scholarly journals A review of wind turbine main-bearings: design, operation, modelling, damage mechanisms and fault detection

2019 ◽  
Author(s):  
Edward Hart ◽  
Benjamin Clarke ◽  
Gary Nicholas ◽  
Abbas Kazemi Amiri ◽  
James Stirling ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Power Plants ◽  
Critical Role ◽  
Complete Removal ◽  
Turbine Rotor ◽  
Theory And Practice ◽  
Future Research ◽  
Main Bearing ◽  
Operational Conditions ◽  
Fault Diagnosis And Prognosis

Abstract. This paper presents a review of existing theory and practice relating to main-bearings for wind turbines. The mainbearing performs the critical role of supporting the turbine rotor, with replacements typically requiring its complete removal. The operational conditions and loading for wind turbine main-bearings deviate significantly from those of more conventional power plants and other bearings present in the wind turbine power-train, i.e. those in the gearbox and generator. This work seeks to thoroughly document current main-bearing theory in order to allow for appraisal of existing design and analysis practices, while also seeking to form a solid foundation for future research in this area. The most common main-bearing setups are presented along with standards for bearing selection and rating. Typical loads generated by a wind turbine rotor, and subsequently reacted at the main-bearing, are discussed. This is followed by the related tribological theories of lubrication, wear and associated failure mechanisms. Finally, existing techniques for bearing modeling, fault diagnosis and prognosis relevant to the main-bearing are presented.

scholarly journals A review of wind turbine main bearings: design, operation, modelling, damage mechanisms and fault detection

2020 ◽  
Vol 5 (1) ◽  
pp. 105-124 ◽  
Author(s):  
Edward Hart ◽  
Benjamin Clarke ◽  
Gary Nicholas ◽  
Abbas Kazemi Amiri ◽  
James Stirling ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Power Plants ◽  
Critical Role ◽  
Complete Removal ◽  
Turbine Rotor ◽  
Theory And Practice ◽  
Future Research ◽  
Main Bearing ◽  
Operational Conditions ◽  
Fault Diagnosis And Prognosis

Abstract. This paper presents a review of existing theory and practice relating to main bearings for wind turbines. The main bearing performs the critical role of supporting the turbine rotor, with replacements typically requiring its complete removal. The operational conditions and loading for wind turbine main bearings deviate significantly from those of more conventional power plants and other bearings present in the wind turbine power train, i.e. those in the gearbox and generator. This work seeks to thoroughly document current main-bearing theory in order to allow for appraisal of existing design and analysis practices, while also seeking to form a solid foundation for future research in this area. The most common main-bearing setups are presented along with standards for bearing selection and rating. Typical loads generated by a wind turbine rotor, and subsequently reacted at the main bearing, are discussed. This is followed by the related tribological theories of lubrication, wear and associated failure mechanisms. Finally, existing techniques for bearing modelling, fault diagnosis and prognosis relevant to the main bearing are presented.

scholarly journals Enhancement of Free Vortex Filament Method for Aerodynamic Loads on Rotor Blades

2014 ◽  
Author(s):  
Hamidreza Abedi ◽  
Lars Davidson ◽  
Spyros Voutsinas
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Boundary Layer Separation ◽  
Turbine Rotor ◽  
Rotor Blades ◽  
Free Vortex ◽  
Irrotational Flow ◽  
Aerodynamic Loads ◽  
Operational Conditions ◽  
Turbine Rotor Blade

The aerodynamics of a wind turbine is governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is one of the most important challenges in wind turbine rotor blade design. Because of the unsteady flow field around wind turbine blades, prediction of aerodynamic loads with high level of accuracy is difficult and increases the uncertainty of load calculations. A free vortex wake method, based on the potential, inviscid and irrotational flow, is developed to study the aerodynamic loads. Since it is based on the potential, inviscid and irrotational flow, it cannot be used to predict viscous phenomena such as drag and boundary layer separation. Therefore it must be coupled to the tabulated airfoil data to take the viscosity effects into account. The results are compared with the Blade Element Momentum (BEM) [1] method and the GENUVP code [2] (see also the acknowledgments).

