bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of helix and wake steering control for varying turbine spacing and wind direction
Authors: Taschner E , Becker M , Verzijlbergh Remco , Van Wingerden JW
Published: June 2024

A variety of wind farm control strategies exist in order to reduce unfavorable wake effects in large wind farms. While strategies like wake steering already reached a high maturity level, it is interesting to compare them to more recently proposed strategies. Such a comparison can form the basis for the development of a symbiotic wind farm control toolbox, from which a control strategy is chosen and activated depending on the operating conditions. The present study compares wake steering with helix control across a wide range of turbine spacings and wind directions using large-eddy simulation (LES). The size of the search space is made computationally tractable for LES by adopting a setup based on one physical upstream turbine and a distribution of virtual downstream turbines which do not exert any thrust force. It is found that helix control is beneficial for full wake overlap and turbine spacing of less than six rotor diameters whereas wake steering proves to be optimal further downstream and for partial wake overlap. Furthermore, the results show that the helix control setpoint in the proximity of full wake overlap scenarios is less susceptible to wind direction variations. This finding indicates that the combination of wake steering and helix control has potential for the design of a wind farm controller which is more robust in full wake overlap scenarios and can reduce the need for large yaw offset adjustments.
Closed-loop coupling of a dynamic wake model with a wind inflow estimator
Authors: Di Cave J , Braunbehrens R , Krause J , Guilloré A , Bottasso C L
Published: June 2024

The estimation of turbine flow evolution provided by low-fidelity dynamic wake models, such as FLORIDyn, can be improved by the introduction of a Kalman filter based on power production measurements. However, it is not possible to infer any information about which side of an impinged rotor is affected by the wake only by the observed power, being itself a single scalar quantity. In this paper, a new closed-loop formulation of the FLORIDyn model is investigated: wind speed estimates, given by a blade load-based wind observer, are implemented into a Kalman Filter, providing information about the position of the wake over the rotor plane. The FLORIDyn model augmented with the wind flow estimator is tested in a layout of two aligned turbines and compared to a corresponding CFD simulation. The results of the proposed approach show an improved ability to predict wind flow quantities and the wake centerline position compared to the open-loop version of the model.
Robust wind farm layout optimization
Authors: Sinner Michael , Fleming Paul
Published: June 2024

Wake interactions in wind farms cause losses in annual energy production (AEP) on the order of 10%. Wind farm designers optimize the layout of the farm to mitigate wake losses, especially in the dominant site-specific wind directions. As wind turbines and wind farms grow in scale, optimization becomes more complex. Offshore wind farms regularly comprise more than 100 wind turbines and are characterized by complex boundaries due to shipping lanes, neighboring wind farms, and other constraints.

Layout optimization methods are broadly split between gradient-based and gradient-free approaches. Gradient-based approaches can converge quickly and perform well for smaller, academic problems but are often sensitive to initial conditions and tuning parameters and require expert knowledge to use. On the other hand, gradient-free approaches can be more robust to problem complexities. We present a robust layout optimization approach based on a random search algorithm. The algorithm is intended for those who are not optimization experts and has few tuning parameters that need specification to achieve satisfactory results. Unlike off-the-shelf methods, which use generally available, non-domain-specific optimization routines that accept as inputs an optimization function and constraint definitions, this approach takes advantage of the relative computational costs of the different evaluations by evaluating cheaper computations first (boundary and minimum distance constraints) and running expensive AEP evaluations only if all other checks pass. Moreover, an outer genetic algorithm allows multiple solutions to evolve in parallel, enabling rapid solution development on high-performance computers. We discuss the relative ease of selecting necessary tuning parameters and demonstrate the efficacy of the genetic random search on a complex layout problem consisting of placing 70 turbines in a nonconvex and unconnected boundary region.
Comparison of 25 MW downwind and upwind turbine designs with individual pitch control
Authors: Phadnis Mandar , Escalera Mendoza Alejandra S. , Jeong Michael , Loth Eric , Todd Griffith D. , Pusch Manuel , Pao Lucy
Published: June 2024

As conventional upwind wind turbines grow larger, the increased mass and flexibility of the longer blades present challenges concerning costs, structural loads, and safety constraints such as tower clearance. At extreme scales, wind turbines in a downwind configuration may provide a feasible alternative to address these challenges by allowing lightweight, flexible blades that can reduce capital costs and blade loads while maintaining safety margins. Downwind turbine blades suffer from increased fatigue loading due to the tower shadow effect. In this study, novel downwind, three-bladed wind turbine designs at 25 MW rating with lightweight, flexible blades are evaluated and compared in terms of power production and structural loading. To obtain a baseline performance, a standard collective blade pitch wind turbine controller is implemented for the two downwind and one upwind turbine designs. Individual pitch control is then added for the downwind turbines to reduce structural fatigue on the turbine blades. In summary, the two downwind turbine designs that differ in rotor pre-coning and shaft tilt angles using collective and individual pitch control are compared against a conventional upwind turbine with collective pitch control at the same scale under turbulent wind conditions.
LES-based validation of a dynamic wind farm flow model under unsteady inflow and yaw misalignment
Authors: Bohrer Jan Kai , Petrović Vlaho , Rott Andreas , Kühn Martin
Published: June 2024

