Segmented Swing-Structured Fur-Based Triboelectric Nanogenerator for Harvesting Blue Energy toward Marine Environmental Applications

Reducing carbon emissions to realize carbon neutrality is crucial to the environmental protection, and developing clean and renewable energy sources is an effective means to achieve this goal. Triboelectric nanogenerators (TENGs) provide a promising energy technology for converting the abundant renewable ocean wave energy on the earth surface. In this work, a segmented swing-structured fur-based TENG (SSF-TENG) is designed and fabricated to harvest low frequency water wave energy. The introduction of soft and dense rabbit furs reduces the frictional resistance and material wear, and the design and optimization of segmented structures further enhance the output performance of TENG. The use of ultra-lubricated bearings makes the SSF-TENG achieve an extended period of energy harvesting of more than 5 min after one triggering, with a total energy conversion efficiency of up to 23.6%. Under the real water wave triggering, the SSF-TENG can deliver a maximum peak power of 6.2 mW and an average power of 0.74 mW. Furthermore, through effective water wave energy harvesting by the SSF-TENG or array, self-powered marine environmental applications are successfully demonstrated, which establishes a solid foundation for large-scale blue energy harvesting and realization of smart oceans.     

涡街提频振荡水柱驱动压电发电理论分析

海洋波浪能频率低(0.3～1 Hz),海浪进入振荡水柱气室压缩空气形成高速气流。在高速气流通道内放置绕流圆柱钝体,采用卡门涡街效应提高波浪能振荡水柱采集气室气压激振频率,实现高频驱动压电发电,提高海洋能量转换效率。推导波浪进入气室形成振荡的水气动力转换理论,计算了气室初级压强和流速。分析了低频高压气流经钝体形成卡门涡街高频涡流激振提频过程,计算出气压作用于钹型压电发电结构输出的电量。研究气体流速、钝体等系统参数与输出能量的关系。计算结果表明,周期为0.65～1.1 s的海浪进入气室经提频作用于钹型压电发电结构,稳定输出电能可达70～80 mW,为新型波浪能采集技术提供了理论基础。     

Dual Mode TENG with Self-Voltage Multiplying Circuit for Blue Energy Harvesting and Water Wave Monitoring

As the most extensive natural energy on earth, ocean wave energy is regarded as a difficult energy to be fully and efficiently utilized because of its low frequency and multi-direction movement. Herein, a versatile blue energy triboelectric nanogenerator (VBE-TENG) fabricated by using dual-mode output terminals with charge excitation strategy is reported, which can harvest varying water-wave energy effectively. Benefiting from the rolling ball on a specific track and the compression rebound characteristics of a spring sheet steel, the carrier can be driven along a specific path through random ocean wave energy, and then the energy is converted into electricity by VBE-TENG. A high peak output power of 34.3 mW is obtained, 2.5 times as much as that of current highest record based on a device unit in blue energy TENG. In addition, the TENG can light 256 LEDs and continuously power commercial electronic devices in wave environments. The average peak voltage of contact-separation TENG is converted into virtual signal via Labview software to provide wave height monitoring as a self-powered sensing system. This work provides a new approach in blue energy TENG toward practical applications.     

Effects of foam on ocean surface microwave emission inferred from radiometric observations of reproducible breaking waves

WindSat, the first satellite polarimetric microwave radiometer, and the NPOESS Conical Microwave Imager/Sounder both have as a key objective the retrieval of the ocean surface wind vector from radiometric brightness temperatures. Available observations and models to date show that the wind direction signal is only 1-3 K peak-to-peak at 19 and 37 GHz, much smaller than the wind speed signal. In order to obtain sufficient accuracy for reliable wind direction retrieval, uncertainties in geophysical modeling of the sea surface emission on the order of 0.2 K need to be removed. The surface roughness spectrum has been addressed by many studies, but the azimuthal signature of the microwave emission from breaking waves and foam has not been adequately addressed. Recently, a number of experiments have been conducted to quantify the increase in sea surface microwave emission due to foam. Measurements from the Floating Instrumentation Platform indicated that the increase in ocean surface emission due to breaking waves may depend on the incidence and azimuth angles of observation. The need to quantify this dependence motivated systematic measurement of the microwave emission from reproducible breaking waves as a function of incidence and azimuth angles. A number of empirical parameterizations of whitecap coverage with wind speed were used to estimate the increase in brightness temperatures measured by a satellite microwave radiometer due to wave breaking in the field of view. These results provide the first empirically based parameterization with wind speed of the effect of breaking waves and foam on satellite brightness temperatures at 10.8, 19, and 37 GHz.     

