Feasibility study on thermal energy harvesting for low powered electronics in high-voltage substations

Electronic devices combining sensors, wireless communications, and data processing capability allow easing predictive maintenance tasks in many applications. This paper applies this approach in power connectors for high-voltage electrical substations, which are transformed into smart connectors. Such connectors are often linked to tubular aluminum bus bars, whose temperature increases due to the Joule losses generated by the combined effect of the electrical resistance and the electric current. Since the human intervention must be minimized, an energy harvesting system is required to supply the electronics of the smart connectors. To this end, a thermoelectric module (TEM) is used to transform heat power into electrical power. Since the voltage provided by the TEM is very low, a suitable power converter is used to supply the electronics of the smart connector. This work analyzes the effect of the various parameters that affect the power generated by the TEM when placed on a substation bus bar. Experiments have been carried out by placing a TEM with different configurations on different types of bus bars for diverse operating conditions.Peer ReviewedPostprint (published version

A Thermoelectric Energy Harvesting System

Thermoelectric generators (TEGs) and their applications have gained momentum for their ability to use waste thermal energy. More contemporary technology must offer more exceptional energy-efficient applications at a lower cost. New technology must also have an ability to generate electric power through the conversion of wasted heat. The TEG has demonstrated its efficiency and how it can offer increased potential by adding an MPPT algorithm to increase the power flow while decreasing the cost of operation. The limitations can be offset by the use of lower cost manufacturing materials and automated systems in the TEG units. It is also important to note the cost per watt found in using a thermoelectric generator is estimated to be $1/W for an installed device. To achieve this goal, the optimum operating point should be monitored by DC to DC converters. The DC to DC converters should also be driven through a generated pulse using an MPPT algorithm

A 1.1 nW Energy-Harvesting System with 544 pW Quiescent Power for Next-Generation Implants

This paper presents a nW power management unit (PMU) for an autonomous wireless sensor that sustains itself by harvesting energy from the endocochlear potential (EP), the 70-100 mV electrochemical bio-potential inside the mammalian ear. Due to the anatomical constraints inside the inner ear, the total extractable power from the EP is limited close to 1.1-6.25 nW. A nW boost converter is used to increase the input voltage (30-55 mV) to a higher voltage (0.8-1.1 V) usable by CMOS circuits in the sensor. A pW charge pump circuit is used to minimize the leakage in the boost converter. Furthermore, ultralow-power control circuits consisting of digital implementations of input impedance adjustment circuits and zero current switching circuits along with Timer and Reference circuits keep the quiescent power of the PMU down to 544 pW. The designed boost converter achieves a peak power conversion efficiency of 56%. The PMU can sustain itself, and a duty-cyled ultralow-power load while extracting power from the EP of a live guinea pig. The PMU circuits have been implemented on a 0.18- μm CMOS process.Semiconductor Research Corporation. Focus Center for Circuit and System Solutions (C2S2)Interconnect Focus Center (United States. Defense Advanced Research Projects Agency and Semiconductor Research Corporation)National Institutes of Health (U.S.) (Grant K08 DC010419)National Institutes of Health (U.S.) (Grant T32 DC00038)Bertarelli Foundatio

Design of low-voltage integrated step-up oscillators with microtransformers for energy harvesting applications

This paper describes the modeling of startup circuits in battery-less micropower energy harvesting systems and investigates the use of bond wire micromagnetics. The analysis focuses on step-up Meissner oscillators based on magnetic core transformers operating with input voltages down to ≈100 mV, e.g. from thermoelectric generators. As a key point, this paper examines the effect of core losses and leakage inductances on the startup requirements obtained with the classical Barkhausen criterion, and demonstrates the minimum transconductance for oscillations to occur. For validation purposes, a step-up oscillator IC is fabricated in a STMicroelectronics 0.32 μm technology, and connected to two bond-wire microtransformers, respectively, with a 1:38 MnZn ferrite core and with a 1:52 ferromagnetic low-temperature co-fired ceramic (LTCC) core. Coherently with the proposed model, experimental measurements show a minimum startup voltage of 228 mV for the MnZn ferrite core and of 104 mV for the LTCC core

