Dissertations / Theses on the topic 'Energy Harvesting and Management'

IoT systems have been massively infiltrating our everyday's life for various applications. One of the main constraints inhibiting the further development of these applications is the limited autonomy of present day batteries. Moreover, energy sustainability is a crucial requirement for systems employed in critical mission applications. A widely used approach to increase the autonomy of IoT systems is the use of renewable sources of energy such as solar, wind, heat, and others to power the devices. For instance, one of the most widespread solutions for wireless sensor nodes is the use of solar panels, which can provide reasonable power input. Their efficiency is determined by the panel's material that defines the conversion efficiency. Renewable sources of energy are too erratic to provide complete system reliability unless over-dimensioned. In reality, energy supply is often limited, which causes the need for adaption of the node operational strategy to ensure the functional reliability of the system. However, the unreliable nature of renewable energy causes several challenges, which we address in this work. In particular, this thesis investigates the effect of battery imperfections caused by inner diffusion processes in the battery on the energy harvesting wireless device operation and effective energy-balancing strategies for different scenarios and system types. We propose 1) the transmission strategy, that takes into account the battery properties (leakage, charge recovery, deep discharge, etc.), and reduces the data losses and discharge events; 2) adaptive sampling algorithms, that balances the erratic energy arrivals, validated on the industrial data-logger powered by a solar panel; and 3) energy cooperation in WSN and Smart City contexts. We also focus on critical-mission IoT systems, where the freshness of delivered packets to the monitoring node by the information sources (communication nodes) is the important parameter to be tracked. In this context, we set the objective of age of information minimization taking into account the battery constraints, asymmetry in reliability of information sources, and stability of energy arrivals, that is, the energy harvesting rate. This array of strategies covers a wide range of applications, scenarios, and requirements. For instance, they can be applied to a smart city represented as a large system of interconnected smart services, or a WSN employed for critical mission applications. We demonstrated that the knowledge of battery and environmental characteristics, and the asymmetric properties of a system is beneficial for designing transmission/sensing strategies.
I sistemi IoT si sono massivamenti entrati nella vita quotidiana per varie applicazioni. Uno dei principali vincoli che inibiscono l'ulteriore sviluppo di queste applicazioni è l'autonomia limitata delle batterie attuali. Inoltre, la sostenibilità energetica è un requisito cruciale per i sistemi impiegati in applicazioni mission-critical. Un approccio ampiamente utilizzato per aumentare l'autonomia dei sistemi IoT è l'uso di fonti energetiche rinnovabili come solare, eolico, termico e altri per alimentare i dispositivi. Ad esempio, una delle soluzioni più diffuse per i nodi di sensori wireless è l'uso di pannelli solari, che possono fornire un ragionevole input di energia. La loro efficienza è determinata dal materiale del pannello che definisce l'efficienza di conversione. Le fonti energetiche rinnovabili sono troppo irregolari per garantire la completa affidabilità del sistema se non sovradimensionate. In realtà, l'approvvigionamento energetico è spesso limitato, il che causa la necessità di adattamento della strategia operativa del nodo per garantire l'affidabilità funzionale del sistema. Tuttavia, la natura inaffidabile delle energie rinnovabili provoca diverse sfide, che affrontiamo in questo lavoro. In particolare, questa tesi studia l'effetto delle imperfezioni della batteria causate dai processi di diffusione interna della batteria sul funzionamento del dispositivo wireless per la raccolta di energia e strategie efficaci di bilanciamento dell'energia per diversi scenari e tipi di sistema. Proponiamo 1) la strategia di trasmissione, che tiene conto delle proprietà della batteria (perdite, recupero della carica, scarica profonda, ecc.) E riduce le perdite di dati e gli eventi di scarica; 2) algoritmi di campionamento adattivo, che bilanciano gli arrivi irregolari di energia, validati sul data logger industriale alimentato da un pannello solare; e 3) cooperazione energetica in contesti WSN e Smart City. Ci concentriamo anche su sistemi IoT di missione critica, in cui la freschezza dei pacchetti consegnati al nodo di monitoraggio da parte delle fonti di informazione (nodi di comunicazione) è il parametro importante da tracciare. In questo contesto, fissiamo l'obiettivo dell'età della minimizzazione delle informazioni tenendo conto dei vincoli della batteria, dell'asimmetria nell'affidabilità delle fonti di informazione e della stabilità degli arrivi di energia, ovvero della velocità di raccolta dell'energia. Questa serie di strategie copre una vasta gamma di applicazioni, scenari e requisiti. Ad esempio, possono essere applicati a una città intelligente rappresentata come un grande sistema di servizi intelligenti interconnessi o come WSN impiegato per applicazioni mission-critical. Abbiamo dimostrato che la conoscenza della batteria e delle caratteristiche ambientali e le proprietà asimmetriche di un sistema sono utili per la progettazione di strategie di trasmissione / rilevamento.

Ultra low power wireless sensors and sensor systems are of increasing interest in a variety of applications ranging from structural health monitoring to industrial process control. Electrochemical batteries have thus far remained the primary energy sources for such systems despite the finite associated lifetimes imposed due to limitations associated with energy density. However, certain applications (such as implantable biomedical electronic devices and tire pressure sensors) require the operation of sensors and sensor systems over significant periods of time, where battery usage may be impractical and add cost due to the requirement for periodic re-charging and/or replacement. In order to address this challenge and extend the operational lifetime of wireless sensors, there has been an emerging research interest on harvesting ambient vibration energy. Vibration energy harvesting is a technology that generates electrical energy from ambient kinetic energy. Despite numerous research publications in this field over the past decade, low power density and variable ambient conditions remain as the key limitations of vibration energy harvesting. In terms of the piezoelectric transducers, the open-circuit voltage is usually low, which limits its power while extracted by a full-bridge rectifier. In terms of the interface circuits, most reported circuits are limited by the power efficiency, suitability to real-world vibration conditions and system volume due to large off-chip components required. The research reported in this thesis is focused on increasing power output of piezoelectric transducers and power extraction efficiency of interface circuits. There are five main chapters describing two new design topologies of piezoelectric transducers and three novel active interface circuits implemented with CMOS technology. In order to improve the power output of a piezoelectric transducer, a series connection configuration scheme is proposed, which splits the electrode of a harvester into multiple equal regions connected in series to inherently increase the open-circuit voltage generated by the harvester. This topology passively increases the rectified power while using a full-bridge rectifier. While most of piezoelectric transducers are designed with piezoelectric layers fully covered by electrodes, this thesis proposes a new electrode design topology, which maximizes the raw AC output power of a piezoelectric harvester by finding an optimal electrode coverage. In order to extract power from a piezoelectric harvester, three active interface circuits are proposed in this thesis. The first one improves the conventional SSHI (synchronized switch harvesting on inductor) by employing a startup circuitry to enable the system to start operating under much lower vibration excitation levels. The second one dynamically configures the connection of the two regions of a piezoelectric transducer to increase the operational range and output power under a variety of excitation levels. The third one is a novel SSH architecture which employs capacitors instead of inductors to perform synchronous voltage flip. This new architecture is named as SSHC (synchronized switch harvesting on capacitors) to distinguish from SSHI rectifiers and indicate its inductorless architecture.

his dissertation proposes novel techniques for assigning resources of wireless networks by considering that the coverage radii are small, implying that some power consumption sinks not considered so far shouldnow be introduced, and by considering that the devices are battery-powered terminals provided with energy harvesting capabilities. In this framework, two different configurations in terms of harvesting capabilities are considered. First, we assume that the energy source is external and not controllable, e.g. solar energy. In this context, the proposed design should adapt to the energy that is currently being harvested. We also study the effect of having a finite backhaul connection that links the wireless access network with the core network. On the other hand, we propose a design in which the transmitter feeds actively the receivers with energy by transmitting signals that receivers use for recharging their batteries. In this case, the power transfer design should be carried out jointly with the power control strategy for users that receive information as both procedures, transfer of information and transfer of power, are implemented at the transmitter and make use of a common resource, i.e., power. Apart from techniques for assigning the radio resources, this dissertation develops a procedure for switching on and off base stations. Concerning this, it is important to notice that the traffic profile is not constant throughout the day. This is precisely the feature that can be exploited to define a strategy based on a dynamic selection of the base stations to be switched off when the traffic load is low, without affecting the quality experienced by the users. Thanks to this procedure, we are able to deploy smaller energy harvesting sources and smaller batteries and, thus, to reduce the cost of the network deployment. Finally, we derive some procedures to optimize high level decisions of the network operation in which variables from several layers of the protocol stack are involved. In this context, admission control procedures for deciding which user should be connected to which base station are studied, taking into account information of the average channel information, the current battery levels, etc. A multi-tier multi-cell scenario is assumed in which base stations belonging to different tiers have different capabilities, e.g., transmission power, battery size, end energy harvesting source size. A set of strategies that require different computational complexity are derived for scenarios with different user mobility requirements.
Aquesta tesis doctoral proposa tècniques per assignar els recursos disponibles a les xarxes wireless considerant que els radis de cobertura són petits, el que implica que altres fonts de consum d’energia no considerades fins al moment s’hagin d’introduir dins els dissenys, i considerant que els dispositius estan alimentats amb bateries finites i que tenen a la seva disposició fonts de energy harvesting. En aquest context, es consideren dues configuracions diferents en funció de les capacitats de l’energia harvesting. En primer lloc, s’assumirà que la font d’energia és externa i incontrolable com, per exemple, l’energia solar. Els dissenys proposats han d’adaptar-se a l’energia que s’està recol·lectant en un precís moment. En segon lloc, es proposa un disseny en el qual el transmissor és capaç d’enviar energia als receptors mitjançant senyals de radiofreqüència dissenyats per aquest fi, energia que és utilitzada per recarregar les bateries. A part de tècniques d’assignació de recursos radio, en aquesta tesis doctoral es desenvolupa un procediment dinàmic per apagar i encendre estacions base. És important notar que el perfil de tràfic no és constant al llarg del dia. Aquest és precisament el patró que es pot explotar per definir una estratègia dinàmica per poder decidir quines estaciones base han de ser apagades, tot això sense afectar la qualitat experimentada pels usuaris. Gràcies a aquest procediment, es possible desplegar fonts d'energy harvesting més petites i bateries més petites. Finalment, aquesta tesis doctoral presenta procediments per optimitzar decisions de nivell més alt que afecten directament al funcionament global de la xarxa d’accés. Per prendre aquestes decisions, es fa ús de diverses variables que pertanyen a diferents capes de la pila de protocols. En aquest context, aquesta tesis aborda el disseny de tècniques de control d’admissió d’usuaris a estacions base en entorns amb múltiples estacions base, basant-se amb la informació estadística dels canals, i el nivell actual de les bateries, entre altres. L'escenari considerat està format per múltiples estacions base, on cada estació base pertany a una família amb diferents capacitats, per exemple, potència de transmissió o mida de la bateria. Es deriven un conjunt de tècniques amb diferents costos computacionals que són d'utilitat per a poder aplicar a escenaris amb diferents mobilitats d’usuaris.

