The Experts below are selected from a list of 951 Experts worldwide ranked by ideXlab platform
J A Rossiter - One of the best experts on this subject based on the ideXlab platform.
-
overcoming fundamental limitations of wind turbine individual Blade pitch control with inflow sensors
Wind Energy, 2018Co-Authors: Ll B Jones, Wai Hou Lio, J A RossiterAbstract:Individual pitch control (IPC) provides an important means of attenuating harmful fatigue and extreme loads upon the load bearing structures of a wind turbine. Conventional IPC architectures determine the additional pitch demand signals required for load mitigation in response to measurements of the flap-wise Blade-Root Bending moments. However, the performance of such architectures is fundamentally limited by bandwidth constraints imposed by the Blade dynamics. Seeking to overcome this problem, we present a simple solution based upon a local Blade inflow measurement on each Blade. Importantly, this extra measurement enables the implementation of an additional cascaded feedback controller that overcomes the existing IPC performance limitation and hence yields significantly improved load reductions. Numerical demonstration upon a high-fidelity and nonlinear wind turbine model reveals (i) 60% reduction in the amplitude of the dominant 1P fatigue loads, and (ii) 59% reduction in the amplitude of extreme wind shear induced Blade loads, compared to a conventional IPC controller with the same robust stability margin. This paper therefore represents a significant alternative to wind turbine IPC load mitigation as compared to LiDAR-based feedforward control approaches.
Vengatesan Venugopal - One of the best experts on this subject based on the ideXlab platform.
-
assessing extreme loads on a tidal turbine using focused wave groups in energetic currents
Renewable Energy, 2019Co-Authors: Samuel Draycott, Anup Nambiar, Brian Sellar, Thomas Davey, Vengatesan VenugopalAbstract:Abstract Tidal stream turbines are subject to large hydrodynamic loads, including those induced by extreme waves. Scale model testing in the laboratory plays an important role in ensuring that full scale tidal turbines are designed and operated in a manner that is appropriate for harsh ocean environments where waves and tidal currents coexist. For the first time, a fully-instrumented scaled tidal turbine is tested in short-duration focused wave groups representative of extreme environmental load cases expected at energetic tidal sites. In this paper, the subsequent variations in rotor-based loads, power and Blade Root Bending moments are reported. These measurements are found to strongly follow the spectral and temporal form of the focused wave conditions, and peak loads and power output are found to exceed current-only values by 85% and 200% respectively. These rotor-averaged values display a high level of repeatability, demonstrating the suitability of focused waves for testing seabed-mounted tidal turbines. Extreme Blade loads, which are dependent on angular position relative to wave phase, are captured through rapidly obtained repeat tests. New insight is subsequently gained into loading and response of tidal turbines in extreme sea conditions.
Allmark Matthew - One of the best experts on this subject based on the ideXlab platform.
-
A Phenomenological Study of Lab-Scale Tidal Turbine Loading under Combined Irregular Wave and Shear Flow Conditions
'MDPI AG', 2021Co-Authors: Allmark Matthew, Lloyd Catherine, Ordonez-sanchez Stephanie, Martinez Rodrigo, O’doherty Tim, Germain Gregory, Gaurier Benoit, Johnstone CameronAbstract:Tidal devices are likely to faced with shear flows and subjected to various wave climates. The paper presents an experimental study of the combined impacts of shear profile and irregular waves on the loading of a 1/20th scale device operating at peak power extraction. The experiments presented were conducted at various depths to facilitate analysis of the effects of the shear flow and wave impact on the device at various positions in the water column. The fluid field was measured at three different upstream positions and at three depths (top, middle and bottom of the rotor) for each experiment; in doing so, data from the device were captured three times. The fluid measurements were of a high quality and were analysed to present the structure flow upstream of the device, which contained velocity and turbulence profiles. The upstream measurement was utilised to understand the development of flow structures in the approach to the device, and the impact of the flow structures measured was confirmed via cross-covariance calculations. The long datasets gathered were used to produce full rotational probability density functions for the Blade-Root-Bending moments for three Blades. The spectral characteristics were also considered, and showed that rotor loading quantities are less reactive to smaller scale flow structures
-
A detailed study of tidal turbine power production and dynamic loading under grid generated turbulence and turbine wake operation
