Nonlinear characteristics of circular-cylinder piezoelectric power harvester near resonance based on flow-induced flexural vibration mode

The nonlinear behaviors of a circular-cylinder piezoelectric power harvester （CCPPH） near resonance are analyzed based on the flow-induced flexural vibration mode. The geometrically-nonlinear effect of the cylinder is studied with considering the in-plane extension incidental to the large defection. The boundary electric charges generated from two deformation modes, flexure and in-plane extension, were distinguished with each other because the charge corresponding to the latter mode produces no contribution to the output current. Numerical results on output powers show that there are multi- valuedness and jump behaviors.

Spiral piezoelectric transducer in torsional motion as low-frequency power harvester

A structure consisting of a spiral piezoelectric transducer and a concentrated mass is proposed as a low-frequency piezoelectric power harvester. A theoretical model is developed for the system from the theory of piezoelectricity. An analysis is performed to demonstrate the low-frequency nature of the system. Other basic characteristics of the power harvester including the output power, voltage, and efficiency are also calculated and examined.

Piezoelectric generator based on torsional modes for power harvesting from angular vibrations

Torsional vibration of a circular piezoelectric shell of polarized ceramics mounted on a rotationally vibrating base is analyzed. The shell is properly electroded and connected to a circuit such that an electric output is generated. The structure analyzed represents a piezoelectric generator for converting mechanical energy from angular vibrations to electrical energy. Analytical expressions and numerical results for the output voltage, current, power, efficiency and power density are given.

Piezoelectric Power Harvesting via Acoustic-Pressure Driven by Low-Speed Wind-Force with Resonating-Tube and Wind-Collector

Wind-driven power harvestings attract attentions since their target wind speeds are quite low less than the so-called cut-in wind speed, which is generally recognized as around 3 m/s. The extant power harvestings driven by wind-induced-air-column-resonations (i.e. acoustic-pressures) are still lacking simplicity, scale flexibility and solid strategies for practical applications. Therefore, the piezoelectric power harvesters via acoustic-pressures driven by low-speedwind-forces with resonating-tubes and wind-collectors were invented so as to complement all the lacks. The wind-collector as well as the resonating-tube contributed to upraise the power harvesting density. The champion power harvesting density of 19.5 nW/dm2 could be procured at 2.3 m/s of an artificial wind and the optimal resonating-tube and wind-collector. Power harvesting proofs from the natural wind with low mean speeds down to about 0.6 m/s were successfully obtained. The cut-in wind speed of the prototype piezoelectric power harvester was found to be quite low as about 0.4 m/s, signifying its ubiquity. Finally, a multi-bundle pendant-type piezoelectric power harvester was specifically presented together with professing the solid and multiple strategies for practical applications.

Piezoelectric Power Harvesting Process via Phase Changes of Low-Boiling-Point Medium Together with Water for Recovering Low-Temperature Heats

Low-temperature thermal energy conversions down to exergy zero to electric power must contribute energy sustainability. That is to say, reinforcements of power harvesting technologies from extremely low temperatures less than 373 K might be at least one of minimum roles for the current generations. Then, piezoelectric power harvesting process for recovering low-temperature heats was invented by using a unique biphasic operating medium of an underlying water-insoluble/low-boiling-point medium (i.e. NOVEC manufactured by 3M Japan Ltd.) in small quantity and upper-layered water in large quantity. The higher piezoelectric power harvesting densities were naturally revealed with an increase in heating temperatures. Excessive cooling of the operating medium deteriorated the power harvesting efficiency. The denser operating medium was surpassingly helpful to the higher piezoelectric power harvesting density. Concretely, only about 5% density increase of main operating medium (i.e. water with dissolving alum at 0.10 mol/dm3) came to the champion piezoelectric power harvesting density of 92.6 pW/dm2 in this study, which was about 1.4 times compared to that with the original biphasic medium of pure water together with a small quantity of NOVEC.

A low frequency piezoelectric power harvester using a spiral-shaped bimorph

We propose a spiral-shaped piezoelectric bimorph power harvester operating with coupled flexural and extensional vibration modes for applications to low frequency energy sources. A theoretical analysis is performed and the computational results show that the spiral structure has relatively low operating frequency compared to beam power harvesters of the same size. It is found that to optimize the performance of a piezoelectric spiral-shaped harvester careful design is needed.

