High-power Energy Harvesting Research Articles

A compact-size and high-power energy harvester using stacked flexible-PCB coils for rotational shaft applications

In this Letter, a compact-size and high-power energy harvester (EH) based on multilayer flexible printed circuit board (F-PCB) sheets is presented for wireless sensor system (WSS) applications on propulsion shafts. A 2 mm thin rotor is designed using two F-PCB sheets that integrate 12 coil bundles with a total number of coil turns of 368. A stator is designed in a fixture that can be installed in the bearing housing. Voltage and power of the fabricated EH were measured and analyzed at a rotational speed of 10–100 rpm. At 80–100 rpm, the average voltage and output increased linearly with increasing speed. In particular, at 100 rpm, the average voltage and power were 5.43 V and 1714 mW, respectively. This performance represents a significant improvement compared to previously published EHs. The proposed EH features the straightforward structure, facilitating easier power design and prediction, and it is adaptable to various rotational shaft applications.

Optimum Performance Analysis and Receiver Design for OFDM-Based Frequency-Splitting SWIPT With Strong Nonlinear Effects

Multicarrier based frequency splitting simultaneous wireless information and power transmission (FS-SWIPT) signals are very prone to nonlinear effects due to the combination of high-power energy harvesting (EH) subcarriers with low-power data subcarriers. In this paper, we study the impact of nonlinear effects in FS-SWIPT signals, as well as ways to minimize these effects on the data transmission performance. We start by analytically characterizing the impact of nonlinear devices on the signals, showing that the nonlinear effects on data subcarriers are exacerbated by a factor close to the ratio between the power spectral densities of EH and data terms. This suggests that conventional receivers, that treat nonlinear distortion as an additional noise term, can have very poor performance. Then, we present an iterative receiver that iteratively estimates and cancels nonlinear distortion, and is able to have a performance close to the linear case. Finally, we study the optimum performance of FS-SWIPT signals with strong nonlinear distortion levels, showing that, by using optimum receivers, the nonlinear distortion term can be used to improve the performance of FS-SWIPT, even outperforming the linear case.

Bio-inspired quad-stable piezoelectric energy harvester for low-frequency vibration scavenging

Due to the unique and diverse nonlinear characteristics, bionic structures can effectively broaden the acquisition bandwidth and improve the performance of harvesters. Inspired by dipteran flight motion, a novel bionic quad-stable piezoelectric energy harvester (BQPEH) is designed to collect low-frequency ambient vibration. The novelty of this bionic energy harvester lies in the combination of the “click” mechanism and “snap-through” motion, thus broadening the application scenarios and improving adaptability for the harvesters. A mass block and a post-buckled piezoelectric beam are connected by a rigid bar to create quadruple-well potentials. The static bifurcation analysis is performed to identify the quad-stable region in the parameter space. The dynamic responses of the system are investigated theoretically and numerically under constant and swept-frequency excitations and then verified experimentally. Broadband low-frequency and high-power energy harvesting are obtained through the inter-well motion induced by the combined nonlinearity of the BQPEH. The results indicate the potential of the bionic strategy for powering wireless devices in low-frequency environments and provide a novel concept for the innovative development of energy harvesters.

A high-performance mini-generator with average power of 2 W for human motion energy harvesting and wearable electronics applications

The sustainability of power supply for mobile electronic devices is a problem that needs to be solved urgently. The energy from human motion is an optimal solution for this problem. As for the traditional energy harvesters based on electromagnetic, triboelectric, and piezoelectric induction, energy management is the largest challenge because of the low conversion efficiency and output power. In this paper, a high-efficiency and high-power energy harvester (EPEH) is presented based on the intersecting beam array structure. It can effectively harvest the pressure energy of humans under the soles at the states of walking, running, and weight-bearing walking. The EPEH does not impair the flexibility of humans compared with joint energy harvesters. The intersecting beam array structure is key component, which can magnify the compression distance in the vertical direction of 3.4 times in the horizontal direction, facilitating maximum energy harvesting within a limited height. On the other hand, the design of rolling friction structure can effectively reduce energy loss and improve energy conversion efficiency. The result shows that the maximum average output power can reach 2 W at 7 km/h. Because of the high output power, the energy management circuits and voltage regulator circuits can be derived and stable work, the energy harvested by the EPEH can be stored in the lithium battery (3.7 V, 50 mAh). Furthermore, the generated energy could supply mobile phones, smart watches, light bulbs, flashlights, children's anti-lost devices, and so on. Through the energy management circuit and voltage regulator circuit (1.5 V and 5 V), the energy conversion efficiency of the device can reach 65.2 % at a compression velocity of 2500 mm/min and a frequency of 1.25 Hz. It is of great significance for the practical application of wearable energy harvesting technology and has multiple application prospects.

