Conventional Wind Turbine Research Articles

A self-regulated wind energy harvester with automatic mode transition strategy enabled by wind-induced centrifugal force

Abstract Natural wind energy distributes over a wide speed range, but conventional wind turbines with high electrical damping can only work under relatively high wind speeds, whereas breeze harvesters with low electrical damping suffer from limited electric outputs despite their low start-up wind speeds. To solve this dilemma, we report herein an automatic mode transition (AMT) strategy for rotary wind energy harvesters (WEHs) to realize self-regulation of electrical damping according to ambient wind speeds. The superior performance achieved with the AMT strategy has been demonstrated through an AMT-WEH comprising a low-damping as well as a high-damping power generation units. Theoretical analysis and experimental tests reveal that the AMT-WEH not only can work in low-damping single-unit mode to harvest weak wind (≥ 2.6 m/s), but also can switch spontaneously to high-damping dual-unit mode to efficiently capture strong wind. As connected with matched electrical loads, the AMT-WEH can switch to dual-unit mode and generate high average power of 188.2 mW under 8.2 m/s wind, which is more than 11.5-fold increase as compared with that (16.3 mW) of a conventional WEH without the AMT design. This study demonstrates a distinctive AMT strategy for WEHs to effectively exploit wide-speed-range wind energy toward self-contained sensors and electronics.

Development and verification of real-time hybrid model test delay compensation method for monopile-type offshore wind turbines

The real-time hybrid model (RTHM) test is adept at addressing the scale contradiction, the lack of fidelity in wind modelling in hydrodynamic testing facilities and spatial constraints inherent in conventional monopile-type offshore wind turbine (OWT) model testing methods, thus emerging as an effective avenue for conducting physical model tests of Monopile-type OWTs. This method entails the reproduction of aerodynamic loads or platform motions using loading device or vibration tables. Time delays in the physical attributes of the loading device and signal transmission processes within the system can result in error accumulation, with the potential to impact overall system stability. Moreover, time delay compensation algorithms for hybrid model test systems with force control loading can easily generate excessive noise, leading to system divergence. As a result, time delay has emerged as a technical challenge in the RTHM test. To address this issue, this paper has developed second-order and third-order polynomial extrapolation algorithms, alongside an adaptive compensation algorithm. The adaptive compensation algorithm employs the least squares method to identify parameters of the loading system, enabling it to address variations in the time delay of the experimental system caused by the nonlinearity of the loading system and changes in the physical properties of the model. The feasibility and effects of time delay compensation for various algorithms are validated through numerical simulation. Results indicate that the adaptive compensation algorithm surpasses second and third-order polynomial extrapolation compensation algorithms in terms of accuracy and compensation effectiveness. To validate the applicability of the adaptive compensation algorithm, a RTHM test was conducted. Across rotor thrust force (RotThrust) and tower top displacement, there was an average reduction of approximately 5 % and 9 % in the maximum and minimum synchronization errors, respectively. This highlights the efficacy of the delay compensation algorithm in practical applications, notably diminishing time delay errors within the experimental system. The adaptive compensation algorithm continuously adjusts and updates parameters, enhancing the adaptability of the compensation process to time-varying systems.

Performance potential of fully-passive airborne wind energy system based on flapping airfoil

In the field of renewable energy, high-altitude wind energy emerges as a promising source, particularly at altitudes (>300 m) where conventional wind turbines cannot reach. Currently, the Airborne Wind Energy System (AWES) stands as the major technology for high-altitude wind energy harvesting, but confronts challenges including increasing performance enhancement, system robustness, and cost reduction. In response to these challenges, we developed a fully-passive AWES that employs a self-excited flapping airfoil to efficiently transfer wind energy to the ground. We study and optimize this fully-passive AWES with fluid-structure interaction method in a numerical wind tunnel, achieving a notable power coefficient of 1.17 and efficiency of 20 % with an average tether angle near 30°. We find that a thin airfoil with a slight camber near the leading edge outperforms other profiles. Increasing the pitching axis distance, the imbalance distance, the spring stiffness, and the pitching moment of inertia can improve the energy harvesting performance, but decreased the system robustness. We offer essential guidelines for setting initial parameters of the AWES, facilitating the design and deployment of this innovative technology. This work underscore that the fully-passive AWES is capable of realizing high-altitude wind energy harvesting with simplified structure and outstanding energy-harvesting performance.