Spherical Triboelectric Nanogenerators Based on Spring‐Assisted Multilayered Structure for Efficient Water Wave Energy Harvesting

Making use of water wave energy at large is one of the most attractive, low‐carbon, and renewable ways to generate electric power. The emergence of triboelectric nanogenerator (TENG) provides a new approach for effectively harvesting such low‐frequency, irregular, and “random” energy. In this work, a TENG array consisting of spherical TENG units based on spring‐assisted multilayered structure is devised to scavenge water wave energy. The introduction of spring structure enhances the output performance of the spherical TENG by transforming low‐frequency water wave motions into high‐frequency vibrations, while the multilayered structure increases the space utilization, leading to a higher output of a spherical unit. Owing to its unique structure, the output current of one spherical TENG unit could reach 120 µA, which is two orders of magnitude larger than that of previous rolling spherical TENG, and a maximum output power up to 7.96 mW is realized as triggered by the water waves. The TENG array fabricated by integrating four units is demonstrated to successfully drive dozens of light‐emitting diodes and power an electronic thermometer. This study provides a new type of TENG device with improved performance toward large‐scale blue energy harvesting from the water waves.     

Secure wireless powered relaying networks: Energy harvesting policies and performance analysis

In this paper, we investigate the problem of secure communication for a scenario, which consists of one pair of source‐destination nodes and one untrusted relay. The source communicates with the destination via the help of energy harvesting–aware untrusted relay, which acts as the helper to forward the source information to the destination; however, the relay also acts as the unintended user to eavesdrop the source information. To keep the source information confidential from untrusted relay, the destination‐assisted jamming technique is deployed. We evaluate the impact of energy harvesting protocols on such a secure communication scenario through the proposed energy transfer protocols, namely, source‐based energy harvesting protocol and maximum energy harvesting protocol. To evaluate the secrecy performance of these proposed schemes, we derive analytical expressions for two important performance metrics including intercept probability and strictly positive secrecy capacity. The numerical analysis reveals the different trade‐off between secure performance and relevant system parameters (i.e., power splitting ratio, time switching ratio, energy conversion efficiency, transmit signal‐to‐noise ratio, and relay location). Simulation results are also provided to demonstrate the accuracy of the developed analytical expression.     

Elastic-Connection and Soft-Contact Triboelectric Nanogenerator with Superior Durability and Efficiency

Triboelectric nanogenerator (TENG) has received tremendous attention in ambient energy harvesting, especially for ocean wave energy. However, the technology is generally challenged to obtain excellent durability and high efficiency simultaneously, which primarily overshadows their further industrial-scale applications. Here, a dual-mode and frequency multiplied TENG with ultrahigh durability and efficiency for ultralow frequency mechanical energy harvesting via the elastic connection and soft contact design is proposed. By introducing the spring and flexible dielectric fluff to the novel pendulum-like structural design, the surface triboelectric charges of TENG are replenished in soft contact mode under the intermittent mechanical excitation, while the robustness and durability are enhanced in non-contact working mode. The fabricated TENG results in a continuous electrical output for 65 s by one stimulus with a high energy conversion efficiency, as well as negligible change of output performance after a total of 2 000 000 cycles. Moreover, integrated with the power management circuit, the TENG array is demonstrated to drive the electronics by effectively harvesting wind and water wave energy as a sustainable energy source. This work paves a new pathway to enhance the robustness, durability, and efficiency of the TENG that resolves the bottleneck of its practical applications and industrialization.     

直管谐振式低频压电声能量回收系统

为了高效回收环境中的声能,基于阵列式压电换能器、直管谐振腔以及能量回收电路提出了一种声能量回收系统.当声波进入直管谐振腔,管中产生谐振驻波作用于压电换能器,将声能转换为电能.本文设计了能量回收电路并且进行理论、仿真分析实验研究了压电振子数量、声波频率、声压级对输出电压的影响,分析了负载电阻对输出电压及功率的影响.实验结果表明,该装置可回收不同频率的声能量,在声波频率为96Hz时发电效果最优.当入射声压级为110dB时,不使用能量回收电路,输出交流电压有效值最高达12.9V,输出交流功率最高达到799μW;使用设计的能量回收电路,最高输出直流电压为64.2V,最高输出直流功率为473μW.该声能量回收系统不仅可以作为声能量采集器,还能对无线传感节点等独立工作的微型电子系统供能.     

