bluuebunny/crossref_metadata_2025_split huggingface dataset:
Including installation logistics costs in the optimal sizing of semi-submersibles for floating wind farms
Authors: Baudino Bessone M , Zaaijer M , von Terzi D , Dykes K , Jump E , Viré A 
Published: June 2022

Abstract
In this research, we explored the potential to reduce the cost of floating wind farms by adopting an integrated approach to optimally size semi-submersible substructures accounting for materials, fabrication and installation-logistics-related costs. A trade-off between manufacturing and installation costs was identified. This trade-off is driven by the growth of shipyard costs when the size of the structure increases, counteracting the reduction of fabrication costs achieved with a larger semi-submersible footprint. For the reference scenario, accounting for this trade-off yields a design that is a few tenths of a percent cheaper than when minimising only fabrication costs. However, the obtained design has a considerably smaller footprint than the fabrication-only case. The sensitivity of this trade-off to different installation strategies affecting the required storage area at the shipyard was assessed. When fabrication costs are dominant, the advantage of accounting for installation costs in the design process is negligible. Instead, larger storage area requirements increase the cost reduction achieved by optimising the semi-submersible while simultaneously accounting for fabrication and installation costs. The coupling effect remained significant for all the cases considered in a further sensitivity analysis of key parameters affecting the cost-optimal design. Furthermore, we identified several different designs that provide enough hydrostatic restoring moment in pitch to counteract the thrust-induced overturning moment within a small cost range from the most cost-effective one. This result suggests that additional criteria than minimising manufacturing and installation costs could drive the final design choice.
An Open-Source Frequency-Domain Model for Floating Wind Turbine Design Optimization
Authors: Hall Matthew , Housner Stein , Zalkind Daniel , Bortolotti Pietro , Ogden David , Barter Garrett 
Published: June 2022

AbstractA new frequency-domain dynamics model has been developed that uses open-source components to efficiently represent a complete floating wind turbine system. The model, called RAFT (Response Amplitudes of Floating Turbines), incorporates quasi-static mooring reactions, strip-theory and potential-flow hydrodynamics, blade-element-momentum aerodynamics, and linear turbine control. The formulation is compatible with a wide variety of support structure configurations and no manual or time-domain preprocessing steps are required, making RAFT very practical in design and optimization workflows. The model is applied to three reference floating wind turbine designs and its predictions are compared with results from time-domain OpenFAST simulations. There is good agreement in mean offsets as well the statistics and spectra of the dynamic response, verifying RAFT’s general suitability for floating wind analysis. Follow-on work will include verification of potential-flow and turbine-control features and application to optimization problems.
A frequency-time domain method for annual energy production estimation in floating wind turbines
Authors: Amaral R , Laugesen K , Masciola M , von Terzi D , Deglaire P , Viré A 
Published: June 2022

Abstract
A new method is proposed to estimate a floating wind turbine’s annual energy production (AEP) using frequency and time-domain design techniques. The approach demonstrated herein estimates the AEP by performing a convolution between the floating platform response and the response power operators (RPOs) that map the average power produced by the turbine as a function of the amplitude and frequency of the platform motions. One advantage of this approach is that it can be performed early in the conceptual design phase to help discover design space trade-offs between the platform and rotor design. The methodology is applied to the IEA Wind 15 MW WindCrete spar-buoy model using OpenFAST. The RPOs are obtained by prescribing single-DOF platform motions to the turbine with a given amplitude and frequency. This methodology is then validated by comparing the AEP estimation from the RPOs with the AEP estimation from fully-coupled simulations. The results indicate that the method is able to estimate the value of AEP for a realistic sea-state and regular waves. However, further validation is needed as, in the first case, the turbine is moving too little and, in the second case, the contribution of the controller may be dominant.
Surging Wind Turbine Simulations with a Free Wake Panel Method
Authors: Ribeiro A F P , Casalino D , Ferreira C S 
Published: June 2022

