Article
Green & Sustainable Science & Technology
Yunliang Li, Zhaobin Li, Zhideng Zhou, Xiaolei Yang
Summary: Large-eddy simulation was used to investigate the effects of forest canopy on wind turbine wakes. Results showed that wake recovery was faster in forest canopies compared to flat terrain. Turbulence kinetic energy (TKE) decreased significantly in the lower part of the wake above the forest, while increased mainly at the top tip. Power spectral density analysis revealed different frequency ranges of TKE increase for forest canopy and flat cases. The leaf area index (LAI) had a greater impact on wake-added TKE and wake-added Reynolds shear stress compared to the vertical distribution of leaf area density (LAD).
Article
Green & Sustainable Science & Technology
W. Chanprasert, R. N. Sharma, J. E. Cater, S. E. Norris
Summary: This study investigates the influence of directionally sheared inflows on wake interaction in a four-inline turbine array using a coupled Large Eddy Simulation (LES) and turbine aeroelastic code. The results show that the lateral velocity of the ambient wind affects wake rotations, resulting in differences in radial wake expansion and wake shape twist angle. Symmetric wakes in the zero directional shear case lead to lower fatigue loads on the blades and rotor shaft compared to skewed wakes. The flapwise blade-root bending moment of downstream turbines is approximately three times higher under wind veering (Northern Hemisphere) than under wind backing (Southern Hemisphere).
Article
Environmental Sciences
Nils Christiansen, Ute Daewel, Bughsin Djath, Corinna Schrum
Summary: The potential impact of offshore wind farms on shear forcing and ocean dynamics is investigated. A new hydrodynamic model setup enables high-resolution analysis of offshore wind farms in the southern North Sea. The simulations show changes in the wind forcing and alterations in local hydro- and thermodynamics, leading to potential impacts on marine ecosystem processes.
FRONTIERS IN MARINE SCIENCE
(2022)
Article
Energy & Fuels
Jagdeep Singh, Jahrul M. Alam
Summary: In this article, the influence of spatial heterogeneity on wind turbine performance in wind farms is investigated. It is found that rough topography significantly enhances the power production of large wind farms, and the primary degree of spatial heterogeneity is in the streamwise direction. The study reveals the importance of considering the effects of complex terrain on wind turbine and wind farm design to improve their efficiency and energy output.
Article
Energy & Fuels
William Correa Radunz, Yoshiaki Sakagami, Reinaldo Haas, Adriane Prisco Petry, Julio Cesar Passos, Mayara Miqueletti, Eduardo Dias
Summary: Based on observations from modern field experiments in complex terrain sites, wind energy models have been improved to incorporate diurnal cycle unsteadiness and atmospheric stability impact. A recent investigation on two similar wind farms found that the back rows of turbines perform better during stable conditions and nighttime. Designing wind power plants of the future should consider accurately incorporating flow phenomena related to atmospheric stability and the diurnal cycle.
Article
Environmental Sciences
Jeanie A. Aird, Eliot W. Quon, Rebecca J. Barthelmie, Mithu Debnath, Paula Doubrawa, Sara C. Pryor
Summary: This study successfully identified and characterized wind turbine wakes using a region-based convolutional neural network, even in complex terrain and varying resolutions. The model exhibited high success rate and robustness in recognizing wakes, with characteristics consistent with expected behaviors under different meteorological conditions.
Article
Engineering, Marine
Heming Bai, Nina Wang, Decheng Wan
Summary: The use of horizontal axis dual-rotor wind turbine (DRWT) is a new strategy to enhance wind energy capture and improve wind farm performance. An actuator line model (ALM) and large eddy simulation (LES) were utilized to study the aerodynamic performance of the DRWT and its impact on downstream turbines in convective and neutral atmospheric boundary layers (CBL and NBL). The results showed that the power production of the front rotor of the DRWT had similar dominant vibration frequencies as the single-rotor wind turbine (SRWT), but with slightly higher amplitude. The yaw moment (Myaw) strength and dominant frequencies for the front rotor of the DRWT were comparable to the SRWT, while the blade-root out-of-plane bending moment (Moop) results differed. There were significant differences in wake development and meandering between the DRWT and the SRWT. The total power production for three turbine cases increased by 3.3% and 3% respectively under NBL and CBL when the DRWT was in the first row with a tandem spacing of 5D, and increased to 5.5% and 4.4% respectively with a tandem spacing of 9D. The stability of Myaw and Moop of the second-row turbine located 5D downstream behind the DRWT, and Moop of all turbines located behind the DRWT at three tandem spacings (5D, 7D, 9D) under CBL, was deteriorated compared to those located behind the SRWT.
