bluuebunny/crossref_metadata_2025_split huggingface dataset:
Piezoelectric Patch Transducers: Can alternative sensors enhance bearing failure prediction?
Authors: Schilling L , Dalhoff P 
Published: October 2019

Abstract
This paper examines the applicability of piezoelectric patch transducers as condition monitoring sensors for the drive train of wind turbines. Three laboratory experiments are conducted to determine the sensor’s temperature stability, sensitivity toward electromagnetic interference and general ability to detect bearing damages. The sensors show little deviation under thermal influence in a tested temperature range between -40 °C and +80 °C. Although they react to electromagnetic interference, the disturbance signal is predominated by the damage signal. Proper shielding is yet recommended to fully eliminate electromagnetic interference. An example of shielding is given through the use of mu-metal. In direct comparison of bearing fault detection capability to a state-of-the-art accelerometer, the patch transducer performs slightly worse in matters of signal-to-noise-ratio. However, when excited by small damage impulses, it yields good signal depth and output. Altogether, the sensor shows fundamental applicability as a condition monitoring sensor in all experiments, though further optimization seems feasible and worthwhile.
Offshore Wind Turbine Loads and Motions in Unstable Atmospheric Conditions
Authors: Putri R M , Obhrai C , Knight J M 
Published: October 2019

Abstract
Even though it is widely known that unstable atmospheric stability conditions can lead to higher turbulence, the use of proper turbulent wind models considering unstable conditions are not often used in the simulation of loads and motions of offshore wind turbines. For this reason, the Højstrup model, which was specifically developed for unstable conditions, is used to simulate a spar-buoy offshore wind turbine (OWT) and investigate the importance of unstable conditions in the design of floating offshore wind turbines. It is found that fatigue damage of a spar-buoy OWT is strongly influenced by unstable conditions, where very unstable condition gives 65% higher fatigue damage than neutral conditions for the tower top torsion, followed by 37% higher for tower base side-side bending and 24% higher for blade root flap-wise mode.
Fatigue sensitivity to foundation modelling in different operational states for the DTU 10MW monopile-based offshore wind turbine
Authors: Katsikogiannis George , Bachynski Erin E. , Page Ana M. 
Published: October 2019

Abstract
The importance of foundation modelling for the support-structure fatigue damage estimation of a 10 MW monopile based offshore wind turbine is investigated in different operational states and wind-wave misalignment conditions. Three different models are used: (1) a non-linear elasto-plastic model including hysteretic behaviour effects, (2) a linear elastic model and (3) a non-linear elastic model, using numerical simulations with an aero-hydro-servo-elastic computational tool. Depending on the environmental condition, different dynamic processes dominate the responses. For parked states, deviations between models up to 160% were found. For wind wave-misalignment over 30° in operational cases, differences up to 180% were found for low sea states and 119% for high sea sates. Both nonlinear foundation damping and stiffness formulation have considerable effect on the responses, with hysteretic effects becoming crucial when aerodynamic damping is negligible in the direction of the response. Attention is required when comparing the fatigue damage only at the mudline, as larger variations between the models may occur in the embedded part of the monopile, where the absolute maximum is found.
On Initial Design and Modelling of a 10 MW Medium Speed Drivetrain for Offshore Wind Turbines
Authors: Wang Shuaishuai , Nejad Amir R. , Moan Torgeir 
Published: October 2019

Abstract
This paper presents the initial design and modelling of a medium speed drivetrain for the DTU 10 MW offshore wind turbine. Design basis and criteria of the drivetrain are described. Minimum weight and volume of the drivetrain are chosen as the main design targets. A four-point support, two main bearings and two torque arms, drivetrain configuration is selected in this study. One conventional gearbox layout, two planetary stages and one parallel stage, which is commonly used in large offshore wind turbines is adopted. Four gearbox layout options are provided and compared, and one optimal option is finally selected with holistic considerations of volume and weight as well as load sharing performance principles. Then, a high fidelity drivetrain numerical model for the 10 MW reference turbine is established using multi-body system (MBS) approach. In addition, model comparison is conducted, which shows that drivetrain eigenfrequencies in torsional mode obtained from the numerical model agree well with the values in the DTU report. Finally, future work relating to dynamic response analysis, critical limit states check for the drivetrain model is proposed.
Resonance Characteristics in Offshore Wind Power Plants with 66 kV Collection Grids
Authors: Holdyk A , Kocewiak Ł H 
Published: October 2019

