System-level modelling and validation of a strain energy harvesting system by directly coupling finite element and electrical circuits

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.— There is a lack of system-level finite element (FE) model which can directly predict the performance of a piezoelectric energy harvester connected with interface circuits and electric load. This work developed a system-level model of piezoelectric strain energy harvesting system by directly coupling the finite element and electrical circuits. The strain energy harvester (SEH) is a macro fibber composite adhesively bonded to a composite beam. Simulations were performed with the SEH connected with three circuits individually (i) a load resistor, (ii) a rectifier terminated with a load resistor and (iii) a rectifier terminated with a smoothing capacitor and a load resistor. Experimental tests were carried out to validate the simulation results. Good agreements were observed between the simulated and measured results. The developed model is able to predict the performance of the energy harvesting system when different circuit was connected. The validated system-level model can be used for the design and optimization of piezoelectric energy harvesting system by investigating the interactions between energy harvester and electrical circuits

Feasibility of an electrostatic energy harvesting device for CFCs aircraft

A novel energy harvesting concept is proposed for treating local electrostatic energy produced on flying composite aircrafts. This work focuses on the feasibility research on collecting static charges with capacitive collectors. The existing energy harvesting system and the electrification of the typical carbon fibre composites (CFCs) aircraft has been reviewed. The detailed model experiments were then designed to characterize different configurations for electrostatic energy harvesting on aeroplane. In the lab, the static charge was produced by a corona discharging device, and a capacitor or a metal sheet was put in the electric field to collect the charges under four different configurations. After that, the rest results for these configurations were analysed, which is followed by the discussion about the results application on the aircraft. This work has proved that it is feasible to collect the local static electricity on flying aircraft, and it could provide a new direction of energy harvesting system in aviation field

Piezoelectric Energy Harvesting Powered WSN for Aircraft Structural Health Monitoring

This is the author accepted manuscript. The final version is available from the Institute of Electrical and Electronics Engineers (IEEE) via the DOI in this record.2016 15th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), Vienna, Austria, 11-14 April 2016This work is supported by EPSRC grant through En-Come project (EP/K020331/1)

Strain Energy Harvesting Powered Wireless Sensor System Using Adaptive and Energy-Aware Interface for Enhanced Performance

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.This paper presents a wireless sensor system (WSS) powered by a strain energy harvester (SEH) through the introduction of an adaptive and energy-aware interface for enhanced performance under variable vibration conditions. The interface is realized by an adaptive power management module (PMM) for maximum power transfer under different loading conditions and an energy-aware interface (EAI) which manages the energy flow from the storage capacitor to the WSS for dealing with the mismatch between energy demanded and energy harvested. The focus is to realize high harvested power and high efficiency of the system under variable vibration conditions, and an aircraft wing structure is taken as a study scenario. The SEH powered WSS was tested under different peak-to-peak strain loadings from 300 to 600 µε and vibrational frequencies from 2 to 10 Hz to verify the system performance on energy generation and distribution, system efficiency, and capability of powering a custom-developed WSS. Comparative studies of using different circuit configurations with and without the interface were also performed to verify the advantages of the introduced interface. Experimental results showed that under the applied loading of 600 µε at 10 Hz, the SEH generates 0.5 mW of power without the interface while having around 670 % increase to 3.38 mW with the interface, which highlights the value of the interface. The implemented system has an overall efficiency of 70 to 80 %, a long active time of more than 1 s, and duty cycle of up to 11.85 % for vibration measurement under all the tested conditions.This work was supported in part by the Engineering and Physical Sciences Research Council, U.K., through the project En-ComE-Energy Harvesting Powered Wireless Monitoring Systems Based on Integrated Smart Composite Structures and Energy-Aware Architecture under Grant EP/K020331/1. All data are provided in full in the results section of this paper