'Elsevier BV', 2020Co-Authors: Allmark Matthew, Ellis Robert, Ebdon Tim, Lloyd Catherine, Ordonez-sanchez Stephanie, Martinez Rodrigo, Mason-jones Allan, Johnstone Cameron, O'doherty TimAbstract:The paper presents an experimental campaign developed to contribute to the current research considering the operation of Horizontal Axis Tidal Turbines within stochastic flow conditions, namely turbulent and wake induced flows. The campaign was conducted at approximately a 1/20th -scale within a recirculating flume. Experiments were conducted over five differing setups, yielding a baseline low Turbulence Intensity case, two high turbulence cases and two upstream device generated wake cases. The experiments were conducted at a range of differing rotor velocities established, in a novel way, by utilising both fixed speed and fixed braking torque control. The paper presents analysis of flow measurements to statistically quantify the stochastic flow conditions impinging on the model-scale tidal turbine. The power, thrust, torque and Blade Root Bending moment of single Blade were recorded and analysed against the flow conditions generated under the five cases. The analysis showed that it may well be possible to exploit the accelerated region around an upstream turbine to capture marginally higher power (6 % increase) from downstream turbines. Lastly, it was found that the control scheme adopted has a significant impact on power and load fluctuations observed at differing rotor velocities
-
The development, design and characterisation of a scale model horizontal axis tidal turbine for dynamic load quantification
'Elsevier BV', 2020Co-Authors: Allmark Matthew, Ellis Robert, Lloyd Catherine, Ordonez-sanchez Stephanie, Johnstone Cameron, Johannesen Kate, Byrne Carlton, O'doherty Timothy, Mason-jones AllanAbstract:The paper describes the development and characterisation of three 0.9 m diameter lab-scale Horizontal Axis Tidal Turbines. The Blade development process has been outlined and was used to generate a design specification. Each turbine houses instrumentation to measure rotor thrust, torque and Blade Root Bending moments on each Blade, in both `flapwise' and `edgewise' directions. A permanent magnet synchronous machine and encoder are integrated to allow for servo-control of the turbine as well as to provide position and rotational velocity measurements, resulting in three turbines that can be individually controlled using speed or torque control. Analogue signals are captured via a real-time operating system and field programmable gate array hardware architecture facilitating sample rates of up to 2 kHz. Results from testing the pilot turbine at three differing facilities during the development process are presented. Here good agreement, less than 7% variation, was found when comparing the testing undertaken at various flume and tow tank facilities. Lastly, the findings of a test campaign to characterise the performance of each of the three turbines are presented. Very good agreement in non-dimensional values for each of the three manufactured turbines was found
-
Analysis of the effects of control strategies and wave climates on the loading and performance of a laboratory scale horizontal axis tidal turbine.
'Elsevier BV', 2020Co-Authors: Martinez Rodrigo, Allmark Matthew, Lloyd Catherine, Ordonez-sanchez Stephanie, O'doherty Timothy, Germain Gregory, Gaurier Benoit, Johnestone CameronAbstract:To understand the influence of complex hydrodynamic loads on tidal turbines, laboratory testing is necessary as a first approach. Previous laboratory work undertaken gave an indication that the use of speed control strategies may disguise the associated loading range that a turbine may be subjected to when this is operated with a variable speed control strategy. However, the preceding work was undertaken in a highly controlled environment without the influence of turbulent flows. The focus of this paper is directed towards the study of wave-induced loads on tidal turbines when these are controlled using two strategies and the impact that these parameters have on the turbine’s performance when this is operated in a recirculating flume. Laboratory tests were undertaken with a 0.9 m diameter horizontal axis tidal turbine subjected to combined wave and current conditions with both regular and irregular waves. Constant speed and constant torque control strategies have been considered, for which rotor thrust, torque and Blade Root Bending moment have been measured. Results show that similar to previous studies, average loads and power capture values remain unchanged between control strategies and the superposition of waves to the current. However, signal fluctuations are 2 to 3 times higher for torque control than for constant speed control strategy. A phase difference between the periodic signals of the turbine thrust and the incoming waves was also identified, in this case, the phase variation was lower when using torque than speed control. This work thus demonstrates the implication of studying strategies to control a marine converter from early stages of development
A Sharma - One of the best experts on this subject based on the ideXlab platform.