Analysis on Output Power for Multi-direction Piezoelectric Vibration Energy Harvester

To predict the performance of multi-direction piezoelectric vibration energy harvester,an equation for calculating its output power is obtained based on elastic mechanics theory and piezoelectricity theory.Experiments are performed to verify theoretical analysis.When the excitation direction is along Y direction,a maximal output power about 0.139 mW can be harvested at a resistive load of 65kΩ and an excitation frequency of 136 Hz.Theoretical analysis agrees well with experimental results.Furthermore,the performance of multi-direction vibration energy harvester is experimentally tested.The results show that the multi-direction vibration energy harvester can harvest perfect energy as the excitation direction changes in XY plane,YZ plane,XZ plane and body diagonal plane of the harvester.

Energy Harvesting in Cognitive Networks with Cooperative Beamforming:Power Allocation and Stability Analysis

Energy harvesting (EH) is a promising technology to improve both energy efficiency and spectral efficiency in cognitive radio (CR) networks. However, due to the randomness of the harvested energy and the interference constraint at the primary users (PUs), the limited transmission power of secondary users (SUs) may reduce the service rate of SUs. To solve this problem, this paper investigates a cooperative transmission method where a zero-forcing beamforming method is used in the EH based secondary network. Considering the transmission power constraint and energy causality, we derive the closed-form solution of the optimal transmission power for the secondary source and relays, which achieves the maximal stable throughput of the secondary network. Numerical results show the impact of different system parameters to the maximal stable throughput. In addition, compared with the traditional decode-and-forward (DF) scheme, the cooperative beamforming method achieves higher stable throughput under an high quality source-to-relay channel.

Power Analysis for Piezoelectric Energy Harvester

Piezoelectric energy harvesting technology is used to design battery less microelectronic devices such as wireless sensor nodes. This paper investigates the necessary conditions to enhance the extracted AC electrical power from exciting vibrations energy using piezoelectric materials. The effect of tip masses and their mounting positions are investigated to enhance the system performance. The optimal resistive load is estimated to maximize the power output. Different capacitive loads are tested to store the output energy. The experimental results validated the theoretical analysis and highlighted remarks in the paper.

Wireless Power Generation Strategy Using EAP Actuated Energy Harvester for Marine Information Acquisition

The energy of a radio wave is reduced through the dispersion, the refraction and the absorption because the medium transferring the vibration of a radio wave is the seawater. In the end the reduced energy of a radio wave causes the reduced transmitting length for communication, the long postponed communication and the frequent error. The subsea communication for the marine environment monitoring which must overcome the weak points of the RF wave and the most practical method for the marine sensor network realization is to use the acoustic wave method, but the energy consumption rate of the acoustic wave communication method is about 100 times greater than the one of the RF wave method. So, the power supply of the sensor node in the marine sensor network system is the most important interest field. In this study, the sample which consists of an acrylic elastomer(VHB4905 film from 3M), conductible carbon grease(from MG chemical) and electric wire for the basic study of an energy harvesting strategy and technique using EAP actuator was fabricated, and the conductible carbon grease was used for an electrode. The characteristics of the fabricated sample were analyzed through the experiment. We also mixed carbon grease with aluminum powder for conductibility improvement, and the effect of the mixed electrode was confirmed through the conductivity measurement.

一种应用于胎压监测的自供电系统研究

设计与制作了一种用于胎压监测的自供电系统,主要利用压电-光电复合能量收集装置及相匹配的能量管理与存储电路采集轮胎转动的机械能和自然界光能。实验测试表明:光电能量收集器在弱光环境下输出功率最低327μW,压电能量收集器在正常车速情况下平均输出功率为452μW,而复合能量输出平均功率达到1.32 mW。同时对胎压监测系统进行功耗分析,从能量收支平衡的角度验证监测系统10 s钟工作一次的可行性,利用轮胎转动的机械能与太阳能复合互补供电的胎压监测系统可长期自我维持,无需额外电池或备用电源,具有一定的应用参考价值。