Abstract
We investigate the aerodynamics of a surging wind turbine with numerical simulations based on a free wake panel method. We start by demonstrating the method’s capability to simulate a plunging airfoil, which provides some insights that are later used to interpret results of a surging rotor. We then validate the method on a non-surging wind turbine and discuss the strengths and weaknesses of our approach. Next, we focus on the UNAFLOW case: a surging wind turbine which was modelled experimentally and with various numerical methods. Good agreement with experimental data is observed for amplitude and phase of the thrust with surge motion. For the first time, we achieve numerical results of a wind turbine wake that accurately reproduce experimentally verified effects of surging motion. Finally, we extend our simulations beyond the frequency range of the UNAFLOW experiments and reach results that do not follow a quasi-steady response. Using the plunging airfoil data, we justify the behavior observed in the non-linear range. Our work seeks to contribute a different method to the pool of results for the UNAFLOW case, while extending the analysis to conditions that have not been simulated before.
Current simulation with Software in the Loop for floating offshore wind turbines
Authors: Otter A , Flannery B , Murphy J , Desmond C 
Published: June 2022

Abstract
The presence of current is an added source of hydrodynamic loading on the platforms of Floating Offshore Wind Turbines (FOWT). Not only will current add viscous loading on the platform and moorings of FOWTs, but it will also affect wave loadings due to the alteration of wave shapes caused by wave-current interactions. Although the effects of current on platform response, mooring tensions and fatigue life have been numerically investigated, they are mostly neglected during scale model experiments for FOWTs. This paper proposes a novel method to simulate current loading and wave-current interactions during scale model tests by using a dynamic winch which is controlled using a Software in the Loop (SIL) approach. The winch is used in combination with a Multi-Propeller Actuator (MPA), for combined wave/wind/current testing in laboratory basins. The proposed current simulation method has lower costs and is more versatile than traditional physical current generation in a basin, as it allows for a wider range of test conditions and can be applied in any wave basin. A description of the experimental procedure is provided along with numerical validation using both AQWA and FAST. Results show that the winch actuator is capable of reliably emulating the drag force exerted by a current on the platform over a range of test conditions.
Surrogate model for fast simulation of turbine loads in wind farms
Authors: Bossanyi Ervin 
Published: June 2022

Abstract
A surrogate model for turbine loading is presented which has been developed for predicting the fatigue loads on each turbine in a wind farm, taking full account of wake effects, for detailed site-specific load assessment and/or to predict the effects of wind farm control on the loads. The model has been implemented in the wind farm simulation code LongSim, where it can be used both for steady-state setpoint optimisation against a merit function which can include both power and turbine loads, and for dynamic time-domain simulations, for example to evaluate the effects of wind farm control on turbine loading. For this application, fatigue loads need to be evaluated much more rapidly than is possible with full aeroelastic turbine simulations. Surrogate models based on fatigue load interpolation from a database of pre-computed aeroelastic turbine simulations are unwieldy and likely to miss important wake effects. The key simplifying approximation of the new model is that the load contributions from different causes can be calculated separately and then combined. This makes it straightforward to account for all relevant effects, at the same time vastly reducing the number of aeroelastic simulations required to populate the model.
Uncertainty quantification of wind turbine airfoil aerodynamics with geometric uncertainty
Authors: Marepally Koushik , Su Jung Yong , Baeder James , Vijayakumar Ganesh 
Published: June 2022

AbstractAn artificial neural network based reduced order model (ROM) is developed to predict the load coefficients and performance of wind turbine airfoils. The model is trained using a representative database of 972 wind turbine airfoil shapes generated by perturbing the design parameters in each of 12 baseline airfoils defining commercially relevant modern wind turbines. The predictions from our ROM show excellent agreement with the CFD data, with a 99thpercentile maximum errors of 0.03 in lift-coefficient, 2 in lift-to-drag ratio and 0.002 in pitching moment coefficient. A Monte-Carlo based uncertainty quantification (UQ) and global sensitivity analysis (GSA) framework is developed using this computationally economical ROM. Using UQ, we observed the stall behavior to be very sensitive to geometric uncertainty, with more than 10% deviation in lift coefficient associated to 5% deviation in geometric features. Sobol’s analysis is used to identify the most influencing geometric feature for the stall behavior to be concentrated at the maximum thickness location on the airfoil suction surface.
Wind turbine blade design with airfoil shape control using invertible neural networks
Authors: Jasa John , Glaws Andrew , Bortolotti Pietro , Vijayakumar Ganesh , Barter Garrett 
Published: June 2022

