scholarly journals Comparison of electrical collection topologies for multi-rotor wind turbines

2020 ◽  
Author(s):  
Paul Pirrie ◽  
David Campos-Gaona ◽  
Olimpo Anaya-Lara
Keyword(s):  
Wind Turbines ◽  
Capital Cost ◽  
Voltage Level ◽  
Academic Literature ◽  
Electrical Systems ◽  
Component Type ◽  
Fair Comparison ◽  
Potential Benefits ◽  
Almost All ◽  
Large Rotor

Abstract. Multi-rotor wind turbines (MRWT) have been suggested in literature as a solution to achieving wind turbine systems with capacities greater than 10 MW. MWRT's utilise a large number of small rotors connected to one support structure instead of one large rotor, with the aim of circumventing the square cube law. Potential benefits of MRWT's include cost and material savings, standardisation of parts, increased control possibilities and improved logistics for assembly and maintenance. Almost all previous work has focused on mechanical and aerodynamic feasibility, with almost no attention being paid to the electrical systems. In this research eight different topologies of the electrical collection network for MRWT's are analysed to assess which are the most economically and practically viable options. AC and DC collection networks are presented in radial, star, cluster and DC series topologies. Mass, capital cost and losses are estimated based on scaling relationships from academic literature and up to date commercial data. The focus of this study is the assessment of the type of electrical collector topology so component type and voltage level are kept consistent between topology designs in order to facilitate a fair comparison. Topologies are compared in terms of four main criteria; capital cost, cost effectiveness, total mass, and reliability. The most suitable collection topology for MRWT's is shown to be of the star type, in which each turbine is connected to the step up transformer via its own cable. DC topologies are generally found to be more expensive when compared to their AC counterparts due to the high cost of DC-DC converters and DC switchgear.

scholarly journals Comparison of electrical collection topologies for multi-rotor wind turbines

2020 ◽  
Vol 5 (4) ◽  
pp. 1237-1252
Author(s):  
Paul Pirrie ◽  
David Campos-Gaona ◽  
Olimpo Anaya-Lara
Keyword(s):  
Wind Turbines ◽  
Cost Effective ◽  
Capital Cost ◽  
Lower Efficiency ◽  
Energy Capture ◽  
Electrical Systems ◽  
Component Type ◽  
Potential Benefits ◽  
Comparison Table ◽  
Almost All

Abstract. Multi-rotor wind turbines (MRWTs) have been suggested in the literature as a solution to achieving wind turbine systems with capacities greater than 10 MW. MRWTs utilize a large number of small rotors connected to one support structure instead of one large rotor with the aim of circumventing the square cube law. Potential benefits of MRWTs include cost and material savings, standardization of parts, increased control possibilities, and improved logistics for assembly and maintenance. Almost all previous work has focused on mechanical and aerodynamic feasibility, with almost no attention being paid to the electrical systems. In this research eight different topologies of the electrical collection network for MRWTs are analysed to assess which are the most economically and practically viable options. AC and DC collection networks are presented in radial, star, cluster and DC series topologies. Mass, capital cost and losses are estimated based on scaling relationships from the academic literature and up-to-date commercial data. The focus of this study is the assessment of the type of electrical collector topology, so component type and voltage level are kept consistent between topology designs in order to facilitate a fair comparison. Topologies are compared in terms of four main criteria: capital cost, cost effectiveness, total mass and reliability. A comparison table is presented to summarize the findings of the research in a convenient way. It is found that the most cost-effective solutions are the AC radial and AC star topologies, with the least cost-effective being the DC series–parallel and DC cluster topologies. This is due to the high cost of DC–DC converters and DC switchgear along with the lower efficiency of DC converters. Radial designs perform best in terms of efficiency and annual energy capture. DC systems achieve a slightly lower nacelle mass compared to their equivalent AC systems. DC topologies are generally found to be more expensive when compared to their AC counterparts due to the high cost of DC–DC converters and DC switchgear. Star topologies are considered to have the best reliability due to having no shared equipment. The most suitable collection topology for MRWTs is shown to be of the star type, in which each turbine is connected to the step-up transformer via its own cable.

