(Invited) triboelectric Nanogenerators for Ultrasound-Driven Wireless Power Transfer: A Sustainable Approach

Based on the Paris Agreement compiled at COP21, many nations are now obligated to have penalties for CO2 emission reductions.As a result, many companies are working to reduce CO2 emissions to ensure their survival.We in the liquor, soft drinks, and food industries are no exception, and all members are working to reduce CO2 emissions, but it is believed that existing technologies alone will not allow them to achieve zero CO2 emissions while continuing their operations.Asahi Quality and Innovations, Ltd. , where I work, is an independent research subsidiary of Asahi Group Holdings, Ltd. and is currently working on a number of technological developments to create a new model for medium- to long-term CO2 emissions reduction at the 212 companies and 70 plants that manufacture and sell Asahi Group beer, liquor, soft drinks and food products sold around the world.This time, we report on one of those technological development items, the successful development of a technology for acquiring carbon-neutral electricity using SOFC, and its contents and results.Asahi Breweries, Ltd. and Asahi Soft Drinks, Ltd. under the Asahi Group began introducing anaerobic wastewater treatment processes in their factories from 1988, and all of their factories in Japan are now operating stably on a daily basis.The anaerobic wastewater treatment process uses methane fermentation as the main reaction, which produces methane gas as a byproduct. This methane gas is defined as carbon-neutral methane gas because they are from beer or beverage production derived from agricultural crops. This methane gas has been combusted in boilers and recovered as thermal energy.However, it was confirmed that converting methane gas into electricity using fuel cells, rather than burning it to convert it into thermal energy, has significant cost advantages and reduces CO2 emissions. Therefore, we decided to change the use of methane gas from boiler fuel to fuel for electricity power generation, and to implement power generation using SOFC.However, although many challenges to fuel cell power generation using biomethane gas had been implemented, there were no reports of successful power generation exceeding 10,000 hours. The most significant reason for this was thought to be the presence of poisoned substances in the methane gas.The poisoned substances present in the fuel will constantly attack the electrodes during power generation and the electrodes become inactive and eventually lose their ability to generate power as a fuel cell.Since highly purified fuel is the key to long-term power generation, the goal of this R&D was to improve the purification accuracy to below the detection limit for all poisoned substances.Based on the results of these studies, we aimed to develop a technology that would enable stable long-term continuous SOFC power generation for more than 10,000 hours by highly purifying biomethane gas, a byproduct of the anaerobic wastewater treatment process.Development goals:1. Remove poisoned substances to below than the detection limit (less than 10 ppb).2. Fuel cell degradation rate of less than 1% after start of power generation(challenge target: less than 0.5%)We analyzed the biomethane gas comprehensively and identified hydrogen sulfide and sulfur compounds as the poisoned substances to be dealt with, aiming to reduce them to below the detection limit.The research was conducted by transporting gas purified in a small bench-scale purification system installed in our brewery to the Kyushu University Next-Generation Fuel Cell Research Center for power generation tests. (manufactured by Mitsubishi Heavy Industries, Ltd.).As a result, continuous power generation for 10,000 hours was successfully achieved. The power generation time was 10,650 hours. Degradation throughout the period was 0.3%, an extremely low result.Based on these results, a hybrid SOFC demonstration power plant that combines an in-house designed biomethane refining facility and a 200kW stationary SOFC power generator, backed up by biomethane gas with city gas, was constructed in our brewery with supported from the Japanese Ministry of the Environment. The plant started its automatic continuous power generation in the fall of 2021. As a result, the total operating hours reached 10,676 hours, and 3,408 hours for biomethane gas alone (end of October,2022). Degradation during this period was less than 0.5%/1,000 hours, and automatic operation is still ongoing.This paper reports the results of this 200 kW biomethane gas SOFC demonstration power plant operation and the key points of the design for practical use. Figure 1

