Multifunctional Triboelectric Nanogenerator Research Articles

A multifunctional triboelectric nanogenerator based on PDMS/MXene for bio-mechanical energy harvesting and volleyball training monitoring

Within the domain of wearable devices that are self-powered and sensory, triboelectric nanogenerators (TENGs) have surfaced as a notable solution to meet the growing needs for energy harvesting. This study unveils an innovative wearable and stretchable multifunctional double-layered TENG, based on PDMS/MXene, known as PM-TENG. Furthermore, PM-TENG can also be used as a joint sensor to monitor the movement of athletes' joints during volleyball training. By augmenting the matrix with PDMS/MXene, which possesses dual capabilities—namely, charge capture and charge movement—the intermediary layer is integrated. This leads to a two fold increase in the ability to trap charges and the overall triboelectric performance. With a power density reaching 11.27 mW, it notably exceeds the performance of its counterparts that solely utilize PDMS, by nearly 11 times. This academic effort elucidates the important role of PM-TENG in biomechanical energy capture and autonomous wearable sports motion sensing.

Conductive dual-network hydrogel-based multifunctional triboelectric nanogenerator for temperature and pressure distribution sensing

Conductive hydrogels are gaining attention in flexible electronics due to their high electrical conductivity and stretchable mechanical properties. Utilizing conductive hydrogels as electrodes in triboelectric nanogenerators (TENG) offers a promising avenue for developing versatile, flexible devices. However, the preparation of a multifunctional hydrogel-based TENG remains a challenging task. Here, a dual-network hydrogel TENG is denoted as DNH-TENG. It comprises poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS)/poly (vinyl alcohol) (PVA)/carboxylated multi-walled carbon nanotube (MWCNT-COOH) and offers the advantages of straightforward fabrication, versatile applications, and efficient output performance. Preparing a double network by combining a conductive network with a soft network improves the tensile properties but reduces its conductivity significantly. Further doping MWCNT-COOH with the dual-network leads to a conjugation effect and hydrogen bonding. This enhancement fortifies the hydrogel structure and augments the electrode's conductivity and mechanical properties. In single electrode mode, the DNH-TENG exhibits a short-circuit current of 16.2 μA, a transfer charge of 97.3 nC, and an open-circuit voltage of 270.5 V. Furthermore, DNH-TENG exhibits an impressive stretchability, allowing it to be extended to 566%. Using DNH-TENG's exceptional stretchability and ultrahigh sensitivity to mechanical and temperature stimuli, we designed DNH-TENG-based sensor arrays to showcase temperature and pressure distribution monitoring applications.

Multifunctional triboelectric nanogenerator for wind energy harvesting and mist catching

Wind and mist, two ubiquitous phenomena in the natural environment, hold considerable reservoirs of energy. As the focus on renewable energy and freshwater resources intensifies, they have become subjects of extensive research. However, there is a notable scarcity of effective technologies capable of concurrently harnessing both these resources. Here, a multifunctional triboelectric nanogenerator (MF-TENG), employing a rotational structure, has been demonstrated to concurrently harvest wind energy for electricity generation and catch freshwater from mist. Distinguished by an innovative sealing structure, the MF-TENG excels in efficiently catching mist while sustaining a high electrical output, and remarkably resilient to environmental humidity. The MF-TENG achieves an impressive peak open-circuit voltage of 5.44 kV and a peak transferred charge of 328 nC. Furthermore, it demonstrates a maximum mist-catching capacity of 1.867 kg m−2 h−1, coupled with an efficiency of 31.19 %. Notably, the incorporation of FEP-2 results in a remarkable surge of 211 % in open-circuit voltage and an impressive enhancement of 158 % in transferred charge for the MF-TENG at a rotation speed of 200 r/min. The work introduces a pioneering perspective for future sustainable energy and freshwater catching from mist, poised to significantly advance in the comprehensive utilization of natural resources.

