Wind Energy Harvesting Research Articles

A dual-beam piezo-magneto-elastic wake-induced vibration energy harvesting system for high-performance wind energy harvesting

A dual-beam piezo-magneto-elastic wake-induced vibration energy harvesting system for high-performance wind energy harvesting

Rotation differential triboelectric nanogenerator for bird-repellent on transmission line towers

The security of transmission line towers is crucial to industrial development. Bird damage is a significant threat to transmission line towers in the field. However, the power supply to the bird-repellent devices is limited. In this work, we propose a rotation differential triboelectric nanogenerator (RD-TENG) to harvest wind energy for supplying electrical power to bird-repellent on transmission line towers. On the transmission line towers, the RD-TENG converts wind energy into electrical energy by rotation differential structure and stores power in a 1000 μF capacitor, then supplies power to the buzzer for bird-repellent. The device mainly consists of a wind cup, an input gear, output gears, and rotors. The RD-TENG can achieve double rotation speed by rotating the differential structure compared to the single gear counterpart, hence doubling the current and power output through triboelectric nanogenerator. The RD-TENG has a starting wind speed of 4 m s−1 and can operate normally at lower wind speeds. At a wind speed of 8 m s−1, the output performance of the RD-TENG is 830 V, 13.5 μA, 330 nC, and the peak power is 19.6 mW. This work realizes a new solution for bird-repellent on transmission lines through the TENG energy harvesting technique and also contributes to the subsequent smart grid construction.

An optimization study of passive flow control mechanism for a seashell-shaped wind turbine

Small wind turbines have a lot of promise in areas that are remote from the power grid. For such small-scale applications, such as off-grid electricity, a spiral wind turbine (SWT), a novel type of horizontal-axis wind turbine, may be employed. Placing wind turbines within a duct is one potential method for increasing the efficiency of wind energy harvesting in low-wind urban locations. In this work, a shroud with a flange at its outlet is created using an optimization approach that attempts to maximize the coefficient of power (CP), which improves SWT performance. An evolutionary algorithm over a Kriging interpolative model serves as the optimizer in use. The shroud's shape is determined using a series of straight lines. Using the commercial code program ANSYS-FLUENT, the Reynolds-averaged Navier-Stokes (RANS) equations are solved along with the SST k–ω turbulence model to determine the turbine CP. The computational results are validated and confirmed with previously published results. The optimal shroud design introduced significant improvements in the CP when applied to the SWT, resulting in a maximum CP of 0.967 (at λ = 3.25), which is 3.6 times the maximum CP of the bare SWT (CP = 0.2668 at λ = 2.5).

Wind Energy Harvesting with Vertically Aligned Piezoelectric Inverted Flags.

Wind-energy-harvesting generators based on inverted flag architecture are an attractive option to replace batteries in low-power wireless electronic devices and deploy-and-forget distributed sensors. This study examines two important aspects that have been overlooked in previous research: the interaction between an inverted flag and a neighboring solid boundary and the interaction among multiple contiguous inverted flags arranged in a vertical row. Systematic tests have been carried out with metal-only 'baseline' flags as well as a 'harvester' variant, i.e., the baseline metal flag covered with PVDF (polyvinylidene difluoride) piezoelectric polymer elements. In each case, dynamic response and power generation were measured and assessed. For baseline metal flags, the same qualitative trend is observed when the flag approaches an obstacle, whether this is a wall or another flag. As the gap distance reduces, the wind speed range at which flapping occurs gradually shrinks and shifts towards lower velocities. The increased damping introduced by attaching PVDF elements to the baseline metal flags led to a considerable narrowing of the flapping wind speed range, and the wall-to-flag or flag-to-flag interaction led to a power reduction of up to one order of magnitude compared to single flags. The present findings highlight the strong dependence of the power output on the flapping frequency, which decreases when the flag approaches a wall or other flags mounted onto the same pole. Minimum flag-to-flag and flag-to-wall spacing values are suggested for practical applications to avoid power reduction in multi-flag arrangements (2-3H and 1-2H respectively, where H is flag height).

