A CFD Simulation of a Ducted Wind Turbine With Ejector Assist

2012 ◽  
Author(s):  
Demos P. Georgiou ◽  
Kypros F. Milidonis ◽  
Nikolaos G. Theodoropoulos
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Cfd Simulation ◽  
Poor Performance ◽  
Turbine Plant ◽  
Commercial Use ◽  
The Past ◽  
The Poor ◽  
Commercial Code ◽  
The Subject

Ducted Wind Turbines have been the subject of numerous studies in the past (both analytic and experimental), but the concept has not found commercial use so far, mainly due to the poor performance of the tested configurations. Our analytical studies, however, have shown that an optimized configuration of a Ducted Wind Turbine with ejector type assist for the exhaust may generated Power Coefficients of the order of CP = 6. This corresponds to the output of nearly 15 conventional un-ducted wind Turbines (with a typical CP = 0.4). The present study simulates the Two Dimensional simplification of such a Wind Turbine Plant by employing the commercial code FLUENT and compares its performance against the case of an open (no turbine) duct.

Fast CFD Simulation of Horizontal Axis Wind Turbines

2010 ◽  
Author(s):  
Fabio De Bellis ◽  
Luciano A. Catalano ◽  
Andrea Dadone
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Cfd Simulation ◽  
Flow Distribution ◽  
Horizontal Axis ◽  
Wall Functions ◽  
Mesh Topology ◽  
Numerical Predictions ◽  
Horizontal Axis Wind Turbines ◽  
Time Required

The numerical simulation of horizontal axis wind turbines (HAWT) has been analysed using computational fluid dynamics (CFD) with the aim of obtaining reliable but at the same time affordable wind turbine simulations, while significantly reducing required overall resources (time, computational power, user skills), for example in an optimization perspective. Starting from mesh generation, time required to extract preliminary aerodynamic predictions of a wind turbine blade has been shortened by means of some simplifications, i.e.: fully unstructured mesh topology, reduced grid size, incompressible flow assumption, use of wall functions, commercial available CFD package employment. Ansys Fluent software package has been employed to solve Reynolds Averaged Navier Stokes (RANS) equations, and results obtained have been compared against NREL Phase VI campaign data. The whole CFD process (pre-processing, processing, postprocessing) has been analysed and the chosen final settings are the result of a trade-off between numerical accuracy and required resources. Besides the introduced simplifications, numerical predictions of shaft torque, forces and flow distribution are in good agreement with experimental data and as accurate as those calcuted by other more sophisticated works.

Some Actuarial Aspects of Unemployment Insurance

1929 ◽  
Vol 60 (2) ◽  
pp. 103-160
Author(s):  
J. G. Kyd ◽  
G. H. Maddex
Keyword(s):  
Unemployment Insurance ◽  
Public Interest ◽  
Early Years ◽  
Royal Commission ◽  
Poor Laws ◽  
The Past ◽  
The Poor ◽  
National Insurance ◽  
The Subject ◽  
The Government

Judged by the amount of space devoted to the subject in the Journal of the Institute, Unemployment Insurance has received but little attention from actuaries in the past Public interest in the problem of relieving distress due to unemployment became pronounced in the early years of the present century and led to the appointment in 1904 of a Royal Commission on the Poor Laws and, eventually, to the passing in 1911 of the first Unemployment Insurance Act. These important events found a somewhat pallid reflection in our proceedings in the form of reprints of extracts from Sir H. Llewellyn Smith's address on Insurance against Unemployment to the British Association in 1910 (J.I.A., vol. xliv, p. 511) and of Mr. Ackland's report on Part II of the National Insurance Bill (J.I.A., vol. xlv, p. 456). At a later date, when the scope of the national scheme was very greatly widened, the Government Actuary's report on the relevant measure—the Unemployment Insurance Bill 1919—was reprinted in the Journal (J.I.A., vol. lii, page 72).

scholarly journals Maintenance Grouping Optimization for Offshore Wind Turbine Considering Opportunities Based on Rolling Horizon Approach

2018 ◽  
Vol 25 (2) ◽  
pp. 123-131 ◽  
Author(s):  
Yang Lua ◽  
Liping Suna ◽  
Jichuan Kanga ◽  
Xinyue Zhang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Poor Performance ◽  
Offshore Wind ◽  
Maintenance Cost ◽  
Offshore Wind Turbine ◽  
Rolling Horizon ◽  
Imperfect Maintenance ◽  
Opportunistic Maintenance ◽  
Maintenance Schedule

Abstract In future, offshore wind turbines may be consider a crucial part in the supply of energy. Maintenance processes are directed to attain a safe and reliable operation of offshore machines and wind turbines. In this paper, an opportunistic maintenance strategy for offshore wind turbine is proposed, considering imperfect maintenance and the preventive maintenance durations. Reliability Centric Maintenance serves as a proactive tactic to operations and maintenance by inhibiting the possible reasons of poor performance and controlling failures. Other components can implement the opportunistic preventive maintenances if one component has reached its reliability threshold. According to the rolling horizon approach, it is of great importance to update the maintenance planning for the sake of the short-term information. By figuring out the best combination, the maintenance schedule in the mission time has been finally determined. Failure information are obtained from previous studies to accomplish the calculations. The outcomes indicate that the maintenance cost has been dramatically reduced through the application of opportunistic maintenance.

