Advances in micro-electronics and miniaturized mechanical systems are redefining the scope and extent of the energy constraints found in battery-operated wireless sensor networks (WSNs). On one hand, ambient energy harvesting may prolong the systems’ lifetime or possibly enable perpetual operation. On the other hand, wireless energy transfer allows systems to decouple the energy sources from the sensing locations, enabling deployments previously unfeasible. As a result of applying these technologies to WSNs, the assumption of a finite energy budget is replaced with that of potentially infinite, yet intermittent, energy supply, profoundly impacting the design, implementation, and operation of WSNs. This article discusses these aspects by surveying paradigmatic examples of existing solutions in both fields and by reporting on real-world experiences found in the literature. The discussion is instrumental in providing a foundation for selecting the most appropriate energy harvesting or wireless transfer technology based on the application at hand. We conclude by outlining research directions originating from the fundamental change of perspective that energy harvesting and wireless transfer bring about.

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Energy Harvesting and Wireless Transfer in Sensor Network Applications: Concepts and Experiences

Efficiency in RF energy harvesting systems: A comprehensive review

In this paper, a comprehensive survey on the key components of a rectenna system, including antenna configurations, rectifier configurations, impedance matching networks, and RF filter, is outlined...

Key Components of Rectenna System: A Comprehensive Survey

Radio Frequency (RF) energy conversion and harvesting topologies gains much attention that promises to operate the low power devices. The base of any RF energy harvesting model is the selection of appropriate RF souce followed by other three main stages which include receiving antenna, converting into DC output and utilisation of that output in any low-power applications. In this context, we present an extensive survey on the various RF sources (DTV, GSM, Wi-Fi) available in the frequency range of 3KHz -3GHz. This paper aims to review the progress of ambient sources which is expected to be useful in designing the RF energy harvesting model.

A Survey Study of Different RF Energy Sources for RF Energy Harvesting

A novel Kinetic Energy Harvester (KEH) has been developed for powering oceanic undrogued drifters. It consists on a double pendulum system capable of transforming the wave oscillations into rotation on a flywheel. This rotation is converted into DC current by an electrical generator and further processed by a power management unit (PMU). The PMU includes a “maximum power point tracking” system to maximize energy production by the generator. An oceanic drifter has also been designed to embed the KEH and a custom-made measurement system to perform real sea tests. It counts on an Inertial Measurement Unit to study the motion of the drifter and an embedded measurement system to estimate the rotation speed of the generator and the power at both the input and output of the PMU. A Wi-Fi connection is also included for data transfer at short distances. The generator was firstly characterized at the laboratory; the drifter was then placed on a linear shaker to assess its performance. Finally, the drifter was deployed in a controlled sea area with average values of wave height and frequency of 1.43 m and 0.29 Hz, respectively. In these conditions, the drifter showed horizontal and vertical oscillations with peak-to-peak accelerations of 0.8 g and power spectra centered around 1.5 Hz and 1 Hz, respectively. As a result, the KEH generated a mean output power of 0.18 mW, with peaks of 2.5 mW.

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Design and Testing of a Kinetic Energy Harvester Embedded Into an Oceanic Drifter

In this paper, analytical modeling of passive rectifying circuits and the harvesting of electromagnetic (EM) power from intentionally generated as well as from ubiquitous sources are presented. The presented model is based on the linearization of rectifying circuits. The model provides an accurate method of determining the output characteristics of rectifying circuits. The model was verified with Advance Design System (ADS) Harmonic balance (HB) simulations and measurements. The results from the presented model were in agreement with simulations and measurements. Consequently design considerations and trade-off of radio frequency (RF) harvesters are discussed. To verify the exploitation of ambient RF power sources for operation of sensors, a dual-band antenna with a size of ~λ/4 at 900MHz and a passive dual-band rectifier that is able to power a commercial Thermo-Hygrometer requiring ~1.3V and 0.5MΩ from a global system for mobile communications (GSM) base station is demonstrated. The RF power delivered by the receiving dual-band antenna at a distance of about 110 m from the GSM base station ranges from -27 dBm to -50 dBm from the various GSM frequency bands. Additionally, wireless range measurements of the RF harvesters in the industrial, scientific and medical (ISM) band 868MHz is presented at indoor conditions.

Analysis of Passive RF-DC Power Rectification and Harvesting Wireless RF Energy for Micro-watt Sensors

In self-powered microsystems, a power management is essential to extract, transfer and regulate power from energy harvesting sources to loads such as sensors. The challenge is to consider all of the different structures and components available and build the optimal power management on a microscale. The purpose of this paper is to streamline the design process by creating a novel reconfigurable testbed called Medlay. First, we propose a uniform interface for management functions e.g., power conversion, energy storing and power routing. This interface results in a clear layout because power and status pins are strictly separated, and inputs and outputs have fixed positions. Medlay is the ready-to-use and open-hardware platform based on the interface. It consists of a base board and small modules incorporating e.g., dc-dc converters, power switches and supercapacitors. Measurements confirm that Medlay represents a system on one circuit board, as parasitic effects of the interconnections are negligible. The versatility regarding different setups on the testbed is determined to over 250,000 combinations by layout graph grammar. Lastly, we underline the applicability by recreating three state-of-the-art systems with the testbed. In conclusion, Medlay facilitates building and testing power management in a very compact, clear and extensible fashion.

Medlay: A Reconfigurable Micro-Power Management to Investigate Self-Powered Systems.

Our aim of research is to understand and to improve the power supply of energy-harvesting powered systems by means of finding the optimal energy management. In this paper we (1) propose a general energy management structure, (2) present a modular platform concept to realize various configurations of energy management, and (3) characterize management modules and prove the feasibility of the construction kit. The energy management components investigated are dc-dc converters, energy-supervisors, super capacitors and a dummy loads. The results show that all modules work properly and that interconnections has a negligible effect. Our tool offers a new approach to thoroughly investigate energy managements.

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1.4.1 - Development and Evaluation of a Modular Energy Management Construction Kit

Micro-Power Management (μPM) is essential to supply power to autarkic sensor nodes from energy harvesting sources. As there are numerous ways to realize a μPM, the question arises of how to benchmark different managements under reproducible boundary conditions. In this paper we present these conditions for solar harvesting. Further, we propose a system efficiency definition, which is applicable to all self-powered systems. For verification, we use our modular construction kit, which is used to set up four different μPM configurations. We examined the interplay of state-of-the-art power converters with a supercapacitor array. As one result, the improvement of using a buck converter compared to an LDO was quantified by an increase of 10 percentage points in the system efficiency. The experiments show that the modular setup and the boundary conditions are suitable for such investigations.

https://iopscience.iop.org/article/10.1088/1742-6596/773/1/012042/pdf

Evaluating Micro-Power Management of Solar Energy Harvesting using a Novel Modular Platform

Development and Evaluation of a Modular Energy Management Construction Kit Modulare Konfigurier- und Testplattform für die Untersuchung des Energiemanagements in selbsversorgten Anwendungen

Tobias Beckedahl

Papers

Analysis of Passive RF-DC Power Rectification and Harvesting Wireless RF Energy for Micro-watt Sensors

Medlay: A Reconfigurable Micro-Power Management to Investigate Self-Powered Systems.

1.4.1 - Development and Evaluation of a Modular Energy Management Construction Kit

Evaluating Micro-Power Management of Solar Energy Harvesting using a Novel Modular Platform

Development and Evaluation of a Modular Energy Management Construction Kit Modulare Konfigurier- und Testplattform für die Untersuchung des Energiemanagements in selbsversorgten Anwendungen