An improved uncertainty and disturbance estimator-based speed control for grid-connected pumping kite wind generator

Pumping kite generator systems (KGS) represent a novel and exciting concept for future wind energy harvesting at higher altitudes where the wind is more reliable, stable, and highly predictable. The configuration of such systems generally employs a flying tethered kite attached to a generator/motor and connected to the grid using a power electronic interface. This work aims to enhance control system efficiency and increase the generated power by improving the speed control of the generator. To this end, an uncertainty and disturbance estimator (UDE) based speed controller is developed to deal with the challenges presented by this new technology, particularly periodical variation of the rotational speed reference in maximum power point tracking. The practicality and effectiveness of the proposed UDE-based control method are demonstrated through simulation and experimental results. It is shown that the proposed control strategy offers improved tracking performance and robustness against model uncertainties and external disturbances.

Self-tuning triboelectric nanogenerator for omnidirectional broadband (1.2–13.8 m/s) wind energy collection and wind vector detection with deep learning

Wind speed and wind direction are not only important meteorological factors in environmental dynamic monitoring but also crucial parameters for harvesting considerable renewable wind energy. Although the multi-uniform unit arrangement of triboelectric nanogenerator (TENG) is a strategy for extending the responsive wind speed and direction, interunit crosstalk, low wind direction resolution, narrow working wind speed range, and unclear complex interaction between wake and wind capture component hinder further applications of wind-driven TENG. Here, a self-tuning triboelectric nanogenerator (S-TENG) is developed to effectively harvest broadband omnidirectional wind energy and simultaneously meet the high-resolution detection of wind vector. The gas-solid interaction model of this device is proposed as a two-step process. Meanwhile, owning to the self-tuning ability, the device greatly expands its working range from 2.4 to 6.4 m/s to 1.2–13.8 m/s, giving an excellent output power of 47.43 W/m3. Additionally, a real-time wind vector sensing system based on LabVIEW software exhibits wind direction resolution of up to 5° with only three channels. The recognition accuracy of wind direction relying on deep learning model reaches 98.98%. This work provides a guidance for designing effective high entropy wind energy harvesters and a deep understanding of gas-solid interaction processes.

Parametric optimisation of a dual cantilever flutter for electromagnetic wind energy harvesting

This paper investigates the parametric optimisation of dual cantilever flutter (DCF) beams for electromagnetic wind energy harvesting application. When two cantilever beams are placed side by side facing the direction of the wind flow, both beams would oscillate in an anti-phase motion once the critical flutter speed has been achieved. This arrangement is known as the DCF and it represents an ideal situation for energy harvesting through electromagnetic induction due to its anti-phase motion. Experimental results showed that the optimum load resistance value for the device is equivalent to a single-degree-of-freedom vibration energy harvester for low electromagnetic coupling case, despite the difference in the type of oscillations. Further analysis showed that there among the two possible arrangements for the magnets one arrangement results in a 51.5% larger magnetic flux density. It was seen that reducing the length of the electromagnetic DCF by 41.2% can increase the power output of the device by approximately six times, although the critical flutter speed also increased by 125.0%. Finally, some suggestions were provided on how to further improve the device.

Assessment of urban wind energy resource in Hong Kong based on multi-instrument observations

Urban wind power is an appealing alternative for electricity supply. Comprehensive urban wind resource assessment is a prerequisite for cost-efficient deployment of wind turbines. Based on observations from multiple instruments, including a Doppler lidar (light detection and ranging) system, a microwave radiometer, and a cup anemometer/wind vane set, this study investigates the temporal (interannual, seasonal, and diurnal) variations of wind resources at various heights in a metropolitan city, Hong Kong. The long-term statistical distributions of wind speed, wind shear coefficient, and air density are analyzed, and their variations with height, wind direction, season, and time of day are thoroughly examined. Moreover, the wind power density and capacity factor of prototype wind turbines are estimated. It is observed that the statistical distributions of wind speed and air density are best represented by the Kappa and Normal-Weibull mixture distributions, respectively. There is a significant diurnal variation of wind shear coefficient, from 0.1 in the daytime to 0.4 at night. Moreover, a moderate potential for wind energy harvesting with wind power density of 110 W/m2 is found at the height of 120 m. This is the first known study that jointly uses lidar, microwave radiometer, and anemometer/wind vane for urban wind resource assessment. These instruments enable the investigation of the temporal variations of wind shear coefficient, air density, and wind power density at multiple heights, which were rarely examined in urban wind energy studies before.