The rationale for a telemedicine system is the use of Information and Communications Technology (ICT) for the remote transmission of biomedical data and the remote control of biomedical equipment, in order to improve the provided health service. The integration of Wireless Body Area Networks (WBANs) in telemedicine systems does not only achieve significant improvements in the patient’s healthcare, but also enhances their quality of life. However, the potential benefits provided by these networks are limited by the energy constraints imposed when traditional batteries are used as the power source, since the replacement or recharging of these is not always an easy task. To that end, harvesting energy from the human environment can be a promising solution to the aforementioned problems. In this context, it is important to design efficient energy-aware medium access and resource management schemes to exploit the benefits of energy harvesting while guaranteeing the Quality of Service (QoS) in the network. This dissertation provides a contribution to the design and evaluation of novel solutions focused on energy-aware resource management for WBANs powered by human energy harvesting. In particular, our proposals are oriented to solve the problems caused by the differences in energy levels experienced by nodes due to their power supply by energy harvesting. The main thesis contributions are divided into two parts. The first part presents HEH-BMAC, an energy-aware hybrid-polling Medium Access Control (MAC) protocol for WBANs powered by human energy harvesting. HEH-BMAC is designed to provide medium access taking into account the capabilities of each node with respect to their energy profile. HEH-BMAC combines two types of access mechanisms, i.e., reserved polling access and probabilistic random access, in order to adapt the network operation to the types of human energy harvesting sources. The HEH-BMAC performance in terms of normalized throughput and energy efficiency is assessed by means of extensive computer-based simulations, revealing a good adaptation to potential changes in the energy harvesting rate, packet inter-arrival time and network size. HEH-BMAC has been proven to outperform IEEE 802.15.6 Standard for WBANs in terms of normalized throughput and energy efficiency, as the number of nodes increases under the same conditions of energy harvesting. The second part of the thesis is dedicated to the design and evaluation of PEH-QoS, a Power-QoS control scheme for body nodes powered by energy harvesting. PEH-QoS is designed to use efficiently the harvested energy and ensure that all transmitted packets are useful in a medical context, hence substantially improving the offered QoS. The obtained results show that this scheme efficiently manages the data queue, thus improving the node operation and optimizing the data transmission, and also provides QoS, while maintaining the node in energy neutral operation state.
1. Introducción La razón de ser de un sistema de telemedicina es utilizar las tecnologías de la información y la comunicación (TIC) para la trasmisión remota de datos médicos, y el control de dispositivos biomédicos a distancia, con el objetivo de mejorar el servicio de salud prestado. Con la integración de las redes inalámbricas de área corporal (WBANs, por sus siglas en ingles) en los sistemas de telemedicina, no solamente se podría mejorar significativamente el cuidado de la salud del paciente, sino que también se conseguiría mejorar su calidad de vida. Las WBANs están compuestas por dispositivos médicos destinados a aplicaciones clínicas. Dichos dispositivos son llamados nodos corporales. En la WBAN cada nodo desempeña una importante función relacionada con el tratamiento, diagnostico o monitoreo de la salud del paciente. Los nodos corporales deben ser capaces de realizar sus tareas eficientemente e interaccionar con el cuerpo humano de una forma cómoda e indetectable para el paciente. Para tal fin, dichos nodos deben ser pequeños y ligeros para poder colocarlos dentro o sobre el cuerpo humano. Dichas características están íntimamente relacionadas con el tamaño de la batería y el consumo energético del nodo. La energía de la batería no solamente restringe al nodo en peso y tamaño sino que también lo hace en su periodo de vida, puesto que se trata de una fuente finita. Los problemas impuestos por la dependencia energética a este tipo de fuente de poder limitan los beneficios potenciales de las WBANs. Además, cambiar o recargar la batería no siempre es factible, ya que esto podría poner en riesgo la vida del paciente o causar daños al mismo nodo. La más innovadora y prometedora técnica para solucionar los problemas relacionados a la energía de las baterías es la captación de energía del entorno humano. Usando captadores de energía, un BN podría aprovechar fenómenos físicos o químicos (ejemplo: calor, luz, movimiento, vibraciones, etc.) en el cuerpo humano para convertirlos en energía eléctrica. El proceso de captación de energía entrega pequeñas cantidades de energía y es dependiente de la clase, disponibilidad de la fuente y la localización del nodo en el cuerpo humano. La idea de una WBAN que trabaje en sinergia con el cuerpo humano es sumamente alentadora. Sin embargo, ciertas consideraciones deben ser tomadas en cuenta para mantener un nivel aceptable de calidad de servicio (QoS, por sus siglas en ingles) en una WBAN alimentada por captación de energía. Los requerimientos de QoS son más exigentes en las WBANs en comparación a las tradicionales redes de sensores inalámbricos (WSNs, por sus siglas en ingles). En WBAN, la QoS es una demanda fundamental por lo tanto la maximización del rendimiento, la reducción del retardo y la extensión de la vida de la red son algunos de los principales retos a alcanzar. En redes alimentadas por baterías, el principal propósito del control del acceso al medio (MAC) es el de prolongar la vida de la red. Por otra parte, en redes alimentadas por captación de energía el principal objetivo es maximizar el rendimiento utilizando la energía disponible. Mediante la captación de energía, se podría extender la vida de la red, pero otras métricas de QoS podrían ser degradadas (ejemplo: rendimiento, retardo, pérdida de paquetes de datos, etc.). Esta tesis ofrece una contribución al diseño y evaluación de novedosas soluciones enfocadas a la gestión de recursos, para WBANs alimentadas por captación de energía (HEH-WBANs, por sus siglas en ingles), de una forma energéticamente consciente. En particular, nuestras propuestas están orientadas a resolver los problemas causados por las diferencias en los niveles de energía que experimentan los nodos debido a sus fuentes de captación. Las principales contribuciones de esta tesis se dividen en dos partes. La primera parte presenta HEH-BMAC, un protocolo híbrido, energéticamente consciente, para el control del acceso al medio de los nodos en este tipo de WBANs. HEH-BMAC está diseñada para proporcionar acceso al medio teniendo en cuenta las capacidades de cada nodo con respecto a sus características energéticas. HEH-BMAC combina de forma dinámica dos tipos de mecanismos de acceso, acceso reservado (basado en identificación de usuario) y acceso aleatorio (basado en probabilidad de contención), con el fin de adaptar el funcionamiento de la red a los tipos de fuentes de captación de los nodos. El funcionamiento del protocolo HEH-BMAC, es evaluado a través de extensas simulaciones por ordenador utilizando las métricas de rendimiento normalizado y eficiencia energética. Los resultados obtenidos en estas pruebas, muestran que nuestro protocolo tiene una buena adaptación a cambios potenciales en las velocidades de captación de energía, frecuencia de arribo de los paquetes de datos, y en el tamaño de la red. La segunda parte de la tesis está dedicada al diseño y evaluación de PEH-QoS, un esquema de control de potencia y QoS para nodos corporales que estén alimentados por captación de energía. PEH-QoS está diseñado para el uso eficiente de la energía captada y asegurar que todos los paquetes de datos trasmitidos sean útiles en el contexto médico, por lo tanto mejorando sustancialmente la QoS ofertada. Los resultados obtenidos muestran que este esquema gestiona eficientemente la cola de datos, mejora la operación del nodo, optimiza la trasmisión de datos, y provee QoS, mientras mantienen al nodo en estado de operación neutral. 2. Objetivos La planificación, el desarrollo, y la realización de esta tesis doctoral persiguen el siguiente objetivo: Diseño y desarrollo de soluciones energéticamente eficientes y conscientes, destinadas a la gestión de recursos que garanticen los requisitos de calidad de servicio de las aplicaciones médicas en WBANs alimentadas por captación de energía en el entorno humano. Al lograr el objetivo antes mencionado, esta tesis constituirá una contribución al avance de la WBANs alimentadas por captación de energía en el entorno humano en términos de una gestión eficiente de su energía enfocada en mejor la calidad de servicio. Para afrontar con éxito el objetivo general, los siguientes objetivos específicos tuvieron que ser también cumplidos: 1. Proporcionar un una amplia revisión del estado del arte en las áreas de protocolos MAC para WBANs y en captación de la energía en el entorno humano. 2. Proponer y evaluar un protocolo MAC consciente de la energía, capaz de adaptar el funcionamiento de la red a la naturaleza aleatoria y variable en el tiempo de las fuentes de captación de energía en el entorno humano. 3. Diseñar y desarrollar un esquema de control que permita el uso óptimo de la escasa energía recogida por un nodo corporal alimentado por captación de energía en el cuerpo humano, con el fin de mejorar la calidad de servicio prestados. 4. Evaluar los resultados de nuestras propuestas y compararlos con sistemas estándares de referencia utilizando diferentes métricas de calidad de servicio. 3. Resultados a) HEH-BMAC: HYBRID POLLING MAC PROTOCOL FOR WIRELESS BODY NETWORKS OPERATED BY HUMAN ENERGY HARVESTING. Tomando en cuenta los últimos avances en las áreas de WBANs y en captación de energía, propusimos un protocolo MAC hibrido al cual llamamos HEH-BMAC. HEH-BMAC es un protocolo de acceso al medio, el primero dentro de nuestro conocimiento, diseñado para WBANs alimentadas por captación de energía del entorno humano. La principal característica de HEH-BMAC es que es un protocolo energéticamente consciente en condiciones de captación de energía, ya que el funcionamiento de cada nodo es adaptado dinámicamente dependiendo de su nivel de energía. En particular nuestro protocolo tiene las siguientes características: i) Este ofrece dos niveles de prioridades a través de la combinación de dos mecanismos diferentes de acceso al medio. El primer mecanismo de acceso es el de identificación de usuario (ID-POLLING) para acceso reservado, dicho mecanismo está pensado para nodos con captación de energía predecible (por ejemplo: Generadores piezoeléctricos que aprovechan los latidos del corazón o de los movimientos respiratorios) o nodos con alta prioridad (por ejemplo: Electrocardiógrafo, electroencefalógrafo, etc.). El segundo método de acceso es por probabilidad de contención (PC-ACCESS) para acceso aleatorio, este mecanismo está destinado para nodos alimentados con fuentes de captación de energía no predecible (por ejemplo: generadores termoeléctricos sobre la piel, generadores piezoeléctricos que aprovechan la locomoción humana, etc.) o nodos con prioridad normal (por ejemplo: termómetros, flujo sanguíneo, etc.). ii) Los periodos de tiempo para los accesos al medio, ya sea ID-POLLING o PC-ACCESS, son ajustados dinámicamente de acuerdo a los niveles energéticos de los nodos. Dicha asignación es realizada a través de un algoritmo ejecutado en el nodo corporal coordinador de la red (BNC). El BNC ejecuta el algoritmo DYNAMIC SCHEDULE ALGORITHM, pudiendo de esta forma manejar la comunicación de todos los nodos que forman la WBAN. Dicho algoritmo contrala de manera conjunta ambos tipos de acceso a través de una lista dinámica para los nodos en ID-POLLING y a través de un algoritmo de actualización del valor de umbral para la contención en los nodos en PC-Access. Los nodos en ID-POLLING acceden al medio de forma expedita y los nodos en PC-Access tienen un acceso probabilístico. iii) Al ejecutarse el acceso al medio de forma dinámica, HEH-BMAC permite la adición y remoción de nodos en la WBAN, puesto que la actualización de la lista dinámica y del algoritmo de actualización del valor umbral de contención son ajustados dependiendo de la respuesta de la cantidad de nodos que están funcionando en la red. RESULTADOS 1: Primeramente brindamos un comprensivo estado del arte, además expusimos nuestros criterios de diseño y explicamos detalladamente cómo funciona nuestra propuesta. Las pruebas realizadas a nuestro protocolo MAC fueron simuladas (a través de un simulador que desarrollamos en MATLAB) con diferentes velocidades de captación de energía. Las métricas utilizadas para la evaluación de nuestra propuesta fueron eficiencia energética y rendimiento normalizado. Como resultado de este estudio pudimos comprobar la buena adaptación que posee HEH-BMAC a diferentes condiciones energéticas, tiempos de arribo de datos y flexibilidad al agregar o remover nodos en la red. Las pruebas las realizamos con cuatro diferentes velocidades de trasmisión de datos. Como resultado de esta investigación, realizamos el trabajo: E. Ibarra, A. Antonopoulos, E. Kartsakli and C. Verikoukis., “HEH-BMAC: Hybrid Polling MAC Protocol for Wireless Body Area Networks Operated by Human Energy Harvesting”. Journal of Telecommunication Systems, Modeling, Analysis, Design and Management. Special Issue on: Research Advances in Energy Efficient MAC protocols for WBANs. (Accepted, December 2012). El siguiente paso en nuestro proceso investigativo fue comparar el desempeño de nuestro protocolo HEH-BMAC con el recién publicado (29 de febrero de 2012) protocolo IEEE 802.15.6 es el protocolo de red para redes de sensores corporales del IEEE diseñado para comunicación dentro y fuera del cuerpo humano. Tomando en cuenta que el protocolo de la IEEE 802.15.6. no fue diseñado para trabajar en redes WBANs alimentadas por captación de energía, escogimos un escenario en que ambos protocolos tuvieran suficiente energía para trabajar correctamente. Comparamos dos configuraciones del protocolo acceso CSMA/CA del IEEE con nuestra propuesta HEH-BMAC. La comparación entre ambos protocolos se realizó a través de las métricas rendimiento normalizado y eficiencia energética. RESULTADOS 2: Como resultado de este trabajo comprobamos que nuestro protocolo HEH-BMAC tiene mejor rendimiento normalizado y comportamiento que el del IEEE 802.15.6 en condiciones de captación de energía. Además, nuestro protocolo tiene un nivel alto de eficiencia energética (ver figura 1) cuando se aumentan el número de nodos a la WBANs, en comparación al protocolo de la IEEE 802.15.6. Como resultado de esta investigación, realizamos el trabajo: E. Ibarra, A. Antonopoulos, E. Kartsakli and C. Verikoukis, “Energy Harvesting Aware Hybrid MAC Protocol for WBANs”, IEEE HEALTHCOM 2013, October 2013, Lisbon, Portugal. b) JOINT POWER-QoS CONTROL SCHEME FOR ENERGY HARVESTING BODY SENSOR NODES En este trabajo desarrollamos un esquema de control para los BNs alimentados por captación de energía con el fin de mejorar la calidad de servicio (QoS) prestada por cada nodo. Dicho esquema lo hemos llamado esquema de control PEH-QoS. PEH-QoS está formado por tres sub-módulos que interaccionan entre sí con el objetivo de conseguir el mejor QoS posible. Los sub-módulos que componen dicho esquema son: i. PHAM: POWER-EH AWARE MANAGEMENT SUB-MODULE: El objetivo del mismo es realizar un uso óptimo de la escasa energía recabada. Solo realizando las funciones de detección o de trasmisión cuando se tenga la cantidad suficiente de energía para completar los procesos. Controlando el consumo energético del BN para mantenerlo en un estado de Operación Energéticamente Neutral (Estado ENO). El estado ENO, es definido como una condición en que el nodo gasta menos o igual cantidad de energía que la recolectada del ambiente, manteniendo un rendimiento deseado. ii. DQAC: DATA QUEUE AWARE CONTROL SUB-MODULE: El objetivo de este sub-modulo es de estabilizar la cola de datos en condiciones de captación de energía. El principal función de DQAC es evitar la saturación de la cola de datos y mantener la validez clínica de la información almacenada por medio de la eliminación de paquetes que han perdido relevancia y actualizando la cola de datos. iii. PASS: PACKET AGGREGATOR/SCHEDULING SYSTEM SUB-MODULE: La función de este sub-modulo es la de optimizar cada trasmisión realizada, enviando en cada proceso de comunicación la mayor cantidad de paquetes posibles. Esto se realiza a través de un sistema de agregación de paquetes dependiendo de la energía disponible (PHAM) y del estado de la cola de datos (DQAC). RESULTADOS 3: Comparamos un BN aplicándole nuestra propuesta, con el mismo nodo sin PEH-QoS. Ambos fueron comparados en las mismas condiciones de captación de energía. Como resultado de dicho estudio obtuvimos que nuestro sistema supero sustancialmente al nodo de referencia en cuanto a rendimiento normalizado, eficiencia energética, perdida de paquetes de datos, y retardo promedio end-to-end. Además, gracias a PEH-QoS alcanzo niveles altos de eficiencia en la detección de eventos y en la eficiencia de almacenaje de datos. Como resultado de esta investigación, realizamos el trabajo: E. Ibarra, A. Antonopoulos, E. Kartsakli and C. Verikoukis, “Joint Power-QoS Control Scheme for Energy Harvesting Body Sensor Nodes”, IEEE ICC 2014, June 2014, Sydney, Australia. 4. Discusiones y Conclusiones HEH-BMAC asigna períodos de tiempo, tanto para ID-POLLING y el PC- ACCESS a través del DYNAMIC SCHEDULE ALGORITHM. La distribución del tiempo se llevan a cabo de una manera dinámica, logrando el uso óptimo del medio. Todos los nodos del WBAN son energéticamente conscientes, es decir, tratan de acceder al medio sólo si tienen los paquetes de datos a transmitir y si tienen suficiente energía para terminar con éxito una secuencia de transmisión. La combinación de estos dos modos de acceso y el DYNAMIC SCHEDULE ALGORITHM, no sólo mejora el rendimiento normalizado y la eficiencia de energía del sistema, sino que también permite la adaptación de la red a los cambios en el número de nodos, el tiempo entre llegadas de datos y la tasa en que se capta energía del ambiente. Por último, para completar nuestro estudio de investigación acerca de HEH-BMAC, se comparó el rendimiento normalizado y la eficiencia energética de nuestro protocolo con el protocolo estándar IEEE 802.15.6. En comparación con el estándar IEEE 802.15.6, HEH-BMAC logra una ganancia de hasta un 20% en la eficiencia de energía y hasta un 56% en el rendimiento normalizado. Además, los resultados mostraron que nuestro protocolo puede adaptarse mejor a un aumento potencial en el número de nodos en la red, en comparación con el estándar en las mismas condiciones de captación de energía. El proceso de captación de energía introduce variaciones en los niveles de energía de los BNs (debido principalmente a las características y la disponibilidad de las fuentes que se captarán) que afectan directamente a su funcionamiento, reduciendo su rendimiento y la eficiencia de las tareas realizadas. Pequeñas cantidades de energía que pueden ser captadas del cuerpo humano deben utilizarse de una manera óptima y eficiente para evitar que se desperdicie. PEH-QoS aborda de manera eficiente estos problemas con el fin de mejorar la calidad de servicio proporcionadas. Los resultados obtenidos mostraron que cuando se aplica PEH-QoS, la eficiencia de energía del nodo se incrementa de 0,78 MB / J hasta 39,6 MB / J (≈ 50 veces), mientras la pérdida de paquetes se reduce hasta 0,39% y el promedio de retardo hasta 130 ms. Nuestro enfoque mejora sustancialmente la calidad de servicio prestado, mientras que también logra una mayor eficiencia de detección y de almacenamiento de datos, lo que demuestra que las técnicas basadas en la conciencia de la energía son excelentes herramientas para mejorar el rendimiento de la BN. En conclusión, los dos esquemas propuestos, HEH-BMAC y PEH QoS, han introducido importantes mejoras en el rendimiento del sistema, tanto a nivel de las HEH-WBANs y como de los BNs.