Flexible Sponge-Based Nanogenerator for Energy Harvesting from Land and Water Transportation

Triboelectric nanogenerator (TENG) devices with high robustness are promising in collecting powerful energy. In this study, highly elastic and pressure-resistance sponge fabricated TENG capable of adapting to high strength impact in land and water transportation and scalable for any shape is demonstrated for harvesting wave energy and mechanical energy. The polydimethylsiloxane sponge prepared by sacrificial template method has interconnected network and large size ratio of cavity-wall suitable for contact and separation. The operation modes of self-contact and extra-contact collaborating with MXene in electron transfer provide options for different operating conditions. The polydopamine-MXene modification of the sponge enables higher output due to the combination of the electronegativity, excellent adhesion, and antioxidant ability. Sponges are used to collect mechanical energy and applied for TENG-powered cathodic protection, making the 304 stainless steel (304 SS, Φ = 2 mm) electrode enter a thermodynamic stable state. What's more, the work also tries the universal strategies of program monitoring wave in the water tank and harvests the mechanical energy created by cars and passers-by, which enrich the applications of sponge TENG.     

Synthetic aperture radar imaging of moving ocean waves

A theory for the radar imaging of ocean waves is presented under the assumptions that a swell propagates through an ensemble of Bragg scatterers and that the integration time of the synthetic aperture radar (SAR) is small compared to the angular velocity of the swell. Results are prsented which show image development and distortions caused by the radial velocities and accelerations of the swell. Neglecting small wave bunching and tilts due to the longer underlying waves, and considering only one-dimensional geometries, the mechanism of wave motions are considered and their efforts on the production of the usual intensity Pattern representing the wave image are studied. The analysis shows that in certain situations a processed image can appear which has twice the spatial period of the actual long wave on the ocean, which can confuse the interpretation of ocean wave analysis.     

Alternating Magnetic Field-Enhanced Triboelectric Nanogenerator for Low-Speed Flow Energy Harvesting

Low-speed flow energy, such as breezes and rivers, which are abundant in smart agriculture and smart cities, faces significant challenges in efficient harvesting as an untapped sustainable energy source. This study proposes an alternating magnetic field-enhanced triboelectric nanogenerator (AMF-TENG) for low-speed flow energy harvesting, and demonstrates its feasibility through experimental results. AMF-TENG's minimum cut-in speed is 1 m s⁻¹, thereby greatly expanding its wind energy harvesting range. When the wind speed is 1–5 m s⁻¹, the open-circuit voltage (V_OC) is 20.9–179.3 V. The peak power is 0.68 mW at 5 m s⁻¹. In a durability test of 100 K cycles, the V_OC decreases from 188.4 to 174.2 V but remain at 92.5% of the initial value. furthermore, the AMF-TENG can harvest low-speed flow energy from the natural environment to power temperature and humidity sensors and wireless light intensity sensor in smart agriculture. This study provides a promising method for low-speed flow energy harvesting in distributed applications.     

Triboelectric Nanogenerator Networks Integrated with Power Management Module for Water Wave Energy Harvesting

Ocean waves are one of the most promising renewable energy sources for large‐scope applications. Recently, triboelectric nanogenerator (TENG) network has been demonstrated to effectively harvest water wave energy possibly toward large‐scale blue energy. However, the absence of effective power management severely restricts the practicability of TENGs. In this work, a hexagonal TENG network consisting of spherical TENG units based on spring‐assisted multilayered structure, integrated with a power management module (PMM), is constructed for harvesting water wave energy. The output performance of the TENG network is found to be determined by water wave frequencies and amplitudes, as well as the wave type. Moreover, with the implemented PMM, the TENG network could output a steady and continuous direct current (DC) voltage on the load resistance, and the stored energy is dramatically improved by up to 96 times for charging a capacitor. The TENG network integrated with the PMM is also applied to effectively power a digital thermometer and a wireless transmitter. The thermometer can constantly measure the water temperature with the water wave motions, and the transmitter can send signals that enable an alarm to go off once every 10 s. This study extends the application of the power management module in the water wave energy harvesting.     

Whirling‐Folded Triboelectric Nanogenerator with High Average Power for Water Wave Energy Harvesting

Ocean wave energy, as one of the most abundant resources on the earth, is a promising energy source for large‐scale applications. Triboelectric nanogenerators (TENGs) provide a new strategy for water wave energy harvesting; however, its average performance in realistic water wave conditions is still not high. In this work, a whirling‐folded TENG (WF‐TENG) with maximized space utilization and minimized electrostatic shielding is constructed by 3D printing and printed circuit board technologies. The flexible vortex structure responds easily to multiform wave excitation with improved oscillation frequency. A standard water wave tank is established to generate controllable water waves to characterize the device performance. It is found to be determined by wave conditions and internal structure, which is also revealed by a theoretical dynamical analysis. The WF‐TENG can produce a maximum peak power of 6.5 mW and average power of 0.28 mW, which can power a digital thermometer to operate constantly and realize self‐powered monitoring on the TENG network to prevent possible damage in severe environments. Moreover, a self‐charge‐supplement WF‐TENG network is proposed to improve the output performance and stability. This study provides an effective strategy for improving the average power and characterizing the performance of spherical TENG towards large‐scale blue energy.     

