Utility-scale electricity produced from offshore wind farms has the potential to contribute significantly to the energy production of the United States. In order for the U.S. to rapidly develop these abundant resources, knowledgeable scientists and engineers with sound understanding of offshore wind energy systems are critical. This paper summarizes the development of an upper-level engineering course (and a directly related short course) in "Offshore Wind Energy Systems Engineering." This course is designed to provide students with comprehensive knowledge of both the technical challenges of offshore wind energy and the practical regulatory, permitting, and planning aspects of developing offshore wind farms in the U.S. This course was offered on a pilot basis in 2011 at the University of Massachusetts and has been reviewed by the National Renewable Energy Laboratory (NREL), TU Delft, and GL Garrad Hassan. As will be summarized in this paper, the course consists of 17 separate topic areas emphasizing appropriate engineering fundamentals as well as development, planning, and regulatory issues. In addition to the course summary, the paper will give the details of a public internet site where references and related course material can be obtained. This course will fill a pressing need for the education and training of the U.S. workforce in this critically important area. Fundamentally, this course will be unique due to two attributes: an emphasis on the engineering and technical aspects of offshore wind energy systems, and a focus on offshore wind energy issues specific to the United States.
Talented workers, capable of applying 21st Century skills to find solutions and further innovation in exciting, complex, diverse and demanding wind energy careers, are needed. In an increasingly technology-driven world, simply earning a high school diploma is no longer enough. In order to compete, students need to be prepared for life after high school. They must be armed with the skills and knowledge essential to continue on in college, be Science, Technology, Engineering, and Mathematics (STEM) literate citizens, and enter the STEM workforce ready to contribute. The wind energy workforce is growing in complexity and skills required and changes in education is needed to lead students into these new and exciting fields. Learn about the importance of career and college readiness, the critical role STEM education plays in preparing K-12 students for today's STEM workforce, explore ways to develop STEM literacy, and learn how industry, INL, Idaho State, and community stakeholders in Idaho have all come together to provide robust resources and opportunities for K-12 educators and their students as they prepare for the workforce of the future. Experience a model that can be transferred to your community, regional education systems, your technical teams, and your workforce complete with examples illustrating successes and lessons learned, and paths forward to bring success to your program. --------------------------------------------------------------------------------
Learning Objective: The conference presentation and discussion will explore training concepts and needs that can help industry training managers develop necessary training activities, hiring managers to identify needed technical skills, or instructors to jointly explore instruction plans. The Idaho State University (ISU) Energy Systems Technology and Education Center (ESTEC) has developed technician training that provides the full gamut of an engineering technician's needs. Skills and competencies, work attitudes, and ethics are all incorporated into the training. Overview: Wind power generation involves electrical and mechanical maintenance with a multitude of critical skills. An ideal wind energy technician will be comfortable and experienced in the tools and tasks that optimize equipment life. They will understand the critical need for routine preventive and predictive maintenance, as well as the intrigue of troubleshooting and identifying the root causes of problems. They will comprehend engineering design and be capable of communicating findings to all levels of industry from the design engineer and the site manager to the control operator. The technician will perform necessary repairs in a timely and cost efficient manner. These skills can be designed into an aggressive training program that allows the student to be work ready upon graduation.
The Department of Energy's Wind for Schools program is most famous for its involvement with supporting the installation of wind turbines at schools and the associated curricular enhancements to the host schools to inspire students to explore futures in wind energy. As important is the mechanism by which this work has been affected, namely via the formation and support of wind application centers in 11 different states. Members of the wind application centers develop and implement the strategies that ultimate result in many thousands of students discovering the relevance of wind energy as well as their relationship to this exciting field. This presentation will explore the how many well-known engineers, policy leaders, developers, future technicians and business leaders trace their roots back to these application centers and programs that inspired the first wind energy application centers. This presentation will show how the Wind for Schools program is learning from these successes and engaging with new programs to replicate success to accelerate the pace of market entry for tomorrow's workforce.
A series of virtual experiments have been documented which outline findings related to wind turbine rotor blade modeling and numerical simulation practice. The motivation of these experiments was to increase understanding of the variational parameters involved and, with this understanding, develop accurate and efficient methods for evaluating blade performance under a multitude of loading conditions. The chosen methods were intended to coincide with the evolution of the design cycle and be generally applicable to small, faster spinning rotor systems as well as extremely large, slow spinning ones. Element formulation, number of span-wise segments, and solution techniques such as finite element analysis and multi-body dynamics, were among the parameters evaluated. Target criteria included critical design factors such as out of plane bending, torsional response, and the relative importance of the nonlinear rotational inertial contributions compared to gravity loading. The rotor model was based on the NREL reference 5 MW offshore turbine for which model definitions and community evaluations are readily available.