Energy harvesting is identified as a promising alternative solution for powering implantable biosensors. It can completely replace the batteries, which are introducing many limitations, and it enables the development of self-powered implantable biosensors. An interface circuit is necessary to correct for differences in the voltage and power levels provided by an energy harvesting device from one side, and required by biosensor circuits from another. This thesis investigates the available energy harvesting sources within the human body, selects the most suitable one and proposes the power management unit (PMU), which serves as an interface between a harvester and biosensor circuits. The PMU targets the efficient power transfer from the selected source to the implantable biosensor circuits. Based on the investigation of potential energy harvesting sources, a thermoelectric energy harvester is selected. It can provide relatively high power density of 100 μW/cm2 at very low temperature difference available in the human body. Additionally, a thermoelectric energy harvester is miniature, biocompatible, and it has an unlimited lifetime. A power management system architecture for thermoelectric energy harvesters is proposed. The input converter, which is the critical block of the PMU, is implemented as a boost converter with an external inductor. A detailed analysis of all potential losses within the boost converter is conducted to estimate their influence on the conversion efficiency. The analysis showed that the inevitable conduction and switching losses can be reduced by the proper sizing of the converter’s switches and that the synchronization losses can be almost completely eliminated by an efficient control circuit. Additionally, usually neglected dead time losses are proved to have a significant impact in implantable applications, in which they can reduce the efficiency with more than 2%. An ultra low power control circuit for the boost converter is proposed. The control is utilizing zero-current switching (ZCS) and zero-voltage switching (ZVS) techniques to eliminate the synchronization losses and enhance the efficiency of the boost converter. The control circuit consumes an average power of only 620 nW. The boost converter driven by the proposed control achieves the peak efficiency higher than 80% and can operate with harvested power below 5 μW. For high voltage conversion ratios, the proposed boost converter/control combination demonstrates significant efficiency improvement compared to state-of-the-art solutions.