This work presents the validation of an extended version of the control-oriented, dynamic wind farm flow solver SPLINTER. The two-dimensional model is applied to use cases of wake steering by yaw misalignment and inflow wind direction variations and the results are compared to large-eddy simulations (LES). While SPLINTER is able to reproduce the antagonal behaviour of decreasing upstream and increasing downstream turbine power under wake deflection, a systematic deviation of the downstream power is detected and quantified, which is connected to underrepresented three-dimensional wake effects. In case of changing inflow wind direction, SPLINTER is capable of computing movement and shape of the bending wakes. The model smooths small-scale turbulent structures and disturbances and does not reproduce wake meandering, but manages to describe the evolution of the mean flow, which is tested by averaging over an ensemble of LES and comparing the resulting flow fields and turbine power time series. Under dynamic inflow conditions, SPLINTER is able to predict at which time intervals and at which rates downstream turbines will be influenced by wakes, which can improve the accuracy of short-term power and load forecasting and enables its application to online model predictive wind farm control.
Model wind turbine performance in turbulent–non-turbulent boundary layer flow
Authors: Neuhaus Lars , Ribnitzky Daniel , Hölling Michael , Wächter Matthias , Avila Kerstin , Kühn Martin , Peinke Joachim
Published: June 2024

With increasing distance from the coast and greater hub heights, wind turbines expand into unknown, hardly researched environmental conditions. As height increases, laminar flow conditions become more likely. With the simultaneous increase in rotor diameter, very different flow conditions, from laminar to turbulent, occur over the rotor area. It is crucial to understand the effects of these different flow conditions on wind turbines. We approach this through wind tunnel experiments, presenting a setup with two different active grids. This setup enables the generation of four different flows – homogeneous, shear, turbulent–non-turbulent, and turbulent–non-turbulent shear flow – each with four different turbulence levels. The turbulent–non-turbulent flows exhibit a turbulence intensity gradient between the quasi-laminar flow at the upper and turbulent flow at the lower rotor half, establishing a turbulent–non-turbulent interface between the two rotor halves. In a second step, we investigate the Model Wind Turbine Oldenburg with a rotor diameter of 1.8 m (MoWiTO 1.8) under these conditions and analyze their effects on power output and blade loads. While the power fluctuations depend directly on the turbulence intensity, an additional turbulence intensity gradient shows no significant effect. A stronger effect can be observed for the blade root bending moments, the fluctuations of which increase with shear and also in turbulent–non-turbulent flow.
Prediction of rain erosion damage progression using disdrometer rain data: The importance of liquid water content
Authors: Hannesdóttir Ásta , Dellwik Ebba , Hasager Charlotte Bay
Published: June 2024

Wind turbine blade erosion poses a significant challenge to the durability and performance of wind turbines. Modeling of rain erosion damage, considering atmospheric conditions, improves our understanding of the progression of leading-edge erosion on wind turbine blades. In this study, we investigate the impact of varying raindrop characteristics on rain erosion damage development. We analyse 2.5 years of data from a disdrometer, which measures the size and velocity of falling rain droplets, at Risø campus. Various post-processing methods of the disdrometer data are used for estimating representative droplet diameters and fall velocities for each rain event. We compare measured droplet fall velocities with theoretical terminal velocities, revealing a necessity for revising theoretical approaches to raindrop fall velocity for erosion damage modeling. The measured rain rates and representative fall velocities are used to calculate the liquid water content in the air. We introduce a bin-wise summation method for estimating the liquid water content, circumventing the need for representative droplet assumptions. As this method provides the most accurate input for the damage model, we benchmark the other post-processing methods against it and employ it to evaluate bias estimates of associated damage predictions. The largest bias (22%) in accumulated damage is found with an arithmetic mean droplet diameter approach and the smallest bias (-2%) with the median volume estimation method for damage model input. Furthermore, we demonstrate that, for a given rainfall volume, smaller droplets contribute to larger accumulated damage compared to larger droplets.
Measuring wake deflection from SCADA data during wake steering using machine learning
Authors: Post Nathan , Zheng Cheng , Kerrigan Daniel , Bertini Enrico , Tory Melanie
Published: June 2024

As wake steering is implemented on large wind plants, methods for evaluating how well these systems optimize plant performance are needed. The data analysis from experiments conducted so far generally focuses on evaluating the improvement in power or energy production of the plant and comparing that to the predicted improvement. In this study, we explore a new approach to provide additional insight and validation of optimization tools by measuring the wake deflection experimentally using only the downstream turbine as a sensor. This approach is demonstrated using the SMARTEOLE wind plant wake steering experimental data. Light gradient boosting machines (LGBM) and Gaussian process (GP) machine learning models are trained and then interrogated by making a set of predictions under defined conditions to determine the wake deflection observed at the downstream turbine. The data set is sparse, particularly for larger yaw angles, and noisy due to factors not captured in the SCADA leading to relatively high uncertainty in the predictions. The GP model is better suited to smoothly fit this data. Using the GP model, a wake deflection of 0.35 rotor diameters at 3.7 rotor diameters downwind is estimated for a yaw error of 20 degrees on the upwind turbine.
Flow around a pair of 2D cylinders using a hybrid Eulerian-Lagrangian solver
Authors: Pasolari R. , Ferreira C. , Van Zuijlen A.
Published: June 2024