EDWIN CHADWICK'S SELF-FASHIONING: PROFESSIONALISM, MASCULINITY, AND THE VICTORIAN POOR

2004 ◽  
Vol 32 (2) ◽  
pp. 353-370 ◽  
Author(s):  
Priti Joshi
Keyword(s):  
Public Health ◽  
Great Britain ◽  
Legislative Politics ◽  
The Past ◽  
Sanitary Condition ◽  
The Poor ◽  
The Subject ◽  
Post War ◽  
First Time ◽  
Scholarly Attention

IN THE PAST DECADE EDWIN CHADWICKhas been the subject of several scholarly inquiries; indeed one can almost speak of a “Chadwick industry” these days. This is not, however, the first time he has attracted significant scholarly attention: in 1952, S. E. Finer's and R. A. Lewis's biographies initiated our century's first evaluation of him, culminating in M. W. Flinn's excellently edited reprint of Chadwick's most important text,The Report on the Sanitary Condition of the Labouring Population of Great Britain(referred to as theSanitary Report). Yet the Chadwick that emerges in recent accounts could not be more different from the mid-century Chadwick. The post-war critics saw him as a visionary, an often-embattled crusader for public health whose enemies were formidable but whose vision, extending the liberal and radical tradition, ultimately prevailed. Cultural critics, on the other hand, present a Chadwick who misrepresented (if not outright oppressed) the poor and who was instrumental in developing a massive bureaucracy to police their lives. Thus, while earlier accounts highlighted Chadwick's accomplishments, the progress of public health reforms, and the details of legislative politics, more recent ones draw attention to his representations of the poor, the erasures in his text, and the growing nineteenth-century institutionalization of the poor that theSanitary Reportpromotes. Chadwick, in other words, is portrayed as either a pioneer of reform or an avatar of bureaucratic oppression.

scholarly journals Results from a wake-steering experiment at a commercial wind plant: investigating the wind speed dependence of wake-steering performance

2021 ◽  
Vol 6 (6) ◽  
pp. 1427-1453
Author(s):  
Eric Simley ◽  
Paul Fleming ◽  
Nicolas Girard ◽  
Lucas Alloin ◽  
Emma Godefroy ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Direction ◽  
Wind Farm ◽  
Poor Performance ◽  
Power Production ◽  
Wind Rose ◽  
Wind Speeds ◽  
Variability Model

Abstract. Wake steering is a wind farm control strategy in which upstream wind turbines are misaligned with the wind to redirect their wakes away from downstream turbines, thereby increasing the net wind plant power production and reducing fatigue loads generated by wake turbulence. In this paper, we present results from a wake-steering experiment at a commercial wind plant involving two wind turbines spaced 3.7 rotor diameters apart. During the 3-month experiment period, we estimate that wake steering reduced wake losses by 5.6 % for the wind direction sector investigated. After applying a long-term correction based on the site wind rose, the reduction in wake losses increases to 9.3 %. As a function of wind speed, we find large energy improvements near cut-in wind speed, where wake steering can prevent the downstream wind turbine from shutting down. Yet for wind speeds between 6–8 m/s, we observe little change in performance with wake steering. However, wake steering was found to improve energy production significantly for below-rated wind speeds from 8–12 m/s. By measuring the relationship between yaw misalignment and power production using a nacelle lidar, we attribute much of the improvement in wake-steering performance at higher wind speeds to a significant reduction in the power loss of the upstream turbine as wind speed increases. Additionally, we find higher wind direction variability at lower wind speeds, which contributes to poor performance in the 6–8 m/s wind speed bin because of slow yaw controller dynamics. Further, we compare the measured performance of wake steering to predictions using the FLORIS (FLOw Redirection and Induction in Steady State) wind farm control tool coupled with a wind direction variability model. Although the achieved yaw offsets at the upstream wind turbine fall short of the intended yaw offsets, we find that they are predicted well by the wind direction variability model. When incorporating the expected yaw offsets, estimates of the energy improvement from wake steering using FLORIS closely match the experimental results.

scholarly journals Results from a Wake Steering Experiment at a Commercial Wind Plant: Investigating the Wind Speed Dependence of Wake Steering Performance