Article
Environmental Sciences
Nils Christiansen, Jeffrey R. R. Carpenter, Ute Daewel, Nobuhiro Suzuki, Corinna Schrum
Summary: This study investigates the structure drag and physical impacts of offshore wind turbines on the marine environment of the German Bight. Two modeling approaches for simulating wind turbine foundation effects are presented, and the use of very high resolution in hydrostatic modeling is discussed. The study demonstrates the impacts of monopile drag on hydrodynamic conditions using a low-resolution structure drag parameterization, validated against in-situ measurements. The simulations show that structure-induced mixing affects regional scales due to additional turbulence production, leading to changes in current velocities and stratification.
FRONTIERS IN MARINE SCIENCE
(2023)
Article
Energy & Fuels
Sadra Sahebzadeh, Abdolrahim Rezaeiha, Hamid Montazeri
Summary: The impact of rotor setting and relative arrangement on the power performance and aerodynamics of double rotor vertical axis wind turbine arrays is investigated. The results show that the power performance is significantly influenced by the relative rotational direction and positioning, while being marginally dependent on relative phase lag. Counter-rotating turbines with windward relative positioning have the highest power coefficient (C-P), while co-rotating turbines with leeward relative positioning have the lowest C-P.
Article
Green & Sustainable Science & Technology
Jian Wei Lin, Wei Jun Zhu, Wen Zhong Shen
Summary: In this paper, two new analytical wake models are developed to predict the wind velocity distribution in the wake region of a wind turbine. These models are validated and compared with existing engineering wake models, showing lower relative errors and better performance. They are recommended for wind farm design.
Article
Thermodynamics
Franciene Izis Pacheco de Sa Sarmiento, Jorge Luiz Goes Oliveira, Julio Cesar Passos
Summary: This study evaluated the combined impact of atmospheric stability, speed-up, and wake effect on the production of wind turbine pairs in a wind farm on complex terrain. It was found that downwind turbines perform better in the early morning, and the errors of speed-up and wake effects models vary at different times of the day.
Article
Green & Sustainable Science & Technology
Hamidreza Abedi, Saptarshi Sarkar, Hakan Johansson
Summary: This paper uses Large-Eddy Simulation to investigate the wind conditions of a wind farm in complex terrain, showing variations in wind speed, shear exponent, and turbulence intensity at different turbine locations. The study emphasizes the importance of turbine-specific assessment in wind resource evaluation in forested complex terrain.
Article
Thermodynamics
Haoze Yang, Mingwei Ge, Mahdi Abkar, Xiang I. A. Yang
Summary: This study uses large-eddy simulations to investigate the effect of swells on turbine arrays. It is found that downwind swells increase wind speeds and weaken turbulence, resulting in higher power outputs downstream. Upwind swells decrease wind speeds and enhance turbulence, leading to lower or slightly higher power outputs. Lateral swells cause changes in wind profiles with height, increasing turbine power outputs.
Article
Energy & Fuels
Tristan Revaz, Fernando Porte-Agel
Summary: The study focuses on using Large-Eddy Simulation (LES) with actuator models to investigate wind turbine flows and evaluates the accuracy of actuator disk models (ADMs). It is found that accurately projecting the forces generated by the turbine into the flow solver grid is crucial for rotor predictions, especially for power, and that a simple model may overestimate rotor velocity predictions compared to an advanced model in the near wake flow analysis. Including the effects of the nacelle and tower is important for both near wake flow and power prediction, due to shadow effects.
Article
Engineering, Civil
Takanori Uchida, Yves Gagnon
Summary: This study investigated the effects of continuously changing wind direction on the wake characteristics of a utility-scale wind turbine using numerical simulations. The results showed that the rapidly changing wind direction significantly impacted the recovery of mean velocity deficits in the wake region.
JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS
(2022)
Article
Energy & Fuels
Jens Norkaer Sorensen, Gunner Christian Larsen
Summary: The study presents a numerical framework for determining the available wind power and associated costs related to the development of large-scale offshore wind farms. It combines an energy production model with a cost model that only requires global input parameters to calculate the production and costs of wind farms. The cost model is based on previous experiences from offshore wind farms and is generally conservative.
Article
Green & Sustainable Science & Technology
V. L. Okulov, I. Naumov, I. K. Kabardin, I. Litvinov, D. M. Markovich, R. F. Mikkelsen, J. N. Sorensen, S. Alekseenko, D. H. Wood
Summary: This study aims to investigate the power production and wakes generated by water turbines in a hydro farm, measuring power and thrust coefficients of model turbines using strain gauges. The laboratory experiments provide data on the efficiency of water turbines in arrays or in a single-line arrangement in a hydro farm.
Article
Geosciences, Multidisciplinary
Huidong Li, Bjorn Claremar, Lichuan Wu, Christoffer Hallgren, Heiner Kornich, Stefan Ivanell, Erik Sahlee
Summary: Accurate wind modeling is crucial for wind resources assessment and wind power forecasting. This study conducted a sensitivity analysis of the WRF model to optimize offshore wind modeling over the Baltic Sea. Improving forcing from reanalysis data and enhancing atmosphere-wave coupling are key factors in enhancing wind modeling accuracy.
GEOSCIENCE FRONTIERS
(2021)
Article
Mechanics
V. L. Okulov, B. R. Sharifullin, N. Okulova, J. Kafka, R. Taboryski, J. N. Sorensen, I. Naumov
Summary: Experiments were conducted using a water-filled elongated cup of a kitchen scale with a rotating disk with micro- and nano-roughness. The results showed that certain nanostructures led to significant growth of vortices while other roughnesses did not impact the flow structure. These findings are important for evaluating the efficiency of surfaces with nanoscale roughnesses and have potential applications in enhancing mixing in chemical and bio-reactors.
Review
Engineering, Aerospace
J. N. Sorensen, V Okulov, N. Ramos-Garcia
Summary: This article presents two rotor models proposed by Joukowsky and Betz a century ago and proposes a technique to solve the induction problem of these models. The technique enables the design of wind turbine rotors and analyzes the performance of three-bladed rotors optimized for different tip speed ratios by comparing the results with blade-element/momentum technique and lifting line theory.
PROGRESS IN AEROSPACE SCIENCES
(2022)
Article
Green & Sustainable Science & Technology
Jiufa Cao, Camilla Marie Nyborg, Ju Feng, Kurt S. Hansen, Franck Bertagnolio, Andreas Fischer, Thomas Sorensen, Wen Zhong Shen
Summary: To reduce CO2 emissions from traditional energy sources, wind energy has been rapidly developed worldwide. However, the noise generated by wind turbines in wind farms can have significant environmental impacts. This study presents a new simulation framework that accurately predicts the sound propagation in wind farms, taking into account the complex flow-field and wakes created by the turbines. The framework shows good accuracy and acceptable computing time, making it suitable for designing and controlling wind farms.
RENEWABLE & SUSTAINABLE ENERGY REVIEWS
(2022)
Article
Energy & Fuels
Emily L. Hodgson, Christian Grinderslev, Alexander R. Meyer Forsting, Niels Troldborg, Niels N. Sorensen, Jens N. Sorensen, Soren J. Andersen
Summary: The actuator line method is a cost-effective technique for modeling wind turbines in computational fluid dynamics. This study introduces a vortex-based smearing correction in the actuator line model and demonstrates its significant improvement in blade loading and thrust prediction. Validation is conducted using a 2.3 MW turbine, showing good agreement with blade resolved simulations in laminar inflow and consistent trends in complex flow cases. The discrepancies in blade loading and thrust prediction can be attributed to differences in wake flow and induction. Overall, this work validates the implementation of the vortex-based smearing correction and showcases the ability of the actuator line method to accurately predict blade loading and deflection in complex flows at a lower computational cost.
FRONTIERS IN ENERGY RESEARCH
(2022)
Article
Computer Science, Interdisciplinary Applications
Nestor Ramos-Garcia, Aliza Abraham, Thomas Leweke, Jens Norkaer Sorensen
Summary: In this study, two flow models of the DTU vortex solver MIRAS were used to simulate the wake generated by a model wind turbine with varying levels of asymmetry. The predictions were validated against experimental measurements and visualizations. Good agreement was observed, especially with the higher-fidelity particle-mesh model, which closely predicted the flow features observed in the experiments. The analysis also revealed that rotor asymmetry triggers a vortex instability, known as leapfrogging, which accelerates the breakdown of tip vortices and promotes faster wake recovery.