QC 20150413

Thesis (M.S.)--University of California, San Diego, 2009.
Title from first page of PDF file (viewed April 1, 2009). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 90-93).

Energy harvesting from environmental energy sources (e.g., sunlight) or from man-made sources (e.g., RF energy) has been a game-changing paradigm, which enabled the possibility of making the devices in the Internet of Things or wireless sensor networks operate autonomously and with high performance for years or even decades without human intervention. However, an energy harvesting system must be correctly designed to achieve such a goal and therefore the energy management problem has arisen and become a critical aspect to consider in modern wireless networks. In particular, in addition to the hardware (e.g., in terms of circuitry design) and application point of views (e.g., sensor deployment), also the communication protocol perspective must be explicitly taken into account; indeed, the use of the wireless communication interface may play a dominant role in the energy consumption of the devices, and thus must be correctly designed and optimized. This analysis represents the focus of this thesis. Energy harvesting for wireless system has been a very active research topic in the past decade. However, there are still many aspects that have been neglected or not completely analyzed in the literature so far. Our goal is to address and solve some of these new problems using a common stochastic optimization setup based on dynamic programming. In particular, we formulate both the centralized and decentralized optimization problems in an energy harvesting network with multiple devices, and discuss the interrelations between these two schemes; we study the combination of environmental energy harvesting and wireless energy transfer to improve the transmission rate of the network and achieve a balanced situation; we investigate the long-term optimization problem in wireless powered communication networks, in which the receiver supplies wireless energy to the terminal nodes; we deal with the energy storage inefficiencies of the energy harvesting devices, and show that traditional policies may be strongly suboptimal in this context; finally, we investigate how it is possible to increase secrecy in a wireless link where a third malicious party eavesdrops the information transmitted by an energy harvesting node.
Energy harvesting from environmental energy sources (e.g., sunlight) or from man-made sources (e.g., RF energy) has been a game-changing paradigm, which enabled the possibility of making the devices in the Internet of Things or wireless sensor networks operate autonomously and with high performance for years or even decades without human intervention. However, an energy harvesting system must be correctly designed to achieve such a goal and therefore the energy management problem has arisen and become a critical aspect to consider in modern wireless networks. In particular, in addition to the hardware (e.g., in terms of circuitry design) and application point of views (e.g., sensor deployment), also the communication protocol perspective must be explicitly taken into account; indeed, the use of the wireless communication interface may play a dominant role in the energy consumption of the devices, and thus must be correctly designed and optimized. This analysis represents the focus of this thesis. Energy harvesting for wireless system has been a very active research topic in the past decade. However, there are still many aspects that have been neglected or not completely analyzed in the literature so far. Our goal is to address and solve some of these new problems using a common stochastic optimization setup based on dynamic programming. In particular, we formulate both the centralized and decentralized optimization problems in an energy harvesting network with multiple devices, and discuss the interrelations between these two schemes; we study the combination of environmental energy harvesting and wireless energy transfer to improve the transmission rate of the network and achieve a balanced situation; we investigate the long-term optimization problem in wireless powered communication networks, in which the receiver supplies wireless energy to the terminal nodes; we deal with the energy storage inefficiencies of the energy harvesting devices, and show that traditional policies may be strongly suboptimal in this context; finally, we investigate how it is possible to increase secrecy in a wireless link where a third malicious party eavesdrops the information transmitted by an energy harvesting node.

The study and deployment of solar energy conversion systems are justified on many grounds: environmental, economic, geopolitical, and societal. Collectively, these justifications provide a dynamic and compelling backdrop for the continuing narrative of solar energy. The energy conversion efficiency of a solar cell is set by the design of the cell and by the properties of the incident sunlight. Thus in addition to works aimed at improving solar cells directly, are those directed towards shaping the solar spectrum incident on the cell, prior to sunlight absorption. So-called spectral management is distinct from, but closely related to, solar cells. Two such techniques are documented here. The first, luminescent concentration, downshifts energy and concentrates photon flux within a luminophore-doped waveguide. Problems associated with luminescence concentrators are reported, motivating a novel arrangement of the light absorbing centers aimed at ameliorating lossy emission by induced photon anisotropy. We present the first experimentally-realised implementation of the design. The second portion of work concerns triplet-triplet annihilation upconversion (TTA-UC), a means by which sub-band gap photon losses in solar cells can be reduced. We present schemes for tethering TTA-UC absorbers to nanostructured solids in a bid to increase chromophore concentration and UC efficiency. Kinetic studies of these materials are presented. Results show the formation of heterogeneous structures dependent on the chromophore, binding mechanism and scaffold. Solar cell enhancement experiments were used to show the enhancement of a H-passivated a-Si solar cell by a solid-tethered upconverter, producing modest gains in short-circuit current. The action spectrum, a novel photoluminescence technique for measuring TTA-UC efficiency, was measured for two materials, and the results corroborated using rate measurements. The action spectrum is a promising new upconversion characterisation method.

This assignment was given by Nordic Semiconductor. In this project a radio frequency energy harvesting system able to harvest ambient power at 900 MHz (GSM) was simulated and designed. A Villard voltage multiplier, boost converter and power management circuit was implemented for the harvesting system. The intention was to implement a system which would give sufficient output power and voltage to supply a load (nRF52810) at all times. The nRF52810 is a power efficient multi protocol SoC made by Nordic Semiconductor. Since the power harvested by the antenna is of AC power, a recti er was needed. A Villard voltage multiplier was proposed as the most suitable application. It not only recti es the voltage, but the voltage doubles for every stage. A 2-stage Villard voltage multiplier was proposed with the advantage that in theory the output voltage should be four times higher in magnitude than the input voltage. There exists several other ways to boost a voltage, a voltage boost converter was combined with the Villard Voltage multiplier. According to calculations the boost converter should boost the voltage up to 2.3 V. Since the assumed power from the harvesting system may be lower than the power consumed by the load, a power managing circuit was also needed, which would avoid the load to drain the current from the storage element before the voltage level was sufficient. Different solutions for a power management circuit was proposed using different variations of MOSFETs. A real-life design was implemented, but the Villard voltage multiplier gave out a much lower e efficiency than expected from simulations. The output power of the VVM was too low to supply the load (nRF52810).