Flexible and multifunctional triboelectric nanogenerator based on liquid metal/polyvinyl alcohol hydrogel for energy harvesting and self-powered wearable human–machine interaction

Flexible and multifunctional triboelectric nanogenerator based on liquid metal/polyvinyl alcohol hydrogel for energy harvesting and self-powered wearable human–machine interaction

A damage-tolerant, self-healing and multifunctional triboelectric nanogenerator

Triboelectric nanogenerators (TENGs) are subjected to repeated contact and separations during operation, which inevitably cause damage from mechanical forces, leading to interface mismatch and function loss. Although self-healing property has been utilized to prolong the service life of flexible TENGs, triboelectric nanogenerators which can work stably in extreme mechanical environments have not been developed. Herein, we report a flexible single-mode triboelectric nanogenerator named V-PANI-TENG which not only have strong damage-tolerant ability including puncture-resistant ability to resist sabotage and tear-resistant ability to defend further crack propagation, but also show excellent self-healing performance upon damage based on the well-designed tribolayer PMBEug-OH-V-2–4 and electrode material PMBEug-OH-PANI-20%. Moreover, the V-PANI-TENG can also be used as an efficient self-powered sensor to monitor the movement of human body or detect the road surface roughness. Given the extraordinary durability and unprecedented applications resulting from novel material designs, this work provides an effective way to develop triboelectric nanogenerators which can work stably in extreme mechanical environments and broaden the application scenarios of triboelectric nanogenerators.

Template‐Assisted Electrospun Ordered Hierarchical Microhump Arrays‐Based Multifunctional Triboelectric Nanogenerator for Tactile Sensing and Animal Voice‐Emotion Identification

AbstractThe development of flexible and adaptable multifunctional sensing systems for human–machine interaction, especially for animal voice‐emotion identification, is highly desirable yet quite challenging. Herein, a multifunctional triboelectric nanogenerator (TENG) based on ordered hierarchical microhump arrays is proposed and fabricated by template‐assisted electrospinning with a facile, low‐cost, and expandable manufacturing process. Performances of a single‐electrode TENG based on the patterned nanofiber films with microhump arrays (NFM‐TENG) are studied in detail by varying mesh number of the template. Electric field structure of the collector is altered by pore sizes, wire diameters, and protrusions of the receiving templates subjected to different mesh numbers, generating different degrees of microhump arrays on the surface of the nanofiber film. NFM‐TENG demonstrates high sensitivity (15.94 mV Pa−1), fast response and recovery time (76 and 58 ms), a large power density of 122 mW m−2, and excellent ability of structural retention. Integrated with four functions of energy harvesting, pressure sensing, human physiological sensing, and animal voice‐emotion identification, NFM‐TENG achieves real‐time monitoring of human physiological, motion, handwriting, and animal voice‐emotion signals without an external power supply. This study shows significant application strategies for self‐powered human–machine interaction devices, novel animal voice‐emotion identification, biodiversity conservation, and so on.

Triboelectric Nanogenerators Based on Super-Stretchable Conductive Hydrogels with the Assistance of Deep-Learning for Handwriting Recognition.

Nowadays, wearable electronic devices are developing rapidly with the internet of things and human-computer interactions. However, there are problems such as low power, short power supply time, and difficulty in charging, leading to a limited range of practical applications. In this paper, a composite hydrogel composed of polyacrylamide, hydroxypropyl methylcellulose, and MXene (Ti3C2Tx) nanosheets was developed, which formed a stable double-chain structure by hydrogen bonding. The configuration endows the hydrogel with excellent properties, such as high strength, strong stretchability, excellent electrical conductivity, and high strain sensitivity. Based on these characteristics, a flexible multifunctional triboelectric nanogenerator (PHM-TENG) was prepared using the hydrogel as a functional electrode. The nanogenerator can collect biomechanical energy and convert it to 183 V with a maximum power density of 78.3 mW/m2. It is worth noting that PHM-TENG can be applied as a green power source for driving miniature electronics. Also, it can be used as an auto-powered strain sensor that distinguishes letters, enabling monitoring under small strain conditions. This work is anticipated to provide an avenue for the development of new intelligent systems for handwriting recognition.