ERS-1 SAR images of atmospheric gravity waves

ERS-1 synthetic aperture radar (SAR) images of atmospheric gravity waves over the ocean are discussed. Several case studies are presented in detail. It is shown that the well-organized long wavelength (1 to 10 km) wave phenomena which often are seen in SAR images over the ocean may be atmospheric gravity waves. The waves appear in the SAR images because they modulate the surface wind speed which in turn modulates the surface roughness and the radar cross section. The wavelength may be measured directly from the SAR image, and the mean wind speed and wind speed modulation near the ocean surface may be estimated from the observed radar cross section modulation using a wind retrieval model. The atmospheric gravity waves usually were generated by the approach or passing of a meteorological front. Atmospheric soundings and a two-layer model for the lower troposphere indicate that, in general, the observed atmospheric wave phenomena could have been supported by accompanying temperature inversion layers and wind shears     

Directional ocean wave measurements in a coastal setting using afocused array imaging radar

A unique focused array imaging Doppler radar was used to measure directional spectra of ocean surface waves in a nearshore experiment performed on the North Carolina Outer Banks. Radar images of the ocean surface's Doppler velocity were used to generate two dimensional spectra of the radial component of the ocean surface velocity field. These are compared to simultaneous in-situ measurements made by a nearby array of submerged pressure sensors. Analysis of the resulting two-dimensional spectra include comparisons of dominant wave lengths, wave directions, and wave energy accounting for relative differences in water depth at the measurement locations. Limited estimates of the two-dimensional surface displacement spectrum are derived from the radar data. The radar measurements are analagous to those of interferometric synthetic aperture radars (INSAR), and the equivalent INSAR parameters are shown. The agreement between the remote and in-situ measurements suggests that an imaging Doppler radar is effective for these wave measurements at near grazing incidence angles     

碎浪在大角度对海面后向散射系数的修正模型

应用双尺度方法(Two-Scale Method,TSM)计算了海面的后向散射系数(Backscattering Coefficient,BSC).由于实测的海面散射系数在大角度与理论不相符,尤其是水平(Horizontal,HH)极化,中等尺度的碎浪模型被用来对海面散射系数进行修正.通过对不同参数的中等尺度碎浪散射系数进行统计平均,可以得到碎浪的平均散射系数.运用碎浪的覆盖率模型,将碎浪模型与海面的散射系数进行结合,得到了含碎浪的海面散射系数修正模型.结果表明,该模型在大入射角下能对HH极化有明显的修正作用,使其与实验数据更为吻合.对于垂直(Vertical,VV)极化,TSM计算的结果本身就与实验数据吻合得较好,碎浪也没有对其有明显的修正.     

基于声矢量场处理的海洋内波预警监测技术

目前的海洋内波检测技术在实际应用中误差大,受海洋环境影响显著,且无法自主识别.针对这一问题,文中提出了一种基于矢量场处理的海洋内波预警的监测方法.该方法基于声压和质点振速联合信息处理,利用超低频矢量水听器拾取的声场三维信息,可在复杂的海洋背景噪声场中根据方位估计算法对非协作目标进行时-空-频三维跟踪与锁定.内波的到来引...     

基于辐射电磁波监测技术的断路器开断性能研究

断路器在开断电流时,当触头两端的电压高于触头间灭弧介质的击穿电压时,动静触头将发生击穿,产生开关电弧,并激发空间高频的电磁波向外辐射。向空间辐射的高频电磁波信号与灭弧气体特性、机械特性及绝缘结构等多种因素相关,反映着断路器的开断能力。本文仿真计算了断路器辐射电磁波的过程,建立试验研究平台,测量对比了全新触头和退役触头开断过程中辐射电磁波的波形,开展了基于辐射电磁波监测技术的高压断路器开断性能研究。研究结果表明:随着触头表面烧蚀程度的增加,断路器开断性能下降,更容易发生电弧重燃,燃弧时间相对于全新触头会有明显的增加,同时对外辐射电磁波的持续也增多,辐射电磁波的持续时间可以作为判定断路器开断性能的判据。本文的研究内容为辐射电磁波监测技术在断路器开断性能的评估提供了技术参考与依据。     

基于二维连续小波变换的SAR图像海洋现象特征检测

 本文对合成孔径雷达(SAR)图像中存在的多种海洋现象,如内波,海洋锋等进行讨论,提出了一种基于二维连续小波变换及能谱思想的新的海洋现象检测方法.针对各种海洋现象在SAR 中反映出来的海浪波形的不同,采用不同的连续小波变换基提取SAR图像中五种典型的海洋现象.通过大量试验,证实了该方法在多种海洋现象的定位检测中的有效性.