Energy harvesting is identified as an alternative solution for powering implantable biosensors. It can potentially enable the development of self-powered implants if the harvested energy is properly handled. This development implies that batteries, which impose many limitations, are replaced by miniature harvesting devices. Customized interface circuits are necessary to correct for differences in the voltage and power levels provided by harvesting devices from one side, and required by biosensor circuits from another. This thesis investigates the available harvesting sources within the human body, proposes various methods and techniques for designing power-efficient interfaces, and presents two CMOS implementations of such interfaces. Based on the investigation of suitable sources, this thesis focuses on glucose biofuel cells and thermoelectric harvesters, which provide appropriate performance in terms of power density and lifetime. In order to maximize the efficiency of the power transfer, this thesis undertakes the following steps. First, it performs a detailed analysis of all potential losses within the converter. Second, in relation to the performed analysis, it proposes a design methodology that aims to minimize the sum of losses and the power consumption of the control circuit. Finally, it presents multiple design techniques to further improve the overall efficiency. The combination of the proposed methods and techniques are validated by two highly efficient energy harvesting interfaces. The first implementation, a thermoelectric energy harvesting interface, is based on a single-inductor dual-output boost converter. The measurement results show that it achieves a peak efficiency of 86.6% at 30 μW. The second implementation combines the energy from two sources, glucose biofuel cell and thermoelectric harvester, to accomplish reliable multi-source harvesting. The measurements show that it achieves a peak efficiency of 89.5% when the combined input power is 66 μW.
Energiskörd har identifierats som en alternativ lösning för att driva inplanterbara biosensorer. Det kan potentiellt möjliggöra utveckling av själv-drivna inplanterbara biosensorer. Denna utveckling innebär att batterier, som sätter många begränsningar, ersätts av miniatyriserade energiskördsenheter. Anpassade gränssnittskretsar är nödvändiga för att korrigera för de skillnader i spänning och effektnivå som produceras av de energialstrande enheterna, och de som krävs av biosensorkretsarna. Denna avhandling undersöker de tillgängliga källorna för energiskörd i den mänskliga kroppen, föreslår olika metoder och tekniker för att utforma effektsnåla gränssnitt och presenterar två CMOS-implementeringar av sådana gränssnitt. Baserat på undersökningen av lämpliga energiskördskällor, fokuserar denna avhandling på glukosbiobränsleceller och termoelektriska energiskördare, som har lämpliga prestanda i termer av effektdensitet och livstid. För att maximera effektiviteten hos effektöverföringen innehåller denna avhandling följande steg. Först görs en detaljerad analys av alla potentiella förluster inom boost-omvandlare. Sedan föreslår denna avhandling en designmetodik som syftar till att maximera den totala effektiviteten och effektförbrukningen. Slutligen presenterar den flera designtekniker för att ytterligare förbättra den totala effektiviteten. Kombinationen av de föreslagna metoderna och teknikerna är varierade genom två högeffektiva lågeffekts energigränssnittskretsar. Den första inplementeringen är ett termoelektriskt energiskördsgränssnitt baserat på en induktor, med dubbla utgångsomvandlare. Mätresultaten visar att omvandlaren uppnår en maximal effektivitet av 86.6% vid 30 μW. Det andra genomförandet kombinerar energin från två källor, en glukosbiobränslecell och en termoskördare, för att åstadkomma en tillförlitlig multi-källas energiskördslösning. Mätresultaten visar att omvandlaren uppnår en maximal effektivitet av 89.5% när den kombinerade ineffekten är 66 μW.

QC 20170508

Mi-SoC

Rainwater harvesting (RWH) refers to the collection of rainwater for subsequent on-site use. Rainwater is most often used for non-potable purposes including toilet flushing, laundering, landscape and commercial crop irrigation, industry, fire fighting, air-conditioning, and vehicle-washing. This study evaluates the potential impacts of RWH on residential housing on Virginia Tech campus in southwestern Virginia in regards to potable water offset, energy conservation, stormwater mitigation, carbon emission reduction, and financial savings. Potential rainwater collection was estimated from three simulations used to approximate the maximum, average, and minimum range of annual precipitation. Collected rainwater estimates were used to calculate the impacts on the areas of interest. Cumulatively, the sample buildings can collect 3.4 to 5.3 millions of gallons of rainwater â offsetting potable water use and reducing stormwater by an equivalent amount, save 320 to 1842 kWh of energy, and reduce carbon emissions by 650 to 3650 pounds annually. Cumulative savings for the nine buildings from combined water and energy offsets range between $5751 and $9005 USD, not substantial enough to serve as the sole basis of RWH implementation on campus. A significant advantage of RWH relates to the management and improvement of the Stroubles Creek watershed in which the majority of the campus sits. Additionally, RWH implementation would benefit sustainable initiatives and provide Virginia Tech additional opportunities for conservation incentives and environmental stewardship funding.
Master of Science

The batteries used to power wireless sensor nodes have become a major roadblock for the wide deployment. Harvesting energy from mechanical vibrations using piezoelectric cantilevers provides possible means to recharge the batteries or eliminate them. Raw power harvested from ambient sources should be conditioned and regulated to a desired voltage level before its application to electronic devices. The efficiency and self-powered operation of a power conditioning and management circuit is a key design issue. In this research, we investigate the characteristics of piezoelectric cantilevers and requirements of power conditioning and management circuits. A two-stage conditioning circuit with a rectifier and a DC-DC converter is proposed to match the source impedance dynamically. Several low-power design methods are proposed to reduce power consumption of the circuit including: (i) use of a discontinuous conduction mode (DCM) flyback converter, (ii) constant on-time modulation, and (iii) control of the clock frequency of a microcontroller unit (MCU). The DCM flyback converter behaves as a lossless resistor to match the source impedance for maximum power point tracking (MPPT). The constant on-time modulation lowers the clock frequency of the MCU by more than an order of magnitude, which reduces dynamic power dissipation of the MCU. MPPT is executed by the MCU at intermittent time interval to save power. Experimental results indicate that the proposed system harvests up to 8.4 mW of power under 0.5-g base acceleration using four parallel piezoelectric cantilevers and achieves 72 percent power efficiency. Sources of power losses in the system are analyzed. The diode and the controller (specifically the MCU) are the two major sources for the power loss. In order to further improve the power efficiency, the power conditioning circuit is implemented in a monolithic IC using 0.18-μ­m CMOS process. Synchronous rectifiers instead of diodes are used to reduce the conduction loss. A mixed-signal control circuit is adopted to replace the MCU to realize the MPPT function. Simulation and experimental results verify the DCM operation of the power stage and function of the MPPT circuit. The power consumption of the mixed-signal control circuit is reduced to 16 percent of that of the MCU.
Ph. D.

The massive use of Information and Communications Technology (ICT) is increasing the amount of energy drained by the telecommunication infrastructure and its footprint on the environment. With the advent of the smartphone, mobile traffic is massively growing driven by both the rising number of user subscriptions and an increasing average data volume per subscription. This is putting a lot of pressure on the mobile network operators side, which are enforced to boost their infrastructure capacity by densifying the network with more Base Stations (BSs) and resources, which translates to a growth in the energy consumption and related costs. Hence, any future development in the ICT sector and its infrastructure has definitely to cope with their environmental and economical sustainability, where energy management is essential. In this thesis, we discuss the role of energy in the design of eco-friendly cost-effective sustainable mobile networks and, in particular, we elaborate on the use of Energy Harvesting (EH) hardware as a means to decrease the environmental footprint of the 5G network. Specifically, we investigate energy management strategies in 5G mobile networks with the main goals of: (i) improving the energy balance across base stations and other network elements, (ii) understanding how the energy can be exchanged either among network elements and the electrical grid, and (iii) investigating how renewable energy sources can be utilized within network elements to maximize the utility for the overall network in terms of better performance for the users (e.g., throughput, coverage, etc.), and lower energy consumption (i.e., carbon footprint) for the 5G network infrastructure. Therefore, we address, formulate and solve some of the problems related to the energy management in different scenarios within the 5G mobile network. The main covered topics are: (i) Wireless Energy Transfer where we investigate the tradeoffs involved in the recharging process from base stations to end users; (ii) Energy Cooperation in Mobile Networks where we target deployments featuring BSs with EH capabilities, i.e., equipped with solar panels and energy storage units, that are able to transfer energy among them; (iii) Energy Trading with the Electrical Grid where energy management schemes to diminish the cost incurred in the energy purchases from the electrical grid are pursued; and (iv) Energy Harvesting and Edge Computing Resource Management where EH and Mobile Edge Computing (MEC) paradigms are combined within a multi-operator infrastructure sharing scenario with the goal of maximizing the exploitation of the network resources while decreasing monetary costs. Online learning techniques, such as Gaussian Processes and Machine Learning Neural Networks, and adaptive control tools, like Model Predictive Control, are put together to tackle these challenges with remarkable results in decreasing costs related to energy purchases from the electrical grid and energy efficiency among network elements.