Abstract
Wind turbine blade design is a highly multidisciplinary process that involves aerodynamics, structures, controls, manufacturing, costs, and other considerations. More efficient blade designs can be found by controlling the airfoil cross-sectional shapes simultaneously with the bulk blade twist and chord distributions. Prior work has focused on incorporating panel-based aerodynamic solvers with a blade design framework to allow for airfoil shape control within the design loop in a tractable manner. Including higher fidelity aerodynamic solvers, such as computational fluid dynamics, makes the design problem computationally intractable. In this work, we couple an invertible neural network trained on high-fidelity airfoil aerodynamic data to a turbine design framework to enable the design of airfoil cross sections within a larger blade design problem. We detail the methodology of this coupled framework and showcase its efficacy by aerostructurally redesigning the IEA 15-MW reference wind turbine blade. The coupled approach reduces the cost of energy by 0.9% compared to a more conventional design approach. This work enables the inclusion of high-fidelity aerodynamic data earlier in the design process, reducing cycle time and increasing certainty in the performance of the optimal design.
Farm wide sensitivity assessments of resonant frequencies of integrated offshore wind turbine finite element models
Authors: Fallais D J M , Winkler K , Sastre Jurado C , Weijtjens W , Stuyts B , Devriendt C 
Published: June 2022

Abstract
To date, despite advancements in the design of offshore wind turbines, the as-designed and identified as-built natural frequencies of offshore wind turbines still show discrepancies. These discrepancies are partially rooted in modelling uncertainties, as well as uncertain input parameters, related to e.g. aero-, fluid- or soil-structure interaction. The first objective of this article is to present a wind farm wide comparison of the first and second, modelled and identified, fore-aft natural frequencies for turbines in parked conditions for a wind farm located in the Belgian north sea. Secondly, the effect of different model parameters on the computed natural frequencies will be assessed using wind farm wide sensitivity studies, with the aim to describe the potential of each considered parametrization in reducing the discrepancy between modelled and measured resonance frequencies. The in-depth considered parametrizations are aimed at assessing the effect of the linearization of the p-y curves, soil stiffness, local scour as well as the mass of the rotor nacelle assembly, whereas results for wall thickness, marine growth, added mass coefficient and sea water level variations will be presented without further discussion. In order to perform this study, turbine specific finite element models have been prepared and verified based on detailed design documents; subsequently updated best-estimate soil data has been used to model the foundation for two different design scenarios. Furthermore, modal parameters have been identified for each turbine, based on vibration data collected in parked condition and state of the art operational modal analysis tools. The results show that the discrepancies between the modelled and identified first fore-aft natural frequencies could potentially be bridged by adjusting combination of the investigated parameters, whereas the discrepancies observed on the second natural frequency cannot be bridged by making changes to the investigated parameters. As such, future work will entail a more detailed investigation on modelling uncertainties.
A blade element momentum model for dual-rotor wind turbines considering inter-rotor velocity interferences
Authors: Yin F F , Chen J J , Li X K , Ye Z L , Tang W , Shen X , Guo X J 
Published: June 2022