基于Sm-PMN-PT和改进型DICH接口电路的压电取能功率提升方法

通过压电取能方式将电力设备表面的机械振动能转化为电能,是实现电力专用传感器无源化的有效途径之一。然而,传感器高集成度和小型化发展趋势对压电取能功率提出了更高要求。为此,提出一种基于钐掺杂铌镁酸铅-钛酸铅(Sm-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3),Sm-PMN-PT)材料和改进型双中间电容回收(improved double intermediate capacitor harvesting,improved-DICH)接口电路的压电取能功率提升方法。首先,制备了不同Sm掺杂质量分数为x和PT质量分数为y的xSm-PMN-yPT压电双晶片,并对压电材料的性能参数进行了测试和对比;其次,在对比分析几种典型接口电路的基础上,设计了一种改进型DICH接口电路,并从理论上进行了取能功率的对比分析;然后,采用Multisim软件对不同接口电路的取能功率进行了仿真分析;最后,对Sm-PMN-PT压电双晶片和锆钛酸铅(Pb(Zr1–xTix)O3,PZT)压电陶瓷在不同接口电路下的取能功率和能量提取效率进行了对比测试。研究结果表明:基于2.5%Sm-PMN-32%PT材料和改进型DICH接口电路的压电取能装置具有516.3μW的高输出功率、61.1%的高能量提取效率和较强的负载适应性,在取能领域具有良好的工程应用前景。

基于磁心与线圈参数优化的非侵入式磁场取能系统功率密度提升方法

非侵入式磁场取能系统具有结构简单、供电稳定等优点,是解决变电站母排环境中状态监测传感器电池供电寿命有限的有效手段,但因功率密度较低制约了其应用。对于非侵入式磁场取能系统,磁心与线圈参数对其功率密度的影响非常显著。然而,现有方法对磁心与线圈参数的分析相对独立,优化磁心时仅以互感为指标,忽略了该过程线圈参数变化对功率密度的影响。对此,该文考虑磁心尺寸对线圈参数的影响,以功率密度为指标,详细分析线圈匝数、线圈线径、磁柱侧面边长与叠片厚度对系统功率密度的影响。并在此基础上,提出一种优化磁心与线圈参数的功率密度提升方法,即设计线圈匝数、线圈线径、磁柱侧面边长与叠片厚度的最优值,以获取更高的功率密度。最后,基于所提出的方法制作了系统样机并进行测试。实验结果表明,对于限定磁心尺寸为30 mm×30 mm×40 mm的系统,在100 A母排电流下,系统经磁心与线圈优化后功率密度可达4.18 mW/cm~3,提升至系统优化前功率密度的35倍,验证了所提出方法提升功率密度的有效性。

钢轨短波波磨对轨道振动俘能器发电性能的影响规律研究

以轮轨摩擦自激振动理论和轨面不平顺反馈振动理论为基础,结合钢轨波磨与轨道振动能量回收两个研究方向,通过建立考虑钢轨波磨的“车轮-钢轨-吸振器”振动分析模型与轨道振动俘能器分析模型,研究了不同波深与波长的钢轨短波波磨对轨道振动俘能器的输出功率的影响规律。分析结果显示,波磨深度的增大会导致轮轨接触力和轨面垂向加速度的振幅增大,但不会影响钢轨的主振频率。波磨波长的增大会导致轮轨接触力和轨面垂向加速度的振幅先增大后减小,钢轨的主振频率随波磨波长的增大而减小。轨道振动俘能器的输出功率会受到波磨深度和波长的影响,表现为波长不变时,波深增加,俘能器的输出功率提高。波深不变时,波长增加,俘能器的输出功率先增大后减小,但仍大于光滑轨道上俘能器的输出功率,并且,采用小波包分解方法得到小波包能量值与波磨波长几乎呈线性关系。上述分析结果表明,该轨道振动俘能器在高效回收轨道振动能量的条件下,能有效地监测钢轨波磨的产生过程和预测钢轨波磨的近似波长。

可穿戴生理信息监测的自供电系统研究

设计与制作了一种应用于可穿戴生理信息监测的自供电系统,利用压电-光电复合能量收集装置采集人体运动时足底的机械能和室内光能。复合能量收集装置以运动鞋为载体,设计了多种结构压电能量收集器固定在鞋底,光电能量收集器粘接在鞋面,收集到的能量存储在超级电容中,同时设计了一套能够定时、按需供电的能量管理控制电路,控制生理信息监测系统每隔20 min上电一次,并且测量结束即刻断电。经测试,光电能量收集装置在室内从早上7点至晚上7点的平均输出功率达到590μW,压电能量收集装置在1.2 m/s的匀速步行状态驱动下的平均输出功率达540μW以上,复合能量输出功率能够稳定在1.124 mW以上,即20 min产电1.349 J。对系统各单元进行数据采集测试以及功耗测试,得出系统一个工作周期耗能1.04 J。从能量收支平衡来看,利用运动机械能与光能复合供电的生理信息采集系统可实现自我维持定时工作,具有一定的应用参考价值。