Les Réseaux de Capteurs Sans Fils (RCSFs) sont composés d'une multitude de nœuds, chacun étant capable de réaliser des mesures (température, pression, etc) et de communiquer par radio fréquence. Ces réseaux forment une pierre angulaire de l'Internet des Objets, en étant au cœur de nombreuses applications, par exemple de domotique ou d'agriculture de précision. La limite d'utilisation des RCSFs provient souvent de leurs durées de vie restreintes, les rendant peu intéressants pour des applications nécessitants de longues périodes de fonctionnement en autonomie. En effet, les RCSFs traditionnels sont alimentés par des piles individuelles équipant chaque nœud, et les nœuds sont ainsi condamnés à une durée de vie finie et courte par rapport aux besoins de certaines applications. De plus, changer les piles n'est pas toujours réalisable si le réseau est dense, ou si les nœuds sont déployés dans des environnements les rendant difficile d'accès. Une solution plus prometteuse est d'équiper chaque nœud d'un ou de plusieurs récupérateur(s) d'énergie individuel(s), et ainsi de le rendre capable de s'alimenter exclusivement à partir de l'énergie récoltée dans son environnent. Plusieurs sources d'énergie sont possibles, telles que le vent ou le solaire. Étant donné que les sources d'énergie sont typiquement dynamiques et non contrôlées, ne pas tomber en panne d'alimentation et nécessaire pour garantir un fonctionnement fiable. Comme l'augmentation de la qualité de service engendre souvent une augmentation de la puissance consommée, une solution simple est de configurer la qualité de service au déploiement à une valeur constante suffisamment faible pour éviter la panne d'alimentation. Cependant, cette solution ne permet pas d'exploiter pleinement l'énergie récoltée, et mène ainsi à un gaspillage d'énergie important ainsi qu'à de faibles qualités de service au vu de l'énergie récoltée. Une solution plus efficace est d'adapter dynamiquement la puissance consommée, et donc la qualité de service. Cette adaptation est faite par un composant logiciel appelé gestionnaire d'énergie. Dans cette thèse, deux nouvelles approches pour l'adaptation en ligne sont proposées, l'une s'appuyant sur la théorie du contrôle floue, et l'autre sur l'apprentissage par renforcement. De plus, comme la communication est souvent la tâche la plus énergivore dans les RCSFs, les wake-up receivers sont utilisées dans cette thèse pour réduire le coût des communications. Un modèle analytique générique a été proposé pour étudier différents protocoles de contrôle d'accès au support (Medium Access Control -- MAC), et combiné à des résultats expérimentaux pour évaluer les wake-up receivers. Aussi, un nouveau protocole MAC permettant la sélection opportuniste de relais a été proposé. Enfin, la combinaison des wake-up receivers et de la récolte d'énergie a été étudiée expérimentalement avec un cas pratique
Wireless Sensor Networks (WSNs) are made of multiple sensor devices which measure physical value (e.g. temperature, pressure...) and communicate wirelessly. These networks form a key enabling technology of many Internet of Things (IoT) applications such as smart building and precision farming. The bottleneck of long-term WSN applications is typically the energy. Indeed, traditional WSNs are powered by individual batteries and a significant effort was devoted to maximizing the lifetime of these devices. However, as the batteries can only store a finite amount of energy, the network is still doomed to die, and changing the batteries is not always possible if the network is dense or if the nodes are deployed in a harsh environment. A promising solution is to enable each node to harvest energy directly in its environment, using individual energy harvesters. As most of the energy sources are dynamic and uncontrolled, avoiding power failures of the nodes is critical to enable reliable networks. Increasing the quality of service typically requires increasing the power consumption, and a simple solution is to set the quality of service of the nodes to a constant value low enough to avoid power failures. However, this solution does not fully exploits the available energy and therefore leads to high energy waste and poor quality of service regarding the available environmental energy. A more efficient solution is online adaptation of the node power consumption, which is performed by an energy manager on each node. In this thesis, two new approaches for online adaptation of the nodes energy consumption were proposed, relying on fuzzy control theory and reinforcement learning. Moreover, as communications are typically the most energy consuming task of a WSN node, emerging wake-up receivers were leveraged to reduce the energy cost of communications. A generic analytical framework for evaluating Medium Access Control (MAC) protocols was proposed, and it was combined to experiments to evaluate emerging wake-up receivers. A new opportunistic MAC protocol was also introduced for "on-the-fly" relay selection. Finally wake-up receivers and energy harvesting were combined and experimentally evaluated in a practical use case

Low-frequency vibrations typically occur in many practical structures and systems when in use, for example, in aerospaces and industrial machines. Piezoelectric materials feature compactness, lightweight, high integration potential, and permit to transduce mechanical energy from vibrations into electrical energy. Because of their properties, piezoelectric materials have been receiving growing interest during the last decades as potential vibration- harvested energy generators for the proliferating number of embeddable wireless sensor systems in applications such as structural health monitoring (SHM). The basic idea behind piezoelectric energy harvesting (PEH) powered architectures, or energy harvesting (EH) more in general, is to develop truly “fit and forget” solutions that allow reducing physical installations and burdens to maintenance over battery-powered systems. However, due to the low mechanical energy available under low-frequency conditions and the relatively high power consumption of wireless sensor nodes, PEH from low-frequency vibrations is a challenge that needs to be addressed for the majority of the practical cases. Simply saying, the energy harvested from low-frequency vibrations is not high enough to power wireless sensor nodes or the power consumption of the wireless sensor nodes is higher than the harvested energy. This represents a main barrier to the widespread use of PEH technology at the current state of the development, despite the advantages it may offer. The main contribution of this research work concerns the proposal of a novel EH circuitry, which is based on a whole-system approach, in order to develop enhanced PEH powered wireless sensor nodes, hence to compensate the existing mismatch between harvested and demanded energy. By whole-system approach, it is meant that this work develops an integrated system-of-systems rather than a single EH unit, thus getting closer to the industrial need of a ready- to-use energy-autonomous solution for wireless sensor applications such as SHM. To achieve so, this work introduces: Novel passive interfaces in connection with the piezoelectric harvester that permit to extract more energy from it (i.e., a complex conjugate impedance matching (CCIM) interface, which uses a PC permalloy toroidal coil to achieve a large inductive reactance with a centimetre- scaled size at low frequency; and interfaces for resonant PEH applications, which exploit the harvester‟s displacement to achieve a mechanical amplification of the input force, a magnetic and a mechanical activation of a synchronised switching harvesting on inductor (SSHI) mechanism). A novel power management approach, which permits to minimise the power consumption for conditioning the transduced signal and optimises the flow of the harvested energy towards a custom-developed wireless sensor communication node (WSCN) through a dedicated energy-aware interface (EAI); where the EAI is based on a voltage sensing device across a capacitive energy storage. Theoretical and experimental analyses of the developed systems are carried in connection with resistive loads and the WSCN under excitations of low frequency and strain/acceleration levels typical of two potential energy- autonomous applications, that are: 1) wireless condition monitoring of commercial aircraft wings through non-resonant PEH based on Macro-Fibre Composite (MFC) material bonded to aluminium and composite substrates; and wireless condition monitoring of large industrial machinery through resonant PEH based on a cantilever structure. shown that under similar testing conditions the developed systems feature a performance in comparison with other architectures reported in the literature or currently available on the market. Power levels up to 12.16 mW and 116.6 µW were respectively measured across an optimal resistive load of 66 277 kΩ for an implemented non-resonant MFC energy harvester on aluminium substrate and a resonant cantilever-based structure when no interfaces were added into the circuits. When the WSCN was connected to the harvesters in place of the resistive loads, data transmissions as fast as 0.4 and s were also respectively measured. By use of the implemented passive interfaces, a maximum power enhancement of around 95% and 452% was achieved in the two tested cases and faster data transmissions obtained with a maximum percentage improvement around 36% and 73%, respectively. By the use of the EAI in connection with the WSCN, results have also shown that the overall system‟s power consumption is as low as a few microwatts during non- active modes of operation (i.e., before the WSCN starts data acquisition and transmission to a base station). Through the introduction of the developed interfaces, this research work takes a whole-system approach and brings about the capability to continuously power wireless sensor nodes entirely from vibration-harvested energy in time intervals of a few seconds or fractions of a second once they have been firstly activated. Therefore, such an approach has potential to be used for real-world energy- autonomous applications of SHM.

Although wireless sensor networks have been successfully used for environmental monitoring, one of the major challenges that this technology has been facing is supplying continuous and reliable electrical power during long-term field deployment. Batteries require repetitive visits to the deployment site to replace them once discharged; admittedly, they can be recharged from solar panels, but this only works in open areas where solar radiation is unrestricted. This dissertation introduces a novel approach to design and implement a reliable efficient solar energy harvester to continuously, and autonomously, provide power to wireless sensor nodes for long-term applications. The system uses supercapacitors charged by a solar panel and is designed to reduce power consumption to very low levels. Field tests were conducted for more than a year of continuous operation and under a variety of conditions, including areas under dense foliage. The resulting long-term field data demonstrates the feasibility and sustainability of the harvester system for challenging applications. In addition, we analyzed solar radiation data and supercapacitor charging behavior and showed that the harvester system can operate battery free, running on the power provided by supercapacitors. A battery is included only for backup in case the supercapacitor storage fails. The proposed approach provides continuous power supply to the system thereby significantly minimizing data loss by power failure and the frequency of visits to the deployment sites.

L'avènement de l'Internet des Objets a permis de déployer de nombreux réseaux de capteurs sans-fil. Ces réseaux sont utilisés dans des domaines aussi variés que l'agriculture, l'industrie ou la ville intelligente, où ils permettent d'optimiser finement les processus. Ces appareils sont le plus souvent alimentés par des piles ou batteries, ce qui limite leur autonomie. De plus, il n'est pas toujours possible ou financièrement viable de changer ou recharger les batteries. Une solution possible est d'alimenter ces capteurs en récupérant l'énergie présente dans l'environnement alentour. Ces sources d'énergie sont cependant peu fiables, et le capteur doit être capable d'éviter de vider complètement sa réserve d'énergie. Afin de moduler sa consommation d'énergie, le capteur peut adapter sa qualité de service à ses capacités énergétiques. L'appareil peut ainsi fonctionner en continu sans interruption de service. Cette thèse présente les méthodes utilisées pour la conception d'un capteur entièrement autonome alimenté par récupération d'énergie ambiante, communiquant sur un réseau longue portée LoRa. Afin d'assurer l'alimentation électrique, une carte permettant de récupérer de l'énergie depuis plusieurs sources d'énergie simultanément a été conçue. Un module logiciel de gestion d'énergie a ensuite été développé afin de calculer un budget énergétique que le capteur peut dépenser, et choisir la meilleure manière de dépenser ce budget pour exécuter une ou plusieurs tâches. Ce travail a ainsi permis le développement d'un prototype de produit industriel entièrement autonome en énergie
The advent of the Internet of Things has enabled the roll-out of a multitude of Wireless Sensor Networks. These networks can be used in various fields, such as agriculture, industry or the smart city, where they facilitate fine optimization of processes. These devices are often powered by primary or rechargeable batteries, which limits their battery life. Moreover, it is sometimes not possible or financially viable to change and/or recharge these batteries. A possible solution is to harvest energy from the environment to power these sensors. But these energy sources are unreliable, and the sensor must be able to prevent the complete depletion of its energy storage. In order to adapt its energy consumption, the node can match its quality of service to its energetical capabilities. Thus, the device can continuously operate without any service interruption. This thesis presents the methods used for the conception of a completely autonomous sensor, powered by energy harvesting and communicating through a long range LoRa network. In order to ensure its power supply, a board has been designed to harvest energy from multiple energy sources simultaneously. A power management software module has then been developed to calculate an energy budget the sensor can use, and to choose the best way to spend this budget over one or multiple tasks. This work has enabled the development of an energy autonomous industrial sensor prototype