Bridging the Gap from the General to the Specific by Linking Knowledge Management to Business Processes

2011 ◽  
pp. 2572-2586
Author(s):  
John S. Edwards ◽  
John B. Kidd
Keyword(s):  
Knowledge Management ◽  
Cultural Change ◽  
Business Processes ◽  
Organisational Learning ◽  
Practical Implementation ◽  
Management Problems ◽  
Potential Benefits ◽  
Almost All ◽  
Different Cultures

A phenomenon common to almost all fields is that there is a gap between theory and practical implementation. However, this is a particular problem in knowledge management, where much of the literature consists of general principles written in the context of a ‘knowledge world’ that has few, if any, references to how to carry out knowledge management in organisations. In this chapter, we put forward the view that the best way to bridge this gap between general principles and the specific issues facing a given organisation is to link knowledge management to the organisation’s business processes. After briefly reviewing, and rejecting alternative ways in which this gap might be bridged, the chapter goes on to explain the justification for, and the potential benefits and snags of, linking knowledge management to business processes. Successful and unsuccessful examples are presented. We concentrate especially on the issues of establishing what knowledge is relevant to an organisation at present, the need for organisational learning to cope with the inevitable change, and the additional problems posed by the growing internationalisation of operations. We conclude that linking knowledge management in terms of business processes is the best route for organisations to follow, but that it is not the answer to all knowledge management problems, especially where different cultures and/or cultural change are involved.

A Systematic Measurement of CSP Based on Fuzzy Analytical Hierarchy Process

2012 ◽  
Vol 195-196 ◽  
pp. 847-852
Author(s):  
Shou Ming Chen ◽  
Jia Si Fan
Keyword(s):  
Analytical Hierarchy Process ◽  
Corporate Social Performance ◽  
Social Performance ◽  
Preliminary Investigation ◽  
Social Awareness ◽  
Fuzzy Analytical Hierarchy Process ◽  
Academic Literature ◽  
Almost All ◽  
Corporate Social ◽  
Hierarchy Process

With increasing social awareness on the issue of corporate social performance (CSP), the measurement of CSP has received considerable attention in both academic literature and managerial practice. Though earlier literature provides several methods for measuring corporate social activities, almost all of them have some limitations. In this paper, we propose a methodology for the development of a systematic measure of CSP based on fuzzy analytical hierarchy process (FAHP). In addition, a preliminary investigation is presented to explain how the approach can help in evaluating CSP in practice.

scholarly journals Why (the Research on) Federalism Matters

2019 ◽  
Vol 15 (1) ◽  
pp. 1-2
Author(s):  
Anna Gamper
Keyword(s):  
Social Sciences ◽  
Constitutional Law ◽  
Separation Of Powers ◽  
Federal State ◽  
Vertical Separation ◽  
Liberal Democracies ◽  
Minority Protection ◽  
Federal States ◽  
Academic Literature ◽  
Almost All

Research on federalism existed even before the first federal state emerged. It is an epic tale about leagues and unions, covenants and constitutions, loyalty and subsidiarity. But federalism is also about peace-making, vertical separation of powers, compound democracy, multi-layered governance and minority protection. It is not by chance, therefore, that almost all federal states are liberal democracies. Although a plethora of academic literature has been written on federalism, including many classical works of leading academics in the fields of constitutional law and social sciences, the research has never been exhaustive...

Overqualification in the Workplace

2017 ◽  
Author(s):  
Berrin Erdogan ◽  
Talya N. Bauer ◽  
Aysegul Karaeminogullari
Keyword(s):  
Interpersonal Relationships ◽  
Job Search ◽  
Work Experience ◽  
Well Being ◽  
Unique Form ◽  
Employment History ◽  
Job Requirements ◽  
Academic Literature ◽  
Potential Benefits ◽  
Health And Well Being