An experimental investigation of a solar chimney integrated with a bladeless wind turbine for sustainable energy harvesting

The current study explores the potential of combining small-scale solar chimney systems with blade-less wind turbines for sustainable energy solutions in Egypt through mathematical modelling, numerical simulation, and experimental work. The integration of a vortex bladeless turbine and a conventional horizontal axis wind turbine in a hybrid energy harvester solar chimney system (VBSCS) was evaluated, as well as the effect of changing the absorber material on improving the system's performance. Shredded rubber improves heat absorption in solar chimney collectors, optimizing energy conversion and providing a sustainable, eco-friendly solution while addressing challenges and cost-effectiveness in implementing this hybrid solution. The mathematical model predicted the highest power at 0.38 W, while the CFD model yielded 0.298 W. Experimental results showed power outputs of 0.18 and 0.25 W for the SCS with concrete and shredded rubber absorbers, respectively. In addition, the VBSCS with a concrete absorber produced 0.29 W. The determined percentage improvement over the SCS with a concrete absorber was 61.1 % for the VBSCS and 38.9 % for the SCS with a black rubber absorber. These findings demonstrate the delicate interplay of design aspects and material choices that influence the performance of both bladeless wind turbines and solar collector systems.

Low-speed wind energy generation devices to facilitate NZEB in urban Pakistan

Energy consumption and its resultant impact on climate change are inextricably linked, with the burning of fossil fuels being a chief contributor to greenhouse gas emissions, furthering global warming. Mitigating these effects necessitates a two-fold approach: reducing energy consumption through enhanced efficiency and behavioral modifications, and concurrently transitioning to renewable and clean energy sources. Of particular concern is the domestic and commercial building sector, which currently accounts for a substantial 40% of the world's total energy usage. Conventional wind turbines, effective in harnessing wind energy, face limitations in urban areas due to the requisite wind speeds. Micro wind turbines, notably Vertical Axis Wind Turbines (VAWT), present a promising solution for achieving net-zero energy buildings in urban settings. VAWTs exhibit advantages such as higher efficiency and lower cut-in speeds. Despite their promise, challenges like reliability, cost, and environmental impact persist. This concise overview suggests potential applications for Pakistan, emphasizing the imperative for further exploration in optimizing VAWT design, developing hybrid systems, and evaluating societal acceptance of rooftop wind farms.

Comparison of 25 MW downwind and upwind turbine designs with individual pitch control

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.

CFD simulation of a multi-rotor system using diffuser augmented wind turbines by lattice Boltzmann method

A diffuser-augmented wind turbine (DAWT) achieves greater power generation efficiency by increasing wind speed through the diffuser. Nevertheless, scaling up this technology is difficult because of the considerable amount of wind drag on the diffusers. To overcome this difficulty, a multi-rotor system with two or more wind turbines on the same structure is one approach to increasing wind turbine power output. This research proposes a computational fluid dynamics (CFD) method to evaluate the hydrodynamic performance of a large-scale multi-rotor system of DAWTs. Compared to conventional wind turbines, CFD simulations of DAWTs necessitate higher computational costs because of the need of high-resolution meshes for the diffuser. Furthermore, the computational cost of a multi-rotor system increases with the number of rotors. To address the issue of high computational cost, we use the Lattice Boltzmann Method (LBM), which is well suited to large-scale CFD simulations. A wind turbine is modeled as an actuator line model and a diffuser as a wall boundary. An adaptive mesh refinement approach generates higher resolution meshes near the rotor and diffuser. LBM simulations were conducted for a single DAWT and a multi-rotor system with five DAWTs. The LBM results of the wake velocity and pressure distributions were in agreement with those obtained from wind tunnel experiments and general CFD methods in earlier studies. To investigate the diffuser gap effects, we simulated five DAWTs with diffuser gaps of 5%–25% of the diffuser diameter. The power gain of each DAWT was assessed. Great performance improvements were found with diffuser gaps of 20% and 25% of the diffuser diameter. On average, the five DAWTs achieved a power gain of more than 10%. These findings confirmed the accurate evaluation capability of the proposed CFD method for hydrodynamic characteristics of multi-rotor systems using DAWTs.

