Special Issue "Wind Turbines"

Guest Editor
Prof. Dr. Frede Blaabjerg
Institute of Energy Technology, Aalborg University, Pontoppidanstraede 101, DK-9220 Aalborg East, Denmark
E-Mail: fbl@et.aau.dk
Phone: +45 9635 9254
Fax: +45 9815 1411
Interests: wind power research; power electronics; control of wind turbines and wind farms; interconnection to grid; generators; power converters; ride-through operation

Guest Editor
Prof. Dr. Lance Manuel
Civil, Architectural and Environmental Engineering Department-STR, The University of Texas at Austin, Austin, TX 78712-0273, USA
Website: http://www.ce.utexas.edu/prof/Manuel/
E-Mail: lmanuel@mail.utexas.edu
Phone: +1 512 232 5691
Fax: +1 512 471 7259
Interests: random vibration; structural dynamics; structural reliability; atmospheric inflow turbulence simulation for wind turbine loads analysis; computational methods for windstorm field generation; performance of deepwater offshore platforms; probabilistic seismic hazard analysis

Guest Editor
Prof. Dr. Mark J. Balas
Department of Electrical & Computer Engineering, College of Engineering and Applied Science, Laramie, WY 82071, USA
Website: http://wwweng.uwyo.edu/electrical/faculty/balas/
E-Mail: mbalas@uwyo.edu
Phone: +1 307 766 5599
Fax: +1 307 766 2248
Interests: aerodynamics including design and optimization; aircraft design; experimental and computational fluid dynamics; biofluiddynamics; wind energy; aero-hydrodynamics of sailing

Dear Colleagues,

This issue focuses on recent advances in the wind energy sector on a wide range  of topics, including: wind resource mapping, wind intermittency issues, aerodynamics,  foundations, aeroelasticity, wind turbine technologies, control of wind turbines, diagnostics, generator concepts incl gearless concepts, power electronic converters, grid interconnection, ride-through operation, protection, wind farm layouts - optimization and control, reliability, operations and maintenance, effects of wind farms on local and global climate, wind power stations, smart-grid and micro-grid related to wind turbine operation.

Prof. Dr. Frede Blaabjerg
Prof. Dr. Lance Manuel
Prof. Dr. Mark J. Balas
Guest Editors

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Title: Summary of Savonius Wind Turbine Development and Future Applications for Small-Scale Power Generation
Authors: J. P. Abraham ^1,*, B. D. Plourde ¹, G. S. Mowry ¹ and W.J. Minkowycz ²
Affiliations:¹University of St. Thomas, School of Engineering, 2115 Summit Ave, St. Paul, MN 55105-1079, USA
²Department of Mechanical Engineering, University of Illinois, Chicago, 842 W. Taylor St. Chicago, IL 60607, USA
Abstract: Wind turbine use is expanding throughout the world as a means to provide electricity without contributing to the increase in global warming gases.  Most commonly, very large, horizontal-axis turbines are constructed in fleets that are connected to national-level electrical grid systems.  More recently, there has been a desire for more local, small-scale power production that can be used to power very specific pieces of equipment or buildings.  Many of the small-scale turbines are designed differently from their larger counterparts – they are driven by drag forces rather than by lift.  Drag-driven turbines are typically called Savonius turbines.  This manuscript which presents a historical perspective on Savonius turbines, will illustrate their potential for providing local power.  Finally, we will discuss recent developments which intend to utilize Savonius turbines to power cellular communication towers in developing parts of the world.

Type of Paper: Article
Title: A Closed-Form Technique for Reliability and Risk Assessment of Wind Turbine Systems
Authors: Akwasi F. Mensah * and Leonardo Dueñas-Osorio
Affiliation: Department of Civil and Environmental Engineering, Rice University, Houston, Texas, USA; E-Mails: afm3@rice.edu (A.F.M.); Leonardo.duenas-osorio@rice.edu (L.D.-O.); Tel.: +1 713 348 5292; Fax: +1 713 348 5268
Abstract: This paper proposes a closed-form approach to evaluate wind turbine system reliability and associated failure consequences. Monte Carlo simulation, a widely used approach for system reliability, usually requires large numbers of computational experiments, while existing analytical methods are limited to simple system configurations focusing on average values of reliability metrics. By analyzing a wind turbine system and its components in a combinatorial yet computationally efficient form, the proposed approach provides an entire probability distribution of system failure that contains all possible configurations of component failure and survival events. The approach is also capable of handling unique component attributes needed for risk estimations, and enables sensitivity analysis for quantifying the criticality of individual components to wind turbine system reliability. Applications of the technique are illustrated by assessing the reliability of a 12-subassemble turbine system. In addition, component downtimes are embedded in the formulation to compute expected annual wind turbine unavailability probabilities and component importance metrics useful for maintenance planning, research and development prioritization. Furthermore, this paper introduces a recursive solution to the combinatorial approach, and applies this to a 45-compont turbine system. The proposed approach proves to be computational efficient and yields vital reliability information that is readily usable by wind farm stakeholders for decision making and risk management.
Keywords: wind turbine; system reliability; closed-form solutions; consequence analysis

Title: Fault Detection of Wind Turbines with Uncertain Parameters: a Set-Membership Approach
Authors: S. Mojtaba Tabatabaeipour *, Thomas Bak, Peter F. Odgaard and Jakob Stoustrup
Affiliation: Automation & Control, Department of Electronic Systems, Aalborg University, Fredrik Bajers Vej 7C, 9220 Aalborg, Denmark
Abstract: In this paper a state estimation set-membership approach for fault detection of a benchmark wind turbine is proposed. We consider sensor faults, actuator faults and system faults. Moreover, uncertainties on the parameters of the systems as well as uncertainties on the power coefficient and torque coefficient which are given in the form of look-up tables are taken into account. Due to high noise on the wind speed measurement, nonlinearities in the aerodynamic torque, and uncertainties on the parameters, the fault detection problem is a challenging one. We use an effective wind speed estimator to estimate the effective wind speed and then using interval analysis and the monotonicity of the aerodynamic torque with respect to the effective wind speed, we find an interval over-approximation of the aerodynamic torque. This enables us to compute the set of states that are consistent with the past measurements and the model of the wind turbine. The fault detection algorithm checks the consistency of the current measurement this set. If the measurement is not consistent with this set, a fault is detected. The result demonstrates effectiveness of the proposed method.

Title: Development of Wind-Lens Technology for Wind Turbines and its Application
Authors: Tomoyuki Nagai, Yuji Ohya and Takashi Karasudani
Affiliaion: Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan
Abstract: A new type of wind turbine system with wind power enhancement technology, named “Wind Lens”, has been developed and reported in various publications, showing power augmentation by a factor of 2-5 compared with conventional turbines. This study reports further development of the system and its application including a floating offshore integrated energy farm experiment in Hakata Bay, Japan. The experiment is a mile stone leading to next generation megawatt-scale floating offshore integrated energy farm. The scope of this paper also includes a brief discussion of a road map to the next generation floating energy farm.