High-power energy harvesting and imperceptible pulse sensing through peapod-inspired hierarchically designed piezoelectric nanofibers

High-performance energy harvesting for human-sensing applications has been achieved through recent progress in piezoelectric-based wearable devices. Piezoelectric nanomaterials can be leveraged for flexibility and biocompatibility while also enhancing piezoelectricity. However, such nanomaterials exhibit low piezoelectricity, limits the industrial-scale development of highly efficient piezoelectric devices. Hence, design of novel materials to significantly enhance piezoelectricity is necessitated. Herein, we demonstrate that a peapod-inspired design in which ZnSnO3 anchored on surface-modified carbon nanotubes (CNT) allows significant enhancement of the piezoelectricity produced by poly(vinylidene fluoride-co-trifluoroethylene)-based (P(VDF-TrFE)-based) nanofibers (a piezoelectric material). The piezoelectric properties were exploited for the application of the as-prepared nanofibers (NFs) in flexible NFs in energy-harvesting and pulse-sensing systems, which demonstrated high output power ((97.5 V and 1.16 μA) as well as imperceptible pulse detection even in posterior tibial arteries. This work provides the scientific and engineering framework for delivering ZnSnO3-surface-modified CNT-P(VDF-TrFE) NFs excellent piezoelectric performance for use in piezoelectric devices.

Global optimisation approach for designing high-efficiency piezoelectric beam-based energy harvesting devices

The paper proposes a novel methodology for developing high-power energy harvesting gravity-based devices using an array of piezoelectric beams for wind energy applications. The methodology incorporates a global multidimensional constrained optimisation algorithm, which accounts for the physical size of the device, the physical, geometrical and electrical properties of the piezoelectric beams, and the power management circuit to increase the device’s efficiency. As the beams are plucked sequentially, they vibrate out-of-phase, which consequently leads to charge cancellation issues. The paper proposes and incorporates an electrical circuit design to avoid such problems, being able to further increase the efficiency of the device by 35% when compared against the output from the standard energy harvesting (SEH) circuit with independent rectifiers. The proposed optimisation methodology is applied to the devices utilising flexible polyvinylidene fluoride beams. The developed dynamic numerical model of the beams’ vibration is validated using the experimental results and the results of a Finite Element Analysis. To study the electro-mechanical coupling of the beams, an electric circuit and the power management circuit are created and modelled in Matlab/Simulink software. The optimised device delivers 6 to 17 times higher energy output compared to the unoptimised device. The performance of this device was also compared to that of the device with much stiffer LiNbO3 beams (Clementi et al., 2021, [1]) to demonstrate the direct applicability of such devices to power sensors and transmitter units for structural monitoring of wind turbine blades. It has been demonstrated that the LiNbO3-beam device yields an energy output with one order of magnitude higher. The applied optimisation methodology enabled a 0.057 × 0.017 × 2 m3 dimension device to produce a power output in the range from 0.5 to 1 W depending on the blades’ speed, resulting in 1.06 mW/cm3 power density of the device.

Sustainable and high-power wearable glucose biofuel cell using long-term and high-speed flow in sportswear fabrics

Wearable electronics have been extensively studied owing to their capability of undertaking continuous multi-task for daily needs. Meanwhile, lightweight, flexible, and wearable power sources that enable high-power and sustainable energy conversion from ambient resources (e.g. bodily fluids) have attracted attention. We propose a wearable and flexible textile-based biofuel cell using moisture management fabric (MMF) widely used in sportswear as a transport layer for sustainable and high-power energy harvesting. The reduction of PB-modified cathode is driven by the oxidation of glucose catalyzed by GOD-modified anode, and this enables a single-compartment structure where MMF acts as biofuel transport media. MMF made of polyester can naturally induce a continuous, high-speed flow which facilitates molecule transport for efficient chemical reactions without an additional pump. The resulting highly efficient power generation in MMF is explored and verified by comparing it with those of cotton and paper. Additionally, multi-stack biofuel cell in both parallel and series was successfully realized, and the open circuit voltage and maximum power reached 1.08 V and 80.2 μW, respectively. Integrated into a bandage and sportswear, a six-stack biofuel cell was able to generate sufficient electrical power from human sweat and turn on a sports watch directly. Owing to low-cost and scalable fabrication process, the proposed biofuel cell has great potential to be systematically integrated into clothes, and generate sufficient and sustainable electrical power for wearable electronics using biofuel (e.g. glucose, lactase) from various bodily fluids, like sweat and urine.