In order to achieve more robust and reliable wind turbines under any condition and operating regime it is necessary to invest in wind farm load predictions. In this context, a better analysis of the rotor-dynamic including real conditions is required.
Traditional codes include a dynamic train model to incorporate the rotational degree of freedom of the rotor considering a single torsional flexibility. This approach loose some further insight drive train dynamics. Furthermore, the traditional Campbell analysis does consider neither the randomness implicit in some dynamic parameters nor the randomness of the generator speed due to the wind speed behavior.
The proposed novel methodology is defined and applied in a real case showing the benefits and outcomes compared with the traditional ones. First, a deterministic Campbell analysis is made including complex drive line model (34DOF). Second, the relevant crossing points and the sensitive components and resonances involved in are identified. Then, the probability density function (pdf) for the resonances, as a function of variability of the dynamic parameters, is established by means of Monte Carlo simulations. Afterwards, a new stochastic Campbell in the regions close to the previous point is performed, including the pdf for the resonances and for the generator speed, delimiting the occurrence probability in this area. And finally, the impact in load assessment of this probability surface is determined.
This methodology allows the designer to know how the site specific conditions and the variables uncertainty affect the dynamic behavior of the wind turbine.
The requirements imposed by the load design cases for the certification of a wind turbine can be difficult to meet in some cases without modifying the central controller or the redesign of the blades. One example of this situation is to maintain the blade loads within the design envelop with extreme turbulent wind conditions (ETM). The objective of most individual pitch control (IPC) implementations, such as those based on the d-q transformation, is the alleviation of rotor loads and so cannot target these ultimate blade loads. The individual blade control presented here focuses on reducing specific blade loads. The reduction of the blade loads also has the added benefit of a reduction of the rotor loads. This characteristic of the individual blade control presented makes it possible to specify the control objective and its design accordingly and, thus maintain certain loads within the design envelop. All this is achieved without any change to the main controller control or algorithms. In this paper the design of the individual blade control is explored for a variety of objectives and thereby a variety of blade loads. In particular, the results of the application of the individual blade control to reduce the ultimate blade loads due to extreme turbulence as specified in standard (IEC 61400-1 Ed.3). A reduction up to 20% is demonstrated.
Conical Concrete Tower Base for Utility Scale Wind Turbines Author: Bryant A. Zavitz P.E. Tindall Corporation Conley Ga. Co-Authors: Kevin L. Kirkley P.E. Tindall Corporation Conley Ga. Markus Wernli PhD P.E. LEED AP BergerABAM Engineers Seattle Wa. Economics are driving development of higher M.W. turbines. Installation at elevated Hub Heights further improves the financial considerations. These two factors significantly increase structural demand on supporting towers and foundations. A conventional gravity footing is the generally accepted solution; however they increase dramatically in size, reinforcement and constructability for a 2-3 M.W. turbine at hub heights beyond 100m. One alternative solution is a conical gravity base comprised of an above grade concrete cone structure attached to a 'ring' foundation. This paper outlines advantages of this concept with comparative examples over a range of turbine sizes at hub heights to 120m. Quick design aids have been developed for controlling design conditions. Rotational stiffness as related to soil parameters is considered. Overburden soil requirements dependant on quasistatic wind demand and turbine weight along with maximum soil bearing demand in function of extreme wind moment and axial load is charted. These aids allow designers to perform a quick check on foundation suitability for a particular site. Additional plots of capacity vs. size and volume for the foundation and concrete cone structure are presented for use in determining estimated base costs. Primary load path and connection strategy is outlined to clarify the structural concept.
The control and safety system is an essential part of wind turbines which has a high influence on the loads. In some designs, it is explicitly employed for load mitigation. As a consequence in certification, the controller behaviour and performance have to be assessed to verify the load assumptions underlying the design.
In GL 2010, Guideline for the Certification of Wind Turbines, Edition 2010, two alternative procedures for controller assessment are given. These procedures comprise the verification of the Load Relevant control and safety system Functions (LRF) by parallel modelling and functional testing.