Smart energy management and conversion

This chapter introduced power management circuits and energy storage unit designs for sub‐1 mW low power energy harvesting technologies, including indoor light energy harvesting, thermoelectric energy harvesting and vibration energy harvesting. The solutions address several of the problems associated with energy harvesting, power management and storage issues including low voltage operation, self‐start, efficiency (conversion efficiency as well as impact of power consumption of the power management circuit itself), energy density and leakage current levels. Additionally, efforts to miniaturize and integrate magnetic parts as well as integrate discrete circuits onto silicon are outlined to offer improvements in cost, size and efficiency. Finally initial results from efforts to improve energy density of storage devices using nanomaterials are introduced

A 32 mV/69 mV input voltage booster based on a piezoelectric transformer for energy harvesting applications

This paper presents a novel method for battery-less circuit start-up from ultra-low voltage energy harvesting sources. The approach proposes for the first time the use of a Piezoelectric Transformer (PT) as the key component of a step-up oscillator. The proposed oscillator circuit is first modelled from a theoretical point of view and then validated experimentally with a commercial PT. The minimum achieved start-up voltage is about 69 mV, with no need for any external magnetic component. Hence, the presented system is compatible with the typical output voltages of thermoelectric generators (TEGs). Oscillation is achieved through a positive feedback coupling the PT with an inverter stage made up of JFETs. All the used components are in perspective compatible with microelectronic and MEMS technologies. In addition, in case the use of a ∼40 μH inductor is acceptable, the minimum start-up voltage becomes as low as about 32 mV

Development of the future generation of smart high voltage connectors and related components for substations, with energy autonomy and wireless data transmission capability