Utilization of woody biomass for energy is expected to increase rapidly and logging residues are a likely feedstock to meet increased demands. Potentials for increased biomass utilization have created concerns regarding possible impacts of using logging residues for energy. The overall goals of this project were to characterize biomass harvesting operations and to evaluate potential impacts on soil erosion and implementation of Best Management Practices (BMPs) for water quality on biomass harvesting sites. Results indicate that biomass harvesting was integrated into a wide range of logging businesses. Existing biomass harvesting businesses reported total production levels ranging from 6 to 250 loads per week. The majority (98%) of biomass harvesting operations utilized integrated harvesting techniques where roundwood and fuel chips were produced concurrently. Potential erosion rates and BMP implementation scores were evaluated on ten biomass and ten conventional harvest sites in the Piedmont of Virginia. This study of 20 sites found no significant differences in overall estimated erosion rates between biomass harvests (0.7 tons ac-1 yr-1) and conventional harvests (0.8 tons ac-1 yr-1) (p=0.8282). Additionally, there were no significant differences observed in overall BMP implementation scores for biomass (85.2%) and conventional (81.3%) harvests (p=0.5930). A separate, but related study evaluated BMP implementation over a three year period on 88 biomass and 284 conventional harvests in the Piedmont of Virginia. Within the seven logging related BMP categories, only the Streamside Management Zones (SMZs) category had significant differences between biomass (83.1%) and conventional harvests (91.4%) (p=0.0010). Implementation score differences were not caused by insufficient residues for stabilization of bare soil but were apparently the result of operational decisions which resulted in lower implementation of BMPs related to SMZs. Overall, these findings indicate that existing BMPs appear adequate to protect water quality on biomass harvesting operations in the Virginia Piedmont when appropriately implemented.
Ph. D.

The great innovations of the last century have ushered continuous progress in many areas of technology, especially in the form of miniaturization of electronic circuits. This progress shows a trend towards consistent decreases in power requirements due to miniaturization. According to the ITRS and industry leaders, such as Intel, the challenge of managing and providing power efficiency still persist as scaling down of devices continues. A variety of power sources can be used in order to provide power to low power applications. Few of these sources have favorable characteristics and can be designed to deliver maximum power such as the novel mini notched turbine used as a source in this work. The MiNT is a novel device that can be used as a feasible energy source when integrated into a system and evaluated for power delivery as investigated in this work. As part of this system, a maximum power point tracking system provides an applicable solution for capturing enhanced power delivery for an energy harvesting system. However, power efficiency and physical size are adversely affected by the characteristics and environment of many energy harvesting systems and must also be addressed. To address these issues, an analysis of mini notched turbine, a RF rectenna, and an enhanced maximum power point tracking system is presented and verified using simulations and measurements. Furthermore, mini notched energy harvesting system, RF rectenna energy harvesting system, and enhanced maximum power point tracking system are developed and experimental data analyzed. The enhanced maximum power point tracking system uses a resistor emulation technique and particle swarm optimization (PSO) to improve the power efficiency and reduce the physical size. This new innovative design improves the efficiency of optimized power management circuitry up to 7% compared to conventional power management circuits over a wide range of input power and range of emulated resistances, allowing more power to be harvested from small energy harvesting sources and delivering it to the load such as smart sensors. In addition, this is the first IC design to be implemented and tested for the patented mini notched turbine (MiNT) energy harvesting device. Another advantage of the enhanced power management system designed in this work is that the proposed approach can be utilized for extremely small energy sources and because of that the proposed work is valid for low emulated resistances. and systems with low load resistance Overall, through the successful completion of this work, various energy harvesting systems can have the ability to provide enhanced power management as the IC industry continues to progress toward miniaturization of devices and systems.

Die wechselhafte Energiebereitstellung für drahtlose Sensorknoten durch Solarzellen stellt das Energiemanagement dieser Systeme vor große Herausforderungen. Bedingt durch saisonale und kurzfristige Effekte treten kontinuierlich Schwankungen in der Eingangsleistung auf, gleichzeitig soll jedoch eine zuverlässige und konstante Systemfunktion realisiert werden. Um dies miteinander zu vereinbaren, wird ein Modell zur Beschreibung der erwarteten Eingangsleistung aufgestellt, mit welchem der planmäßige Energieverlauf bestimmt werden kann. Dieser kann wiederum mit der realen Eingangsleistung verglichen werden, um den tatsächlichen energetischen Zustand des Sensorknotens zu bestimmen. Daraus lassen sich beispielsweise Entscheidungskriterien für die Steuerung der Energieverteilung oder Betriebszustände ableiten. Im Rahmen der Arbeit werden die physikalischen Hintergründe zur Modellierung der eingehenden Sonnenenergie beschrieben, der Stand der Technik zur Modellierung aufgezeigt und ein Modell als Basis für die weiteren Untersuchungen ausgewählt. Dieses wird auf die stark limitierte Hardware von drahtlosen Sensorknoten angepasst. Die Herausforderungen liegen dabei hauptsächlich in der geringen verfügbaren Rechenleistung, wenig Datenspeicher im System und dem Ziel, möglichst wenig Energie für die Berechnung zu verbrauchen. Im Ergebnis zeigt sich, dass ein angepasstes Modell auf drahtlosen Sensorsystemen umgesetzt werden kann und trotz der starken Limitierungen lauffähig ist. Es wird eine deutliche Verbesserung in der Verteilung der Energie über den Tag ermöglicht, wodurch sich trotz wechselhafter Quelle eine konstante Systemfunktion ergibt. Nebenher wird die Zuverlässigkeit und Ausfallsicherheit erhöht und Überdimensionierungen in Energiespeicher und Solarzelle können verringert werden. Das modellbasierte Energiemanagement stellt somit einen wichtigen Baustein für eine gesicherte Energieversorgung drahtloser Sensorsysteme dar
The volatile energy supply by solar cells for wireless sensor nodes causes vast challenges for the energy management of such systems. Conditioned by seasonal and short time effects, the incoming power continuously varies. Simultaneously a reliable and constant function of the system has to be realized. To reconcile this, a model for the expected incoming solar power has been derived, which enables the estimation of the planned energy curve. This curve can be compared with the real progression of incoming power measured in parallel, to determine the current state of energy of a sensor node. This comparison is used to derive decision criteria for the control of the energy distribution or operating conditions. Within this work, the physical backgrounds for the modelling of the incoming solar energy and the state of the art of modelling solar power are described. A model is chosen as basis for further investigations and adapted to the limited hardware of wireless sensor nodes. The main challenges are the reduced processing power, few data memory in the system and the objective to consume as few energy as possible for the calculation. The results show that an adapted model can be implemented on wireless sensor systems and that it is executable despite the heavy limitations. This enables a distinct improvement of the distribution of energy across the day, which results in a constant systems function, despite the varying incoming power. At the same time the reliability and failure safety are being improved and the oversizing of the solar cell and the storage elements can be reduced. Therefore the model based energy management is an important component for a stable power supply of wireless sensor systems

This work presents an energy system design for wireless sensor networks (WSNs) after applying our design the WSN should theoretically have an infinite lifetime. Energy harvesting sources can provide suitable energy for WSN nodes and reduce their dependence on battery. In this project, an efficient energy harvesting and storage system is proposed. By using (two supercapacitors and four DC/DC converters with step up /step down capabilities) all of them controlled by Microcontroller via switches to consider the best way to save energy to keep the WSN alive as long as possible. The usage of supercapacitors as an energy buffer to supply the sensor components (microcontroller and radio) with energy it needs to work. We could control the energy flow according to a specific voltage levels in supercapacitors to guaranty the full functionality for WSN with minimizing the loss of energy, and that’s leads to long time life for the wireless sensor node WSN. Another important thing we find in our experiment that is the inner leakage of the supercapacitor and how it has a critical effect on how long it can serve our system with energy. This paper contains on two theoretical sections (Part one and part two) which are based on literature reviews, and one experimental section (Part three) based on experimental building the prototype, coding and testing.

The main objectives of this dissertation is to investigate the prospects of embedded thermoelectric devices integrated in a chip package and to develop a design methodology aimed at taking advantage of the on-chip on-demand cooling capabilities of the thermoelectric devices. First a simulation framework is established and validated against experimental results, which helps to study the cooling capabilities of embedded thermoelectric coolers (TEC) in both a transient and steady state. The potential for up to 15°C of total cooling has been shown. The thermal simulation framework allows for rapid assessment of TEC and system level thermal performance. Next, the thesis develops a co-simulation environment that is capable of simulating the thermal and electrical domain and couples them to design intelligent TEC controllers. These controllers are implemented on chip and can leverage the transient cooling capability of the device. The controllers are simulated within the co-simulation environment and their potential to control high power chip events are thoroughly investigated. The system level overheads are considered and discussions on implementation techniques are presented. The co-simulation framework is also extended to allow for simulation of real predictive technology microprocessor cores and their workloads. Finally the thesis implements a fully on-chip autonomous energy system that takes advantage of the TEC in its reverse energy harvesting mode and uses the same device to harvest energy and use the energy to power the on-chip cooling circuit. This increases the overall energy efficiency of the cooler and verifies the TEC control methods.