-
A Novel Dual-Rotor Turbine for Increased Wind Energy Capture
2020Co-Authors: A Rosenberg, S Selvaraj, A SharmaAbstract:Abstract. Horizontal axis wind turbines suffer from aerodynamic inefficiencies in the Blade Root region (near the hub) due to several non-aerodynamic constraints. Aerodynamic interactions between turbines in a wind farm also lead to significant loss of wind farm efficiency. A new dual-rotor wind turbine (DRWT) concept is proposed that aims at mitigating these two losses. A DRWT is designed that uses an existing turbine rotor for the main rotor, while the secondary rotor is designed using a high lift-to-drag ratio airfoil. Reynolds Averaged NavierStokes computational fluid dynamics simulations are used to optimize the design. Large eddy simulations confirm the increase energy capture potential of the DRWT. Wake comparisons however do not show enhanced entrainment of axial momentum. Introduction A single-rotor horizontal axis wind turbine (HAWT) can capture a maximum of 59.3% of the flow energy passing through the turbine rotor disk. This remarkable result can be derived by applying mass, momentum, and energy conservations laws across a rotor disk assuming the flow to be one-dimensional, steady, and incompressible. This limit was found at around the same time by Albert Betz, Frederick Lanchester, and Nikolay Zhukovsky, but is now referred to simply as the Betz limit. It should be emphasized that this limit assumes the turbine to have a single, un-ducted rotor. On one hand, this limit can be easily surpassed if multiple rotors, or ducted rotors are employed. On the other hand, the Betz limit of achieving 59.3% aerodynamic efficiency is not realizable by any real single-rotor, finite-Bladed, un-ducted HAWT. Physical laws and other constraints limit the efficiency to be no greater than around 53% (see Maximum C P of modern utility-scale HAWT's is only a few percentage points short of this practical limit. A good portion of this shortfall is due to aerodynamic losses in Blade Root region. Rotor Blades in the Root region (approximately bottom 25% of a rotor) is designed to withstand Blade Root Bending moments. For structural integrity, relatively thick (high thickness-to-chord ratio) airfoils are chosen in the Root region, which are aerodynamically poor. Flow separation in the Root region causes span-wise (cross) flow, which deteriorates the aerodynamic performance of the outboard Blade sections as well. Blade thickness, twist, and chord in the Root region ar
-
This content has been downloaded from IOPscience. Please scroll down to see the full text. A Novel Dual-Rotor Turbine for Increased Wind Energy Capture A Novel Dual-Rotor Turbine for Increased Wind Energy Capture
2020Co-Authors: A Rosenberg, S Selvaraj, A SharmaAbstract:Abstract. Horizontal axis wind turbines suffer from aerodynamic inefficiencies in the Blade Root region (near the hub) due to several non-aerodynamic constraints. Aerodynamic interactions between turbines in a wind farm also lead to significant loss of wind farm efficiency. A new dual-rotor wind turbine (DRWT) concept is proposed that aims at mitigating these two losses. A DRWT is designed that uses an existing turbine rotor for the main rotor, while the secondary rotor is designed using a high lift-to-drag ratio airfoil. Reynolds Averaged NavierStokes computational fluid dynamics simulations are used to optimize the design. Large eddy simulations confirm the increase energy capture potential of the DRWT. Wake comparisons however do not show enhanced entrainment of axial momentum. Introduction A single-rotor horizontal axis wind turbine (HAWT) can capture a maximum of 59.3% of the flow energy passing through the turbine rotor disk. This remarkable result can be derived by applying mass, momentum, and energy conservations laws across a rotor disk assuming the flow to be one-dimensional, steady, and incompressible. This limit was found at around the same time by Albert Betz, Frederick Lanchester, and Nikolay Zhukovsky, but is now referred to simply as the Betz limit. It should be emphasized that this limit assumes the turbine to have a single, un-ducted rotor. On one hand, this limit can be easily surpassed if multiple rotors, or ducted rotors are employed. On the other hand, the Betz limit of achieving 59.3% aerodynamic efficiency is not realizable by any real single-rotor, finite-Bladed, un-ducted HAWT. Physical laws and other constraints limit the efficiency to be no greater than around 53% (see Maximum C P of modern utility-scale HAWT's is only a few percentage points short of this practical limit. A good portion of this shortfall is due to aerodynamic losses in Blade Root region. Rotor Blades in the Root region (approximately bottom 25% of a rotor) is designed to withstand Blade Root Bending moments. For structural integrity, relatively thick (high thickness-to-chord ratio) airfoils are chosen in the Root region, which are aerodynamically poor. Flow separation in the Root region causes span-wise (cross) flow, which deteriorates the aerodynamic performance of the outboard Blade sections as well. Blade thickness, twist, and chord in the Root region ar
Ll B Jones - One of the best experts on this subject based on the ideXlab platform.
-
overcoming fundamental limitations of wind turbine individual Blade pitch control with inflow sensors
Wind Energy, 2018Co-Authors: Ll B Jones, Wai Hou Lio, J A RossiterAbstract:Individual pitch control (IPC) provides an important means of attenuating harmful fatigue and extreme loads upon the load bearing structures of a wind turbine. Conventional IPC architectures determine the additional pitch demand signals required for load mitigation in response to measurements of the flap-wise Blade-Root Bending moments. However, the performance of such architectures is fundamentally limited by bandwidth constraints imposed by the Blade dynamics. Seeking to overcome this problem, we present a simple solution based upon a local Blade inflow measurement on each Blade. Importantly, this extra measurement enables the implementation of an additional cascaded feedback controller that overcomes the existing IPC performance limitation and hence yields significantly improved load reductions. Numerical demonstration upon a high-fidelity and nonlinear wind turbine model reveals (i) 60% reduction in the amplitude of the dominant 1P fatigue loads, and (ii) 59% reduction in the amplitude of extreme wind shear induced Blade loads, compared to a conventional IPC controller with the same robust stability margin. This paper therefore represents a significant alternative to wind turbine IPC load mitigation as compared to LiDAR-based feedforward control approaches.