Double smart energy harvesting system for self-powered industrial IoT

312 p. 335 p. (confidencial)Future factories would be based on the Industry 4.0 paradigm. IndustrialInternet of Things (IIoT) represent a part of the solution in this field. Asautonomous systems, powering challenges could be solved using energy harvestingtechnology. The present thesis work combines two alternatives of energy input andmanagement on a single architecture. A mini-reactor and an indoor photovoltaiccell as energy harvesters and a double power manager with AC/DC and DC/DCconverters controlled by a low power single controller. Furthermore, theaforementioned energy management is improved with artificial intelligencetechniques, which allows a smart and optimal energy management. Besides, theharvested energy is going to be stored in a low power supercapacitor. The workconcludes with the integration of these solutions making IIoT self-powered devices.IK4 Teknike

Multiple-input multiple-output energy processing for energy-harvesting applications

This project belongs to energy harvesting field, which is a method of collecting energy from the environment to power small devices. This type of energy use is growing exponentially due to the appearance of many of these devices (sensors, wearables...). The objective of this project is to design and implement an ultra-low-power boost converter, designed for energy harvesting applications, which is able to add different types of energy coming from the environment to charge a battery or to feed another electronic device. It is a very innovative project and therefore, the methodology used has contemplated a lot of time for studying, doing simulations, optimizing and testing a prototype. This has allowed us to carry out a study of great value and usefulness which establishes the basis to construct a device that adds energies of our surroundings. Finally, to verify the feasibility of the application, a two-input boost converter is built to add energy coming from two different sources (with the possibility of expanding this number) and also offers different types of output storage elements. In conclusion, the work has confirmed the possibility of adding energy from our environment and has shown the great potential of the application studied through a functional prototype

Energy Harvesting Techniques for Small Scale Environmentally-Powered Electronic Systems

The continuous advances in integrated circuit fabrication technologies, circuit design, and networking techniques enable the integration of an in-creasing number of functionalities in ever smaller devices. This trend de-termines the multiplication of possible application scenarios for tiny em-bedded systems such as wireless sensors, whose utilization has grown more and more pervasive. However, the operating life time of such sys-tems, when placed in locations not allowing a wired connection to a de-pendable power supply infrastructure, is still heavily limited by the finite capacity of currently available accumulators, whose technology has not improved at the same pace of the electronic systems they supply. Energy harvesting techniques constitute a real solution to power un-tethered computing platforms in this kind of spatially-distributed applica-tions. By converting part of the energy freely available in the surrounding environment to electrical energy, the operating life of the system can be extended considerably, potentially for an unlimited time. In recent years an increasing number of researchers have investigated this possibility. In this dissertation we discuss our results about the study and design of systems capable of harvesting energy from various regenerative sources. We start with the design of an airflow energy harvester, focusing on the optimization of its power generation and efficiency performances, and obtaining superior results with respect to similar works in literature. Then we deal with the improvement of this architecture to implement a fully autonomous vibrational harvester, featuring uncommon in-the-field configuration capabilities. Afterwards we investigate the applicability of self-powered wireless sensor nodes to heavy duty and agricultural machinery, finding attractive vibration sources capable of providing enough power to sustain remarkable data transmission rates. To address remote monitoring applications with stringent needs in terms of power supply availability, we present a truly flexible multi-source energy harvester, along with a simulation framework expressly developed to anticipate the harvester performance when placed in a specific operating environment. Furthermore, the design strategies allowing energy harvesters to fully exploit the locally generated power can be profitably applied in the field of distributed electricity generation from renewable energy sources, to enhance the self-consumption capabilities of microgeneration systems. Based on this motivation, we finally propose a grid-assisted photovoltaic power supply to improve the self-sustainability of ground-source heat pumps, and analyze original data on the consumption profiles of these systems to assess the effectiveness of the design. Energy harvesting techniques have the potential to enable many cut-ting-edge applications, especially in remote sensing and pervasive computing areas, which can bring innovations in several fields of human activity. In this thesis we contribute tackling some of the numerous open research challenges still hampering the widespread adoption of this technology

Nano-Power Integrated Circuits for Energy Harvesting

The energy harvesting research field has grown considerably in the last decade due to increasing interests in energy autonomous sensing systems, which require smart and efficient interfaces for extracting power from energy source and power management (PM) circuits. This thesis investigates the design trade-offs for minimizing the intrinsic power of PM circuits, in order to allow operation with very weak energy sources. For validation purposes, three different integrated power converter and PM circuits for energy harvesting applications are presented. They have been designed for nano-power operations and single-source converters can operate with input power lower than 1 μW. The first IC is a buck-boost converter for piezoelectric transducers (PZ) implementing Synchronous Electrical Charge Extraction (SECE), a non-linear energy extraction technique. Moreover, Residual Charge Inversion technique is exploited for extracting energy from PZ with weak and irregular excitations (i.e. lower voltage), and the implemented PM policy, named Two-Way Energy Storage, considerably reduces the start-up time of the converter, improving the overall conversion efficiency. The second proposed IC is a general-purpose buck-boost converter for low-voltage DC energy sources, up to 2.5 V. An ultra-low-power MPPT circuit has been designed in order to track variations of source power. Furthermore, a capacitive boost circuit has been included, allowing the converter start-up from a source voltage VDC0 = 223 mV. A nano-power programmable linear regulator is also included in order to provide a stable voltage to the load. The third IC implements an heterogeneous multisource buck-boost converter. It provides up to 9 independent input channels, of which 5 are specific for PZ (with SECE) and 4 for DC energy sources with MPPT. The inductor is shared among channels and an arbiter, designed with asynchronous logic to reduce the energy consumption, avoids simultaneous access to the buck-boost core, with a dynamic schedule based on source priority