2021 ◽  
Author(s):  
Eric Simley ◽  
Paul Fleming ◽  
Nicolas Girard ◽  
Lucas Alloin ◽  
Emma Godefroy ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Direction ◽  
Wind Farm ◽  
Poor Performance ◽  
Power Production ◽  
Wind Rose ◽  
Wind Speeds ◽  
Variability Model

Abstract. Wake steering is a wind farm control strategy in which upstream wind turbines are misaligned with the wind to redirect their wakes away from downstream turbines, thereby increasing the net wind plant power production and reducing fatigue loads generated by wake turbulence. In this paper, we present results from a wake steering experiment at a commercial wind plant involving two wind turbines spaced 3.7 rotor diameters apart. During the three-month experiment period, we estimate that wake steering reduced wake losses by 5.7 % for the wind direction sector investigated. After applying a long-term correction based on the site wind rose, the reduction in wake losses increases to 9.8 %. As a function of wind speed, we find large energy improvements near cut-in wind speed, where wake steering can prevent the downstream wind turbine from shutting down. Yet for wind speeds between 6–8 m/s, we observe little change in performance with wake steering. However, wake steering was found to improve energy production significantly for below-rated wind speeds from 8–12 m/s. By measuring the relationship between yaw misalignment and power production using a nacelle lidar, we attribute much of the improvement in wake steering performance at higher wind speeds to a significant reduction in the power loss of the upstream turbine as wind speed increases. Additionally, we find higher wind direction variability at lower wind speeds, which contributes to poor performance in the 6–8 m/s wind speed bin because of slow yaw controller dynamics. Further, we compare the measured performance of wake steering to predictions using the FLORIS (FLOw Redirection and Induction in Steady State) wind farm control tool coupled with a wind direction variability model. Although the achieved yaw offsets at the upstream wind turbine fall short of the intended yaw offsets, we find that they are predicted well by the wind direction variability model. When incorporating the predicted achieved yaw offsets, estimates of the energy improvement from wake steering using FLORIS closely match the experimental results.

scholarly journals CFD SIMULATION AND VISUALIZATION BASED INVESTIGATION OF SMALL WIND TURBINE POTENTIAL: A CASE STUDY “NEUER STÖCKACH” FOR STUTTGART

2021 ◽  
Vol VIII-4/W1-2021 ◽  
pp. 17-24
Author(s):  
M. Brennenstuhl ◽  
M. von der Gruen ◽  
S. Harbola ◽  
A. Koukofikis ◽  
R. Padsala ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Urban Areas ◽  
Cfd Simulation ◽  
Low Voltage ◽  
Global Radiation ◽  
Energy Transition ◽  
Small Wind Turbine ◽  
Energy Concept ◽  
Small Wind Turbines

Abstract. In the face of climate change and the energy transition that the German federal government is aiming for, all renewable energy potentials need to be tapped. Unfortunately, small wind turbines play a niche role in Germany and most other countries despite the fact, that although they offer advantages as e.g. almost seasonal independent energy production in close proximity to the consumer on the same low-voltage grid level. One reason beside the lower wind speeds that can be expected closer to the ground is, that in comparison to PV (photovoltaic), for which good yield forecasts can be made using global radiation measurements from nearby weather stations or online databases, the yield of small wind turbines, especially in urban areas, can only be forecasted using on-site measurements due to the influence of the surrounding buildings and topography. This method is time-consuming and costly. To address this, within this work a Computational Fluid Dynamics (CFD) simulation based visualization framework for the investigation of the small wind turbine potential is presented. In this specific case the energy supply company EnBW is planning to refurbish the “Neuer Stöckach” urban quarter on the former “Stöckach” company site. As part of the redevelopment, a comprehensive energy concept is planned to integrate renewable energies. In this context the integration of small wind turbines into the energy concept is examined according to this new methodology.

Operational Model Updating of Low-Order HAWT Models for Structural Health Monitoring Applications

2013 ◽  
Author(s):  
Antonio Velazquez ◽  
R. Andrew Swartz
Keyword(s):  
Global Optimization ◽  
Structural Health Monitoring ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Health Monitoring ◽  
Model Updating ◽  
Structural Health ◽  
The Past ◽  
Operation Conditions ◽  
Computer Aided

