The power quality in this paper is investigated using total harmonic distortion (THD) of the grid current, dc-link voltage ripple and battery current ripple. The study shows that the addition of a hybrid energy storage system lowers the grid current THD at the point of common coupling (PCC), stabilizes the dc-link voltage ripple and reduces the stress of the battery.","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"175 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126943274","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}
Riccardo Novo, G. Giorgi, G. Cervelli, N. Faedo, G. Mattiazzo
Driven by climate issues and geopolitical uncertainties, Europe faces the need to transform its energy supply dramatically and quickly. Various renewable technologies are proposed as a medium- to long-term solution for an environmentally and economically sustainable energy mix: among the available solutions, wave energy converters (WECs) are attracting growing interest due to the large untapped wave energy potential in European seas. In this context, the choice of optimal locations for the use of wave energy is fundamental to limit the technological gap with other fully developed conversion technologies, and to ensure competitive energy costs. In this paper, we compare different possible strategies to identify suitable sites for the installation of WECs, namely the one based on pure analysis of the wave energy resource, and that considering the productivity of the device in different sea states, i.e., its power matrix. Using the performance matrices of notional WECs, particularly an Oscillating Surge Wave Energy Converter (OSWEC) and a Heaving Point Absorber (HPA), we estimate optimal locations on the Italian coasts and highlight the advantages and disadvantages of the two approaches. The analysis shows the importance of a technology-based approach for the spatial planning of future wave power plants and highlights significant differences compared to the approach that can be used for the preliminary identification of sites for wind farms and, especially, for photovoltaic plants. We use the obtained results to introduce the MORE-EST platform, a novel web-based tool for straightforward estimation of wave resources and WECs productivity in European seas. The proposed platform is able to integrate information on wave resource assessment, bathymetry, marine space use and technological features, and represents a tool aimed at researchers, WECs developers, and policy makers.
{"title":"Identification of optimal sites for the deployment of wave energy converters: the importance of a technology-centred approach","authors":"Riccardo Novo, G. Giorgi, G. Cervelli, N. Faedo, G. Mattiazzo","doi":"10.36688/ewtec-2023-378","DOIUrl":"https://doi.org/10.36688/ewtec-2023-378","url":null,"abstract":"Driven by climate issues and geopolitical uncertainties, Europe faces the need to transform its energy supply dramatically and quickly. Various renewable technologies are proposed as a medium- to long-term solution for an environmentally and economically sustainable energy mix: among the available solutions, wave energy converters (WECs) are attracting growing interest due to the large untapped wave energy potential in European seas. In this context, the choice of optimal locations for the use of wave energy is fundamental to limit the technological gap with other fully developed conversion technologies, and to ensure competitive energy costs. In this paper, we compare different possible strategies to identify suitable sites for the installation of WECs, namely the one based on pure analysis of the wave energy resource, and that considering the productivity of the device in different sea states, i.e., its power matrix. Using the performance matrices of notional WECs, particularly an Oscillating Surge Wave Energy Converter (OSWEC) and a Heaving Point Absorber (HPA), we estimate optimal locations on the Italian coasts and highlight the advantages and disadvantages of the two approaches. The analysis shows the importance of a technology-based approach for the spatial planning of future wave power plants and highlights significant differences compared to the approach that can be used for the preliminary identification of sites for wind farms and, especially, for photovoltaic plants. We use the obtained results to introduce the MORE-EST platform, a novel web-based tool for straightforward estimation of wave resources and WECs productivity in European seas. The proposed platform is able to integrate information on wave resource assessment, bathymetry, marine space use and technological features, and represents a tool aimed at researchers, WECs developers, and policy makers.","PeriodicalId":201789,"journal":{"name":"Proceedings of the European Wave and Tidal Energy Conference","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115083163","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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