The increased dependency on electricity of modern society, makes reliability of power transmission systems a key point. This goal can be achieved by continuously monitoring power grid parameters, so possible failure modes can be predicted beforehand. It can be done using existing Information and Communication Technologies (ICT) and Internet of Things (10T) technologies that include instrumentation and wireless communication systems, thus forming a wireless sensor network (WSN). Electrical connectors are among the most critical parts of any electrical system and hence, they can act as nodes of such WSN. Therefore, the fundamental objective of this thesis is the design, development and experimental validation of a self-powered IOT solution for real-time monitoring of the health status of a high-voltage substation connector and related components of the electrical substation. This new family of power connectors is called SmartConnector and incorporates a thermal energy harvesting system powering a microcontroller that controls a transmitter and several electronic sensors to measure the temperature, current and the electrical contact resistance (ECR) of the connector. These measurements are sent remotely via a Bluetooth 5 wireless communication module to a local gateway, which further transfers the measured data to a database server for storage as well as further analysis and visualization. By this way, after suitable data processing, the health status of the connector can be available in real-time, allowing different appealing functions, such as assessing the correct installation of the connector, the current health status or its remaining useful life (RUL) in real-time. The same principal can also be used for other components of substation like spacers, insulators, conductors, etc. Hence, to prove universality of this novel approach, a similar strategy is applied to a spacer which is capable of measuring uneven current distribution in three closely placed conductors. This novel IOT device is called as SmartSpacer. Care has to be taken that this technical and scientific development has to be compatible with existing substation bus bars and conductors, and especially to be compatible with the high operating voltages, i.e., from tens to hundreds of kilo-Volts (kV), and with currents in the order of some kilo-pm peres (kA). Although some electrical utilities and manufacturers have progressed in the development of such technologies, including smart meters and smart sensors, electrical device manufacturers such as of substation connectors manufacturers have not yet undertaken the technological advancement required for the development of such a new family of smart components involved in power transmission, which are designed to meet the future needs.La mayor dependencia de la electricidad de la sociedad moderna hace que la fiabilidad de los sistemas de transmisión de energía sea un punto clave. Este objetivo se puede lograr mediante la supervisión continua de los parámetros de la red eléctrica, por lo que los posibles modos de fallo se pueden predecir de antemano. Se puede hacer utilizando las tecnologías existentes de Tecnologías de la Información y la Comunicación (1CT) e Internet de las cosas (lo T) que incluyen sistemas de instrumentación y comunicación inalámbrica, formando así una red de sensores inalámbricos (WSN). Los conectores eléctricos se encuentran entre las partes más críticas de cualquier sistema eléctrico y, por lo tanto, pueden actuar como nodos de dicho VVSN. Por lo tanto, el objetivo fundamental de esta tesis es el diseño, desarrollo y validación experimental de una solución IOT autoalimentada para la supervisión en tiempo real del estado de salud de un conector de subestación de alta tensión y componentes relacionados de la subestación eléctrica. Esta nueva familia de conectores de alimentación se llama SmartConnector e incorpora un sistema de recolección de energía térmica que alimenta un microcontrolador que controla un transmisor y varios sensores electrónicos para medir la temperatura, la corriente y la resistencia del contacto eléctrico (ECR) del conector. Esta nueva familia de conectores de alimentación se llama SmartConnector e incorpora un sistema de recolección de energía térmica que alimenta un microcontrolador que controla un transmisor y varios sensores electrónicos para medir la temperatura, la corriente y la resistencia al contacto eléctrico (ECR) del conector. De esta manera, después del procesamiento de datos adecuado, el estado de salud del conector puede estar disponible en tiempo real, permitiendo diferentes funciones atractivas, como evaluar la correcta instalación del conector, el estado de salud actual o su vida útil restante (RUL) en tiempo real. El mismo principio también se puede utilizar para otros componentes de la subestación como espaciadores, aislantes, conductores, etc. Por lo tanto, para demostrar la universalidad de este enfoque novedoso, se aplica una estrategia similar a un espaciador, que es capaz de medir la distribución de corriente desigual en tres conductores estrechamente situados. Hay que tener cuidado de que este desarrollo técnico y científico tenga que sea compatible con las barras y "busbars" de subestación existentes, y sobre todo para ser compatible con las altas tensiones de funcionamiento, es decir, de decenas a cientos de kilovoltios (kV), y con corrientes en el orden de algunos kilo-Amperes (kA). Aunque algunas empresas eléctricas y fabricantes han progresado en el desarrollo de este tipo de tecnologías, incluidos medidores inteligentes y sensores inteligentes, los fabricantes de dispositivos eléctricos, como los fabricantes de conectores de subestación, aún no han emprendido el avance tecnológico necesario para el desarrollo de una nueva familia de componentes intel

Energy Harvesting and Energy Storage for Wireless and Less-Wired Sensors in Harsh Environments

Engineering requires sensors to control and understand the environment. This is particularly important in harsh environments. The drawbacks, especially in gas turbines is the complexity of installing a wired sensor and the weight of the wires. This makes wireless sensors attractive.A wireless sensor requires a power source for transmission of data. Batteries have previously taken the role of power source for most wireless sensors, but is unfortunately not suitable for all applications. Lately, with energy harvesting and supercapacitors in the picture, sensor applications in high temperature environments, with high power requirements or with long life requirements have the possibility of wireless interface.A supercapacitor can handle higher temperatures, higher power output and can have a cycle life that exceeds batteries by a factor of 10000. The lower energy density and high self-discharge makes it unsuitable to power a wireless sensor without power source. However, connected to an energy harvester converting waste energy into electricity makes this a powerful combination.Energy harvesters thrives in environments where waste energy is plentiful and low conversion efficiencies can be enough to power both the sensor and the transmitter. A thermoelectric harvester is designed and fabricated for the middle to rear part of a gas turbine. The temperature in this region can reach 1600 ◦ C and require extensive cooling. In the cooling channels the wall temperature reach 800-950 ◦ C when the cooling air is 450-600 ◦ C. In this location a thermoelectric harvester will have access to high thermal gradients and active cooling.To harvest the vibrations a piezoelectric energy harvester was built. To harvest enough energy the resonance frequency of the energy harvester is frequency-matched with the high energy vibrations. In many applications these frequencies drift and thus require a broad bandwidth harvester. Simulation and assembly of a broadband coupled piezoelectric energy harvester is presented in the thesis.A piezoelectric harvester require electronics and energy storage to gather enough energy to power up and run a wireless sensor. The thesis covers the fabrication of a high temperature supercapacitor capable of temperatures up to 181 ◦ C