大负载高功率振动能量收集同步整流方法

针对振动能量收集电路整流二极管损耗大、非线性电路控制复杂以及优化负载不高的问题,提出了大负载高功率振动能量收集同步整流与电荷提取方法。通过同步电感翻转电压提高整流电压,采用短时能量提取缩短整流器件导通时间,减小能量损耗,实现高功率能量收集。基于压电等效模型设计了自供电同步整流与电荷提取电路(self-powered synchronous rectification and electric charge extraction,简称SP-SREE),对一个振动周期电路各工作阶段进行分析,推导出SP-SREE电路理论收集功率,并对电路进行功能测试和负载功率特性测试。理论分析与实验对比表明,所提出的方法在大负载下具有更高的收集功率,可为机械振动无线传感器网络等能源受限场景下自供电提供重要参考。

面向新型电力传感器的能量收集技术

电力传感器作为能源互联网的关键基础设施,其持续稳定的电力供应是保证能源互联网高效运行的前提。然而,传统供电方式存在诸多局限。全面梳理了面向新型电力传感器的能量收集技术,包括振动能量收集、温差能量收集、光伏能量收集和电磁能量收集等,这些技术利用环境中的分布式能源,通过不同的转换机理为传感器提供电力,有望解决供电难题。阐述了各种能量收集技术的应用现状,分析了目前所面临的关键技术挑战,如能量转换效率低、工作条件要求苛刻、器件可靠性和集成度有待提高等;探讨了未来能量收集技术的创新方向,包括开发新型高性能材料、优化器件结构设计、使用复合式收集技术等,以期实现更高的能量利用效率,满足新型电力传感器的实际需求,推动智能电网等相关领域的技术创新。

用于微波无线输能的高增益柔性天线研究

为克服传统有线供能方式的接入不便问题,提出了一种用于5.8 GHz微波无线输能(MWPT)高增益柔性天线。天线以聚酰亚胺(PI)为基底,采用广义迭代设计方法得到3层圆环结构,并选用共面波导(CPW)方式馈电。此外,为提高天线增益,在天线背面加载空气层和柔性反射板,并对天线性能进行了测试。测量结果显示:该天线在频率5.8 GHz处的峰值增益为9.51 dBi;当天线弯曲在曲率半径为85,60,45 mm时,增益始终保持在8.89 dBi以上,S_(11)幅值始终小于-10 dB。最后,通过微波无线输能实验测得该天线最大能量捕获效率可达71.3%,在弯曲状态下也能保持59%以上的捕获效率。该天线的高增益、高能量捕获效率以及稳定性证明了其在微波无线输能中具有潜在的应用价值。

无人机辅助无线供能通信系统优化算法研究

文章研究了无人机辅助无线供能数据收集系统的资源分配优化方案,其中无人机发送射频信号能量,装配能量收集电路的地面节点从无人机发送的射频信号中收集能量,并使用收集到的能量发送一定量的数据至无人机。针对此系统,通过联合优化能量传输区间、信息传输区间以及无人机在这两个区间的飞行速度和时间,在满足无人机数据收集约束条件下,最小化无人机飞行时间。文章建立的优化问题是难以求解的非凸优化问题,为求解此问题,将其分解为与能量传输区间和信息传输区间分别对应的且易于解决的两个子问题,并结合迭代优化方法,提出了一种高效的系统优化算法。仿真结果表明,与已有的基准方案相比,文章提出的无人机辅助通信系统优化方案可以显著地减少无人机飞行时间。

层合磁电能量采集器的研究进展

层合磁电(ME)能量采集器具有微型化、柔性化和功能多样化等优点,在植入医疗、物联网(IoT)和微机电系统(MEMS)等低功耗设备的自供电监测中具有广阔的应用前景。评述了该采集器的最新研究进展,介绍了其磁-机-电耦合能量转换机理,梳理了各种高频、低频磁能采集器和低频混合能采集器的类型与结构特点,综合比较分析了器件性能,指出高频磁能采集器在植入设备无线供电医疗诊治中的潜在优点和低频采集器在载流IoT设备自供电传感监测中的显著优势。最后总结了该采集技术目前存在的问题和未来发展方向。