After motivating the importance of the controller and its assessment for stability and performance of the whole turbine system, the steps to undergo in each method of controller assessment are described in detail to illustrate the process of the assessment which aims at achieving a high quality standard for controller synthesis by the designer.
Important new aspects are the possibility of controller assessment by software and hardware functional testing, the plausibility check for the transfer of the controller code from the simulation stage to the on-site wind turbine, and for system version control.
The new features of the controller assessment aim at closing the gap between simulation model and onsite wind turbine. It is important to guarantee that the controller, which is implemented in the wind turbine, has similar performance and robustness properties in closed- loop as the controller, which showed good performance in simulation studies.
The wind industry is under pressure to reduce the cost of power production and the utility-scale turbine market has become more competitive, spurring new innovation that has to be delivered to the market as fast as possible. The steady increase of power rating of utility-scale turbines has increased the turbine efficiency, but continuously pushed up the average hub height. However, the hub height in the United States has stalled at around 80 meters within the past years as the cost of fabrication and erection of larger towers and foundations has become a major cost item of the overall turbine. For hub heights beyond 100 meters, concrete or concrete/steel-hybrid towers become more cost effective, so that wind turbine manufacturers increasingly consider such towers in their product range. However, a supply chain for concrete towers is still in the beginning and the tower design and certification process is lengthy, as design codes are limited and details often have to be subjected to qualification testing. The definition of a generic load envelope can reduce the number of design iterations needed and, thus, speed up the design and certification process. This paper presents how a load envelope can be generic by covering a range of turbine types, hub heights, and power ratings, and how it relates to the required design checks for concrete towers. It outlines how the design with a generic load envelope can then accelerate the design and certification of a tower for a specific turbine.
The Center for Innovation through Visualizaton and Simulation at Purdue University Calumet received a grant from the US Department of Education to develop Mixed Reality Simulators for Wind Turbine Education. One simulator being developed is being integrated into college wind energy courses. This simulator aims to improve student learning and interest using 3d models to examine wind turbine components and perform aerodynamic analysis. The simulator is for both PC and 3D environments, developed using OpenSceneGraph and QT. The current version of the software has two main sections: The components section allows students to view and interact with a 1.5 MW horizontal axis wind turbine. Students can interact with the 3D model, adjust transparency, examine energy transfer between components, and learn detailed information. The aerodynamics section of the software allows students to analyze the important aerodynamic parameters of turbine blades. Students can move a cutting plane to view cross-sections along the length of the turbine blade. An interactive diagram is overlaid on top of the cross-section showing dynamically chaning parameters such as the angle of attack, blade pitch angle, and section twist angle as the cross-section is moved along the blade. CFD simulations for different aerodynamic conditions are also displayed, allowing students to observe and compare lift coefficient, drag coefficient, and pressure field distribution for each case. The software has been used in pilot studies and will be made Open Source, available for public download and use at any academic institution.
Clemson is in the process of building the world's largest and most capable wind turbine nacelle testing dynamometers. Two separate dynamometers will be built, both with off-axis, non-torque hydraulic loading systems. A 7.5 MW dynamometer will be built that will have static off axis loading capabilities, expandable to dynamic forcing, while a 15 MW dynamometer will have full dynamic forcing capabilities to simulate the hub forces transmitted into an operation nacelle. The dynamometers will have the capability of testing complete nacelles or individual drivetrain components under a variety of real and overstressed loading conditions as a means of performing Highly Accelerated Load Testing, HALT. This testing will enhance and improve the reliability and performance of the next generation of larger on and off-shore turbines by allowing testing to occur during design prior to any field installations. The focus of the testing is to lower the cost and improve reliability of the next generation of turbines thru early identification of any design weaknesses. The poster will provide an overview of the facility and its testing capabilities along with progress on the test facility construction. In addition, electrical fault and ride through testing will be provided through a 15 MW Hardware-in-the-Loop-Grid Simulator.