Start-Up and Saturation Optimization of High-Power Energy Harvester With Compound Topologies Overhead AC Transmission Line

With the continuous development of power automation and smart grids, online monitoring equipment has been utilized more widely for inspection of the state of high-voltage ac transmission lines. To ensure the stable and effective work of the monitoring device, the problem of power supply needs to be solved urgently. Although the inductive energy harvester penetrated through line has been extensively researched, the practical process has been greatly hindered caused by the core materials, which cannot simultaneously combine two advantages of both high permeability and high saturation. Based on the inherent contradiction of the inductive energy harvester, the structure of compound cores with different intrinsic properties is adopted. In addition, three optimization topologies for the structure are proposed. Theoretical analysis and experimental results show that the proposed structures and topologies have certain advantages over the conventional structure in terms of effective start-up sensitivity, saturation performance, and gained power. The proposed energy harvesters also broaden the effective working range by enduring the primary current fluctuation. The simulation and experimental results verify the correctness of the theoretical analysis and the validity of the topologies.

Energy harvesting from aperiodic low-frequency motion using reverse electrowetting.

Mechanical energy harvesting can provide a promising alternative to electrochemical batteries, which are currently widely utilized to power mobile electronics. In this work we present a theoretical analysis of a recently proposed method of mechanical energy harvesting, which combines a reverse electrowetting phenomenon with the fast self-oscillating process of bubble growth and collapse. We investigate the details of the bubble dynamics and analyze the dependence of the energy generation process on the system parameters. The results demonstrate that self-oscillation frequencies of several kHz are possible, which can lead to very high power generation densities in excess of 104 W m-2. The obtained results indicate the possibility of high-power energy harvesting from mechanical energy sources with very low frequencies, well below 1 Hz.

A wideband integrated piezoelectric bistable generator: Experimental performance evaluation and potential for real environmental vibrations

Bistable generators have been proposed as potential solutions to the challenge of variable vibration frequencies. This article presents a novel mono-block design of bistable generator based on mechanical buckling effect. A bistable structure composed of four thin beams as flexible hinges, two amplified piezoelectric stacks as electromechanical springs, and a dynamic mass is fabricated. Its volume is 5.46 cm3, and it reaches a power density of 0.48 mW/cm3. The wideband and high-power energy harvesting properties are first validated using chirp excitations with an obtained bandwidth of 11 Hz (812% improvement compared with the linear equivalent case). The generator’s good performance is then further confirmed for bandlimited noise excitations and a real vibration signal from a driving car wheel.

Correction: Corrigendum: Reverse electrowetting as a new approach to high-power energy harvesting

Nature Communications 2, Article number: 448 (2011); Published: 23 August 2011; Updated: 7 February 2012 This article was published without any declaration of competing financial interests. A revised competing financial interests statement is provided below: The authors declare competing financial interests.

Reverse electrowetting as a new approach to high-power energy harvesting

Over the last decade electrical batteries have emerged as a critical bottleneck for portable electronics development. High-power mechanical energy harvesting can potentially provide a valuable alternative to the use of batteries, but, until now, a suitable mechanical-to-electrical energy conversion technology did not exist. Here we describe a novel mechanical-to-electrical energy conversion method based on the reverse electrowetting phenomenon. Electrical energy generation is achieved through the interaction of arrays of moving microscopic liquid droplets with novel nanometer-thick multilayer dielectric films. Advantages of this process include the production of high power densities, up to 103 W m−2; the ability to directly utilize a very broad range of mechanical forces and displacements; and the ability to directly output a broad range of currents and voltages, from several volts to tens of volts. These advantages make this method uniquely suited for high-power energy harvesting from a wide variety of environmental mechanical energy sources.