Current State of Research at Imperial College London in RF Harvesting and Inductive Power Transfer

This paper presents simulation and experimental results for ambient RF energy harvesting and Inductive Power Transfer systems. End-to-end and dc-load efficiency measurements and calculations were performed to demonstrate the capabilities of both systems, respectively. An RF spectral survey was conducted across all the 270 underground stations in London. DTV, GSM900, GSM1800 and 3G were selected as the highest contributors and single banded rectennas were fabricated for all frequencies. Ground level measurements demonstrate that more than 50 stations have suitable channel power levels per band to allow ambient RF energy harvesting. Efficiencies of up to 40% were achieved with a single banded rectenna operating at GSM 900, and efficiencies higher than 20% were achieved for TV and 3G. Furthermore a high frequency, semi-resonant Class-E driver was used to transfer 60 W of power across a 30 cm distance with a dc-load efficiency of 66%

SUSTAINABLE ENERGY HARVESTING TECHNOLOGIES – PAST, PRESENT AND FUTURE

Chapter 8: Energy Harvesting Technologies: Thick-Film Piezoelectric Microgenerato

Radio Frequency Energy Harvesting - Sources and Techniques

Energy harvesting technology is attracting huge attention and holds a promising future for generating electrical power. This process offers various environmentally friendly alternative energy sources. Especially, radio frequency (RF) energy has interesting key attributes that make it very attractive for low-power consumer electronics and wireless sensor networks (WSNs). Ambient RF energy could be provided by commercial RF broadcasting stations such as TV, GSM, Wi-Fi, or radar. In this study, particular attention is given to radio frequency energy harvesting (RFEH) as a green technology, which is very suitable for overcoming problems related to wireless sensor nodes located in harsh environments or inaccessible places. The aim of this paper is to review the progress achievements, the current approaches, and the future directions in the field of RF harvesting energy. Therefore, our aim is to provide RF energy harvesting techniques that open the possibility to power directly electronics or recharge secondary batteries. As a result, this overview is expected to lead to relevant techniques for developing an efficient RF energy harvesting system

TFET-Based power management circuit for RF energy harvesting

This paper proposes a Tunnel FET (TFET)-based power management circuit (PMC) for ultra-low power RF energy harvesting applications. In contrast with conventional thermionic devices, the band-to-band tunneling mechanism of TFETs allows a better switching performance at sub-0.2 V operation. As a result, improved efficiencies in RF-powered circuits are achieved, thanks to increased rectification performance at low power levels and to the reduced energy required for a proper PMC operation. It is shown by simulations that heterojunction TFET devices designed with III-V materials can improve the rectification process at received power levels below -20 dBm (915 MHz) when compared to the application of homojunction III-V TFETs and Si FinFETs. For an available power of -25 dBm, the proposed converter is able to deliver 1.1 µW of average power (with 0.5 V) to the output load with a boost efficiency of 86%.Postprint (author's final draft

Ambient RF energy harvesting and efficient DC-load inductive power transfer

This thesis analyses in detail the technology required for wireless power transfer via radio frequency (RF) ambient energy harvesting and an inductive power transfer system (IPT). Radio frequency harvesting circuits have been demonstrated for more than fifty years, but only a few have been able to harvest energy from freely available ambient (i.e. non-dedicated) RF sources. To explore the potential for ambient RF energy harvesting, a city-wide RF spectral survey was undertaken in London. Using the results from this survey, various harvesters were designed to cover four frequency bands from the largest RF contributors within the ultra-high frequency (0.3 to 3 GHz) part of the frequency spectrum. Prototypes were designed, fabricated and tested for each band and proved that approximately half of the London Underground stations were found to be suitable locations for harvesting ambient RF energy using the prototypes. Inductive Power Transfer systems for transmitting tens to hundreds of watts have been reported for almost a decade. Most of the work has concentrated on the optimization of the link efficiency and have not taken into account the efficiency of the driver and rectifier. Class-E amplifiers and rectifiers have been identified as ideal drivers for IPT applications, but their power handling capability at tens of MHz has been a crucial limiting factor, since the load and inductor characteristics are set by the requirements of the resonant inductive system. The frequency limitation of the driver restricts the unloaded Q-factor of the coils and thus the link efficiency. The system presented in this work alleviates the use of heavy and expensive field-shaping techniques by presenting an efficient IPT system capable of transmitting energy with high dc-to-load efficiencies at 6 MHz across a distance of 30 cm.Open Acces