Abstract
This paper presents a study of the influence of doubling the collection grid voltage on the electric resonances in the collection grid of large offshore wind power plants. This was done using wide-band models of most important passive components such as transformers and cables. Wide-band models based on measurements (black box) of transformers were used. Scaling of admittance matrix elements was used in order to adjust the voltage ratio of the measured wind turbine transformers to take into account the doubled voltage at the medium voltage side.
It was shown that doubling the collection grid voltage decreases the main resonance frequency seen at the medium voltage terminal of the wind turbine transformers as well as the offshore substation transformer. The decrease was approximately 25 per cent when doubling the voltage and keeping the same number of turbines in a radial. When the number of turbines was doubled, there was a proportional decrease of the resonance frequency.
Decreasing the main resonance frequency in offshore wind power plants might have an impact on the harmonic and transient behaviour and should therefore be investigated by developers.
The X-Rotor Offshore Wind Turbine Concept
Authors: Leithead William , Camciuc Arthur , Amiri Abbas Kazemi , Carroll James 
Published: October 2019

Abstract
The following paper provides an overview of a novel wind turbine concept known as the X-Rotor Offshore Wind Turbine. The X-Rotor is a new wind turbine concept that aims to reduce the cost of energy from offshore wind. Cost reductions are achieved through reduced capital costs and reduced maintenance costs. The following paper includes results from an early feasibility study completed on the concept. In the feasibility study exemplary designs were created and structural analyses were carried out. Turbine capital costs and maintenance cost of the X-Rotor concept were then roughly estimated. X-Rotor turbine costs and O&M costs were compared to four existing wind turbine types to investigate potential cost savings from the X-Rotor concept. Results show that the X-Rotor has potential to reduce O&M costs by up to 55% and capital costs by up to 32%. The combination of the capital cost and O&M cost savings show potential to reduce the CoE by up to 26%.
Power Losses in Electrical Topologies for a Multi-Rotor Wind Turbine System
Authors: Sunde Ingvar Hinderaker , Torres-Olguin Raymundo E. , Anaya-Lara Olimpo 
Published: October 2019

Abstract
Multi-rotor wind turbine systems are proposed as an additional technology to the future of wind energy, and a way of achieving wind turbines generating 20 MW or more. Research regarding the electrical connections of such a system is lacking, and this is key parts of the system. The controllability and power losses are important factors in the different topology options. In this study, three different electrical topologies are proposed and their controllers are implemented respectively. The systems are fairly simplified. Further, ways to measure the power losses within the power converters are researched, and a way of doing so is implemented on the three systems. The simulations performed on the system show the validity of the controllers as well as the power loss calculation method. In this study, the power losses found in the different topologies in total are quite similar to each other, right above 1%, so it is hard to prefer on of the topologies based on this. However, this serves as a tool that can be adjusted and used on more complex systems, and in this way contribute to finding an optimal electrical collector topology for a multi-rotor wind turbine system.
Prediction of dynamic response of semi-submersible floating offshore wind turbines by a novel hydrodynamic coefficient model
Authors: Liu Yuliang , Ishihara Takeshi 
Published: October 2019

Abstract
A novel hydrodynamic coefficients model is proposed for the components of floating offshore wind turbine (FOWT). First, the formulas for evaluation of the added mass and drag coefficient for the components of FOWT are proposed to consider the interaction effects between columns as well as the frequency and amplitude dependencies. The global matrices of hydrodynamic coefficients are then evaluated by the proposed formulas and validated by the experimental data from the forced oscillation test. The predicted dynamic response of FOWT is also validated by the water tank test. Finally, the improvement of dynamic behaviour of the platform by the skirts is investigated. The decrease of amplitude and the increase of natural period for the heave motion of the platform with skirts are successfully simulated by the proposed model.
The need for dynamic inflow models for vertical axis wind turbines
Authors: Tavernier D. De , Ferreira C. 
Published: October 2019

Abstract
This paper investigates the need for dynamic inflow models for vertical axis wind turbines (VAWTs). The approach is two-fold. First, dynamic inflow is realised by dynamic thrust on an actuator disk in OpenFOAM. The induction phase shift and amplitude showed a significant dependency on the streamwise location. Second, a reference turbine in surging motion is studied using an actuator line OpenFOAM model as reference and an actuator cylinder model (with and without dynamic inflow model). The Larsen and Madsen dynamic inflow model is able to capture the overall behaviour in dynamic inflow conditions, however, it may be improved in the most upwind and downwind location. This study indicates that the modelling of VAWTs in dynamic inflow conditions may be enhanced by improving the dynamic inflow models.
Uncertainties in offshore wind turbulence intensity
Authors: Caires S. , Schouten J.-J. , Lønseth L. , Neshaug V. , Pathirana I. , Storas O. 
Published: October 2019