The potential role of airborne and floating wind in the North Sea region

Abstract Novel wind technologies, in particular airborne wind energy (AWE) and floating offshore wind turbines, have the potential to unlock untapped wind resources and contribute to power system stability in unique ways. So far, the techno-economic potential of both technologies has only been investigated at a small scale, whereas the most significant benefits will likely play out on a system scale. Given the urgency of the energy transition, the possible contribution of these novel technologies should be addressed. Therefore, we investigate the main system-level trade-offs in integrating AWE systems and floating wind turbines into a highly renewable future energy system. To do so, we develop a modelling workflow that integrates wind resource assessment and future cost and performance estimations into a large-scale energy system model, which finds cost-optimal system designs that are operationally feasible with hourly temporal resolution across ten countries in the North Sea region. Acknowledging the uncertainty on AWE systems’ future costs and performance and floating wind turbines, we examine a broad range of cost and technology development scenarios and identify which insights are consistent across different possible futures. We find that onshore AWE outperforms conventional onshore wind regarding system-wide benefits due to higher wind resource availability and distinctive hourly generation profiles, which are sometimes complementary to conventional onshore turbines. The achievable power density per ground surface area is the main limiting factor in large-scale onshore AWE deployment. Offshore AWE, in contrast, provides system benefits similar to those of offshore wind alternatives. Therefore, deployment is primarily driven by cost competitiveness. Floating wind turbines achieve higher performance than conventional wind turbines, so they can cost more and remain competitive. AWE, in particular, might be able to play a significant role in a climate-neutral European energy supply and thus warrants further study.

Design of Solar Energy Based System Using Artificial Neural Network Controller

A key component of energy generation and the safe operation of the electrical system is solar energy. The solar energy system for producing the required voltage is presented in this paper. It is managed by an artificial neural network (ANN) controller, which performs significantly better than a conventional PI controller. It aids in lowering the system's total harmonic distortion (THD). The sole PI controller, which produces an erratic output response, is utilized in conventional wind turbines. It is swapped out in the suggested system for an ANN controller, which offers smooth voltage and current response. Two inputs and two outputs are used in the system's development. Six pulse-fired IGBTs that reduce excess voltage and current in the circuit operate this system. The MATLAB/Simulink tool was used to create the results, which were shown to be superior to traditional results. To regulate the impact of a variable power factor, an output variable load is connected. Every outcome has been validated and confirmed to be superior than traditional outcomes.

Innovative Compact Twin Whirly Bird-based Wind Turbine: A Sustainable Solution for EV Charging Infrastructure

The global adoption of whirly bird vent roofs across various industries underscores their utility in harnessing wind energy for cooling purposes within warehouses and similar environments. The innovation proposed in the current study builds upon this established technology by integrating semi-perpetual motion principles into a compact twin whirly bird-inspired wind turbine design. This novel approach aims to enhance power generation efficiency, thereby offering a sustainable solution for energy production. The compact twin whirly bird turbine concept represents a significant advancement, particularly in the context of powering electric vehicle (EV) chargers. As the demand for EVs continues to surge, concerns persist regarding the availability of charging infrastructure. By integrating the proposed innovative wind turbine technology into the EV charging ecosystem, we address this critical issue while simultaneously promoting the adoption of renewable energy sources. The key to our proposal is the deployment of small-scale wind turbines in diverse public locations, thereby democratizing access to clean energy generation. Unlike conventional large-scale wind turbines, our whirly bird-inspired turbines boast versatility in installation, akin to streetlamps, facilitating widespread deployment across urban landscapes. While these turbines may yield comparatively modest power outputs relative to megawatt-scale counterparts, their strategic placement ensures a decentralized network capable of powering EV charging stations. In summary, our research presents a compelling solution that bridges the gap between EV charging infrastructure availability and the utilization of renewable energy sources. By leveraging the inherent advantages of whirly bird-inspired wind turbines, we offer a practical pathway towards sustainable energy provision in public spaces, thereby facilitating the widespread adoption of electric vehicles.