Stretchable and self-healable conductive hydrogel-based multifunctional triboelectric nanogenerator for energy harvesting and dance motion sensing

Hydrogels with the integrated characteristics of adhesion, self-healing, deformability, and conductivity hold enormous potential for the design of next-generation flexible human body posture sensor and energy device. Here, we proposed a double-network hybrid polyacrylamide/poly(acrylic acid)/MXene/PEDOT:PET (PPMP) hydrogel with excellent flexibility, self-healing capabilities, and stability. Furthermore, the proposed PPMP conductive hydrogel with MXene/PDMS encapsulation layer can play the role of a wearable strain sensor that can be used to detect various dance movement postures, including those of facial expressions, blinking, and elbow joints. Additionally, the proposed PPMP hydrogel with MXene/PDMS encapsulation layer can function as a flexible and stretchable triboelectric nanogenerator (FS-TENG) to harvest human motion energy. The FS-TENG can obtain an open-circuit voltage (Voc) of 169.2 V and a short-circuit current (Isc) of 9.6 µA. Moreover, the electric energy generated by these FS-TENGs can be used to drive hygrothermographs. This research offers a feasible strategy to design self-powered strain sensors for use in dance posture monitoring and energy harvesting in human motion.

Multifunctional triboelectric nanogenerator based on flexible and self-healing sandwich structural film

Triboelectric nanogenerators (TENGs) represent an emerging technology in energy harvesting and sensing applications. The use of self-healing materials can not only improve the service life but also reduce the cost of TENGs. Here, we developed a flexible and self-healing sandwich structural film which is composed of two layers of nitrile butadiene rubber (NBR) with one layer of MXene in the middle. The NBR/MXene/NBR film is capable of self-healing quickly under heating by a hairdryer in 5 s, and even under a skin temperature of ~37 ℃ for 4 h. The as-prepared TENG, which consists of NBR/MXene/NBR film and basketball epidermis, can play the role of a triboelectric sensor (TS). The corresponding sensing capability was demonstrated by tracing finger touch position and monitoring the dribbling posture of a basketball player. Furthermore, the practical application of energy harvester was also explored by combining the NBR/MXene/NBR film with PTFE film. The as-prepared energy harvester can produce a peak-to-peak voltage of 170 V and a current of 160 μA under periodic compressing motion by human hand. This work suggests great potential for developing self-powered TSs and energy harvesters with excellent flexibility, recoverability, and self-healing properties.

Triboelectric nanogenerator-integrated structural supercapacitor with in situ MXene-dispersed N-doped Zn–Cu selenide nanostructured woven carbon fiber for energy harvesting and storage

A woven carbon fiber (WCF)-based triboelectric nanogenerator (TENG)-cum-structural supercapacitor is an excellent multifunctional device for clean energy harvesting and storage. This type of device has high load-bearing capacity and functions smoothly under severe outdoor conditions. Herein, WCF-based multifunctional TENG is reported that generated 8.9 W m−2 power with 84% energy conversion efficiency. The energy generated by the TENG was simultaneously stored in a connected supercapacitor that provide 1.93 Wh kg−1 of energy density and delivers 39.23 W kg−1 of power density. The specific surface area of the WCF was enhanced several hundred-fold by coating with an N-doped Zn–Cu selenide nanoporous material, thereby enabling higher energy generation and elevated storage capacity of the device. The TENG use a polyester-based solid polymer electrolyte as the negative electrode and polydimethylsiloxane-coated WCF as the positive electrode. The device has a very high coulombic efficiency with high mechanical strength and ability to resist massive impact. An application of the multifunctional device was demonstrated. These types of multifunctional devices have great potential in the self-charging automobile, aerospace, sensor, and electronics sectors.

Flexible and stretchable triboelectric nanogenerator fabric for biomechanical energy harvesting and self-powered dual-mode human motion monitoring

Simultaneous monitoring of human motion and collecting ambient energy are important for the development of personal healthcare monitoring and artificial intelligence. Here, a flexible and stretchable coaxial triboelectric nanogenerator (TENG) yarn is designed and fabricated by using coil spring as the inner support layer and mechanoluminescent ZnS:Cu/PDMS composite as the outer friction layer. By weaving coaxial TENG yarns, or mix-weaving with other yarns, a multifunctional TENG fabric can be manufactured for energy harvesting external mechanical energy from human motion or ambient environment. More important, it can self-powered sense human motion in both electrical (through TENG) and optical (from mechanoluminescent ZnS:Cu/PDMS composite) methods. This work provides a new strategy for wearable TENG fabrics with dual-mode sensing and energy harvesting which have potential applications in long-term medical monitoring and human-machine interaction systems. A multifunctional triboelectric nanogenerator fabric is manufactured for energy harvesting external mechanical energy from human motion or ambient environment. Moreover, on the basis of coupling effects between the mechanical luminescence and triboelectrification important, it can self-powered sense human motion in both electrical (through TENG) and optical (from mechanoluminescent ZnS: Cu/PDMS composite) methods. • The wearable fiber is fabricated for energy harvesting and monitoring human signals in medical rehabilitation. • A dual-mode strain sensor is designed by triboelectricity and mechanoluminescence. • A fiber-shaped sensor possesses mechanical luminescence performance, which can sense the force variation more intuitively. • The triboelectric fiber exhibit good washing resistance and reusability.