Abstract
A blade element momentum model for predicting the aerodynamic performance of dual-rotor wind turbines (DRWTs) as an aerodynamic design tool is introduced in this paper. The model considers the inter-rotor axial velocity reduction and the tangential velocity components in the front rotor’s wake to model the inter-rotor velocity interferences for the inflow velocity as the input of the BEM theory. A DRWT with two NREL 5MW rotors is studied using the present model and CFD simulations. Results from the two methods show good agreements with each other in the trends of power, thrust, and aerodynamic loads on the blades despite the error in near-tip regions. The present DRWT configurations have lower optimum tip speed ratios and a wider range of high-CP
speeds. The maximum efficiency of the present turbine is improved by only 5%, indicating that a dedicated blade design for DRWT aerodynamics is required to enhance power output and lower the aerodynamic loads.
Optimum Turbine Design for Hydrogen Production from Offshore Wind
Authors: Mehta Mihir , Zaaijer Michiel , Terzi Dominic von 
Published: June 2022

Abstract
To limit the consequences of climate change, generation from renewables coupled with large scale electrification is necessary. However, the deployment of renewables has its own challenges and not all sectors can be electrified. Hydrogen production from wind energy emerges as a promising solution that can alleviate these challenges. The current costs of green hydrogen production are high due to the high costs of electricity used for electrolysis. This study looks into the benefits of optimizing a turbine specifically for hydrogen production and the reduction in the Levelized Cost of Hydrogen (LCoH) compared to the use of conventional Levelized Cost of Energy (LCoE) optimized turbine. The case presented shows that turbines designed specifically for hydrogen production tend to have a higher specific power but these provide only a marginal advantage over using LCoE-optimized turbines for hydrogen production. Oversizing the electrolyzer compared to the turbine was shown to be a good design strategy. In the future, designing turbines specifically for hydrogen production could have certain benefits, depending on how the electrolyzer efficiencies, hydrogen production costs and the hydrogen market evolve.
Sensitivity analysis of a Ground-Gen Airborne Wind Energy System design
Authors: Trevisi Filippo , Riboldi Carlo E.D. , Croce Alessandro 
Published: June 2022

Abstract
The architecture of a new multidisciplinary design and optimization framework for rigid wing Airborne Wind Energy Systems, named T-GliDe, is introduced and a Ground-Gen AWES is analyzed to illustrate the features of the design approach. T-GliDe features an optimization module and an uncertainty quantification module, allowing for a number of algorithm-based design techniques. T-GliDe performs an AWES design optimizing market-based objective functions, while satisfying constraints related to fight stability. The fight dynamics is modelled with analytical aerodynamic theories, allowing for fast and consistent design evaluations, without the use of time simulation codes and thus of active control. In this work, a reduced optimization problem is run to find optimal working-set points of a Ground-Gen AWES with respect to power production. The reel-out factor and the pitch angle as function of wind speed are considered as design variables and output trends are shown. A variance based sensitivity analysis is then run to investigate how the rigid body eigenvalues are influenced by a set of independent variables. Among the chosen independent variables, a sub-set of variables which bear an impact on the dynamics is identified and they will be considered in future design and optimization activities as design variables.
Techno-economic analysis of power smoothing solutions for pumping airborne wind energy systems
Authors: Joshi R , von Terzi D , Kruijff M , Schmehl R 
Published: June 2022

Abstract
In pumping airborne wind energy (AWE) systems, the kite is operated in repetitive crosswind patterns, pulling the tether from a winch that drives a generator on the ground. During the reel-out phase of its operation, it produces power, whereas, during the reel-in phase, it consumes a small fraction of the produced power. This leads to an oscillating power profile that requires smoothing before it can be supplied to the electricity grid. This paper proposes three drivetrain concepts as a solution to this power smoothing challenge. The three concepts are based on three different types of storage technologies: electrical, hydraulic and mechanical. Techno–economic models of the drivetrains were developed and a case-study on sizing and costing of the three drivetrain concepts for a MW–scale AWE system was performed. Conclusions were drawn that provide guidance to AWE developers for choosing a suitable drivetrain concept for their systems.
3D printed rotor blades for a research wind turbine: Aerodynamic and structural design and testing
Authors: Alber J , Assfalg L , Nayeri C N , Paschereit C O , Lahr M , Semmler L , Twele J , Fortmann J , Fischer J , Latoufis K , Dorn I 
Published: June 2022