The field of external aerodynamics encompasses various engineering disciplines with a significant impact on wind energy technology. Aerodynamic investigations provide insights not only into the characteristics of individual blades or standalone wind turbines but also into entire wind farms. As advancements in wind turbine design continue, understanding the interactions between turbines in close proximity becomes crucial, presenting a multi-body problem. Researchers require efficient and accurate tools to comprehensively study such dynamics. This paper presents a hybrid Eulerian-Lagrangian solver designed to leverage the strengths of Eulerian solvers in resolving boundary layers and Lagrangian solvers in convecting wakes downstream without introducing significant numerical diffusion. The solver adeptly handles multi-body simulations, allowing the construction of independent Eulerian meshes that communicate seamlessly through Lagrangian particles. In this way, the computational study of multibody problems does not require very large and dense meshes. Validation in single-body cases has already been conducted, with this paper demonstrating the solver’s application to a pair of cylinders in different configurations. A comparative performance analysis is carried out against pure Eulerian solvers. The results highlight that the hybrid solver efficiently reproduces the accuracy of the Eulerian solver, demonstrating its effectiveness in handling complex aerodynamic simulations.
A New Perspective on Offshore Wind Turbine Certification Using High Performance Computing
Authors: Papi Francesco , Bianchini Alessandro
Published: June 2024

A correct estimation of fatigue and ultimate loads on the structure is key for wind turbine design and certification. In a greater perspective, wind turbines are large structures placed in the natural environment and are thus subject to environmental loads that are stochastic in nature. In the case of offshore turbines, the design space is even vaster, as wind speed, turbulence intensity, wave height and period, and wind/wave direction need to be considered. Due to this complexity, standardization is a challenge, and current design standards prescribe load calculations to be performed on a site-per-site basis. Performing this task requires obtaining a long-term statistical representation of the installation site, which can be complex. Moreover, this process is affected by uncertainties. This work explores an alternative to this approach, i.e., partially, or entirely simulating the lifetime of the offshore asset. Results show how this method can reliably predict fatigue loads even using as little as one year of data. On the other hand, prediction of extreme loads is influenced by the sample size and time-period.
Comprehensive analysis of rotor edgewise whirling mode interaction with rotor speed harmonics
Authors: Torres Antonio , Gil Javier , Plaza Aitor , Aginaga Jokin
Published: June 2024

This paper presents a model that investigates the interaction between rotor edgewise whirling modes and rotor speed harmonics in wind turbines. The model is based on kinematic and dynamic principles, with a focus on the multi-blade coordinate transformation, which is critical for simulating the behaviour of the rotor whirling modes in wind turbines. The research has two objectives: to investigate the interaction between the rotor edgewise whirling modes and the rotor speed harmonics, and to provide clearer graphs that explain the complex nature of this non-intuitive rotor dynamics. The paper concludes by highlighting the practical implications of the research findings, in particular the effectiveness of visualisation techniques in identifying and explaining unexpected interactions.
VAST as a generic, modular aeromechanics code for wind turbine simulation
Authors: Michels Benedikt , Seelemeyer Philipp
Published: June 2024

In order to leverage the full potential wind energy, more research is needed both in the field and numerically. At DLR, the need for simulation competencies is expected to be met by the in-house developed generic and highly flexible multi-physics code VAST. While initially aimed at low- to medium-fidelity simulations of helicopter aeromechanics, the code is applicable to other problems like wind turbine computations. The goal of this paper is to present the general concept of VAST and briefly introduce the available physics models. Next to examples of successful application to helicopter simulation problems, first results in the field of wind energy are shown. The well-known IEA 15 MW reference wind turbine is used as a basis to compare VAST — both with a BEMT and a vortex theory inflow model — to other tools with similar and higher-fidelity physics modeling. For the rigid turbine, blade loads are compared with results of other tools using engineering models as well as CFD, showing good overall agreement. A more detailed evaluation of aerodynamic quantities like the angle of attack and the induced velocity field is presented for VAST and the CFD results. An outlook on the ongoing VAST developments is given.
Aeroelastic analysis of a very large wind turbine in various atmospheric stability conditions
Authors: Dangi Nirav , Yu Wei , Sodja Jurij , Ferreira Carlos Simão
Published: June 2024

With the growing trend towards larger wind turbine rotor diameters, the impact of wind shear on rotor performance and loads becomes increasingly significant. Atmospheric stability strongly influences wind shear, leading to higher wind shear under stable atmospheric conditions. In this study, the aeroelastic performance of the IEA 22 MW rotor is assessed under inflow conditions generated by different methods. Inflow conditions were generated using turbulence models specified in the IEC Standards and also by Large Eddy simulations. Standalone OpenFAST simulations were conducted with the respective inflow conditions.