Overqualification is a unique form of underemployment, which represents a state where the employee’s education, abilities, knowledge, skills, and/or experience exceed job requirements and are not utilized on the job. Potentially conflicting upsides and downsides of the phenomenon created a fruitful area of research. Thus, overqualification has received considerable attention both in the academic literature and popular press. Studies of overqualification have emerged and received considerable attention in diverse fields including education, labor economics, sociology, management, and psychology. Antecedents of overqualification include individual differences (such as education, personality, age, sex, job search attitudes, previous work experience, past employment history, vocational training and type of degree, migrant status) and environmental dynamics (such as the characteristics of the position held and size of the job market). Commonly studied outcomes of overqualification include job attitudes, performance, proactive behaviors and creativity, counterproductive behaviors, absenteeism and turnover, health and well-being, feelings of job security, wages, upward mobility, and interpersonal relationships. While the effects are typically negative, there are some contemporary findings revealing the potential benefits of overqualified employees for their work groups and organizations. In recent years, boundary conditions shaping the effects of overqualification have also been identified, including factors such as empowerment and autonomy, overqualification of referent others, personality traits, and values. Despite the accumulating research on this topic, many unanswered questions remain. Conflicting findings on some of the outcomes and limited empirical investigations of theory-based mediators promise a lively and still developing field of research.

scholarly journals Assessing the Factors Impacting on the Reliability of Wind Turbines via Survival Analysis—A Case Study

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3034 ◽  
Author(s):  
Samet Ozturk ◽  
Vasilis Fthenakis ◽  
Stefan Faulstich
Keyword(s):  
Survival Analysis ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Direct Drive ◽  
Maintenance Costs ◽  
Electrical Systems ◽  
Geographical Factors ◽  
History Of ◽  
Risk Rate

The failure of wind turbines is a multi-faceted problem and its monetary impact is often unpredictable. In this study, we present a novel application of survival analysis on wind turbine reliability, including accounting for previous failures and the history of scheduled maintenance. We investigated the operational, climatic and geographical factors that affect wind turbine failure and modeled the risk rate of wind turbine failure based on data from 109 turbines in Germany operating for a period of 19 years. Our analysis showed that adequately scheduled maintenance can increase the survival of wind turbine systems and electric subsystems up to 2.8 and 3.8 times, respectively, compared to the systems without scheduled maintenance. Geared-drive wind turbines and their electrical systems were observed to have 1.2- and 1.4- times higher survival, respectively, compared to direct-drive turbines and their electrical systems. It was also found that the survival of frequently-failing wind turbine components, such as switches, was worse in geared-drive than in direct-drive wind turbines. We show that survival analysis is a useful tool to guide the reduction of the operating and maintenance costs of wind turbines.

Diffusion of blockchain technology

2019 ◽  
Vol 32 (5) ◽  
pp. 735-757 ◽  
Author(s):  
Purva Grover ◽  
Arpan Kumar Kar ◽  
Marijn Janssen
Keyword(s):  
Social Media ◽  
Decision Process ◽  
Manufacturing Industry ◽  
Content Type ◽  
Academic Literature ◽  
Blockchain Technology ◽  
Data Source ◽  
Single Data ◽  
Almost All ◽  
Media Data

Purpose Although blockchain is often discussed, its actual diffusion seems to be varying for different industries. The purpose of this paper is to explore the blockchain technology diffusion in different industries through a combination of academic literature and social media (Twitter). Design/methodology/approach The insights derived from the academic literature and social media have been used to classify industries into five stages of the innovation-decision process, namely, knowledge, persuasion, decision, implementation and confirmation (Rogers, 1995). Findings Blockchain is found to be diffused in almost all industries, but the level of diffusion varies. The analysis highlights that manufacturing industry is at the knowledge stage. Further public administration is at persuasion stage. Subsequently, transportation, communications, electric, gas and sanitary services and trading industry had reached to the decision stage. Then, services industries have reached to implementation stage while finance, insurance and real estate industries are the innovators of blockchain technologies and have reached the confirmation stage of innovation-decision process. Practical implications Actual implementations of blockchain technology are still in its infancy stage for most of the industries. The findings suggest that specific industries are developing specific blockchain applications. Originality/value To the best of the authors’ knowledge this is the first study which is using social media data for investigating the diffusion of blockchain in industries. The results show that the combination of Twitter and academic literature analysis gives better insights into diffusion than a single data source.

scholarly journals Assessing Factors Impacting on Reliability of Wind Turbines by Use of Survival Analysis – A Case Study