scholarly journals Exploring Resident–Tourist Interaction and its Impact on Tourists’ Destination Image

2020 ◽  
pp. 004728752096986 ◽  
Author(s):  
Dimitrios Stylidis
Keyword(s):  
Critical Role ◽  
Theory And Practice ◽  
Destination Image ◽  
Future Research ◽  
Limited Evidence ◽  
Local Residents ◽  
Intention To Return ◽  
The Impact ◽  
The City

Although previous research has widely acknowledged the critical role residents play in tourism, limited evidence exists on the impact their interactions with tourists have on tourists’ own image formulation and intention to return/recommend the destination to others. Grounded in the mere exposure and contact theories, this research offers insights into tourists’ destination image formation in light of their interactions with local residents and tourism employees at a destination. Two independent studies were conducted in 2019 to establish the soundness of the model; a preliminary one in the city of Kavala (n = 353) and a follow-up study on the island of Thasos (n = 397), both located in Greece. Findings suggest that interaction between the two parties positively affect cognitive, affective, and conative image, predicting 64% (study 1) and 54% (study 2) of the latter’s variance. Implications to theory and practice along with recommendations for future research are provided.

scholarly journals Opportunities and Threats in Reviewing Entrepreneurship Theory and Practice

2019 ◽  
Vol 44 (5) ◽  
pp. 847-860 ◽  
Author(s):  
Andreas Rauch
Keyword(s):  
Critical Role ◽  
Theory Development ◽  
Theory And Practice ◽  
Theory Testing ◽  
Future Research ◽  
Research Gaps ◽  
Knowledge Accumulation ◽  
Testing Theory ◽  
Entrepreneurship Theory

Reviews have a critical role in knowledge accumulation in entrepreneurship. Good reviews do not just summarize the literature but provide unique contributions on theory testing, theory development, the identification of research gaps, and suggestions for future research. This editorial discusses different forms for reviews, their strengths and weaknesses, and how they best contribute to the field.

scholarly journals A Review on the Meandering of Wind Turbine Wakes

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4725 ◽  
Author(s):  
Xiaolei Yang ◽  
Fotis Sotiropoulos
Keyword(s):  
Wind Turbine ◽  
Large Scale ◽  
Computational Models ◽  
Critical Role ◽  
Low Frequency ◽  
Wind Farms ◽  
Future Research ◽  
Work Related ◽  
Eddy Simulation ◽  
Future Research Directions

Meandering describes the large-scale, low frequency motions of wind turbine wakes, which could determine wake recovery rates, impact the loads exerted on turbine structures, and play a critical role in the design and optimal control of wind farms. This paper presents a comprehensive review of previous work related to wake meandering. Emphasis is placed on the origin and characteristics of wake meandering and computational models, including both the dynamic wake meandering models and large-eddy simulation approaches. Future research directions in the field are also discussed.

Attachment Organization in Suicide Prevention Research

Crisis ◽  
2014 ◽  
Vol 35 (1) ◽  
pp. 60-66 ◽  
Author(s):  
Amanda Venta ◽  
Carla Sharp
Keyword(s):  
Risk Factors ◽  
Suicidal Ideation ◽  
Suicide Attempt ◽  
Interpersonal Relationships ◽  
Suicide Ideation ◽  
Suicide Attempts ◽  
Critical Role ◽  
Self Report ◽  
Future Research ◽  
Self Harm