It was found that at rated and above-rated wind speeds, the time-averaged wind turbine design loads were higher in stable atmospheric conditions, in comparison to the IEC NTM inflow conditions, while the opposite held for below-rated wind speeds. Specifically, the time-averaged root flapwise bending moment and rotor thrust were found to be higher by up to 7% in stable atmospheres. However, maximum design and fatigue loads were considerably higher in the IEC NTM case due to elevated turbulence levels. Compared to the IEC NTM case, the damage equivalent root flapwise bending moment was found to be 30% to 70% lower in the different scenarios.
A grid deformation method for wind turbine CFD applications
Authors: Sørensen Niels N.
Published: June 2024

The desire for low cost of energy is driving the development of modern wind turbines toward more and more flexible designs. With respect to aerodynamic evaluation of these designs based on CFD this pose a requirement for the capability to compute the flow on deforming grids around heavily deforming geometries. The present paper describes an efficient explicit method suited for deforming geometries in a structured grid approach, here illustrated for airfoil and a wind turbine rotor simulations. Based on the present investigation, it is illustrated that the solution on the deformed grids deviates less than a fraction of a percent from the solution on the original grids both for the airfoil and the rotor case.
Mesoscale-coupled Large Eddy Simulation for Wind Resource Assessment
Authors: Storey Rupert , Rauffus Rene
Published: June 2024

Turbulence, a key driver of wind turbine loads, is central in the assessment of turbine suitability and performance, and consequently impacts the expected energy production of a wind farm. Conventional flow modeling methods for wind resource assessment (WRA) typically lack the ability to resolve turbulence due to key simplifications in their formulation. This work applies Large Eddy Simulation (LES) to address these limitations and deliver high-fidelity wind condition predictions at 24 wind farm sites. The model includes recently improved boundary conditions to downscale information from global weather models via a mesoscale layer. Validation of the model is presented through comparison to over 100 years of measurements, with comparison of the time-series, distributions and spectra. Validation results indicate excellent performance of the model for key flow quantities including wind speed, turbulence and direction. Comparison of spectra indicates a significant improvement in the representation of the atmospheric energy cascade when compared to previous approaches. The results are significant for wind-farm site assessment as they demonstrate the feasibility of applying accurate LES at a commercial scale. LES also provides a step change in the quality of model predictions through resolving time and site-specific turbulence characteristics. The application of the model for WRA is a step towards improved understanding of the wind resource, as well as an improved suitability assessment process itself.
Accuracy assessment of Beddoes-Leishman and IAG dynamic stall models for wind turbine applications
Authors: Mohamed Omar Sherif , Melani Pier Francesco , Bangga Galih , Aryan Navid , Greco Luca , Bianchini Alessandro
Published: June 2024

The study presents a systematic comparison between two of the most-credited dynamic stall models for wind turbine applications: the original Beddoes-Leishman (BL) model and the newly-developed IAG. The scope of such comparison, supported by experimental data, is to shed new light on the actual suitability of current dynamic stall models for their integration into modern wind turbine simulation codes, and on the best practices to calibrate them. Two different strategies are followed for the calibration of the BL model: 1) standard one, compliant with common practices found in the literature; 2) a physics-oriented one, focusing on the constants defining the dynamic stall onset as well as on the parameters governing the duration of the vortex shedding process. The IAG model, initially developed based on the first-order BL formulation and recently improved by reducing the number of constants and removing compressibility effects, is applied instead in its standard form only. The two models are compared across a range of oscillation mean angles, amplitudes, and reduced frequencies. Results demonstrate that the original BL model, although with a challenging calibration process, when properly tuned, can provide a very good description of aerodynamic unsteady loads. While showing consistent results, the IAG formulation appears to be more robust, as it employs fewer constants and extracts most of the needed information directly from the input polar data. The comparison between the calibrated BL and IAG models highlights critical modelling aspects, the computation of drag and determination of the stall onset above all, offering valuable insights for the future development of dynamic stall formulations.
Techno-economic designs of hybrid wind-wave offshore energy systems and comparison with TOPSIS analysis: an Italian case study
Authors: Petracca E. , Sirigu M. , Issoglio D. , Ghigo A. , Bracco G.
Published: June 2024

This study assesses multiple hybrid wind and wave floating offshore systems, utilizing a preliminary approach for dimensioning and the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) analysis method for comparison. It aims to provide an initial evaluation of diverse concepts, emphasizing state-of-the-art combinations of Floating offshore Wind Turbine (FOWT) with Wave Energy Converters (WECs). The criteria for evaluation include system cost, power extraction, WEC integration, dynamic and environmental responses, offering a comprehensive view of performance, economic viability, constructability, operational efficiency, and environmental impact. The findings, derived from the application of these methodologies, are informed by an Italian case study, enriching the insights and illustrating the practical implications of the evaluated hybrid systems within the Italian context. Preliminary results suggest a tendency for semi-submersible platforms to be more suitable for combined with WEC devices.
Adhesive Snap-Fit Joints for Modular Wind Turbine Blades: A Numerical Feasibility Study
Authors: Ansari Muhammad Basit , Maes Vincent , Macquart Terence , Kim Byung Chul , Pirrera Alberto
Published: June 2024