The drive to reduce the production cost of energy from wind turbines has led to the development of larger MW turbines with blade lengths beginning to exceed 60m. With the expected growth the challenges to enhance the performance of reinforcement solutions to enable the increase in blade length whilst reducing total blade cost has gained in importance. New material solutions deliver now a modulus increase of 17% reaching 49-50 GPa when compared to traditional materials. Measured static tension strength of 1066 MPa and a compression strength of 907MPa show an improvement of more than 30% versus traditional reinforcements, which increases admissible survival loads. The measured fatigue strength of 292MPa at R=-1 (tension-compression) at 10e+6 cycles show an improvement of more than 60% versus traditional reinforcements. The evaluation of the economics and gain in reliability has been demonstrated using new computational non linear simulation models of the whole turbine. A specific blade load simulation carried out on 40m and 60m blades showed cost saving in the magnitude of 17% to 20% if the material is used in specifc areas as spar caps. When comparing different blade sizes the saving is higher for larger blades. A more favorable load spectrum on components such as pitch and main bearings was also observed. This paper will describe the development of the new generation high modulus glass fabric solution and highlight the potential impact of this technology for future more advanced designs and the advantages for production cost and energy yield.
Site suitability of a wind turbine for a specific site can be analyzed using the full meteorological data set (i.e., all observed turbulence values) for the site. Alternatively, the IEC 61400-1 code allows an effective turbulence to be identified at each wind speed which represents the total fatigue damage equal to all the observed turbulence values at that wind speed. Utilizing the effective turbulence approach reduces the number of aeroelastic calculations in the design validation process and is commonly done. This paper explores the implications of using the effective turbulence method by comparing results obtained using a single effective turbulence value with results using the full meteorological data set. The comparison is applied using observed winds at two onshore sites in the United States. The study concludes that the use of an effective turbulence is conservative and leads to overestimation of loads in some circumstances. The overestimation was greater at the site with the lower ambient turbulence level. The damage equivalent load (DEL) of the blade root flap-wise bending moment was 7% higher than the value calculated with the full meteorological data. Investigating the DELs as a function of wind speed indicates that the use of effective turbulence underestimates at low wind speeds and overestimates at high wind speeds. A better understanding of the implications of the effective turbulence approach will enable turbine manufacturers and project developers to optimize project designs and thus reduce the cost of energy.
The ability to effectively and independently control the pitch of individual turbine blades is essential for extracting maximum energy and reducing premature wear on new large utility scale wind turbines. It is the only near term method to mitigate stress and vibration induced by wind shear, veer and gusts. However, limitations in sensing technology have prevented having real time spatial information about the wind velocity profiles in the inflow needed for employment of blade algorithms with the required response time and accuracy. The emergence of look ahead LIDARs for turbine control has created the opportunity to develop robust individual blade pitch control. This presentation will describe the developmental path for a new generation of turbine controls from advanced yaw control to individual blade pitch control. We will present field test data showing that using look-ahead LIDAR measurements in the current and in optimized yaw control algorithms greatly increase power output and reduces loads on large utility scale wind turbines. We also will present simulations of feed forward collective blade pitch based on having LIDAR wind data showing power increases at the transition points between Region II and Region III of the power curve. Representing work on the next step in controls improvement, results will be presented of new feed-forward individual blade pitch control algorithms showing improved performance in the FAST simulation due to the look-ahead LIDAR measurements.
As wind turbines increase in size, combined with increased lifetime demands, new methods for load reduction needs to be examined. One method is to make the yaw system of the turbine soft/ﬂexible and hereby dampen the loads to the system, which is the focus of the current paper. The paper ﬁrst presents work previous done on this subject with focus on hydraulic yaw systems.
By utilizing the HAWC2 aeroelastic code and an extended model of the NREL 5MW turbine combined with a simpliﬁed linear model of the turbine, the parameters of the soft yaw system are optimized to reduce loading in critical components. Results shows that a signiﬁcant reduction in fatigue and extreme loads to the yaw system and rotor shaft is possible, when utilizing the soft yaw drive concept compared to the original stiff yaw system. The physical demands of the hydraulic yaw system are furthermore examined for a life time of 20 years. Based on the extrapolated loads, the duty cycles show that it is possible to construct a hydraulic soft yaw system, which is able to reduce the loads on the wind turbine signiﬁcantly.