Power Management ICs for Internet of Things, Energy Harvesting and Biomedical Devices

This dissertation focuses on the power management unit (PMU) and integrated circuits (ICs) for the internet of things (IoT), energy harvesting and biomedical devices. Three monolithic power harvesting methods are studied for different challenges of smart nodes of IoT networks. Firstly, we propose that an impedance tuning approach is implemented with a capacitor value modulation to eliminate the quiescent power consumption. Secondly, we develop a hill-climbing MPPT mechanism that reuses and processes the information of the hysteresis controller in the time-domain and is free of power hungry analog circuits. Furthermore, the typical power-performance tradeoff of the hysteresis controller is solved by a self-triggered one-shot mechanism. Thus, the output regulation achieves high-performance and yet low-power operations as low as 12 µW. Thirdly, we introduce a reconfigurable charge pump to provide the hybrid conversion ratios (CRs) as 1⅓× up to 8× for minimizing the charge redistribution loss. The reconfigurable feature also dynamically tunes to maximum power point tracking (MPPT) with the frequency modulation, resulting in a two-dimensional MPPT. Therefore, the voltage conversion efficiency (VCE) and the power conversion efficiency (PCE) are enhanced and flattened across a wide harvesting range as 0.45 to 3 V. In a conclusion, we successfully develop an energy harvesting method for the IoT smart nodes with lower cost, smaller size, higher conversion efficiency, and better applicability. For the biomedical devices, this dissertation presents a novel cost-effective automatic resonance tracking method with maximum power transfer (MPT) for piezoelectric transducers (PT). The proposed tracking method is based on a band-pass filter (BPF) oscillator, exploiting the PT’s intrinsic resonance point through a sensing bridge. It guarantees automatic resonance tracking and maximum electrical power converted into mechanical motion regardless of process variations and environmental interferences. Thus, the proposed BPF oscillator-based scheme was designed for an ultrasonic vessel sealing and dissecting (UVSD) system. The sealing and dissecting functions were verified experimentally in chicken tissue and glycerin. Furthermore, a combined sensing scheme circuit allows multiple surgical tissue debulking, vessel sealer and dissector (VSD) technologies to operate from the same sensing scheme board. Its advantage is that a single driver controller could be used for both systems simplifying the complexity and design cost. In a conclusion, we successfully develop an ultrasonic scalpel to replace the other electrosurgical counterparts and the conventional scalpels with lower cost and better functionality

Pico-grid: Multiple Multitype Energy Harvesting System

This thesis focuses on the development of a low power energy harvesting system specifically targeted for wireless sensor nodes (WSN) and wireless body area network (WBAN) applications. The idea for the system is derived from the operation of a micro-grid and therefore is termed as a pico-grid and it is capable of simultaneously delivering power from multiple and multitype energy harvesters to the load at the same time, through the proposed parallel load sharing mechanism achieved by a voltage droop control method. Solar panels and thermoelectric generator (TEG) are demonstrated as the main energy harvesters for the system. Since the magnitude of the output power of the harvesters is time-varying, the droop gain in the droop feedback circuitry should be designed to be dynamic and self-adjusted according to this variation. This ensures that the maximum power is capable to be delivered to the load at all times. To achieve this, the droop gain is integrated with a light dependent resistor (LDR) and thermistor whose resistance varies with the magnitude of the source of energy for the solar panel and TEG, respectively. The experimental results demonstrate a successful variation droop mechanism and all connected sources are able to share equal load demands between them, with a maximum load sharing error of 5 %. The same mechanism is also demonstrated to work for maximum power point tracking (MPPT) functionality. This concept can potentially be extended to any other types of energy harvester. The integration of energy storage elements becomes a necessity in the pico-grid, in order to support the intermittent and sporadic nature of the output power for the harvesters. A rechargeable battery and supercapacitor are integrated in the system, and each is accurately designed to be charged when the loading in the system is low and discharged when the loading in the system is high. The dc bus voltage which indicates the magnitude of the loading in the system is utilised as the signal for the desired mode of operation. The constructed system demonstrates a successful operation of charging and discharging at specific levels of loading in the system. The system is then integrated and the first wearable prototype of the pico-grid is built and tested. A successful operation of the prototype is demonstrated and the load demand is shared equally between the source converters and energy storage. Furthermore, the pico-grid is shown to possess an inherent plug-and-play capability for the source and load converters. Few recommendations are presented in order to further improve the feasibility and reliability of the prototype for real world applications. Next, due to the opportunity of working with a new semiconductor compound and accessibility to the fabrication facilities, a ZnON thin film diode is fabricated and intended to be implemented as a flexible rectifier circuit. The fabrication process can be done at low temperature, hence opening up the possibility of depositing the device on a flexible substrate. From the temperature dependent I-V measurements, a novel method of extracting important parameters such as ideality factor, barrier height, and series resistance of the diode based on a curve fitting method is proposed. It is determined that the ideality factor of the fabricated diode is high (> 2 at RT), due to the existence of other transport mechanism apart from thermionic emission that dominates the conduction process at lower temperature. It is concluded that the high series resistance of the fabricated diode (3.8 kΩ at RT) would mainly hinder the performance of the diode in a rectifier circuit.Yayasan Khazanah & Cambridge Trus