Larger rotor diameters are sought by wind turbine manufacturers as they favour cost-effective energy generation. However, manufacturing, transporting, and installing longer blades gets increasingly complicated, time-consuming, and costly. While a potential solution lies in spanwise segmentation, available modular blade technologies are still relatively immature, have drawbacks, and are yet to be used for blades exceeding 80 meters. A key challenge to blade segmentation is the addition of joints, which can result in both structural as well as aeroelastic penalties, when comparing segmented designs to their monolithic counterparts. To tackle these issues, in this study, we present the proof of concept and initial feasibility of an adhesively bonded snap-fit joint. The study assesses the joint’s load carrying capacity under quasi-static loading conditions at two levels: first, at the component level, focusing on the snap-fit elements, and second, at the system level, examining the integration of these components into the blade section. Under the specified assumptions, the results highlight the hybrid joint’s capability to withstand substantial loads of the order of magnitude required to meet operating requirements.
Should Small Wind Pursue Traditional Region 3 Control?
Authors: Bomze B , Visser K , Helenbrook B
Published: June 2024

A strategy to eliminate Region 3 control for small, fixed pitch turbines and utilize an extension of Region 2 is presented. Variations in wind probability distribution, capacity factor, and percent overshoot were examined. The relative performance of different control objectives was compared based on projected annual energy production. The results indicated that the Region 2 only control objective can produce energy equivalent to that of the currently employed Region 3 control objective over a range of wind regime-turbine combinations and capacity factors. It is suggested that the additional complexity required to provide Region 3 control for small turbines may not be warranted by the energy extraction benefits, particularly when factoring in additional equipment costs.
Multi-model approach for wind resource assessment
Authors: Sengers Balthazar A.M. , Vollmer Lukas , Dörenkämper Martin
Published: June 2024

This study presents a multi-model approach for wind resource assessment of a wind farm affected by external wakes. The Weather Research and Forecasting model (WRF), a mesoscale model, is employed to simulate external wind farm wakes, while the Farm Optimization and eXtended yield Evaluation Software (FOXES), an engineering model, is used to simulate the wind farm of interest. This hybrid approach addresses the limitation of both models, mainly the lack of layout effects in mesoscale models and the poor representation of cluster wakes in engineering models. A case study, focusing on the Kaskasi wind farm in the Heligoland cluster, shows that the WRF model predicts larger wake losses compared to FOXES, with the multi-model approach yielding intermediate results. Systematic differences are found as a function of wind speed and seasonality, while the models behave differently as a function of turbulence intensity. The external wake effect was clearly identified for one wind direction sector in WRF and the multi-model approach, while FOXES failed to represent this. The proposed methodology does not only enhance classic resource assessment, but also facilitates efficient layout optimization using cluster waked inflow and allows for wind farm control studies, contributing to both planning and operational phases of wind farm management.
Is the free wind speed sufficient to determine aerodynamic turbine performance in complex terrain?
Authors: Zengler C P , Troldborg N , Gaunaa M
Published: June 2024

The performance of a wind turbine is usually characterized by its power curve, which relates the wind speed at hub height with its energy production. This relation does not take streamwise inhomogeneities of the inflow – as they might be present in complex terrain – into account. In this work, the consequences of this simplification for performance predictions are analyzed. Simulations using Reynolds-averaged Navier Stokes equations (RANS) with the k-ϵ-fp model as closure are performed. An actuator disc (AD) on the ridge of a quasi two-dimensional Gaussian hill subject to a neutral atmospheric inflow is investigated. Roughness length, hill width and thrust coefficient are varied and the respective induction evaluated. Results indicate that the induction at a given thrust coefficient depends on the terrain configuration; it can be higher or lower than predictions by momentum theory, translating to a decrease or increase in the power coefficient. In this work, a power decrease by up to 15.3 % compared to flat terrain is observed. The maximum power increase is approximately 1.6 %. It is concluded that hub height wind speed or rotor equivalent wind speed are no sufficient measures to universally characterize aerodynamic turbine performance in complex terrain.
Meteorological measurements affected by wind farm cluster wakes: How to deal with waked wind in AEP assessments?
Authors: Mayol ML , Navarro Diaz GP , Vermeij R , Rowen M , Erbslöh S
Published: June 2024