COMPUTERS & FLUIDS
(2023)
Article
Green & Sustainable Science & Technology
Jens N. Sorensen
Summary: A new generalized analytical model for representing body forces in numerical actuator disc models of wind turbines is proposed and compared to results from a blade element momentum (BEM) model. The model is validated for different wind turbines operating under a wide range of operating conditions, showing generally excellent agreement with the BEM model even at very small thrust coefficients and tip-speed ratios.
WIND ENERGY SCIENCE
(2023)
Proceedings Paper
Energy & Fuels
Jens N. Sorensen, Gunner C. Larsen
Summary: A study was conducted to evaluate the potential of offshore wind power in the North Sea, including the prediction of wind resources and associated costs. The study considered factors such as turbine size, distance between turbines, wind resources, and water depths. The findings indicate that exploiting 180,000 km(2) of the North Sea with 60,000 20 MW wind turbines could generate electricity equivalent to Europe's consumption at a cost of 6.2 cents/kWh. Additionally, increasing the number of turbines in the same area can capture more energy but at a higher cost.
WAKE CONFERENCE 2023
(2023)
Proceedings Paper
Energy & Fuels
Aliza Abraham, Nestor Ramos-Garcia, Jens Norkaer Sorensen, Thomas Leweke
Summary: The study investigates the use of rotor asymmetry as a passive method for mitigating the detrimental effects of tip vortices in wind turbine wakes. It is found that the asymmetric rotor successfully triggers the instability, increasing the wake average velocity by a maximum of 3.5% and the power available to a downstream turbine by up to 11%. The findings suggest that rotor asymmetry has strong potential as a wake control method and should be further investigated for its effects on inflow turbulence and rotor loading.
WAKE CONFERENCE 2023
(2023)
Article
Green & Sustainable Science & Technology
Gonzalo Pablo Navarro Diaz, Alejandro Daniel Otero, Henrik Asmuth, Jens Norkaer Sorensen, Stefan Ivanell
Summary: Two new variants of the actuator line technique are proposed to simulate transient wind turbine wake interaction problems using generic load data. The models only require thrust and power coefficients, and the tip speed ratio as input parameters. The proposed models are compared to the actuator disk model and the classical actuator line model based on blade element theory, showing their effectiveness.
WIND ENERGY SCIENCE
(2023)
Article
Green & Sustainable Science & Technology
Jana Fischereit, Kurt Schaldemose Hansen, Xiaoli Guo Larsen, Maarten Paul van der Laan, Pierre-Elouan Rethore, Juan Pablo Murcia Leon
Summary: This study compares different wind farm models of different complexity, fidelity, scale, and computational costs and evaluates their performance in simulating wind farm wakes. The results show that the WRF model with FIT or EWP parameterization performs well in capturing wind farm effects, and the engineering wake models from the PyWake suite simulate peak intra-farm wakes comparable to high fidelity simulations. However, they underestimate the wake effect of an upstream farm to some extent.
WIND ENERGY SCIENCE
(2022)
Proceedings Paper
Energy & Fuels
J. N. Sorensen, G. C. Larsen, A. Cazin-Bourguignon
Summary: A minimalistic model complex was developed by Sorensen and Larsen to determine the available wind power and associated costs for the development of large-scale offshore wind power. Utilizing global input parameters, the model was used to map annual energy production and levelized cost of energy for wind farms in the North Sea, finding that the wind resources in the North Sea can meet the electrical demand of Europe.
WAKE CONFERENCE 2021
(2021)
Proceedings Paper
Energy & Fuels
E. L. Hodgson, S. J. Andersen, N. Troldborg, A. Meyer Forsting, R. F. Mikkelsen, J. N. Sorensen
Summary: The study verifies the effectiveness of actuator disc and actuator line techniques in wind turbine modeling, showing good agreement between the three different methods. The higher fidelity modeling of coupled simulations explains most of the differences observed, while some overpredictions of loading in the actuator methods can be attributed to Gaussian smearing.
WAKE CONFERENCE 2021
(2021)