Fully enclosed microbeads structured TENG arrays for omnidirectional wind energy harvesting with a portable galloping oscillator

To facilitate the transition of triboelectric nanogenerators (TENG) from early stages to large-scale real-world applications, urgent mass production is imperative, necessitating standardized manufacturing processes. In this study, a novel “pause-and-insert” and “print-in-place” 3D printing approach has been devised, employing widely available fused deposition modeling (FDM) printers along with conductive (as electrodes) and nonconductive (for casing and support) filaments to make encapsulate microbeads triboelectric nanogenerator (MB-TENG). This innovation results in a fully enclosed freestanding-mode TENG pack, seamlessly integrated with a lightweight wind-induced oscillator featuring tuning systems, thus enabling efficient, safe, and noiseless omnidirectional wind energy harvesting. Through adept design and manufacturing techniques, systematic inner-structure optimization has been achieved, yielding superior output and industrialization levels compared to similar efforts. MB-TENG’s surface charge density is as high as 19.9 µC/m2. The average power density is 13.8 W/m3. Moreover, the elimination of postprocessing significantly streamlines standard manufacturing, enhancing the prospects for device commercialization. Beyond its wind energy application, the versatile energy packs can serve as both ocean wave and human motion harvesters within network configurations, capable of powering a massive real-time monitoring sensor array.

Mixformer: Mixture transformer with hierarchical context for spatio-temporal wind speed forecasting

Wind energy has attracted more and more attention due to its sustainability and pollution-free nature. As wind energy is highly dependent on wind speed, wind speed forecasting is of great importance for fully harvesting wind energy and ensuring the stability and reliability of wind energy systems. By accurately predicting the future wind speed, we can make efficient power schedules and consequently improve the utilization of wind power. Although existing forecasting methods have achieved satisfactory wind forecasting performance, they may still fail to discover the intricate spatio-temporal dependencies obscured in entangled patterns. To resolve this issue and further improve the prediction accuracy, we propose Mixformer, a novel mixture Transformer with hierarchical context for spatio-temporal wind speed forecasting. Mixformer first applies seasonal-trend decomposition, and then employs an MLP to predict the trend part and an attention model to predict the seasonal part. Besides, Mixformer innovatively proposes a spatio-temporal Gaussian mixture attention (ST-GMA) layer, which fuses the periodic temporal and long-term spatial context. To capture intricate long-term spatial characteristics, Mixformer extracts global information by the Dynamic Time Warping algorithm. Moreover, with the ST-GMA layer, Mixformer builds a hierarchical encoder–decoder architecture to fully utilize the context at different scales for seasonal forecasting and further enhance the spatio-temporal modeling. Empirical experiments on four real-world benchmark datasets show that Mixformer yields the lowest prediction errors with the MAE scores of 1.66, 1.68, 3.14 and 0.70 and the RMSE scores of 2.07, 2.01, 3.99 and 0.98, and improves the prediction accuracy by 8.43%, 5.36%, 4.14%, 6.57% in term of MAE scores and 9.18%, 6.92%, 4.01%, 5.75% in term of RMSE scores compared to state-of-the-art methods, which demonstrates the superiority of Mixformer. In a nutshell, Mixformer presents a promising method for spatio-temporal wind speed forecasting and may achieve desirable performance in real-world applications of wind power systems.