Dynamically Reconfigurable SIR Filter Using Rectenna and Active Booster

Obrađeni su populacijski parametri čaglja (Cannis aureus L.) u proteklom desetogodišnjem razdoblju. Istraživanjem su se obuhvatila lovišta koja pripadaju širem području plavljenja rijeke Save. Rezultati ovog istraživanja pomažu boljem razumijevanju dinamike populacije čaglja i širenju areala ove vrste koja je već prisutna na čitavom prostoru Republike Hrvatske

Towards Battery-Free Internet of Things (IoT) Sensors: Far-Field Wireless Power Transfer and Harmonic Backscattering

RÉSUMÉ Notre vie tend à être plus agréable, plus facile et plus efficace grâce à l'évolution rapide de la technologie de l'Internet des objets (IoT). La clef de voute de cette technologie repose essentiellement sur la quantité de capteurs IoT interconnectés, que l’on est en mesure de déployer dans notre environnement. Malheureusement, l’électronique conventionnelle fonctionnant sur piles ou relié au réseau électrique ne peut pas constituer une solution durable en raison des aspects de coût, de faisabilité et d'impact environnemental. Pendant ce temps, le changement climatique dû à la consommation excessive de combustibles fossiles continue de s'aggraver. Il devient donc urgent de trouver une solution pour l’alimentation électrique des capteurs IoT géographiquement répartis à grande échelle, afin de simultanément soutenir la mise en oeuvre de nombreux capteurs IoT tout en limitant leur poids environnemental. L'énergie radiofréquence (RF) ambiante, qui sert de support à l'information sans fil, est non seulement capitale pour notre société, mais aussi omniprésente dans les zones urbaines et suburbaines. Elle permet de réaliser des communications et des détections sans fil. Cependant, l'énergie RF ambiante est majoritairement « gaspillée » car seule une toute petite partie de la puissance transmise est effectivement reçu ou « consommée » par le destinataire. C'est pourquoi le recyclage de l'énergie RF ambiante est une solution prometteuse pour alimenter les capteurs IoT. Pour certains capteurs IoT consommant une puissance plus élevée, l’apport d'énergie sans fil pourra similairement se faire par des centrales électriques spécialisées, suivant le même schéma d’alimentation sans fil. Pour utiliser et récupérer cette énergie RF, cette thèse présente deux techniques principales : la récupération/réception de puissance sans fil en champ lointain (wireless power transfer: WPT) et la rétrodiffusion d'harmoniques. Le chapitre 2 aborde les différents mécanismes de conversion de fréquence entre le WPT en champ lointain et la rétrodiffusion d'harmoniques. La récupération de WPT en champ lointain consiste à convertir l'énergie RF en puissance continue. En revanche, la rétrodiffusion d'harmoniques a pour but de convertir l'énergie RF dans une autre fréquence, dans la plupart des cas, la composante harmonique de rang 2. A titre d'étape préliminaire de recherche et d'étude de faisabilité, une cartographie de la densité de l'énergie RF ambiante dans les zones centrales de l'île de Montréal est résumée au chapitre 3. Contrairement aux mesures traditionnelles précédentes effectuées à des endroits fixes, cette mesure dynamique a été réalisée le long des rues, des routes, des avenues et des autoroutes pour couvrir une large zone.----------ABSTRACT Our life is becoming more convenient, efficient, and intelligent with the aid of fast-evolving Internet of Things (IoT) technology. One essential foundation of IoT technology is the development of numerous interrelated IoT sensors that are distributed extensively in our environment. However, conventional batteries/cords-based powering solutions are certainly not an acceptable long-term solution, considering the incurred cost, feasibility, most of all, environmental impact. Meanwhile, climate change due to excessive consumption of fossil fuels is worsening day by day. Therefore, a transformative powering solution for such large-scale and geographically scattered IoT sensors is of extreme importance in support of such extensive IoT sensors implementation while simultaneously mitigating its environmental burden. Serving as a critical information carrier, ambient radiofrequency (RF) energy is pervasive in urban and suburban areas to realize wireless communication and sensing. However, part of ambient RF energy is dissipated due to path loss if not fully consumed by end-users. Hence, recycling the wasted ambient RF energy to power IoT sensors is a promising solution. The concept of harnessing wireless energy for powering IoT sensors requiring a higher power supply is also feasible through the dedicated wireless power delivery from specialized power stations, which can be an effective supplement. To realize the RF power scavenging, this thesis research introduces two mainstream techniques: far-field wireless power transfer (WPT) and harmonic backscattering. Chapter 2 discusses the different frequency conversion mechanisms applied for far-field or ambient WPT harvesting and harmonic backscattering. Far-field WPT harvesting converts RF energy into dc power (zeroth harmonic). In contrast, harmonic backscattering upconverts RF energy into its harmonics, in most cases, the second harmonic component. As a preliminary research step and a feasibility study, a survey of ambient RF energy density in the core areas on Montreal Island is summarized in Chapter 3. Different from the previously published traditional measurements at fixed locations, this dynamic measurement is carried out along streets, roads, avenues, and highways to cover a large area. Also, a stationary measurement in Downtown Montreal is to reveal whether human activities are able to bring visible change to ambient RF energy levels. This work demonstrates how much ambient RF energy is available in free space and acts as a significant reference for researchers and engineers designing ambient RF energy harvesting circuits/systems for practical applications