Abstract
This study combines the design, the 3D printing and the testing of a small 3-bladed wind turbine rotor for research and teaching purposes. The objective is the additive manufacturing of a rotor with a radius of one meter, as an alternative to subtractive methods, such as computerized milling. The blade design is developed using freely available software packages. The aerodynamic considerations include the airfoil selection, the calculation of the blade geometry and the simulation of the ultimate load cases. The structural considerations are focussed on the printable materials, the infill structures and the retrofit of a load-carrying spar. The rotor blades are 3D printed with the BigRep One at the maker space of the TH Wildau. The structural integrity of the prototype blade is tested in terms of the ultimate root bending moments and the centrifugal forces at the HTW Berlin. The aerodynamic run-up tests are performed at the large wind tunnel of the TU Berlin measuring the power curves. The successful prototype paves the way for follow-up projects, such as open field tests and the 3D printing of larger rotor blades.
Using Small Wind Turbine Technology to Design an AntiFrost Fan
Authors: Sessarego Matias , Wood David 
Published: June 2022

Abstract
Anti-frost fans (AFFs) are widely used in agriculture to reduce the frost damage to crops. The small wind turbine rotor design code (SWRDC) was adapted to design the blades of an anti-frost fan to maximize the mass flow rate through the rotor while minimizing the blade mass and aerodynamic noise. Using a random sample set of 60 baseline designs, the design is iterated using a genetic algorithm to obtain an optimized design with a mass flow rate of 3.11 kg/s, a blade mass of 6.96 kg, and with a noise level of 72.8 dB.
Challenges and Possible Solutions in Aeroelastic Modeling for the Distributed Wind Industry
Authors: Damiani R , Davis D , Summerville B 
Published: June 2022

Abstract
Aeroelastic modeling (AM) is the primary methodology for structural and performance assessment of any wind turbine; it provides an understanding of the impact of design parameters on turbine loading and power response before witnessing it in the field. Despite these advantages, the use of AM in the distributed wind technology (DWT) sector is limited. This article represents a short summary of an in-depth assessment by the authors of the status of AM and its role within the distributed wind technology design standards. The research gathered input and feedback from a large number of U.S. and international stakeholders, reviewed technical strengths and weaknesses of the current edition of the design standards, analyzed the minutes from recent industry workshops and meetings, collected publicly available AM templates, and provided an evaluation of the existing AM codes. Several goals were achieved including providing strategies for the load assessment categorization of turbines based on rotor swept area and archetype, and guidance for AM verification and validation. Recommendations within this study will advance the value and the ease-of-use of AM, thereby allowing the industry to better capitalize this underutilized tool, resulting in a more efficient design process, an easier path to certification, and overall better and more reliable distributed wind technology products.
Engineering a Reduction of the Levelized Cost of Energy of Distributed Wind Turbines via Rotor and Control Enhancements
Authors: Damiani R , Davis D 
Published: June 2022

Abstract
Distributed wind turbines (DWTs), with rated capacity less than 100 kW, are penalized by high balance-of-system costs that lead to a high levelized cost of energy (LCOE). As a result, to contain the capital expenditure and thus LCOE, traditional designs have avoided active control systems that are standard in larger machines, e.g., active yaw and pitch control. In this paper, we present the key results of a trade-off study between larger rotor diameter, loads abatement, and simplicity in the pitch design for a typical mid-sized DWT with the overarching goal of increasing performance and decreasing LCOE. We focused on the upgrade potential for a generic downwind, passive-yaw, stall-controlled turbine model with high-speed shaft (HSS) brake and rated capacity of ∼ 60kW.
A rotor and control redesign proved successful in increasing power capture through the deployment of a blade-root extender and an innovative, low-cost, independent pitch system for overspeed protection. The improvements remove the need for a mechanical brake and yield a significant decrease in LCOE. The loads in all components were kept under the target threshold by a combination of optimum blade extender length and rotor rotational velocity. The failsafe and redundant aerodynamic braking system is economical and can lend itself to retrofit applications to other turbine models.