Functional sponge-based triboelectric nanogenerators with energy harvesting, oil–water separating and multi-mode sensing performance

A multi-functional triboelectric nanogenerator (TENG) is developed, which enables to sense mechanical/magnetic stimuli in the self-powered manner, and presents favorable magneto-driven and target recognization performance for spilled oil treatment.

Tunable output performance of triboelectric nanogenerator based on alginate metal complex for sustainable operation of intelligent keyboard sensing system

As a renewable power source, the triboelectric nanogenerator (TENG) can effectively harvest mechanical energy and can convert it into remarkable electrical output. However, also worth considering is to exploit the new triboelectric material to promote the practical application of TENGs in the field of intelligent sensing. Here, we firstly proposed a novel multifunctional TENG based on the alginate-metallic complex (AMC-TENG), which can provide tunable electrical output via synthesis of the alginate complexes with different metal ions. Through some comparative experiments, the AMC has a strong ability to lose electrons. As displayed in the experimental results, the AMC-TENG can achieve the highest electrical output, and the order of the electrical output from high to low is Copper alginate (Alg-Cu), ferric alginate (Alg-Fe), sodium alginate (Alg-Na), magnesium alginate (Alg-Mg), and aluminum alginate (Alg-Al). Besides, we design a self-powered sensing array based on the binary-decimal conversion system to demonstrate its practical application. We all think this work can provide a new perspective and possibility for the research of multifunctional triboelectric material and the development of self-powered sensing array. • We firstly report a novel TENG based on the alginate-metallic complex (AMC-TENG) to harvest mechanical energy and provide tunable electrical output via synthesis of the alginate complexes with different metal ions. • Through a series of experiments, the AMC-TENG can achieve the highest electrical output, and the order of the electrical output from high to low is copper alginate (Alg-Cu), ferric alginate (Alg-Fe), sodium alginate (Alg-Na), magnesium alginate (Alg-Mg), and aluminum alginate (Alg-Al). • Furthermore, we measured the corresponding electrical performance of Alg-Cu complex-based TENG (size: 3 cm × 3 cm), peak values of 40.16 μA, 629 V, 83.57 nC, and 438 μW/cm 2 are realized for the short-circuit current ( I sc ), open-circuit voltage ( V oc ), transferred charge ( Q sc ), and power density, respectively. • According to the tunable electrical output function of AMC-TENG, a self-powered sensing array based on the binary-decimal conversion system has been designed, and good results have be observed.

A multifunctional TENG yarn integrated into agrotextile for building intelligent agriculture

Raining as a common phenomenon in agricultural environment sometimes may bring adverse effects on agricultural production, to remedy this, agrotextiles are extensively utilized. In this study, the technology of triboelectric nanogenerator (TENG) is firstly integrated into agrotextiles. To construct a robust TENG yarn, a facile and effective method for the fabrication of stretchable electrode is developed, i.e. coating an elastic fibre with MXene ink, followed by spontaneous growth of Ag nanoparticles (AgNPs). By consecutively coating the conductive fibre with PDMS, the final developed triboelectric yarn (diameter of ~400 μm) is demonstrated to possess extraordinary output performance, generating a voltage of 7.7 V with a effective contact length of 3 cm. Moreover, the excellent mechanical property, highly stretchability, outstanding robustness, and considerable hydrophobicity of the TENG yarn also make it be capable of being woven into net or integrated into agrotextile. Thus, in the meantime of providing protection for crop plantation and animal husbandry to improve the quality and yield of agricultural products, the raindrop energy can also be harvested. Moreover, it can also act as a self-powered sensor to monitor dynamic force, which provide a basic information of weather condition. All in all, this developed TENG yarn enables many promising advantages such as being easily engineered and scaled up, therefore possessing great potential to apply in agrotextile for building intelligent agriculture. • A facile method for fabricating highly stretchable electrode is firstly presented. • The TENG yarn is easily engineered and scaled up for various applications. • The technology of TENG is firstly proposed to combine with the agrotextile. • The TENG yarn can harvest raindrop energy and protect crops at the same time. • The constructed TENG yarn can self-powered monitor dynamic forces.