Abstract
In the development, design and operation of wind farms the knowledge of wind turbulence intensity is of paramount importance, particularly at hub height. Given that measurements are rare, turbulence intensities are often determined using simplified formulations. These formulations only account for a dependence on wind speed and include a neutral stability assumption. There are, therefore, large uncertainties associated with the results of such formulations. In order to quantify these uncertainties we determine the dependence of turbulence intensity at different heights on the surface wind velocity, wave conditions and vertical temperature gradients from offshore LiDAR wind observations in the North Sea. The turbulence intensity is shown to depend strongly on the atmospheric stability and less strongly on the sea surface roughness. The lower turbulence intensity values are observed under stable atmospheric conditions. The dependence of the turbulence intensity on the surface roughness is higher at the lower levels, with the significant wave height being the sea surface roughness parameters with the stronger correlation with the turbulence intensity.
Hierarchy and complexity in control of large offshore wind power plant clusters
Authors: Kavimandan A , Das K , Hansen A D , Cutululis N A 
Published: October 2019

Abstract
The scope of this paper is to review the hierarchical control architectures for offshore wind power plants (OWPPs) described in the state-of-art literature. A typical WPP control architecture consist of three levels: local wind turbine control level, WPP control level and control of group of WPPs. With more and more OWPPs development in close proximity and integration with the grid, future trends are favourable for large OWPP cluster formations, resulting in the growing need to better outline and interpret the WPP control strategies and propose means to establish coordination between the WPPs within large OWPP clusters. Coordination is essential for large WPP clusters to ensure the variable and stochastic wind power production does not adversely impact the overall grid stability and fulfil the requirement at PCC with optimised operation. Additionally, the paper also highlights the complexities associated with the hierarchical and coordinated control of large OWPPs and recommends ways to address them.
Effect of Wake Meandering on Aeroelastic Response of a Wind Turbine Placed in a Park
Authors: Panjwani B , Kvittem M , Eliassen L , Ormberg H , Godvik M 
Published: October 2019

Abstract
A wind turbine operating inside a wind farm is subjected to increased turbulence intensity and reduced wind speeds resulting in increased fatigue loadings and reduced power production. Furthermore, meandering of the wakes results in increased dynamic loading of the wind turbine. In the present study, a standalone dynamic wake meandering (DWM) model has been developed and implemented in commercial code SIMA. The standalone DIWA model does not require a direct coupling with aeroelastic code, hence it is computationally fast. Although the standalone tool is a good alternative for power and thrust prediction, it does not have the capability to predict the turbine aeroelastic loads. The new DWM program is referred as “Disturbed Inflow Wind Analyzer” (DIWA). Benchmarking studies of DIWA with the literature data are presented and discussed. Overall the DIWA compares well with the literature data and the discrepancies between DIWA and the literature data are discussed. The present studies show that the wake deficit profiles are very sensitive to the eddy viscosity parameters. Finally, the turbulence boxes generated using DIWA have been used for understanding the aeroelastic behaviour of NREL 5MW turbine and one of the wind turbines from the Lillgrund wind park. The estimated power production using both aeroelastic coupled with DIWA turbulence boxes and standalone DIWA (without aeroelastic) are in good agreement with the literature data. The trends of fatigue loads are predicted well, with a few exceptions.
Recommended key performance indicators for operational management of wind turbines
Authors: Pfaffel S , Faulstich S , Sheng S 
Published: October 2019

Abstract
Operational managers of wind turbines usually monitor a big fleet of turbines and thus need highly condensed information to identify underperforming turbines and to prioritize their work. Key performance indicators (KPIs) are a solid and frequently used tool for this purpose. However, the KPIs used in the wind industry are not unified to date, which makes comparison in the industry difficult. Further, comprehensive standards on a set of KPIs for the wind industry are missing. This article identifies and recommends KPIs and provides detailed definitions to make KPIs comparable and to enable benchmarking. The starting point of this work is an industry survey with 28 participants intended to identify commonly used KPIs, collect various possible definitions, and prioritize them. Out of a total of 50 KPIs, we discuss in a next step 33 selected KPIs on performance, maintenance, and reliability in detail and recommend definitions, most of which are based on international standards. As a result, operators can easily use these recommendations to base their system of KPIs. By using this unified set of KPIs, operators can be well-prepared to conduct industrywide comparisons and benchmarks. The survey and this article will also serve as a basis for committee work of the FGW e.V. to develop a corresponding technical guideline.
On the effects of environmental conditions on wind turbine performance: an offshore case study
Authors: Gonzalez E , Valldecabres L , Seyr H , Melero J J 
Published: October 2019