This research explores a spectrum of correction methods to predict free wind speed conditions from offshore wind measurements influenced by nearby wind farm clusters. Three of these methods (reference data, wake model and mesoscale model correction) were evaluated at two measurement sites in the German Bight, and a matrix of wake correction factors was obtained for each method. Comparison among methods reveals that all can identify sectors affected by upstream clusters. However, using reference data for correction overestimates impacts at sector limits. Wake and mesoscale model corrections are similar in their proposed correction factors, but the wake method yields lower values due to underestimation of wind farm wake deficits over long distances. When applying the correction factors to the waked measurements, the resulting series did not show significant statistical differences. The choice of correction method is contingent upon factors such as time constraints, availability of information on surrounding wind farms, and desired level of accuracy. The reference method is suggested in the absence of relevant information, while the wake method is recommended when there are time constraints. The mesoscale method can be considered when more time is available.
Generalization of single wake surrogates for multiple and farm-farm wake analysis
Authors: Pish F , Göçmen T , Van Der Laan M P
Published: June 2024

Wind farm efficiency is influenced by atmospheric turbulence and wake interactions from preceding turbines. Optimal performance necessitates effective control strategies, encompassing collective/individual pitch (and/or torque) control, yaw control, and innovative techniques, significantly boosting energy capture. Wake effects are crucial, impacting downstream turbines and reducing overall energy extraction. For this purpose, the study of wind farm flow control (WFFC) holds significant relevance in this context. In this study, a Deep Neural Network predicts downstream flow features of a wind turbine under diverse control scenarios, including varying thrust coefficient and yaw control. A feed-forward neural network models the deficit and added turbulent intensity of a single wake, trained using Computational Fluid Dynamics (CFD) simulations as reference data. Linear superposition establishes the wind farm flow field, allowing examination of downstream effects. Another feedforward neural network encompasses wind farm physics such as blockage and wake recovery in and around wind turbine arrays which are overlooked by the single wake model. The methodology employed in this study yields results that are more time-efficient compared to traditional CFD models while maintaining a higher level of accuracy (ideally) than the engineering models, especially when implemented for WFFC without calibration.
Alternative household water affordability metrics using water bill delinquency behavior
Authors: Skerker Jennifer B , Verma Aniket , Edwards Morgan , Rachunok Benjamin , Fletcher Sarah
Published: June 2024

Rising water prices threaten affordable access to basic water service in the U.S., especially in low-income communities. Faced with unaffordable water bills, households may use less water than is healthy, forgo other essential services, or fall behind on water bill payments, risking water shutoffs. Affordability ratios (ARs), which express water bills as a fraction of income, are the most common measure of water affordability. However, ARs can underestimate unaffordability due to both spatial aggregation bias and their reliance on indirect proxies for ability to pay. New metrics are needed to identify households at risk of water insecurity due to affordability challenges. Here we investigate alternative water affordability metrics that use water bill late payments and debt to track actual payment behavior at the household level. We define metrics that capture the frequency, duration, and severity of water bill delinquency. We apply these metrics to a case study in Santa Cruz, California, using monthly billing data for approximately 40 000 households from 2009 through 2021. We find large variation in delinquency across households and over time, with higher delinquency linked to proxies for low wealth such as lower assessed home value. Census blocks with similar ARs often have distinct patterns of delinquency behavior, suggesting that block-level median affordability estimates may be masking sub-populations facing affordability challenges. These results highlight the benefits of using multiple, household-level metrics to capture the role affordability plays in household water security.
Integrating multi-source remote sensing data for mapping boreal forest canopy height and species in interior Alaska in support of radar modeling
Authors: Zhao Yu-Huan , Bakian-Dogaheh Kazem , Whitcomb Jane , Chen Richard H , Yi Yonghong , Kimball John S , Moghaddam Mahta
Published: June 2024

Vegetation information is essential for analyzing aboveground biomass and understanding subsurface characteristics, such as root biomass, soil organic matter, and soil moisture conditions. In this study, we mapped boreal forest canopy height (FCH) and forest species (FS) distributions in the Delta Junction region of interior Alaska, by integrating multi-source remote sensing observations within a machine learning framework based on the extreme gradient boosting technique. Model inputs included multi-frequency (C-/L-/P-band) SAR observations from Sentinel-1, UAVSAR (Uninhabited Aerial Vehicle SAR) and AirMOSS (Airborne Microwave Observatory of Subcanopy and Subsurface), and Sentinel-2 optical reflectance data. LVIS (Land Vegetation and Ice Sensor) LiDAR measurements (RH98) and Tanana Valley State Forest timber inventory data were used as respective canopy height and species ground truth data. The combination of multi-source datasets produced the best model performance (RMSE 1.62 m for FCH, and 84.27% overall FS classification accuracy) over other models developed from single source observations. The resulting FCH and FS maps using multi-source datasets were derived at 30 m spatial resolution and showed favorable agreement with plot level field measurements from the Forest Inventory and Analysis record. The model results also captured characteristic differences in stand structure between dominant species and from post-fire vegetation succession. Our results show the potential of multi-source remote sensing observations, including low frequency microwave sensors, for monitoring boreal forest complexity and changes due to global warming.
Combustion Characteristics of Coal with Palm Kernel Shells (PKS) Using Thermogravimetric Analysis
Authors: Chaeruni W , Hadiyanto  , Cahyadi  , Sutardi T
Published: June 2024