A self-powered multi-broadcasting wireless sensing system realized with an all-in-one triboelectric nanogenerator

The ubiquitous sensors at the core network of Internet of Things (IoT) have accelerated the realization of micro/nano systems that necessitate not only the development of self-powered sensors but also requires a reliable wireless communication mode. Here, a self-powered multi-broadcasting wireless sensing system based on an all-in-one triboelectric nanogenerator (TENG) is reported, which can simultaneously power up a custom-made wireless node and act as a sensor. The whole device and the system are encapsulated in a unique compact structure, in which the top segment consists of a spring-assisted multifunctional TENG (MTENG) and, the bottom section contains an integrated energy management and Bluetooth transmitter module. Following the structural and material modifications, the top unit of the MTENG is used to detect vibration frequency and amplitude by correlation with the TENG output voltage. The device has been employed to successfully detect the running frequency of a linear shaker and various generated signals. Owing to the nanostructured material surfaces, the device yields an output current of 300 μA and a power density of 4 W/m2 with the normal hand pressing. Moreover, the developed portable MTENG is also assessed to remotely monitor automobile engine vibration and is expected to result in a myriad of applications.

Multifunctional triboelectric nanogenerator towards impact energy harvesting and safeguards

The widespread impact kinetic energy always causes injury and property loss in daily life. Conventional safeguarding systems protect human beings by passively insulating and dissipating impact energy but have ignoring exploring them. Triboelectric nanogenerator (TENG) proves to be a favorable device in harvesting mechanical energy but shows no protection property. Thus, developing novel safeguarding material with energy-harvesting performance is essential in future generation personal security field. Here, a multifunctional TENG capable of collecting impact kinetic energy with safeguarding property is reported by assembling Al foil with hybrid polymer matrix. The matrix is fabricated by incorporating polytetrafluoroethylene (PTFE) nano-particles into shear stiffening (SST) gel and polydimethylsiloxane (PDMS). The optimized TENG (6 mm) after introducing 1% PTFE nano-fillers into hybrid polymer attains the maximum electrical voltage, current and output power of 44.20 V, 8.84 μA and 390.73 μW, respectively. More importantly, SST/PDMS/PTFE-based TENG generates an instantaneous power density of 135.57 μW/m2 under low velocity impact. The impact force simultaneously decreases from 1971.90 to 839.72 N, exhibiting a remarkable safeguarding property. Finally, a wearable TENG-based electronic skin can capture external impact energy into electrical energy, resist the impact and precisely map force distribution which demonstrates promising application in next generation smart wearable systems.

Waterproof Fabric-Based Multifunctional Triboelectric Nanogenerator for Universally Harvesting Energy from Raindrops, Wind, and Human Motions and as Self-Powered Sensors.

Developing nimble, shape‐adaptable, conformable, and widely implementable energy harvesters with the capability to scavenge multiple renewable and ambient energy sources is highly demanded for distributed, remote, and wearable energy uses to meet the needs of internet of things. Here, the first single waterproof and fabric‐based multifunctional triboelectric nanogenerator (WPF‐MTENG) is presented, which can produce electricity from both natural tiny impacts (rain and wind) and body movements, and can not only serve as a flexible, adaptive, wearable, and universal energy collector but also act as a self‐powered, active, fabric‐based sensor. The working principle comes from a conjunction of contact triboelectrification and electrostatic induction during contact/separation of internal soft fabrics. The structural/material designs of the WPF‐MTENG are systematically studied to optimize its performance, and its outputs under different conditions of rain, wind, and various body movements are comprehensively investigated. Its applicability is practically demonstrated in various objects and working situations to gather ambient energy. Lastly, a WPF‐MTENG‐based keypad as self‐powered human–system interfaces is demonstrated on a garment for remotely controlling a music‐player system. This multifunctional WPF‐MTENG, which is as flexible as clothes, not only presents a promising step toward democratic collections of alternative energy but also provides a new vision for wearable technologies.

