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Piezoelectric energy harvester (PEH) arrays are practical solutions to the low and unreliable power output of a single PEH. However, most PEH circuits are developed for addressing the one-channel ac input from a single PEH. In this article, an extensible rectifier-less synchronized switch harvesting on inductor (ReL-SSHI) array interface with the maximal power point tracking (MPPT) function to manage the multiple ac inputs from the PEH arrays is designed. The ac–dc conversion is performed by the ReL-SSHI topology with passive peak switches featured with self-powered characteristic and fast cold-start. Only one shared inductor is employed, greatly reducing the circuit volume and cost. The MPPT module for each channel is implemented by a simple envelope detector and an ultra-low power hysteresis controller and achieves continuous energy extraction by adapting the fractional normal-operation voltage method. A developed discrete array interface able to handle three PEHs effectively executes the MPPT for each channel with the uphill and downhill response speeds of 2.0 and 7.1 V/s, and a maximal MPPT efficiency of 97.1%. This circuit boosts the power output by 485% compared with that by the traditional full-bridge rectifier, around 33% higher than that from existing synchronous electric charge extraction array interfaces. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvester (PEH) arrays are promising in many application scenarios. However, few interface circuits have been developed to manage the multiple ac inputs from PEHs. This article proposes an extensible parallel synchronized switch harvesting on inductor array interface scheme to realize a multiinput conversion from PEH arrays. We develop a split-inductor-capacitor topology that can extract electrical energy from multiple PEHs. The proposed circuit topology effectively handles the inductor access conflict in the cases of PEHs with close, identical, and opposite vibration phases, insensitive to ac input phase changes. For demonstrating the capability of dealing with multiple ac inputs from PEHs and the enhancement effect on power output, we construct and test a self-powered three-channel array circuit with the passive peak detection function. Excited by sinusoidal vibrations, our circuit effectively avoids the energy return and efficiently achieves the power combination of the three PEHs. Compared with the classic full-bridge circuit, the proposed circuit helps increase the power output by 4.8 times. Also, to show the universality of the circuit, the circuit's operation under various excitations istested and analyzed. [ABSTRACT FROM AUTHOR]

To merge the gap between the low-power output of piezoelectric energy harvesters (PEHs) and the high-power demand of sensors of Internet of Things, researchers recently start to explore PEHs arrays. However, few circuits have been developed to manage the multiple ac inputs from PEHs arrays. This article presents a self-powered PEH array interface circuit based on the synchronized switching and discharging to a storage capacitor through an inductor (SSDCI) technique. The array interface can output a maximum total power greater than the sum of each individual peak power, and achieve a high efficiency when multiple PEHs connect to the SSDCI array circuit. Simulation and experiment are performed to demonstrate the advantages of the SSDCI array interface. The tested results show that the designed SSDCI array circuit achieves an efficiency of 82.3% with three input sources, and allows a gain up to 300% in terms of maximal output power compared to the full-bridge rectifier. In addition, only the peak detection is utilized for the switching control; therefore, the SSDCI array circuit is realized more easily and with fewer components compared to the existing synchronous electric charge extraction array interfaces. [ABSTRACT FROM AUTHOR]

[Display omitted] Bulk piezoceramics are widely used and functional materials, but they are hard to be shaped to adapt to complex 3D surfaces. Most existing ceramic shaping techniques, like 3D printing, come at the cost of physical properties such as piezoelectricity and thermal stability. Here to fabricate 3D piezoceramic sheets, we report a mold-assisted sintering (MAS) method that can replicate 3D surfaces with nonzero Gaussian curvatures while maintaining the intrinsic properties. Assisted with supporting molds, the MAS exploits elastic-to-viscous transition of piezoceramic powder compacts during sintering, bypassing the boundaries of deformation and surface development in an elastic continuum. We successfully replicate shapes to sintered lead zirconate titanate (PZT) ceramics from designed molds with saddle, sine and spherical surfaces, respectively. The PZT ceramic replicas show high piezoelectricity and excellent conformability towards nonplanar surfaces (maximum deviation 90 μm). We further demonstrate the advantage of the conformal curved piezoceramics by using them for wirelessly transferring power over a pipeline. The MAS method is low-cost, simple, scalable and applicable to various 3D energy transducers. [ABSTRACT FROM AUTHOR]

Previous droplet-based electricity generator has made breakthroughs in efficient water energy harvesting through taking advantage of the contact electrification, however, the kinetic energy of water remains to be tapped into. In this work, we develop a leaf-mimic rain energy harvester (REH) that allows for the collection of electrostatic and kinetic energy simultaneously based on the synergy of the liquid-solid contact electrification and the piezoelectric effect. Impinged by a water droplet, the REH generates a boosted transferred charge value (101 nC) and high output power density (82.66 W m−2). We also show that such performances enable the construction of self-charged wireless sensor systems with continuous operational capability. The REH is also low-cost and facile for fabrication, paving a new way towards high-efficiency power generation from raindrops as well as other water sources. [Display omitted] • A mechanism of harvesting energy from both the liquid-solid contact and kinetic motion inspired by the leaf-rain interaction. • A new explicit theoretical model that links key parameters on the liquid-solid contact electrification. • Continuous operation of a wireless sensor system powered by the proposed droplet energy harvesters. [ABSTRACT FROM AUTHOR]

Sensors that provide critical information about jet engine performance are widely installed on static components but are rarely found on rotors because of their inaccessibility and extremely high rotation speeds. We present a new monitoring method, integrating energy harvesting technology with wireless sensors to achieve real-time self-powered engine monitoring. Energy harvesters, used to generate power from ambient vibration, are sustainable alternatives to batteries for achieving self-sustained long-term operation of electronic devices. By utilising structural nonlinearity, force amplification mechanism, and the piezoelectric effect, we show a 22.52-g energy harvester capable of high power output (78.87 mW), broad working bandwidth (22.5 Hz), and strong reliability (2100 RPM). Our approach breaks limitations from wired connections that are weighty and vulnerable to failures. We theoretically and experimentally analyse the nonlinear responses and demonstrate the harvester by constantly lighting 112 LEDs and a self-powered wireless sensor system in a jet engine. This work paves a new way for developing future monitoring systems for advanced jet engines and other rotating machinery applications. The self-powered wireless sensor system consists of an energy harvester as the power supply and a wireless sensor node as the communication device. When the jet engine operates, the energy harvester that installs on the rotational component generates power for the wireless sensor node and then the real-time monitoring information of the engine components will be sent wirelessly to a local area network (LAN) in the aircraft for working condition analysis and failure prediction. The energy harvester of the monitoring system exhibits great compatibility in the rotational environment of jet engines and excellent power generation capability (max. to 78.87 mW) and working bandwidth (22.5 Hz in 0–2100 RPM). A combination of such characteristics guarantees the realization of the self-powered and wireless operation of sensor systems in jet engines. Image 1 • A brand-new sensor architecture for real-time and self-powered jet engine monitoring. • A maximum output power 78.87 mW and efficiency 36.43%, capable of powering 112 LEDs simultaneously. • A demonstration of a self-powered wireless sensor system in jet engine components for the first time. • A comprehensive study on the compressive-mode piezoelectric energy harvester used in the rotational environment. • A comparative study the compressive-mode and bending-mode PEHs under vibration and rotational excitations. [ABSTRACT FROM AUTHOR]