Aeroacoustic investigation of a ducted wind turbine employing bio-inspired airfoil profiles

Ducted wind turbines for residential purposes are characterized by a lower diameter with respect to conventional wind turbines for on-shore applications. The noise generated by the rotor plays a significant role in the overall aerodynamic noise. By making modifications to the blade sections of the wind turbine, we can alter the contributions of aeroacoustic noise sources. This study introduces innovative wind turbine blade designs inspired by owl wing characteristics, achieving significant noise reduction without compromising aerodynamic performance. A three-dimensional scan of an owl wing was first employed to derive a family of airfoils. The airfoils were employed to modify the blade of a referenced wind turbine airfoil section at various positions on the blade span to determine a blade operating more efficiently at the tip-speed ratio of the original one. While maintaining the same aerodynamic performance, the bio-inspired profiles show a more uniform pressure coefficient distribution, considerably decreasing in the noise level. Furthermore, this study makes considerable progress in ducted wind turbine design by obtaining an 8 dB noise reduction and a 12% improvement in sound pressure level. An in-depth aerodynamic examination shows a 6.4% rise in thrust force coefficient and optimized power coefficients, reaching a peak at a tip speed ratio of 8, demonstrating improved energy conversion efficiency. The results highlight the dual advantage of the innovative design: significant noise reduction and enhanced aerodynamic efficiency, offering a promising alternative for urban wind generation.

A novel structure of magnetic geared generator in dual-rotor wind turbine

Variable-speed constant-frequency generating systems are commonly employed in wind turbines to enhance efficiency and minimize losses. Additionally, the utilization of dual-rotor wind turbines enables the capture of a greater amount of wind energy, leading to a significant increase in efficiency. Traditionally, dual-rotor wind turbines are managed by a full-scale power converter, and the rotor current is transmitted through brushes, which substantially raises the system's cost. To address these challenges, this study introduces a novel configuration that enables power control with a smaller power converter. In contrast to conventional dual-rotor wind turbines that generate power using both rotors, the proposed structure designates one rotor as a system controller. Apart from these benefits, the proposed structure greatly enhances conversion performance by notably improving the power factor. A comparison with existing configurations described in literature is conducted to demonstrate the superiority of the proposed structure.

Analysis of Contra-Rotating Brushless Integrated Flux-Modulation Machine With Open-Slot Structure for Wind Power Generation

This paper presents a contra-rotating (CR) brushless integrated flux-modulation (BIFM) machine with open-slot structure for wind power generation, termed CR-BIFM machine. The presented machine employs two contra-rotating rotors coupled with two sets of wind turbine blades, thus being able to capture more wind energy than conventional single-rotor wind turbines. Due to the dual flux-modulation effect and flux-bridge effect, the presented machine exhibits high torque/power density, making it suitable for direct-drive wind power generation without issues related to mechanical gearboxes. As two sets of windings share the same stator slots in the presented machine, the decoupling design of windings is systematically investigated from the perspective of air-gap modulated magnetic field, considering the influence of both stator and rotors. The advantages of the presented machine are comprehensively evaluated compared to the baseline machine, showing that the presented machine exhibits higher torque/power density, higher efficiency, higher power factor, higher PM utilization, and better vibration performance. Finally, a prototype is fabricated and tested to validate the analysis.