Piezoelectric Energy Harvesting: Enhancing Power Output by Device Optimisation and Circuit Techniques

Energy harvesting; that is, harvesting small amounts of energy from environmental sources such as solar, air flow or vibrations using small-scale (≈1cm 3 ) devices, offers the prospect of powering portable electronic devices such as GPS receivers and mobile phones, and sensing devices used in remote applications: wireless sensor nodes, without the use of batteries. Numerous studies have shown that power densities of energy harvesting devices can be hundreds of µW; however the literature also reveals that power requirements of many electronic devices are in the mW range. Therefore, a key challenge for the successful deployment of energy harvesting technology remains, in many cases, the provision of adequate power. This thesis aims to address this challenge by investigating two methods of enhancing the power output of a piezoelectric-based vibration energy harvesting device. Cont/d

A POWER DISTRIBUTION SYSTEM BUILT FOR A VARIETY OF UNATTENDED ELECTRONICS

A power distribution system (PDS) delivers electrical power to a load safely and effectively in a pre-determined format. Here format refers to necessary voltages, current levels and time variation of either as required by the empowered system. This formatting is usually referred as "conditioning". The research reported in this dissertation presents a complete system focusing on low power energy harvesting, conditioning, storage and regulation. Energy harvesting is a process by which ambient energy present in the environment is captured and converted to electrical energy. In recent years, it has become a prominent research area in multiple disciplines. Several energy harvesting schemes have been exploited in the literature, including solar energy, mechanic energy, radio frequency (RF) energy, thermal energy, electromagnetic energy, biochemical energy, radioactive energy and so on. Different from the large scale energy generation, energy harvesting typically operates in milli-watts or even micro-watts power levels. Almost all energy harvesting schemes require stages of power conditioning and intermediate storage - batteries or capacitors that reservoir energy harvested from the environment. Most of the ambient energy fluctuates and is usually weak. The purpose of power conditioning is to adjust the format of the energy to be further used, and intermediate storage smoothes out the impact of the fluctuations on the power delivered to the load. This dissertation reports an end to end power distribution system that integrates different functional blocks including energy harvesting, power conditioning, energy storage, output regulation and system control. We studied and investigated different energy harvesting schemes and the dissertation places emphasis on radio frequency energy harvesting. This approach has proven to be a viable power source for low-power electronics. However, it is still challenging to obtain significant amounts of energy rapidly and efficiently from the ambient. Available RF power is usually very weak, leading to low voltage applied to the electronics. The power delivered to the PDS is hard to utilize or store. This dissertation presents a configuration including a wideband rectenna, a switched capacitor voltage boost converter and a thin film flexible battery cell that can be re-charged at an exceptionally low voltage. We demonstrate that the system is able to harvest energy from a commercially available hand-held communication device at an overall efficiency as high as 7.7 %. Besides the RF energy harvesting block, the whole PDS includes a solar energy harvesting block, a USB recharging block, a customer selection block, two battery arrays, a control block and an output block. The functions of each of the blocks have been tested and verified. The dissertation also studies and investigates several potential applications of this PDS. The applications we exploited include an ultra-low power tunable neural oscillator, wireless sensor networks (WSNs), medical prosthetics and small unmanned aerial vehicles (UAVs). We prove that it is viable to power these potential loads through energy harvesting from multiple sources

Wind-Induced Vibration Energy Harvesting Using Piezoelectric Transducers Coupled with Dynamic Magnification

Flexible cylindrical structures subjected to wind loading experience vibrations from periodic shedding of vortices in their wake. Vibrations become excessive when the natural frequencies of the cylinder coincide with the vortex shedding frequency. In this study, cylinder vibrations are transmitted to a beam inside the structure via dynamic magnifier system. This system amplifies the strain experienced by piezoelectric patches bonded to the beam to maximize the conversion from vibrational energy into electrical energy. Realworld applicability is tested using a wind tunnel to create vortex shedding and comparing the results to finite element modeling that shows the structural vibrational modes. A crucial part of this study is conditioning and storing the harvested energy, focusing on theoretical modeling, design parameter optimization, and experimental validation. The developed system is helpful in designing wind-induced energy harvesters to meet the necessity for novel energy resources