Externally motionless triboelectric nanogenerator based on vortex-induced rolling for omnidirectional wind energy harvesting

Wind-driven triboelectric nanogenerators (WTENGs) are an emerging technology that holds the potential for sustainable wind energy harvesting. Although recent efforts have proposed various strategies for developing WTENGs, realizing their practical utility, characterized by high output performance, lightweight design, compact dimensions, and omnidirectional energy capture, remains a formidable challenge. This study introduces an innovative WTENG that leverages a rolling-based mechanism to achieve effective omnidirectional wind energy harvesting. The distinctive design features a guide vane and a deformable rolling cylinder, both of which play pivotal roles in enhancing triboelectrification, optimizing power output, and ensuring consistent performance despite fluctuations in wind direction. Specifically, the guide vane generates a rotating flow, facilitating the rolling of the cylinder. The electrical energy is generated through triboelectrification occurring between the cylinder and the inner surface of the vane as the cylinder rolls during operation. Numerical simulations and experimental validation have underscored the critical significance of the design of the guide vane and the structural parameters of the rolling cylinder in determining the output performance of the device. Remarkably, the proposed WTENG has demonstrated a root-mean-square area power density of 89.723 mW/m2 at a wind speed of 8 m/s, thus attesting to its superior energy harvesting capabilities. Furthermore, the versatility of this device was evident as it effectively powered a wireless environmental monitoring system and functioned as a self-powered wind speed sensor. With a mere 42 g weight, a compact footprint of 22.062 cm2, and an internal rolling-based mechanism enabling motionless operation from an external perspective, this WTENG offers substantial advantages in spatial efficiency. Consequently, it is an ideal choice for deployment in constrained environments.

Enhance vortices vibration with Y-type bluff body to decrease arousing wind speed and extend range for flag triboelectric energy harvester

The Internet of Things (IoT) has approached network construction by billions of intelligent wireless sensor nodes (WSNs). The major challenge is the desirable self-power generator by environment local energy. This paper presents a novel flag-type triboelectric nanogenerator with a Y-type bluff body that is YF-TENG to harvest wind energy. It exhibits a wider range and lower wind velocities for energy harvesting. The Y-type bluff body enhances YF-TENG vibration of the vortices shedding which is recorded by high-speed camera. The mounting position, designing dimension, and windward angle of the Y-type bluff body are investigated to enhance the flag vibration and the output triboelectric power. The test results show that the power is twice as much as the traditional flag-type triboelectric nanogenerator with a wind velocity of 6 m/s. Furthermore, a proof-of-concept application of the arrayed YF-TENG units supplies sufficient electric power for the wireless temperature and humidity sensor in a wind tunnel. It is envisioned that the enhancement of YF-TENG sensitivity and stability via a Y-type bluff body affords significant potential power for a large number of sensor nodes in a wide wind region.

YPR-alignment angles for wind energy harvesting kite arrangement: α,β,γ-coefficients for control and maintenance of regenerative flow patterns

Esta investigación propone maximizar la eficiencia de un sistema captador de energía, a través de cometas eólicas incorporando una técnica de remediación del patrón de flujo, para el restablecimiento de las condiciones ambientales. El método de diseño plantea un modelado matemático en VHDL para los ángulos de alineación (YPR: yaw, pitch, roll) del arreglo de captadores eólicos, para establecer una tecnología cognitiva de actualización del sistema, minimizando los componentes hardware para el control activo de flujo y disminuyendo el impacto ambiental de los aerogeneradores. Se obtiene como resultado las ecuaciones de soporte en función de coeficientes de optimización α,β,γ del sistema eólico, considerando trayectorias sobre curvas cíclicas y transmisión por levitación magnética, para el control, mantenimiento y reconfiguración de patrones de flujo regenerativo. Esto permite concluir acerca de la importancia de diseñar mecanismos de remediación como patrones de vórtices a partir del control de ángulos de salida del captador eólico, en un compromiso por obtener un sistema sostenible.

A hybrid nanogenerator based on wind energy harvesting for powering self-driven sensing systems

The increase in energy demand makes it urgent to explore green energy sources. And wind energy is one of the most promising renewable energy sources. In this paper, a rotating hybrid nanogenerator with a combination of a direct-current triboelectric nanogenerator (DC-TENG) and an electromagnetic generator (EMG) is designed; the design concept is to harvest wind energy. First, an optimized ternary DC-TENG is designed based on the ternary dielectric triboelectrification effect. A soft contact structure is designed, which can effectively increase the frictional area as well as reduce the frictional resistance. Then, by introducing the EMG unit, the output power of the device and the speed of charging the capacitor are increased. The high output voltage of the DC-TENG and the high output current of the EMG complement each other to produce excellent power output. At 180 rpm/min, the output power of DC-TENG and EMG can reach 1.78 mW and 215 mW, respectively. With a simple power management circuit design, the device is successfully implemented to power small electronic devices. By charging a suitable capacitor, the device can be used as a power supply to power the sensor. Together with the sensor and power management circuit, it forms a self-powered sensing system that can drive the sensor for continuous operation. This work provides a simple, convenient, and reliable design that offers new insights into energy harvesting in nature.