Développement de nouvelles rectennas pour la récupération d'énergie RF ambiante

La récupération d'énergie a attiré beaucoup d'intérêt ces dernières années. Cette technologie permet d'exploiter l'énergie ambiante RF disponible dans notre environnement en la convertissant en énergie continue à l'aide de la technologie des Rectennas. La Rectenna, qui est associée à un redresseur et une antenne, permet de récupérer l’énergie RF sans fil dans l’air pour la convertir en un courant continu (batterie). L’objectif de ce mémoire est de proposer un nouveau système Rectenna de type mono-bande et double-bandes pour les applications de récupération d'énergie radiofréquence (RF). Un état de l’art des différentes Rectennas utilisées dans la littérature a été introduit, avec une explication de principe de fonctionnement. Plusieurs prototypes ont été développés et simulés : le premier prototype est une Rectenna à gain élevé, constituée d’une antenne micro-ruban à substrat multicouche alimentée par couplage et fonctionnant dans la bande de fréquence 5,8 GHz et un redresseur à base d’une seule diode Schottky. Pour améliorer le gain de cette antenne, la technologie des métamatériaux (FSS) a été utilisée pour atteindre un gain final de (la structure (antenne + FSS)) 13.1 dBi. La deuxième structure est basée sur un nouveau réseau hexagonale constitué du Rectenna (conçu précédemment) permettant de récupérer l’énergie à 360 degrés. Le troisième prototype concerne une nouvelle Rectenna à double bande fonctionnant à 3,5 GHz et 5,8 GHz, pour les applications de la récupération d’énergie. La Rectenna proposée consiste en une antenne double-bande à gain élevé et un redresseur double bande utilisant la diode Schottky comme élément de redressement. Une procédure d’optimisation utilisant l’algorithme génétique a été appliquée sur l’antenne pour atteindre un gain maximal de 10.2 dBi et 8.92 dBi dans les deux bandes, respectivement