Low-Power Energy Efficient Circuit Techniques for Small IoT Systems

Although the improvement in circuit speed has been limited in recent years, there has been increased focus on the internet of things (IoT) as technology scaling has decreased circuit size, power usage and cost. This trend has led to the development of many small sensor systems with affordable costs and diverse functions, offering people convenient connection with and control over their surroundings. This dissertation discusses the major challenges and their solutions in realizing small IoT systems, focusing on non-digital blocks, such as power converters and analog sensing blocks, which have difficulty in following the traditional scaling trends of digital circuits. To accommodate the limited energy storage and harvesting capacity of small IoT systems, this dissertation presents an energy harvester and voltage regulators with low quiescent power and good efficiency in ultra-low power ranges. Switched-capacitor-based converters with wide-range energy-efficient voltage-controlled oscillators assisted by power-efficient self-oscillating voltage doublers and new cascaded converter topologies for more conversion ratio configurability achieve efficient power conversion down to several nanowatts. To further improve the power efficiency of these systems, analog circuits essential to most wireless IoT systems are also discussed and improved. A capacitance-to-digital sensor interface and a clocked comparator design are improved by their digital-like implementation and operation in phase and frequency domain. Thanks to the removal of large passive elements and complex analog blocks, both designs achieve excellent area reduction while maintaining state-of-art energy efficiencies. Finally, a technique for removing dynamic voltage and temperature variations is presented as smaller circuits in advanced technologies are more vulnerable to these variations. A 2-D simultaneous feedback control using an on-chip oven control locks the supply voltage and temperature of a small on-chip domain and protects circuits in this locked domain from external voltage and temperature changes, demonstrating 0.0066 V/V and 0.013 °C/°C sensitivities to external changes. Simple digital implementation of the sensors and most parts of the control loops allows robust operation within wide voltage and temperature ranges.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/138743/1/wanyeong_1.pd

Contribution to modeling and realization of ultralow voltage oscillators with application to energy harvesting