Wake characteristics of a balloon wind turbine and aerodynamic analysis of its balloon using a large eddy simulation and actuator disk model

Abstract. In the realm of novel technologies for generating electricity from renewable resources, an emerging category of wind energy converters called airborne wind energy systems (AWESs) has gained prominence. These pioneering systems employ tethered wings or aircraft that operate at higher atmospheric layers, enabling them to harness wind speeds surpassing conventional wind turbines' capabilities. The balloon wind turbine is one type of AWESs that utilizes the buoyancy effect to elevate the turbine to altitudes typically ranging from 400 to 1000 m. In this paper, the wake characteristics and aerodynamics of a balloon wind turbine were numerically investigated for different wind scenarios. Large eddy simulation, along with the actuator disk model, was employed to predict the wake behavior of the turbine. To improve the accuracy of the simulation results, a structured grid was generated and refined by using an algorithm to resolve about 80 % of the local turbulent kinetic energy in the wake. Results contributed to designing an optimized layout of wind farms and stability analysis of such systems. The capabilities of the hybrid large eddy simulation and actuator disk model (LES–ADM) when using the mesh generation algorithm were evaluated against the experimental data on a smaller wind turbine. The assessment revealed a good agreement between numerical and experimental results. While a weakened rotor wake was observed at the distance of 22.5 diameters downstream of the balloon turbine, the balloon wake disappeared at about 0.6 of that distance in all the wind scenarios. Vortices generated by the rotor and balloon started to merge at the tilt angle of 10∘, which intensified the turbulence intensity at 10 diameters downstream of the turbine for the wind speeds of 7 and 10 m s−1. By increasing the tilt angle, the lift force on the wings experienced a sharper increase with respect to that of the whole balloon, which signified a controlling system requirement for balancing such an extra lift force.

Feasibility of Hydrostatic Transmission in Community Wind Turbines

This study investigates the potential improvement of a community wind turbine through replacing the conventional drivetrain with a hydrostatic transmission (HST). Conventional wind turbines use a fixed-ratio gearbox, a variable-speed induction generator, and power electronics to match the grid frequency. Because of unsteady wind, the reliability of the gearbox has been a major issue. An HST, a continuously variable transmission with a high power density, can replace a conventional transmission. The resulting wind turbine has the potential to offer the advantages of a lower cost, decreased weight, and increased reliability. For the application considered in this study, the main source of LCOE increase is due to the inefficiencies in the system. Even if the cost of the proposed HST transmission is free, because of inefficiency, the levelized cost of electricity will be higher than for a turbine with a conventional fixed-ratio gearbox. For the HST solution to be cost-competitive, increases in efficiency and reductions in cost are required.

EFFICIENCY ANALYSIS OF ELECTROMECHANICAL CONVERSION SYSTEMS OF WIND TURBINES WITH AERODYNAMIC MULTIPLICATION

In this article, we have considered the state of development of high-power horizontal wind turbines. The most common wind turbines for operation with variable wind flow speed usually include a frequency converter to ensure the compatibility of generator with network. It leads to decrease in the efficiency of wind energy conversion system, while the use of direct connection of the generator to the axis of wind wheel leads to a significant increase in the weight and cost of the generator. The wind turbine with aerodynamic multiplication is an alternative to such systems. Its prototype with 750 kW power is manufactured and studied in Ukraine. This wind energy conversion system with the synchronous or induction generators offers the property to generate energy under optimal condition with invariable rotational speed of generator rotor within the wide range of variable speed of wind flow. In this case, it is not necessary to apply the frequency converter that contributes to increasing the efficiency and reducing the cost of wind turbine. As shown, the relative performances of mass, cost and efficiency of generators in proposed system comparatively to conventional one depend on the multiplication factor (i.e. ratio of the rotational speeds of wind turbine and generator). When the power of wind turbines is from 750 to 2500 kW, the multiplication factor is within the limits of 10.72 to 4.75. The theoretical and experimental study shows that the wind turbines with aerodynamic multiplication can be competitive as compared to conventional horizontal wind turbines. This article is aimed to comparative analysis of the quantitative and qualitative characteristics of the equipment used in high-power horizontal wind turbines with direct connection of generators to the axis of wind turbine and in wind turbines with aerodynamic multiplication. References 27, tables 1, figures 6.