Energy-aware Approaches for Energy Harvesting Powered Wireless Sensor Systems

Energy harvesting (EH) powered wireless sensor systems (WSSs) are gaining increasing popularity since they enable the system to be self-powering, long-lasting, almost maintenance-free, and environmentally friendly. However, the mismatch between energy generated by harvesters and energy demanded by WSS to perform the required tasks is always a bottleneck as the ambient environmental energy is limited, and the WSS is power hunger. Therefore, the thesis has proposed, designed, implemented, and tested the energy-aware approaches for wireless sensor motes (WSMs) and wireless sensor networks (WSNs), including hardware energy-aware interface (EAI), software EAI, sensing EAI and network energy-aware approaches to address this mismatch. The main contributions of this thesis to the research community are designing the energy-aware approaches for EH Powered WSMs and WSNs which enables a >30 times reduction in sleep power consumption of WSNs for successful EH powering WSNs without a start-up issue in the condition of mismatch between the energy generated by harvesters and energy demanded by WSSs in both mote and network systems. For EH powered WSM systems, the energy-aware approaches have (1) enabled the harvested energy to be accumulated in energy storage devices to deal with the mismatch for the operation of the WSMs without the start-up issue, (2) enabled a commercial available WSMs with a reduced sleep current from 28.3 μA to 0.95 μA for the developed WSM, (3) thus enabled the WSM operations for a long active time of about 1.15 s in every 7.79 s to sample and transmit a large number of data (e.g., 388 bytes), rather than a few ten milliseconds and a few bytes. For EH powered WSN systems, on top of energy-aware approached for EH powered WSM, the network energy-aware approaches have presented additional capabilities for network joining process for energy-saving and enabled EH powered WSNs. Once the EH powered WSM with the network energy-aware approach is powered up and began the network joining process, energy, as an example of 48.23 mJ for a tested case, has been saved in the case of the attempt to join the network unsuccessfully. Once the EH-WSM has joined the network successfully, the smart programme applications that incorporate the software EAI, sensing EAI and hardware EAI allow the EH powered WSM to achieve (4) asynchronous operation or (5) synchronised operation based on the energy available after the WSM has joined the network.Through designs, implementations, and analyses, it has been shown that the developed energy-aware approaches have provided an enabled capability for EH successfully powering WSS technologies in the condition of energy mismatch, and it has the potential to be used for wide industrial applications

Design analysis and fabrication of a mobile energy harvesting device to scavenge bio-kinetic energy.

The increasing prevalence of low power consumption electronics brings greater potential to mobile energy harvesting devices as a possible power source. The main contribution of this thesis is the study of a new piezoelectric energy harvesting device, called the piezoelectric flex transducer (PFT), which is capable of working at non- resonant and low frequencies to harvest bio-kinetic energy of a human walking. The PFT consists of a piezoelectric element sandwiched between substrate layers and metal endcaps, the endcaps are specifically designed to amplify the axial force load on the piezoelectric element, instead of conventional designs of piezoelectric energy harvesters that focus on utilising resonant frequency in order to increase power harvested. This thesis presents the analyses, design, prototyping and characterisation of the PFT using a coupled piezoelectric-circuit finite element model (CPC-FEM) to show the energy harvesting capability of the proposed and developed novel device to harvest bio-kinetic energy. Prior to the study of the new PFT, an initial focus was given to a traditional Cymbal device to investigate its potential as a bio-kinetic energy harvesting device. To gain an understanding, effects of geometrical parameters and material properties of the device on its energy harvesting capability were studied and in doing so issues and problems were identified with the traditional Cymbal device for use as a bio-kinetic energy harvesting device. Its structural materials were not able to withstand higher than a 50N applied load and it was proposed that a small adhesion area connection in a fundamental part of the structure may have been at high risk of delamination. In order to study these, the CPC-FEM model was developed using the commercial software of ANSYS and validated by experimental methods. Later, based on a modelling and experimental study, a novel PFT was proposed and implemented to overcome the issues and problems of the traditional Cymbal device. For this initial study, the Cymbal was analysed by studying how key dimensional parameters affect the energy harvesting performance of the Cymbal. In addition to this, how piezoelectric material properties affect the energy harvesting performance were studied using the developed CPC-FEM model through comparisons of different piezoelectric materials and their electrical performances to aid with selecting high power producing materials for the final PFT design. It was found that (1) d₃₁ is a more dominant material property over other material properties for higher power output, (2) Figure of Merit (FOM) was more linear related to the power output than either the k₃₁ or the d₃₁, and (3) εᵀ r₃₃ had some role when the materials have an identical d₃₁; a lower ε ᵀ₃₃ was preferred. A combined FOM with d₃₁ parameters is recommended for selection of piezoelectric material for a higher power outputs. The design of the new PFT is partly based on the traditional Cymbal however, the new PFT has more potential for withstanding higher forces due to an addition of substrate layers that reduced delamination risks. Using a similar approach to designing the traditional Cymbal, the new PFT was designed and tested with force frequencies of less than 5Hz and forces of up to 1kN. In the design process, the validated CPC-FEM was used 1) to analyse then utilise correlations between geometric parameters and power outputs, and 2) to ensure structural integrity by monitoring mechanical stress in the PFT. The PFT was retrofitted into a shoe and the harvested power was used to power an in-house developed wireless sensor module whilst the subject with a body weight of 760N was wearing the shoe and ran at 3.1mph (equivalent to 1.4Hz on the shoe), the PFT produced an average maximum power of 2.5mW over 2MΩ load and the power produced is able to power the wireless module approximately every 10 seconds.Engineering and Physical Sciences (EPSRC)PhD in the School of Applied Science