Indonesian government is commitment to reduce greenhouse gas emissions, so it is necessary to utilize biomass in power generation as an alternative fuel. This study aims to analyze and evaluate combustion characteristics using TG-DTA (Thermo et al.) with coal, palm kernel shells (PKS), and a mixture of palm kernel shells (PKS) with coal. Sample testing was carried out with four variations of the mixture between PK and coal, namely 10%, 20%, 30%, and 40%, Tests were carried out with nitrogen gas and air with a constant heating rate of 20 °C/min at flow gas of 50 mL/min. Then, the mass reduction is calculated as the heating rate increases up to a temperature of 900 °C. Combustion characteristics can be analyzed by observing the combustion profile graph to obtain derived thermogravimetric data (DTG) to obtain the initiation temperature, temperature burnout, maximum combustion temperature, combustion reactivity, and energy activity of palm kernel shells (PKS), and a mixture of palm kernel shells (PKS) with coal with various composition variations. This research obtained the optimal composition for mixing palm kernel shells (PKS) and coal by TG-DTA.
The performance of floating Photovoltaic system over a small pond in Jakarta.
Authors: Hendarti R , Linggarjati J , Hernawan R A
Published: June 2024

It is recognized that photovoltaic (PV) cells exhibit a drawback when subjected to significant temperature increases. This paper presents an initial study of the performance of Floating PV (FPV) over a pond, encompassing the effect of the PV panel’s surface temperature on the variation of the PV cell efficiency. To facilitate this study, an experimental study was conducted. The experiment deployed four monocrystalline PV panels with a maximum power output (Pmax) of 100 Watts for each panel. These four panels were divided into two sets that each set contain two PV panels. The first set was installed over a small pond with an area of 24 m2 and a depth of 1.2 m, while the other set was placed over a concrete surface with the same area size. The steps of the experiment study were as follows: (1) to measure the PV panel’s surface temperature of the two sets, and (2) to calculate the operating PV cell efficiency using an energy balance equation. The measurement of the PV panel’s temperature was taken hourly from 08.00 AM to 04.00 PM on clear and cloudy day. The data on rainy day was excluded. The study was conducted in an urban area of Jakarta, where the average ambient temperature ranges between 25°C and 30°C. The experimental site conditions are relatively clear, only several trees located on the south of the area. The results indicated that pond has a significant effect on the reduction of the PV panel’s surface temperature as compared to the PV set over the concrete surface. The average temperature reduction is around 3.5°C on a clear day, whereas the maximum reduction is 7.8°C, when the irradiance level rises to around 1000 W/m2. Indeed, the observed improvement of the PV cell efficiency was approximately 3.9% at the highest and in average was around 2%.
Techno-economic Analysis of 100 kWp Floating Solar Photovoltaic for Renewable Energy Mix in Bali – Indonesia
Authors: Abiyasa Agus Putu , Otniel Sihombing Richard Benjamin
Published: June 2024

To achieve renewable energy mix target and support the Indonesian Government’s policy on the use of solar power, PT. PLN Indonesia Power Bali has installed Floating Solar Photovoltaic (PV) above the surface of the Muara Nusa Dua reservoir. The 100 kWp Floating Solar PV was showcased at the G20 meeting held in Bali. In this study, a techno-economic analysis was carried out for the 100 kWp Floating Solar PV. The data collected was the real time data from the production of the 100 kWp Floating Solar PV and the costs incurred for the investment. The results of this study showed an average energy yield of 145.93 MWh with expected revenue of Rp 236,406,729.60 annually. Furthermore, the NPV and IRR were calculated and the resulted values were Rp 2,810,168,240.00 and 5.73 %, respectively with payback period approximately of 13 years. This showed that the 100 kWp Floating Solar PV is feasible investment to increase renewable energy mix in Bali – Indonesia.
Characterisation of Polyurethane-urea as Leading-Edge Erosion Resistant Materials of Wind Turbine Blades
Authors: Restasari Afni , Naderizadeh Sara , Kaur Anureet , Akutagawa Keizo , Busfield James , Tan Wei
Published: June 2024

Surrounded by oceans, building offshore wind turbines is a great strategy for archipelago countries, like Indonesia, to harvest renewable energy from wind. However, because of high rainfall rate, water droplet erosion on wind turbine blades is inevitably to be one of the most challenging problems. It causes decreasing produced energy and increasing cost of maintenance and repairment. A novel coating material which has better mechanical properties is therefore required. As a preliminary step, this work aims to characterise thermal and mechanical properties of soft and hard polyurethane-urea (PUU). In this work, the materials are soft PUU30 which has a hardness of 30 shore A, and hard PUU95 which has a hardness of 95 shore A. Thermal properties are characterised by Differential Scanning Calorimetry (DSC), while mechanical properties are investigated by tensile test at various strain rates. The results show that PUU95 has a higher strain rate dependence on modulus, tensile strength, and strain at break, which need to be considered for application regarding the range of wind speeds.
Correlation between Two Sunshine Parameters and Three Hydrometeorological Parameters
Authors: Maftukhah Tatik , Wijonarko Sensus , Purwowibowo  , Rustandi Dadang , Prakosa Jalu A. , Mahmudi  , Hidayat Siddiq Wahyu , Sirenden Bernadus H.
Published: June 2024