Background: Identifying risk factors for suicide-related thoughts and behaviors (SRTB) is essential among adolescents in whom SRTB remain a leading cause of death. Although many risk factors have already been identified, influential theories now suggest that the domain of interpersonal relationships may play a critical role in the emergence of SRTB. Because attachment has long been seen as the foundation of interpersonal functioning, we suggest that attachment insecurity warrants attention as a risk factor for SRTB. Aims: This study sought to explore relations between attachment organization and suicidal ideation, suicide attempts, and self-harm in an inpatient adolescent sample, controlling for demographic and psychopathological covariates. Method: We recruited 194 adolescents from an inpatient unit and assigned them to one of four attachment groups (secure, preoccupied, dismissing, or disorganized attachment). Interview and self-report measures were used to create four variables reflecting the presence or absence of suicidal ideation in the last year, single lifetime suicide attempt, multiple lifetime suicide attempts, and lifetime self-harm. Results: Chi-square and regression analyses did not reveal significant relations between attachment organization and SRTB, although findings did confirm previously established relations between psychopathology and SRTB, such that internalizing disorder was associated with increased self-harm, suicide ideation, and suicide attempt and externalizing disorder was associated with increased self-harm. Conclusion: The severity of this sample and methodological differences from previous studies may explain the nonsignificant findings. Nonsignificant findings may indicate that the relation between attachment organization and SRTB is moderated by other factors that should be explored in future research.

Overview of Subsynchronous Oscillation in Grid-connected Wind Farm

2020 ◽  
Vol 13 (7) ◽  
pp. 969-979
Author(s):  
Xu Pei-Zhen ◽  
Lu Yong-Geng ◽  
Cao Xi-Min
Keyword(s):  
Power Systems ◽  
Wind Turbine ◽  
Large Scale ◽  
Wind Farm ◽  
Wind Farms ◽  
Induction Generator ◽  
Future Research ◽  
Stable Operation ◽  
Subsynchronous Oscillation ◽  
Different Types

Background: Over the past few years, the subsynchronous oscillation (SSO) caused by the grid-connected wind farm had a bad influence on the stable operation of the system and has now become a bottleneck factor restricting the efficient utilization of wind power. How to mitigate and suppress the phenomenon of SSO of wind farms has become the focus of power system research. Methods: This paper first analyzes the SSO of different types of wind turbines, including squirrelcage induction generator based wind turbine (SCIG-WT), permanent magnet synchronous generator- based wind turbine (PMSG-WT), and doubly-fed induction generator based wind turbine (DFIG-WT). Then, the mechanisms of different types of SSO are proposed with the aim to better understand SSO in large-scale wind integrated power systems, and the main analytical methods suitable for studying the SSO of wind farms are summarized. Results: On the basis of results, using additional damping control suppression methods to solve SSO caused by the flexible power transmission devices and the wind turbine converter is recommended. Conclusion: The current development direction of the SSO of large-scale wind farm grid-connected systems is summarized and the current challenges and recommendations for future research and development are discussed.

scholarly journals Impact of the Wind Turbine on the Parameters of the Electricity Supply to an Agricultural Farm

2021 ◽  
Vol 13 (13) ◽  
pp. 7279
Author(s):  
Zbigniew Skibko ◽  
Magdalena Tymińska ◽  
Wacław Romaniuk ◽  
Andrzej Borusiewicz
Keyword(s):  
Power Plant ◽  
Wind Turbine ◽  
Wind Power ◽  
Rural Areas ◽  
Power Plants ◽  
Reactive Power ◽  
Supply Voltage ◽  
Common Source ◽  
Voltage Fluctuations ◽  
The Impact

Wind power plants are an increasingly common source of electricity located in rural areas. As a result of the high variability of wind power, and thus the generated power, these sources should be classified as unstable sources. In this paper, the authors attempted to determine the impact of wind turbine operation on the parameters of electricity supplied to farms located near the source. As a result of the conducted field tests, variability courses of the basic parameters describing the supply voltage were obtained. The influence of power plant variability on the values of voltage, frequency, and voltage distortion factor was determined. To estimate the capacity of the transmission lines, the reactive power produced in the power plant and its effect on the value of the power factor were determined. The conducted research and analysis showed that the wind power plant significantly influences voltage fluctuations in its immediate vicinity (the maximum value registered was close to 2%, while the value required by law was 2.5%). Although all the recorded values are within limits specified by the current regulations (e.g., the THD value is four times lower than the required value), wind turbines may cause incorrect operation of loads connected nearby. This applies mainly to cases where consumers sensitive to voltage fluctuations are installed in the direct vicinity of the power plant.