A liquid metal-based triboelectric nanogenerator as stretchable electronics for safeguarding and self-powered mechanosensing

In recent years, high performance triboelectric nanogenerator (TENG) shows distinguished energy-harvesting property which guarantees its potential applications as a power source. However, collision and harsh impact, occurred in daily life, always injure human beings. Developing novel multifunctional TENG with self-powered mechanosensing and protection properties from violent impact is an urgent and meaningful work. Here, a multifunctional TENG with energy-harvesting, safeguarding and self-powered force-sensing properties was fabricated by assembling shear stiffening gel/polydimethylsiloxane (SSG/PDMS) matrix with GaInSn liquid metal. Operating at 10 Hz, TENG with a size of 50 × 50 × 4 mm3 obtains an output voltage of 35.72 V, current of 5.10 μA, and maximum output power of 182.17 μW. In addition, TENG device generates enhanced output power of 323.97 μW under tensile strain of 80%. Besides harvesting mechanical energy, TENG with fast stimuli-responsive character, has been proven as a self-powered sensor to monitor varieties of physiological movements. More importantly, the TENG device with high damping property enables to dissipate 66.43% of external impact force which provides favorable protection effect. Correspondingly, the distinguished output voltage signals can also reveal and assess different impulsive loads. This work proposes a multifunctional TENG device with energy-harvesting, and utilizing the flexible TENG for safeguarding and self-powered mechanosensing.

Rolling friction contact-separation mode hybrid triboelectric nanogenerator for mechanical energy harvesting and self-powered multifunctional sensors

Collecting mechanical energy in the surrounding environment to power small electronic devices is an ideal method as a green and clean power source. Based on the working mechanism and the advantages of triboelectric nanogenerator (TENG), a robust rolling friction contact-separation mode TENG (CS-TENG) has been fabricated for harvesting vertical rotation energy by utilizing the integrated cylindrical surface with the conjunction of rolling contact electrification and electrostatic induction. The output current of the CS-TENG can maintain 96% (origin: 1.72 μA, final: 1.66 μA) after two days continuous work a rotation speed of 300 r/min. Furthermore, an electromagnetic and triboelectric hybrid contact-separation mode nanogenerator (HCS-TENG) has been further designed by coupling magnets in the rolling cylinders with copper coils as an electromagnetic generator (EMG) in the acrylic cylinder to implement the multi-functional properties. The gear transmission structure makes the device more facile to be installed on the rotation objects. The output performances of CS-TENG and EMG under various rotation speeds were systematically studied. It shows that the CS-TENG with six units can deliver an output power of 0.15 mW/cm2 and the 100 μF capacitor can be charged to 6 V in less than 1 min by the hybridized nanogenerator at a rotating rate of 700 r/min. In addition, utilizing the output signal's intrinsic characteristics of CS-TENG, a self-powered rotation speed and displacement sensor using the dual cylinder structure TENG has been achieved for these rotating mobile devices that are inconvenient to get an additional power supply in the grimmest circumstances such as moon car or other celestial and tough environment detection equipment. This multifunctional TENG device reveals a significantly potential application in the grimmest circumstances as power source, self-powered electronics and sensor systems.

Multifunctional TENG for Blue Energy Scavenging and Self‐Powered Wind‐Speed Sensor

Triboelectric nanogenerator (TENG) has been considered to be a more effective technology to harvest various types of mechanic vibration energies such as wind energy, water energy in the blue energy, and so on. Considering the vast energy from the blue oceans, harvesting of the water energy has attracted huge attention. There are two major types of “mechanical” water energy, water wave energy in random direction and water flow kinetic energy. However, although the most reported TENG can be used to efficiently harvest one type of water energy, to simultaneously collect two or more types of such energy still remains challenging. In this work, two different freestanding, multifunctional TENGs are successfully developed that can be used to harvest three types of energies including water waves, air flowing, and water flowing. These two new TENGs designed in accordance with the same freestanding model yield the output voltages of 490 and ≈100 V with short circuit currents of 24 and 2.7 µA, respectively, when operated at a rotation frequency of 200 rpm and the movement frequency of 3 Hz. Moreover, the developed multifunctional TENG can also be explored as a self‐powered speed sensor of wind by correlating the short‐circuit current with the wind speed.