In designing the correct capacity of solar panels that will be used for any project, the designer should know the solar radiation in that area. Next, the UV index data is needed to know if that area is safe from ultraviolet (UV) radiation. Unfortunately, solar radiation and UV index data from many hydrometeorological stations are usually rare. Hence, there is a necessity to solve this scarcity. The study, using the correlation method, intends to make the connection between two sunshine parameters (solar radiation and the ultraviolet (UV) index) and three hydrometeorological parameters (air temperature, humidity, or pressure). If these variable couplings are known, we can find the data of solar radiation (or UV index) based on air temperature, humidity, or pressure, which are usually much easier to obtain than solar radiation or UV index. The results showed that the correlation between solar radiation (or UV index) and air temperature, humidity, and pressure was strong positive-linear, strong negative-linear, and no strong correlation, respectively. Because it has a positive correlation, the temperature data have a strong potential to replace solar radiation or UV index data.
Performance Evaluation of High-Energy LiFePO4 Battery Pack for Electric Shuttle
Authors: Firdaus Himma , Supono Ihsan , Lailiyah Qudsiyyatul , Kasiyanto Iput , Kusnandar Nanang , Hanifa Rizky , Ma’arif Riky Alam , Triputra Fadjar Rahino , Purwoadi Michael Andreas , Rahardjo Sasono , Setianingrum Lesti , Hamidah Maratul , Dewi Mustika Fitriana , Purnomo Edhi , Honggowiranto Wagiyo
Published: June 2024

For tourism-based electric shuttles, high-energy batteries are crucial. A 200 Ah Lithium Iron Phosphate (LiFePO4) battery pack has been designed yet lacks performance evaluation. We conducted performance tests based on ISO 12405-4:2018. The battery comprises 24 cells connected in series, resulting in a 72 V output voltage. Under controlled conditions at 23°C, the test assessed charging and discharging at defined C-rates. The study assessed the resistance, capacity, and efficiency. We also monitored heat distribution in the battery system during test to detect abnormalities. The results revealed that the maximum attainable battery charge rate was C/3. Under this rate, the discharge capacity reached 160 Ah, and the battery temperature rose to just below 36.2°C. On the other hand, charging the battery at C/6 yielded 191.5 Ah, which increased the battery temperature to 31°C. Thus, the energy round-trip efficiency was measured at 86.5%. However, charging the battery at C/3 led to the Battery Management System (BMS) overheating, indicated by the casing temperature exceeding 67 °C. The overheating caused severe damage to the BMS charging component and triggered an automatic cut-off. The higher total battery resistance during charging was identified as the root cause of the issue, emphasizing the need for future research to focus on enhancing the BMS for faster and more efficient charging, improving the service reliability of the electric shuttle.
EU Food Law
Authors: Schebesta Hanna , Purnhagen Kai
Published: June 2024

This book provides a panorama of EU food law and legislation. It covers European Integration and Food Law (Part I); Food Safety Umbrella Laws: The General Food Law Regulation and the Official Controls Regulation (Part II); The Food Law Acquis (Parts III–VII), which comprises food technology law, food safety law, food information law, food quality law, food nutrition law; international food law (Part VIII) and a final chapter that presents the conclusions and an outlook on the future of food law. The book demonstrates that EU food law is currently predominantly food-safety oriented, and outlines initiatives and opportunities for a future of food law that is more oriented towards aspects of sustainability, health, and integrated food system regulation.
Introduction
Authors: Schebesta Hanna , Purnhagen Kai
Published: June 2024

This introductory chapter explains the purpose of the book, which is to present a panorama of EU food law and legislation. It introduces the main structure of the book, which comprises the following parts: European Integration and Food Law (Part I), Food Safety Umbrella Laws: The General Food Law Regulation and the Official Controls Regulation (Part II), The Food Law Acquis (Parts III–VII), International Food Law (Part VIII), and a final chapter that presents the conclusions and an outlook on the future of food law.
Nutrition and Health Claims
Authors: Schebesta Hanna , Purnhagen Kai
Published: June 2024

This chapter analyses the provisions of the Nutrition and Health Claims Regulation. After a general introduction of its legal basis, scope, and major definitions (sections 14.3–14.5), the general requirements for nutrition and health claims are elaborated (section 14.6). Subsequently, the chapter discusses the specific provisions for nutrition claims (section 14.7) and for the different types of health claims, that is generic health claims, reduction of disease risk claims, and claims referring to children’s development and health (section 14.8), respectively. The chapter concludes by pointing out the limitations of the NHCR in contributing to a food and health agenda (section 14.13).