The present thesis focuses on the development of a new generation of miniature electronic devices by employing nano-scale materials. Specifically, ZnO nanowire arrays were investigated to increase the conversion efficiency of energy harvesting devices and graphene nano-platelets employed to enhance supercapacitors' energy storage capability. The results obtained in this work pave the way to the possibility of conceiving novel autonomous devices integrating both energy units. The present thesis has been structured in five chapters. A first introduction chapter reviews the pros and cons of renewable energies against the conventional ones produced from fossil fuels as well as their impact on the modern societies. The theoretical background on vibration energy harvesting and electrochemical energy storage is provided. Vibration energy harvesting mechanism relies on piezoelectric phenomena, where a pressure applied on a piezoelectric material turns ultimately into energy. Instead, supercapacitors store large quantity of energy for time unit by high surface material dielectric polarization. In this chapter, the reasons why ZnO nanowire arrays and graphene nano-platelets were considered are introduced. The second chapter presents promising methods to synthesize piezoelectric ZnO nano-materials prior their integration into energy harvesting devices. Since the highest piezoelectric properties of the ZnO-crystal are along its c-axis, the most suitable growing methods were selected to tailor the crystal's unit-cell best orientation. In this chapter physical and chemical growing methods are reported. Physical vapor deposition (PVD) was used to grow ZnO thin film, then employed as a seed layer for the growth of 1D-ZnO nanowires by chemical methods in a second step. ZnO nanowires were synthesized either with or without a nanoporous template by: i) electrochemical deposition (ECD), and ii) hydrothermal technique. The fundamental process parameters to tailor the chemical growth are reported as well as the morphological and microstructural characterization of the structures fabricated. In the third chapter, the characteristics of the energy harvesting device fabricated from the piezoelectric ZnO nanostructures are reported. Piezoresponse force microscopy was initially used to measure the d33 piezoelectric coefficient of the ZnO nanostructures fabricated fairly matching the theoretical expectations. Finally, this chapter reports the energy harvested by the devices fabricated, measured by connecting an external resistive load to it: a maximum energy harvested equal to 2 μJ/cm2 was found. The fourth chapter focuses on nano-scale graphene based materials for supercapacitors' electrodes. Specifically, the synthesis and the characterization of the graphene nano-platelets used in this work is described. XRD and Raman spectroscopy were used to distinguish pure graphite from graphene, BET and SEM to measure its specific surface area and morphology. To determine the graphene's properties functional to the application thermogravimetric analysis (TGA) was carried out. To identify the types of oxygen groups present in the graphene materials, the corresponding Fourier Transform Infrared spectra (FTIR) were recorded and their contribution in rGO was examined by X-Ray photoelectron spectroscopy (XPS) analysis. Overall this chapter reviews the relevant analysis to be performed in candidate materials for fabrication of supercapacitor electrodes. The fifth chapter discusses the fabrication of supercapacitor electrodes made with the graphene nano-platelets previously described as well as the methods for their electrochemical characterization. As being the standard of the energy storage industry, cyclic voltammetry (CV) and constant current charge and discharge experiments were carried out for capacitance estimation. The electrochemical characteristics of the device were then linked to the properties of the graphene nano-materials employed. All measurements were done in a full-scale electrochemical cell mimicking a real supercapacitor device. The results suggest that mechanically exfoliated graphene nano-platelets (GNP) best perform among the variety of materials investigated

The energy harvesting and storage seem to be the most important energy-related technologies in the XXI century. The increasing global energy consumption resulted in gained attention to development of renewable, sustainable, and green power sources which will be competitive to the traditional fossil fuels. The charge storage devices play a key role in driving the electronic devices. Since chalcohalide materials exhibit outstanding piezoelectric and electromechanical properties, they can be used in nanogenerators for mechanical energy harvesting as well as sensors for detection of low frequency vibrations and ultrasonic waves. In addition, the chalcohalides in the form of nanowires are expected to be more flexible and accommodate higher deformation in comparison to their two- or three-dimensional counterparts. This chapter presents a comprehensive review of the conversion of mechanical energy into the electric energy using piezoelectric and triboelectric nanogenerators based on the chalcohalide nanomaterials. Recent achievements in development of the pyroelectric nanogenerators for a waste heat recovery are also described. The applications of bismuth and antimony chalcohalides as electrode materials in the supercapacitors are summarized. The properties of low-dimensional chalcohalides are analyzed in respect to their further applications in hybrid devices for the multisource energy harvesting, charge storage and self-powered sensing of various stimuli, including a strain, stress, mechanical vibrations or thermal signals.KeywordChalcohalide nanomaterialsEnergy harvestingPiezoelectric nanodevicesTriboelectric nanogeneratorsPyroelectric nanogeneratorsSupercapacitors