2018 ◽  
Author(s):  
Samet Ozturk ◽  
Vasilis Fthenakis ◽  
Stefan Faulstich
Keyword(s):  
Survival Analysis ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Direct Drive ◽  
Maintenance Costs ◽  
Electrical Systems ◽  
History Of ◽  
Risk Rate ◽  
Reliability Performance

Failure of wind turbines is a multi-faceted problem and its monetary impact is often unpredicted. In this study, we present a novel application of survival analysis on wind turbine reliability performance that includes accounting of previous failures and history of scheduled maintenance. We investigate the operational, climatic and geographical factors which affect wind turbine failures and model the risk rate of wind turbine failures based on data from 109 turbines in Germany operating during a period of 19 years.  Our analysis showed that adequately scheduled maintenance can increase the survivorship of wind turbine systems and electric subsystems up to 2.8 and 3.8 times, respectively compared to the ones without scheduled maintenance. Geared-drive wind turbines and their electrical systems were observed to have 1.2- and 1.4-times higher survivorship, respectively, compared to direct-drive turbines and their electrical systems. It is also found that survivorship of frequently-failed wind turbine components, such as switches, is worse in geared-drive than in direct-drive wind turbines. We show that survival analysis is a useful tool for guiding the reduction of operating and maintenance costs of wind turbines.

An accelerated test stand to assess wear in offshore wind turbines rolling bearings

2018 ◽  
Vol 42 (2) ◽  
pp. 136-140
Author(s):  
Nicola Pio Belfiore ◽  
Carlo Costa ◽  
Rosanna Pileggi ◽  
Fabio Botta ◽  
Claudio Guarnaschelli
Keyword(s):  
Wind Turbines ◽  
Offshore Wind ◽  
Rolling Bearings ◽  
Offshore Wind Turbines ◽  
Revolute Joints ◽  
Turbine Generators ◽  
Rolling Contacts ◽  
Load Carrying ◽  
Almost All ◽  
Test Current

Rolling bearings are universally adopted to serve as revolute joints in almost all mechanisms or machines, because they offer a convenient solution to the problem of minimizing friction and, simultaneously, providing a large load-carrying capacity at any kinematic regime, including slow or alternate rotations. However, in offshore wind turbines not only they reach large dimensions but also they move within strong electromagnetic fields created by the turbine generators. For example, considering the last amplification stadium epicyclic gearbox, they may serve to sustain elements rotating around floating shafts (planetary) which also move around a fixed principal shaft (solar). This article illustrates an original experimental test bench that simulates sliding and rolling contacts through which a test current is flowing. Unexpected and interesting results disclose how this particular field is challenging and how more investigations are still required to achieve an adequate and complete interpretation. The understanding of this phenomenon could give rise to modification to the composition and the microstructure of rollers and rings employed in offshore wind turbines.

Automatic speech recognition in the booth

Target ◽  
2020 ◽  
Author(s):  
Bart Defrancq ◽  
Claudio Fantinuoli
Keyword(s):  
Speech Recognition ◽  
Automatic Speech Recognition ◽  
Machine Learning Techniques ◽  
Computer Assisted ◽  
Psychological Benefits ◽  
Error Matrix ◽  
Simultaneous Interpreting ◽  
Subjective Perceptions ◽  
Potential Benefits ◽  
Almost All

Abstract Automatic Speech Recognition (ASR) has been proposed as a means to enhance state-of-the-art computer-assisted interpreting (CAI) tools and to allow machine-learning techniques to enter the workflow of professional interpreters. In this article, we test the usefulness of real-time transcription with number highlighting of a source speech for simultaneous interpreting using InterpretBank ASR. The system’s precision is high (96%) and its latency low enough to fit interpreters’ ear–voice span (EVS). We evaluate the potential benefits among first-time users of this technology by applying an error matrix and by investigating the users’ subjective perceptions through a questionnaire. The results show that the ASR provision improves overall performance for almost all number types. Interaction with the ASR support is varied and participants consult it for just over half of the stimuli. The study also provides some evidence of the psychological benefits of ASR availability and of overreliance on ASR support.

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