For the past decade, wind turbines have become the largest source of installed renewable-energy capacity in the United States. Economical, maintenance and operation are critical issues when dealing with such large slender structures, particularly when these structures are sited remotely. Because of the chaotic nature of non-stationary rotating-machinery systems such as the horizontal-axis wind turbines (HAWTs), in-operation modeling and computer-aided numerical characterization is typically troublesome, and tends to be imprecise while predicting the real content of the actual aerodynamic loading. Loading environment under operation conditions is usually substantially different from those driven by modal testing or computer-aided model characterization and difficult to measure directly in the field. In addition, rotational machinery such as HAWTs exhibit complex and nonlinear dynamics (i.e., precession and Coriolis effects, torsional coupling, nonlinear geometries, plasticity of composite materials); and are subjected to nonlinear constrained conditions (i.e., aeroelastic interaction). For those reasons, modal-aeroelastic and computer-aided models reproduced under controlled conditions may fail to predict the correct non-stationary loading and resistance patterns of wind turbines in actual operation. Operational techniques for extracting modal properties under actual non-stationary loadings are needed in order to (1) improve computer-aided elasto-aerodynamic models to better characterize the actual behavior of HAWTs in operational scenarios, (2) improve and correlate models, (3) monitor and diagnose the system for integrity and damage through time, or even (4) optimize control systems. For structural health monitoring (SHM) applications, model updating of stochastic aerodynamic problems has gained interest over the past decades. For situations where optimizing objective functions are not differentiable, convex or continuous in nature that is the case of gradient methods such as Modal Assurance Criterion (MAC), global optimization (metaheurstic) methods based on probability principles have emerged. These search engine techniques are promising suitable to cope with non-stationary-stochastic system identification methods for model updating of HAWT systems. A probability theory framework is employed in this study to update the wind turbine model using such a stochastic global optimization approach. Structural identification is addressed under regular wind turbine operation conditions for non-stationary, unmeasured, and uncontrolled excitations by means of the eigensystem realization theory (ERA). This numerical framework is then tied up with an adaptive simulated annealing (ASA) numerical engine for solving the problem of model updating. Numerical results are presented for an experimental deployment of a small HAWT structure. Results are benchmarked and validated with other empirical mode-decomposition and time-domain solutions.

scholarly journals Design and Fabrication of Multi-Rotor Horizontal Axis Wind Turbine

2019 ◽  
Vol 8 (6) ◽  
pp. 3500-3504 ◽  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Poor Performance ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Wind Speeds ◽  
Start Up ◽  
Overall Performance ◽  
Low Wind Speeds ◽  
The Cost

Wind is an endless resource which is abundantly found in nature. Harnessing wind energy for producing electricity is one of the ways for buildings for a sustainable future. Small-scale wind turbines could be a reliable energy source for usage in homes and in autonomous applications in locations that are far away from the grid power. Small wind turbines operating at low wind speeds regularly face the problem of poor performance due to small rotor size. To increase the power production additional wind turbines are installed. This increases the overall cost of the project. To reduce the cost and to improve the efficiency, multiple rotors are connected through a single shaft to the fixed single generator. The Implementation of this design permits start up at lower wind speeds, increasing the start-up torque and thus improving the overall performance of the turbine. This paper elaborates the design and fabrication of such a wind turbine. [1] [2] [3]

Aerodynamic Analysis of a Wind Turbine With Elevated Inflow Turbulence and Wake Using Harmonic Method

2019 ◽  
Author(s):  
Shine Win Naung ◽  
Mohammad Rahmati ◽  
Hamed Farokhi
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Cfd Simulation ◽  
Pressure Coefficient ◽  
Computational Cost ◽  
Frequency Domain Method ◽  
Wind Flow ◽  
Horizontal Axis Wind Turbine ◽  
Aerodynamic Analysis ◽  
Cfd Method

Abstract This paper presents aerodynamic simulation and analysis of a horizontal axis wind turbine using Computational Fluid Dynamics (CFD) method. The MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine is selected for simulation as the experimental data are available and can be used for validation of the CFD model used. CFD method has been used by a number of studies to predict aerodynamic behaviour of wind turbines. However, the majority of studies consider a steady wind flow at the inlet. Sometimes this is not the case when the wind flow is not steady or there are other wind turbines nearby. In this paper, the steady simulations are first conducted using different turbulence models without considering inflow wake at the inlet. Afterwards, a harmonic wake is generated at the inlet and unsteady CFD simulation is performed. Unsteady CFD simulation usually requires long runtime and therefore harmonic (frequency domain) method, which is an efficient computational method to study unsteady periodic flow at a computational cost in the order of steady-state solutions, is used for unsteady computation in this study. This paper first discusses the pressure coefficient distributions with and without harmonic wake at the inlet and compares them against the experiment. Afterwards the detailed analysis of flow around the blade subject to the unsteady harmonic wake is conducted in the meridional view and the blade-to-blade view. Next, the effect of pressure distribution on the blade structure is briefly discussed. Finally this paper concludes based on the results from the aerodynamic analysis as well as the analysis of the effect of aerodynamic loads on the blade structure.

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