A full scale hydraulic yaw test rig is available for experiments and tests. This is done along with a complete non-linear and linear model of the system for analysis and control purposes
The trend for large wind turbines with a capacity over 5 MW is clearly recognizable among the international manufacturers, especially in the offshore wind market. These large wind turbines will transform the global energy market because of economies of scale and the new technology. Engineers and designers all over the world are in a race to design and build offshore wind turbines (up to 10 MW and more) with the size, technology and power of anything seen before. The goal is the domination of the global energy market. If they prove themselves as technically and financially practicable, one large turbine should be able to generate enough electricity to provide thousands of homes. The world's largest wind turbine is the Enercon E-126, officially rated at 7.5 MW, which is installed in Emden, Germany. Other well-known manufacturers also develop prototypes, e.g: –Alstom -> 6 MW (2012) –American Superconductor -> 10 MW(2012/13) –Clipper -> 10 MW (2012) –Gamesa -> 7 MW (2014) –Mitsubishi -> 10 MW (2013) –Samsung -> 7 MW (2013) –United Power -> 10 MW (2015) Areva, BARD and Repower, for instance, have already gone into production with their 5 and 6MW turbines, Repower with grid installations (onshore) of 7,5 MW and Asian manufactures, like Doosan, Goldwind and Sinovel, will follow this trend in the next years.
With the increase in size and scale of turbines, their susceptibility to the damaging effects of stochastic wind loads increases. Thus, the implementation of 'intelligent control' of each individual rotor blade becomes increasingly important for achieving higher system reliability, durability, and precision. While the advantages of pitch control are undisputed, this research seeks to investigate whether overall control can be enhanced by incorporating data from a remote wind sensor (LIDAR) into the turbine controller to minimize the fatigue damage while optimizing energy output. A variety of analytical tools will be utilized to evaluate efficacy of a LIDAR-enhanced individual pitch control strategy for increasing system fatigue life. Using the output response from the turbine modeled in FAST we can generate a histogram of system load amplitudes and respective fatigue damage as a function of mean wind speeds and turbulence intensities. Comparing this reference histogram with the measured LIDAR data enables effective pitch decisions to be made based on whether the predicted damage by incoming wind is above a predetermined level. Using this control technique discrete pitch decisions proportional to the size, structure and magnitude of the incoming turbulence structure will be made. Furthermore, fatigue damage endured by the turbine will then be compared with that of a conventional system to compute the potential increase in fatigue life and the total energy output. This economic advantage will also be assessed to determine whether the additional cost of installing a remote sensor is economically justified.
During the last 20 years, a great attention has been paid to the Structural Health Monitoring (SHM) of wind turbines with the aim of diagnosing and supervision of time varying degradation as regards different structure failure modes. Wind turbine manufacturers are increasingly investing growing resources in wind farm maintenance in order to achieve more robust and reliable wind turbines under any condition and under any operating regime. Needless to say, this requisite is even more demanding whenever and wherever maintenance operations are challenging practices due to logistics or access difficulties, i.e. offshore sites. In this paper, the application and implementation of an on-line monitoring algorithm is presented. This novel algorithm will be focused in the task of tracking one eigenfrequency linked to a wind turbine structural component. Such technique is based on the phase lag comparison established between two phasors. The first one is a reference phasor that spins at a constant speed, at a frequency related with normal operating condition. Second phasor is obtained through the complex analytical signal obtained by filtering the real measured signal using a Hilbert transformer. This algorithm is especially suited to detect and locate (on line) sudden changes in resonance frequency when a structural damage starts to progress abruptly. In addition, this work will demonstrate the time localization and accurate prognostic skills when a structural change in one structural wind turbine component abruptly drops its frequency resonance value. This will be demonstrated by means of the algorithm application to simulations results.
Wind turbines are complex electromechanical devices interacting with a constantly changing environment. Modelers of wind turbines often concentrate on the details of subsystems or aspects of the turbine that they are interested in, while using simplistic representations of other subsystems. In particular, aerodynamic models of wind turbines tend to oversimplify the turbine's electrical systems and grid connection, while electrical models of wind turbines typically used in plant or grid simulations likewise ignore or oversimplify turbine aerodynamics. This approach may lead to incomplete and unrealistic models. For example, torque pulsations due to wind-rotor interactions may impact electrical systems, but most electrical models do not account for these effects. This paper is intended for those interested in comprehensive wind turbine models that include detailed aerodynamics, mechanics, and electrical systems using the FAST tool developed by NREL, interfaced with the popular MATLAB/Simulink modeling platform. Because FAST's built-in functionality already represents state-of-the-art wind turbine aerodynamics and mechanics, this paper concentrates on the modeling of the electrical systems in MATLAB/Simulink and on how to interface these electrical system models with the FAST tool. This paper will also be particularly useful for non-electrical engineers looking to evaluate turbine performance with a realistic generator model. For example, what happens to the mechanical loading during electrical faults on the grid, or analyzing possible impacts to the mechanical structures of the turbine when providing inertial response to the grid during under-frequency events.