scholarly journals Training may enhance early childhood educators’ self-efficacy to lead physical activity in childcare

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Brianne A. Bruijns ◽  
Andrew M. Johnson ◽  
Jennifer D. Irwin ◽  
Shauna M. Burke ◽  
Molly Driediger ◽  
...  
Keyword(s):  
Physical Activity ◽  
Early Childhood ◽  
Self Efficacy ◽  
Critical Role ◽  
Early Childhood Educators ◽  
Outdoor Play ◽  
Future Research ◽  
Intervention Component ◽  
Space Extension ◽  
The Impact

Abstract Background Early childhood educators (ECEs) play a critical role in promoting physical activity (PA) among preschoolers in childcare; thus, PA-related training for ECEs is essential. The Supporting PA in the Childcare Environment (SPACE) intervention incorporated: 1. shorter, more frequent outdoor play sessions; 2. provision of portable play equipment; and, PA training for ECEs. An extension of the SPACE intervention (the SPACE-Extension) incorporated only the shorter, more frequent outdoor play periods component of the original SPACE intervention. The purpose of this study was to explore the individual impact of these interventions on ECEs’ PA-related self-efficacy and knowledge. Methods ECEs from the SPACE (n = 83) and SPACE-Extension (n = 31) were administered surveys at all intervention time-points to assess: self-efficacy to engage preschoolers in PA (n = 6 items; scale 0 to 100); self-efficacy to implement the intervention (n = 6 items); and, knowledge of preschooler-specific PA and screen-viewing guidelines (n = 2 items). A linear mixed effects model was used to analyze the impact of each intervention on ECEs’ self-efficacy and knowledge and controlled for multiple comparison bias. Results The SPACE intervention significantly impacted ECEs’ self-efficacy to engage preschoolers in PA for 180 min/day (main effect), and when outdoor playtime was not an option (interaction effect). Further, the interaction model for ECEs’ knowledge of the total PA guideline for preschoolers approached significance when compared to the main effects model. Participants within the SPACE-Extension did not demonstrate any significant changes in self-efficacy or knowledge variables. Conclusions Findings from this study highlight the benefit of ECE training in PA with regard to fostering their PA-related self-efficacy and knowledge. Future research should explore the impact of PA training for ECEs uniquely in order to determine if this intervention component, alone, can produce meaningful changes in children’s PA behaviours at childcare.

scholarly journals A Review on Thermal Energy Modelling for Optimal Microgrids Management

Thermo ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 63-76
Author(s):  
Mengxuan Yan ◽  
Dongxiao Wang ◽  
Chun Sing Lai ◽  
Loi Lei Lai
Keyword(s):  
Energy Management ◽  
Thermal Energy ◽  
Critical Role ◽  
Distribution Networks ◽  
Energy Resources ◽  
Future Research ◽  
Renewable Energy Resources ◽  
Energy Modelling ◽  
Microgrid Energy Management ◽  
Combined Cooling

Microgrids have become increasingly popular in recent years due to technological improvements, growing recognition of their benefits, and diminishing costs. By clustering distributed energy resources, microgrids can effectively integrate renewable energy resources in distribution networks and satisfy end-user demands, thus playing a critical role in transforming the existing power grid to a future smart grid. There are many existing research and review works on microgrids. However, the thermal energy modelling in optimal microgrid management is seldom discussed in the current literature. To address this research gap, this paper presents a detailed review on the thermal energy modelling application on the optimal energy management for microgrids. This review firstly presents microgrid characteristics. Afterwards, the existing thermal energy modeling utilized in microgrids will be discussed, including the application of a combined cooling, heating and power (CCHP) and thermal comfort model to form virtual energy storage systems. Current trial programs of thermal energy modelling for microgrid energy management are analyzed and some challenges and future research directions are discussed at the end. This paper serves as a comprehensive review to the most up-to-date thermal energy modelling applications on microgrid energy management.

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