Aerodynamic shape optimization of bluff body for galloping-based wind energy harvester by the class function/shape function transformation technique

This paper presents an aerodynamic modification scheme by using the class function/shape function transformation (CST) method to determine the optimal shape of the bluff body and hence improve the performance of the associated galloping-based wind energy harvester (WEH). The CST method, accompanying with the Latin Hypercube sampling method, is used to generate 50 representative samples of galloping bluff bodies with varying sectional geometries, by using only four parameters to describe each sectional geometry. Wind tunnel tests are conducted to measure the output power of each WEH and the transverse wind force acting on the associated bluff body. A Kriging surrogate model is constructed based on the results from wind tunnel test, to determine the optimal shape in terms of the output power. Results show that the optimal shape has the tapered leeward side and concave windward side, which can double the output power compared to a square shape. The underlying mechanism for the high performance is explained by analyzing the measured transverse force in the wind tunnel and the vorticity contours of the flow field generated by CFD analysis. On the one hand, the tapered leeward side avoids flow attachment on the two lateral sides of the shape, providing considerable transverse force that sustains the unstable steady-state galloping. On the other hand, the concave windward side promotes the development of large circulation bubbles, causing significant asymmetry of wind flow and hence remarkable galloping. The findings of the research can guide the design for the bluff body of the galloping-based WEHs, and the CST method can be used as a powerful tool for aerodynamic shape optimization.

A Rolling-Bead Triboelectric Nanogenerator for Harvesting Omnidirectional Wind-Induced Energy toward Shelter Forests Monitoring.

Shelter forests (or shelter-belts), while crucial for climate regulation, lack monitoring systems, e.g., Internet of Things (IoT) devices, but their abundant wind energy can potentially power these devices using the trees as mounting points. To harness wind energy, an omnidirectional fluid-induced vibration triboelectric nanogenerator (OFIV-TENG) has been developed. The device is installed on shelter forest trees to harvest wind energy from all directions, employing a fluid-induced vibration (FIV) mechanism (fluid-responding structure) that can capture and use wind energy, ranging from low wind speeds (vortex vibration) to high wind speeds (galloping). The rolling-bead triboelectric nanogenerator (TENG) can efficiently harvest energy while minimizing wear and tear. Additionally, the usage of double electrodes results in an effective surface charge density of 21.4µCm-2 , which is the highest among all reported rolling-bead TENGs. The collected energy is utilized for temperature and humidity monitoring, providing feedback on the effect of climate regulation in shelter forests, alarming forest fires, and wireless wind speed warning. In general, this work provides a promising and rational strategy, using natural resources like trees as the supporting structures, and shows broad application prospects in efficient energy collection, wind speed warning, and environmentally friendliness.

Bionic Blade Lift‐Drag Combination Triboelectric‐Electromagnetic Hybrid Generator with Enhanced Aerodynamic Performance for Wind Energy Harvesting

AbstractThe triboelectric nanogenerator (TENG) is a promising technology with unique advantages for harvesting environmental high‐entropy energy like wind power. However, inefficient wind energy harvest devices have limited the operating wind speed and practical application of TENGs. In this work, a bionic blade lift‐drag hybrid turbine‐driven triboelectric‐electromagnetic hybrid generator (HT‐TEHG) is designed for broadband wind energy harvesting. The lift‐drag hybrid turbine combines the benefits of drag‐type blades enabling low wind speed start‐up and bionic lift‐type blades generating high torque, achieving an 11% increase in performance. The TENGs are designed with appropriate dielectric layer gaps to balance the output performance and friction torque and are independently driven by two types of blades to achieve self‐adaptive graded power generation at different wind speeds. The starting wind speed of the HT‐TEHG is 2 m s−1 and achieves a peak power of 202.4 mW with an energy conversion efficiency of 9.1% at a wind speed of 4 m s−1. The durability of the TENG is verified by continuous operation for 1 × 105 cycles with almost no performance degradation. Moreover, the HT‐TEHG can power a wireless weather station using natural wind. The study introduces a valuable approach to harvest broadband wind energy and enable distributed power for Internet of Things devices.