Orientadores: José Antenor Pomilio, Saulo FincoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Sistemas autônomos como dispositivos implantáveis, redes de sensores sem fio e sistemas embarcados requerem uma fonte de energia usualmente na forma de bateria ou supercapacitor. A miniaturização e a redução do consumo de potência em dispositivos eletrônicos modernos permite o uso de fontes alternativas como forma de estender a vida útil destes sistemas. A energia pode ser fornecida pelo ambiente, na forma de luz solar, vibração, calor ou ondas eletromagnéticas. O processo de captação e adequação desta energia é chamado de extração ou coleta de energia. O desenvolvimento de sistemas de extração de energia envolve desafios. Algumas fontes fornecem apenas dezenas de milivolts ou nanoamperes. Uma abordagem para extrair energia de fontes de baixa tensão é o projeto de osciladores que possam operar nestas condições. Esta área do conhecimento vem sendo objeto de intensa pesquisa. Várias estratégias são utilizadas, e sistemas operando com até 3,5 mV são descritos. Há, contudo um compromisso entre mínima tensão de operação, capacidade de potência e volume/complexidade. O comportamento de osciladores em tensão ultrabaixa é altamente não-linear e dependente dos parâmetros dos dispositivos e condições de operação. Técnicas convencionais são inadequadas para a análise destes circuitos em situação tão extrema. A impossibilidade de prever com precisão aceitável parâmetros como excursão de tensão e frequência de oscilação e a falta de compreensão mais profunda do mecanismo de funcionamento tornam difícil a especificação dos blocos seguintes ao oscilador no sistema de extração de energia. Este trabalho propõe a aplicação do oscilador com acoplamento nas portas como um módulo de extração de energia de tensão ultrabaixa. O comportamento do circuito é tipicamente como multivibrador astável e uma modelagem utilizando a teoria de oscilações não lineares é apresentada, tanto para circuitos com transistores MOS (MOSFETs) como com transistores bipolares (BJTs). A validade do modelo é verificada através de experimentos com protótipos discretos e uma boa concordância é obtida entre a teoria e a prática. A topologia necessita de uma tensão nas bases dos BJTs ou portas de MOSFETs convencionais de forma que a oscilação possa se iniciar. Um novo módulo, chamado de bloco de partida, é proposto que deriva esta tensão de polarização da fonte de alimentação, tornando o circuito independente de uma tensão preexistente. Um modelo linear para este bloco é apresentado e verificado através da caracterização de um protótipo. Experimentos com circuitos discretos utilizando o bloco de partida mostram que os osciladores podem iniciar sua operação com uma tensão única tão baixa quanto 50 mV. Os protótipos com BJTs e MOSFETs foram capazes de fornecer 173 µW e 560 µW para uma alimentação de 100 mV, respectivamente, demonstrando que a topologia pode ser uma alternativa competitiva em termos de desempenho, tensão de operação e complexidade quando comparada a outras já apresentadas na literaturaAbstract: Autonomous systems, such as implanted devices, wireless sensor networks, and embedded systems, require an energy source which is usually in the form of a battery or a supercapacitor. The miniaturization and reduction of power consumption in modern electronic devices enables the use of alternative energy sources as a way of extending the life-span of these systems. The energy can be supplied by the environment, such as sunlight, vibration, heat, or RF waves. The process of extracting and fitting this energy is usually called energy harvesting. The development of energy harvesting systems presents challenges. Some sources can only supply dozens of millivolts or nanoamperes. One approach to harvest the energy of low-voltage sources is by designing oscillators that can operate in these conditions. This knowledge area is subject of intensive research. Many approaches are proposed, and systems operating with voltages as low as 3.5 mV are described. However, there is a tradeoff between minimum operating voltage, power capacity and volume/complexity. The behavior of oscillators at ultralow voltage is very nonlinear and dependent of the device parameters and operational conditions. Conventional techniques are not able to give reasonable results in the analysis of circuits in such extreme levels. The lack of a prediction of parameters like voltage excursion and oscillation frequency with acceptable precision and a deeper understanding of the working mechanism turn difficult the specification of the blocks that follow the oscillator in the energy harvesting system. This work proposes the application of the oscillator with coupling at the gates as an ultralow voltage energy harvesting module. The behavior of the circuit is typically as astable multivibrator and a modeling using the theory of nonlinear oscillations is presented, when applying MOS transistors (MOSFETs) or bipolar junction transistors (BJTs). The validity of the models is verified through experiments with discrete prototypes and good agreement is found between theory and practice. The topology needs a voltage biasing at the bases of the BJTs or gates of the conventional MOSFETs in order it starts oscillating. A new module, called starting block, is proposed that derives this biasing voltage from the voltage source, turning the circuit independent of a preexistent voltage. A linear model for this block is presented and checked by the characterization of a prototype. Experiments with discrete prototypes with the starting block show that the oscillators can start operating with a unique source as low as 50 mV. Prototypes with BJTs and MOSFETs were able to provide 173 µW and 560 µW from a supply of 100 mV, respectively, demonstrating that the proposed topology can be a competitive option regarding performance, operating voltage and complexity when compared with those previously presentedDoutoradoEletrônica, Microeletrônica e OptoeletrônicaDoutor em Engenharia Elétric