Abstract
Monitoring wind turbine (WT) performance offers a means of identifying abnormal operation, but only if natural disturbances of the operating regime change can be excluded. WT performance monitoring usually relies on the analysis of operational power curves, generally based on data from the supervision control and data acquisition system. However, these curves do not reflect the source of variability, negatively affecting the capabilities for detecting WT abnormal performance. This work aims at understanding and quantifying changes in WT performance variability due to different environmental conditions during normal and wake-free operating conditions, based on an offshore case study. The magnitude of performance fluctuations is highly influenced by environmental conditions, being higher during high turbulence intensity and low wind shear conditions. The Taylor law, with small time windows, is suitable to describe them for low-mid winds in the absence of dedicated wind measurements, often not permanently available offshore, and could potentially result in more effective performance monitoring solutions. Nevertheless, the heteroskedastic nature of the power deviations negatively affects fitting possibilities. The results support the importance of using low data aggregation periods to understand the dynamics of WT performance.
Analysis Lean Construction Application to Reduce Material Waste at Bridge Construction Project
Authors: Sebastian A E 
Published: October 2019

Abstract
This abstract discusses the amount of concrete and steel waste that are produced at the manufacturing stage in Precast Plant as well as examines the processes that cause the generation of waste. This abstract also discusses the implementation of Lean Construction concept in bridge construction projects and the influence of this concept on waste minimization in the construction processes. The study was qualitative research using study case method and also through unstructured interviews to seek information according to the approach used in this research that is Last Planner System. This result of this research proves lean construction contribution to reduce waste.
Spatial analysis for the selection of landfill in Jepara Regency
Authors: Nugroho A , Suharyanto  , Sudarno  
Published: October 2019

Abstract
There are three landfills in Jepara Regency, which are Bandengan, Gemulung, and Krasak. Bandengan uses a controlled landfill system and is estimated to be full in the next 1.68 years. The Gemulung and Krasak still use an open dumping landfill, and they were closed in 2013 complying the Law No. 18 of 2008. Due to the prolonging problems, it is necessary to plan a new landfill with sufficient capacity. The landfill should have sufficient capacity and meet the standard environmental requirements. The objective of this study is to examine the appropriate zones for landfill in Jepara Regency in line with the standards of SNI 19-3241-1994 and literature review. SNI uses two stages of analysis, the regional level stage, which is determining the regions considered to be feasible, i.e. inappropriate zones and stage of elimination, choosing the best site from the location that emerges from the regional stage. The analysis was conducted using the multi spatial criteria with the aid of Geographic Information Systems (GIS). From this spatial analysis, the same scoring technique was then performed which produced a map of recommendations for the various locations. The results showed that there were six feasible zones for the landfill site covering 129.53 ha or 0.13% of the total area of Jepara Regency. The Keling District was chosen as the best location for landfill among the six feasible zones.
The Role of Renewable Energy to Reduce Climate Change: Perspective of Policy Content and Context
Authors: Respitawulan A , Rahayu A Y S 
Published: October 2019

Abstract
Energy needs have increased each year along with economic growth and increasing population number. Indonesia still relies on fossil fuels as an energy source that dominates the national energy mix. Fossil energy has an impact on greenhouse gas emissions that threatens climate change. The role of the government through energy diversification policies has not provided maximum contribution to fulfil energy needs. This study aims to analyze the policy of developing renewable energy in reducing greenhouse gas emissions based on content and context policy, using qualitative method to explain and describe implementation of the renewable energy policy. Data were derived from primary and secondary sources which are conducted in the period of October – December 2018. The result shows that there were several factors from the content and context of policy that have a significant correlation in the renewable energy policy implementation. The political environment has a role in the implementation of policy content related to the benefits that will be perceived by the community. Other policies that influence renewable energy consumption like fuel and electricity subsidy and allocation of resources are needed to implement the policy.
Performance Evaluation and Crack Repair in Building Infrastructure
Authors: Dermawan A S , Dewi S M , Wisnumurti  , Wibowo A 
Published: October 2019

Abstract
The implementation of building infrastructure development to improve people’s lives is important. The use of reinforced concrete structures has increased very rapidly. But many buildings are failed and are not safe because of overloading, changes in function and configuration of buildings, poor maintenance, and natural disasters. Many methods developed to reduce the damage caused by earthquakes so that the development of methods to strengthen and repair building structures is needed to anticipate damage to buildings. This study focuses on beam-column joint cracks with simple building characteristics, column size 20/20 and beam 15/20 (monolithic) with concrete quality fc’= 21 MPa, so it is necessary to evaluate and repair beam-column joint cracks in buildings because of overload. The method used was experimental and testing in a laboratory with a single static load and Ultrasonic Pulse Velocity (UPV) test to determine the density after repair. Test specimens are SK (control-specimens) and SK-repairing. The results showed that the beam-column joint performance before and after repairs had relatively the same flexural strength of 1,669 kg and 1,686 kg, while the stiffness was lower at 14.48%. The velocity after repair average is 3,327.5 m/s (medium-category). The elasticity average modulus of the test is 20.43 GPa.