Recent progress in human body energy harvesting for smart bioelectronic system

Energy harvesting devices have emerged as an auspicious sustainable energy source for low-power electronics, where delivering electricity using conventional means is not feasible nor desirable. This clear technological impact has drawn huge attention and driven research into energy harvesting materials and devices. Reports are often published, even in high-caliber journals claiming high-efficiency devices. However, these are typically based on poorly defined or even undefined metrics and lack the details needed for re-evaluation and comparing different devices for peer assessment. The enthusiasm to publish is pushing the field towards qualitative rather than quantitative research. Here, after introducing the basic concepts of energy harvesting, randomly selected research papers on piezoelectric energy harvesting devices published over the last two decades, have been assessed. It is shown that essential parameters which are needed for a quantitative evaluation of materials and devices are missing from nearly 90% of the reviewed papers, thus rendering them less reproducible (or even irreproducible) for peer assessment. Such a frequent occurrence of improper data reporting damages the credibility and reliability of the energy harvesting field. To enhance reproducibility and facilitate progress, we herein suggest a measurement and data reporting protocol that should be followed when reporting energy harvesting devices and concomitant performances. The standardized protocol can be further adapted for other vibrational harvesters based on other mechanisms such as triboelectricity.

Energy Harvesting (EH) is now becoming popular due to promising long lasting life time of communication system. Some of the communication systems use EH device as their energy source. However, EH also has a limitation that is shown in its characteristics as random arrival and scarce of energy. Both of limitation is very influencing the system performance and the number of transmitted data. As we know the more energy is harvested, the longer system can operate. Because of EH limitation, the system with EH device needs to adjust to get the maximal channel capacity. This paper proposes the cooperative communication system with modified decode and forward (DF) method and EH device as a source energy. The modified DF method incorporate adaptive modulation at relay node to transmit data to the destination node. To test the proposed system, in this paper, three different scenarios are simulated, i.e. the non cooperative communication system with EH device as source energy, the cooperative communication system with DF method but fixed modulation level and EH device as a source energy and the proposed system. The simulation result shows the channel capacity of the proposed system is better than two other scenarios.

Energy harvesting devices which convert low frequency mechanical energy sources such as human motions and ocean waves into electricity are attractive for powering portable devices and for green‐energy generation. To date the state‐of‐the‐art mechanical energy harvesting devices can only work efficiently at high vibration frequencies. Here, a biocompatible and flexible mechanical energy harvesting device is reported utilizing ionic diode as the transducer. This device utilizes the redistribution of cations and anions at the two hydrogel electrodes under stress to convert mechanical energy to electricity. It is shown that the device can be operated at low frequencies with high output current, e.g., 13.5 µA cm−2, owing to the high ion concentration and unique working mechanism of the device. Moreover, the output current density and power density can be improved further by employing a multilayer configuration. By stacking five units with parallel structure, the hydrogel diode device can generate an output current of 64.3 µA cm−2 and power density of 0.48 µW cm−2. Considering the very high electric energy density of ionic devices, the hydrogel energy harvesting device demonstrated herein paves a way for efficient mechanical energy harvesting from many common low frequency sources.

Energy harvesting is an increasingly important capability for a lot of applications. It can be used in biomedical implants but also in other embedded systems. An energy harvesting device needs a functional and efficient power management. Because of the low energy yield it is important to store the harvested energy until enough power is available to accom-plish a task like sending data outside the human body. Therefore Li-ion batteries and capacitors are used in this work. Furthermore a typical arrangement of an efficient energy harvesting circuit is discussed and tested. 1 Introduction Power management in Energy Harvesting Devices for use in human bodies needs to meet ambitious requirements. Thus long term stability is as important as energy self-sufficiency and implantability of applied biosensors. Ener-gy harvesting manifests several non-idealities, such as power fragmentation, inefficiency of energy storage ele-ments and unpredictability [1]. 1.1 Component requirements As a result of smaller components and lower energy con-sumption, particular attention is paid to microprocessors and A/D converters. Due to more efficient DC/DC con-verters and a higher energy density of lithium ion batteries named aims can be achieved. The operating conditions of the harvester and its state are essential criteria for the pow-er management [1].

Energy harvesting from structure vibration, human motion or environmental source has been the focus of researchers in the past few decades. This paper proposes a novel design that is suitable to harvest energy from human motions such as dancing or physical exercise and use the device to engage young students in Science, Technology, Engineering and Math (STEM) fields and outreach activities. The energy harvester (EH) device was designed for a dominant human operational frequency range of 1–5 Hz and it can be wearable by human. We proposed to incorporate different genres of music coupled with energy harvesting technologies for motivation and energy generation. Students will learn both science and art together, since the energy harvesting requires understanding basic physical phenomena and the art enables various physical movements that imparts the largest motion transfer to the EH device. Therefore, the systems are coupled to each other. Young people follow music updates more than robotics or energy harvesting researches. Most popular videos on YouTube and VEVO are viewed more than 100 million times. Perhaps, integrating the energy harvesting research with music or physical exercise might enhance students’ engagement in science, and needs investigation. A multimodal energy harvester consisting of piezoelectric and electromagnetic subsystems, which can be wearable in the leg, is proposed in this study. Three piezoelectric cantilever beams having permanent magnets at the ends are connected to a base through a slip ring. Stationary electromagnetic coils are installed in the base and connected in series. Whenever the device is driven by any oscillation parallel to the base, the unbalanced rotor will rotate generating energy across the stationary coils in the base. In another case, if the device is driven by an oscillation perpendicular to the base, a stress will be induced within the cantilever beams generating energy across the piezoelectric materials.