Experimental Study Influence of High Fin on Naca Airfoil 0018 On Performance Of H-Type Darrieus Wind Turbine

Energy is something that is needed in life, as technology develops the need for energy is increasing as well, while the role of New Energy Darrieus wind turbine is one of the solutions for renewable energy because it utilizes energy from wind and is converted into electrical energy, but this turbine has a low starting torque. In this study, the performance of the Darrieus wind turbine was improved by adding a fin to each blade with variations in height (0 cm, 1,5 cm, 2,5 cm, and 3,5 cm). In addition, testing was also carried out with variations in fluid flow speeds (3 m / s; 5 m / s; and 7 m / s). The subjects used in this study were H-type Darrieus wind turbines with a diameter of 40 cm and a height of 50 cm. Experiments were carried out to find out how the effect of fin addition with variations in height on the coefficient of power (Cp) and coefficient of torque (Ct) of the darrieus wind turbine. The final results showed the best performance improvement of the savonius wind turbine occurred at a variation in the fin height of 2.5 cm at a wind speed of 5 m/s. The coefficient of torque (Ct) increased by 7.64% and the coefficient of power (Cp) by 48.38% against conventional H-type darrieus wind turbines. This is because the addition of an effective fin is to reduce the tip of the vortex at the end of each blade so that the flow of fluid that flows becomes more regular and maximum.

Yaw control strategies for 20 MW multi-rotor systems

In this paper, the control of an active yaw system for a 20 MW multi-rotor wind turbine system (MRS) is considered. The MRS under investigation consists of five 4 MW turbines in two rows, which are connected to the tower via a space frame. A central yaw bearing at the height of the lower rotors is provided for active yaw. The paper aims to show that active aerodynamic yaw is possible by changing the thrust of certain rotors and should be considered for further research in the field of yawing of an MRS. Two different simulation environments are used in the paper. The MRS is modeled and simulated in Matlab/Simulink. Simulink’s own control modules are used as controllers. In the other simulation approach, the same MRS is modeled and simulated in Bladed and controlled with an external controller based on C++. The use of Bladed and Matlab/Simulink enables the plausibility and verification of the results. Matlab/Simulink is faster based of its simpler models but Bladed is more sophisticated. This paper also briefly presents the state of the art for yaw systems and yaw control of conventional single rotor wind turbines and initial research literature on yaw control of MRS.

New model for structural optimisation of airborne wind energy systems with rotary transmission

Rotary Airborne Wind Energy Systems (RAWES) are networks of wings that act as flying wind turbines. The power extracted from the wind can be transmitted to ground-based generators through open tensegrity structures. In recent years, there have been different approaches to the topology of the Tensile Rotary Power Transmission (TRPT) and prototype designs are often driven by trial-and-error. This paper proposes a steady-state model with numerical optimisation to accelerate the development and prototyping of AWES by supporting the evaluation of new design concepts.The coupled steady state model uses aerodynamics and structural dynamics to analyse the AWES performance. A novelty is, that the model includes both cross-wind pressure drag and axial friction drag acting on the tethers and frames in the tensegrity structure. Validation of the model has been achieved using data from field measurements of two prototypes.In conclusion, using the proposed optimisation, RAWES with TRPT can be designed to maximise power density, coefficients of performance or power harvesting factor. While RAWES will not be able to outperform conventional wind turbines, they have the potential advantages in niche applications due to reduced costs and simplified logistics resulting from reduced material usage.

Efficient floating offshore wind realization: A comparative legal analysis of France, Norway and the United Kingdom

Floating offshore wind (FOW) has the potential to play a key role in many states' decarbonization policies going forward. The reason is that the majority of the world's wind energy potential is located offshore at depths where deployment of conventional bottom-fixed offshore wind turbines is not economically profitable. To realize FOW's potential as a key decarbonization technology policy makers and legislators must design legal frameworks that properly address the three main barriers to efficient deployment: (a) spatial competition, (b) need for state financing and (c) allocation of grid connection responsibilities. This article analyses and compares Norway, France and the United Kingdom's regulation of the three main barriers to efficient FOW deployment with respect of their ability to ensure efficient realisation. The article concludes with best practices and recommendation to policy makers and legislators on how to regulate the three main barriers to accomplish efficient FOW deployment.