Harvesting low-speed wind energy by bistable snap-through and amplified inertial force

One of current research focuses in wind energy harvester (WEH) design is improving electric output in low-speed wind environments. A desired WEH should work efficiently and produce large output in low-speed wind conditions. For this aim, a novel piezoelectric harvester is presented, which introduces multi-stability and applies amplified inertial forces on the piezoelectric material to improve the WEH's performance for low-speed wind. Under the action of wind, galloping will drive the cantilever beam to oscillate, and multi-stability will increase its response amplitude. Finally, the resulted inertial force will be amplified by two branches and act on the piezoelectric sheets to produce electric outputs. The theoretical model is established, and corresponding analyses are carried out. The results prove that a desired potential energy function can be obtained by adjusting the distances between magnets. The validation experiments are conducted in a wind tunnel. The experimental results prove that the harvester can start the snap-through motion from a relatively low wind speed of 1.30 m/s and keeps it in a low-speed area (1.30 m/s-1.85 m/s). Especially, the force's acting mode on piezoelectric material and the attraction between magnets can improve the harvester's reliability and sustainability.

A Versatile Strategy for Concurrent Passive Daytime Radiative Cooling and Sustainable Energy Harvesting.

Developing versatile systems that can concurrently achieve energy saving and energy generation is critical to accelerate carbon neutrality. However, challenges on designing highly effective, large scale, and multifunctional photonic film hinder the concurrent combination of passive daytime radiative cooling (PDRC) and utilization of sustainable clean energies. Herein, a versatile scalable photonic film (Ecoflex@h-BN) with washable property and excellent mechanical stability is developed by combining the excellent scattering efficiency of the hexagonal boron nitride (h-BN) nanoplates with the high infrared emissivity and ideal triboelectric negative property of the Ecoflex matrix. Strikingly, sufficiently high solar reflectance (0.92) and ideal emissivity (0.97) endow the Ecoflex@h-BN film with subambient cooling effect of ≈9.5°C at midday during the continuous outdoor measurements. In addition, the PDRC Ecoflex@h-BN film-based triboelectric nanogenerator (PDRC-TENG) exhibits a maximum peak power density of 0.5W m-2 . By reasonable structure design, the PDRC-TENG accomplishes effective wind energy harvesting and can successfully drive the electronic device. Meanwhile, an on-skin PDRC-TENG is fabricated to harvest human motion energy and monitor moving states. This research provides a novel design of a multifunctional PDRC photonic film, and offers a versatile strategy to realize concurrent PDRC and sustainable energies harvesting.

Triboelectric nanogenerator with asymmetric multilayer arc electrodes to improve performance

The role of wind energy in the emerging energy market is crucial and it holds the potential to emerge as a promising clean energy source. The triboelectric nanogenerator represents a revolutionary paradigm in wind energy harvesting devices, having engendered considerable scholarly interest due to its innovative approach and potential implications. Among its various working modes, freestanding mode is considered the most effective for harvesting rotating energy. In this paper, a freestanding mode multilayer triboelectric nanogenerator is proposed, which is characterized by asymmetric arc electrode structure, and the usual freestanding mode electrodes are positioned at a certain angle to improve the output of the generator. Operating at a frequency of 1 Hz, it is exclusively the single-layer arc electrode that can yield an instantaneous power output of 1.625 mW, while concurrently facilitating the transfer of a charge quantified at 197 nC. Compared to an untreated electrode, exhibiting an enhancement of 11-fold in terms of power output and 3.5-fold with respect to charge transfer. Additionally, the generator’s electrodes are cleverly designed with an asymmetric multilayer structure, resulting in higher space utilization within the generator. The asymmetric arc triboelectric nanogenerator (AA-TENG) presents a viable solution for effectively harvesting wind energy in nature.