This paper proposes a power aggregation scheme using small energy harvesting (EH) devices distributed on a special cloth embroidered with conductive threads. Each EH device is removable, like a pin badge, by using a special connector consisting of a tack and a clutch, without one-to-one wiring. In a conventional EH system, each device, such as a sensor node, has its own individual EH element. Power aggregation systems using a wide variety of EH devices can supply more power than conventional EH systems, to a power-intensive device. The aggregation efficiency with respect to the number of connected devices and the variation in the output of each device are demonstrated by circuit simulation. The experimental results demonstrate the feasibility of power aggregation circuits.

PurposeThis paper aims to deal with the development of a software tool to simulate and study vehicle – road interaction (VRI) to quantify the forces induced and energy released from vehicles to the road pavement, in different vehicle motion scenarios, and the energy absorbed by the road surface, speed reducers or a specific energy harvester surface or device. The software tool also enables users to quantify the energetic efficiency of the process.Design/methodology/approachExisting software tools were analysed and its limitations were identified in terms of performing energetic analysis on the interaction between the vehicle and the road pavement elements, such as speed reducers or energy harvest devices. The software tool presented in this paper intends to overcome those limitations and precisely quantify the energy transfer.FindingsDifferent vehicle models and VRI models were evaluated, allowing to conclude about each model precision: bicycle car model has a 60 per cent higher precision when compared with quarter-car model, and contact patch analysis model has a 67 per cent higher precision than single force analysis model. Also, a technical study was performed for different equipment surface shapes and displacements, concluding that these variables have a great influence on the energy released by the vehicle and on the energy harvested by the equipment surface.Originality/valueThe developed software tool allows to study VRI with a higher precision than existing tools, especially when energetic analyses are performed and when speed reduction or energy harvesting devices are applied on the pavement.

AlN piezoelectric thin films for energy harvesting and acoustic devices

A portable or self-powered power source is required to meet the current energy demand. Conventional energy sources are depleting or resulting in an environmental impact. Energy sources such as wind, solar, and hydropower are much studied to harvest renewable energy and storage for future use. But with emerging wearable, smart devices, and health monitoring devices the need for self-powered devices is growing rapidly. These devices can be powered using traditional batteries, but it has certain limitations and concerns. Energy harvesting devices such as nanogenerators are booming as they can generate electricity from applications for self-powered systems, sensors, the Internet of Things (IoT), medical devices, and Biomechanical energy harvesting. The invention of nanogenerators paved the way for lightweight, flexible, easy-to-fabricate, and low-maintenance devices for applications such as energy harvesting and self-powered devices. In this paper, various types of nanogenerators, their fabrication techniques, and their applications are studied and outlined.

Future devices are likely to have the capability to harvest energy from radio-frequency (RF) signals. In this paper, we consider such energy harvesting (EH) devices operating in a two-tier orthogonal frequency-division multiple access-based heterogeneous network. Critically, we investigate how such EH devices can be supported alongside non-RF harvesting or legacy devices. Our aim is to minimize the downlink sum transmit power of both femto and macro base stations and ensure that legacy and EH devices receive a given data rate and amount of energy, respectively. Critically, we study sub-carrier and power allocation to both types of devices and investigate novel questions related to interference, which reduces network capacity but improves the amount of harvested energy by EH devices. To study these questions, we formulate a mixed-integer non-linear program (MINLP) and propose three linear approximations to the MINLP where devices are either assigned one or multiple sub-carriers. Numerical results show that EH devices will not affect network capacity if they can harvest sufficient energy from data transmissions to legacy devices. In addition, if multiple sub-carriers can be assigned to devices, our results show that the sum transmit power decreases by approximately 15% as compared with assigning a single sub-carrier to these devices.

Optimized design for integrated sensing and communication in secure MIMO SWIPT systems