Although the locomotive of a train is energized, in general, other railcars are not. This prevents commercial rail companies from installing sensor equipment on the railcars. Thus, several different solutions have been proposed to provide energy for commercial railcars. One such solution is a vibration-based energy harvester which can be mounted in the suspension coils of the railcar. The harvester translates the linear motion of the suspension vibration into rotational motion to turn a 3-phase AC generator. When subjected to real-world suspension displacements, the harvester is capable of generating peak energy levels in excess of 70 W, although the average energy harvested is much lower, around 1 W. A battery pack can be used to store the useful energy harvested. However, a power conditioning circuit is required to convert the 3-phase AC energy from the harvester into DC for the battery pack. The power converter should be capable of extracting maximum power from the energy harvester as well as acting as a battery manager. Experimental results with the energy harvester conclude that maximum power can be extracted if the harvester is loaded with 2 . In order to maintain a constant input impedance, the duty cycle of the power converter must be fixed. Conversely, output regulation requires the duty cycle to change dynamically. Consequently, there is a tradeoff between extracting maximum power and prolonging the battery life cycle. The proposed converter design aims to achieve both maximum power transfer and battery protection by automatically switching between control modes. The proposed converter design uses an inverting buck-boost converter operating in discontinuous conduction mode to maintain a constant input impedance through a fixed duty cycle. This constant input impedance mode is used to extract maximum power from the harvester when the battery is not close to fully charged. When the battery is near fully charged, extracting maximum power is not as important and the duty cycle can be controlled to regulate the output. Specifically, one-cycle control is used to regulate the output by monitoring the input voltage and adjusting the duty cycle accordingly. Finally, the converter is designed to shut down once the battery has been fully charged to prevent overcharging. The result is a power converter that extracts maximum power from the energy harvester for as long as possible before battery protection techniques are implemented. Previous related studies are discussed, tradeoffs in converter design are explained in detail, and an experimental prototype is used to confirm operation of the proposed control scheme.
Master of Science

Die wechselhafte Energiebereitstellung für drahtlose Sensorknoten durch Solarzellen stellt das Energiemanagement dieser Systeme vor große Herausforderungen. Bedingt durch saisonale und kurzfristige Effekte treten kontinuierlich Schwankungen in der Eingangsleistung auf, gleichzeitig soll jedoch eine zuverlässige und konstante Systemfunktion realisiert werden. Um dies miteinander zu vereinbaren, wird ein Modell zur Beschreibung der erwarteten Eingangsleistung aufgestellt, mit welchem der planmäßige Energieverlauf bestimmt werden kann. Dieser kann wiederum mit der realen Eingangsleistung verglichen werden, um den tatsächlichen energetischen Zustand des Sensorknotens zu bestimmen. Daraus lassen sich beispielsweise Entscheidungskriterien für die Steuerung der Energieverteilung oder Betriebszustände ableiten. Im Rahmen der Arbeit werden die physikalischen Hintergründe zur Modellierung der eingehenden Sonnenenergie beschrieben, der Stand der Technik zur Modellierung aufgezeigt und ein Modell als Basis für die weiteren Untersuchungen ausgewählt. Dieses wird auf die stark limitierte Hardware von drahtlosen Sensorknoten angepasst. Die Herausforderungen liegen dabei hauptsächlich in der geringen verfügbaren Rechenleistung, wenig Datenspeicher im System und dem Ziel, möglichst wenig Energie für die Berechnung zu verbrauchen. Im Ergebnis zeigt sich, dass ein angepasstes Modell auf drahtlosen Sensorsystemen umgesetzt werden kann und trotz der starken Limitierungen lauffähig ist. Es wird eine deutliche Verbesserung in der Verteilung der Energie über den Tag ermöglicht, wodurch sich trotz wechselhafter Quelle eine konstante Systemfunktion ergibt. Nebenher wird die Zuverlässigkeit und Ausfallsicherheit erhöht und Überdimensionierungen in Energiespeicher und Solarzelle können verringert werden. Das modellbasierte Energiemanagement stellt somit einen wichtigen Baustein für eine gesicherte Energieversorgung drahtloser Sensorsysteme dar.
The volatile energy supply by solar cells for wireless sensor nodes causes vast challenges for the energy management of such systems. Conditioned by seasonal and short time effects, the incoming power continuously varies. Simultaneously a reliable and constant function of the system has to be realized. To reconcile this, a model for the expected incoming solar power has been derived, which enables the estimation of the planned energy curve. This curve can be compared with the real progression of incoming power measured in parallel, to determine the current state of energy of a sensor node. This comparison is used to derive decision criteria for the control of the energy distribution or operating conditions. Within this work, the physical backgrounds for the modelling of the incoming solar energy and the state of the art of modelling solar power are described. A model is chosen as basis for further investigations and adapted to the limited hardware of wireless sensor nodes. The main challenges are the reduced processing power, few data memory in the system and the objective to consume as few energy as possible for the calculation. The results show that an adapted model can be implemented on wireless sensor systems and that it is executable despite the heavy limitations. This enables a distinct improvement of the distribution of energy across the day, which results in a constant systems function, despite the varying incoming power. At the same time the reliability and failure safety are being improved and the oversizing of the solar cell and the storage elements can be reduced. Therefore the model based energy management is an important component for a stable power supply of wireless sensor systems.

Questo elaborato affronta il tema dell’energy harvesting analizzando una serie di nuovi circuiti integrati. I chip verranno confrontati tra loro per studiarne punti forti, peculiarità e utilizzi possibili. Tali dispositivi permettono di lavorare con sorgenti differenti in ingresso (TEG, PV, RF, ecc.) e possiedono buone prestazioni grazie al convertitore boost integrato. Alla fase di studio seguirà la realizzazione del progetto PCB, sfruttando il software Kicad come ambiente di sviluppo, di un circuito per la gestione di micropotenze per applicazioni di energy harvesting a radio frequenza con lo scopo di ottenere un circuito, in cui non è presente il collegamento di una batteria primaria, autosufficiente dal punto di vista energetico. In particolare, il progetto includerà un circuito per la gestione di micropotenze selezionato tra i precedenti, oltre a un circuito esterno e a una rectenna in grado di gestire l’energia a ricevuta dalla sorgente sotto forma di radio-frequenza. Tale energia verrà immagazzinata in elementi di accumulo, in particolare è stato predisposto un supercondensatore a tale scopo. Il circuito realizzato consente di interfacciarsi con due dispositivi, alimentati a tensioni differenti, in uscita. Il progetto vedrà implementato un modulo contenente tutte le predisposizioni disponibili del chip analizzato, in modo tale da rendere possibile il riutilizzo in diverse applicazioni future, apportando semplici modifiche alla configurazione.

Dynamic Spectrum Access (DSA) is now a commonly used spectrum sharing paradigm to mitigate the spectrum shortage problem. DSA technology allows unlicensed secondary users to access the unused frequency bands without interfering with the incumbent users. The key technical challenges in DSA systems lie in spectrum allocation problems and spectrum user's security issues. This thesis mainly focuses on spectrum monitoring technology in spectrum allocation and incumbent users' (IU) privacy issue. Spectrum monitoring is a powerful tool in DSA to help commercial users to access the unused bands. We proposed a crowdsourcing-based unknown IU pattern monitoring scheme that leverages the power of masses of portable mobile devices to reduce the cost of the spectrum monitoring and demonstrate the ability of our system to capture not only the existing spectrum access patterns but also the unknown patterns where no historical spectrum information exist. Due to the energy limit of the battery-based system, we then leverage solar energy harvesting and develop an energy management scheme to support our spectrum monitoring system. We also provide best privacy-protection strategies for both static and mobile IUs in terms of hiding their true location under the detection of Environmental Sensing Capabilities system. In this thesis, the heuristic approach for our mathematical formulations and simulation results are described in detail. The simulation results show our spectrum monitoring system can obtain a high spectrum monitoring coverage and low energy consumption. Our IU privacy scheme provides great protection for IU's location privacy.
Master of Science
Spectrum relates to the radio frequencies allocated to the federal users and commercial users for communication over the airwaves. It is a sovereign asset that is overseen by the government in each country to manage the radio spectrum and issue spectrum licenses. In addition, spectrum bands are utilized for various purposes because different bands have different characteristics. However, the overly crowded US frequency allocation chart shows the scarcity of usable radio frequencies. The actual spectrum usage measurements reflect that multiple prized spectrum bands lay idle at most time and location, which indicates that the spectrum shortage is caused by the spectrum management policies rather than the physical scarcity of available frequencies. Dynamic spectrum access (DSA) was proposed as a new paradigm of spectrum sharing that allows commercial users to access the abundant white spaces in the licensed spectrum bands to mitigate the spectrum shortage problem and increase spectrum utilization. In DSA, two of the key technical challenges lie in how to dynamically allocate the spectrum and how to protect spectrum users’ security. This thesis focuses on the development of two types of mechanisms for addressing the above two challenges: (1) developing efficient spectrum monitoring schemes to help secondary users (SU) to accurately and dynamically access the white space in spectrum allocation and (2) developing privacy preservation schemes for incumbent users (IU) to protect their location privacy. Specifically, we proposed an unknown IU pattern monitoring scheme that leverages the power of masses of portable mobile devices to reduce the cost of common spectrum monitoring systems. We demonstrate that our system can track not only the existing IU spectrum access patterns but also the unknown patterns where no historical spectrum information exists. We then leverage the solar energy harvesting and design energy management scheme to support our spectrum monitoring system. Finally, we provide a strategy for both static and mobile IUs to hide their true location under the monitoring of Environmental Sensing Capabilities systems.

This thesis investigates resource management procedures, within the Multi-access Edge Computi ng (MEC) paradigm, to obtain energy savings and guarantee Quality of Service(QoS) in Mobile Networks (MNs). Here, we enable energy savings within green-aware network apparatuses (i.e., communication and computing facilities) through the application of learning and control techniques, together with energy management procedures (BS sleep mode, VM soft-scaling, tuning of transmission drivers). In this study, we consider the MEC deployment scenarios suggested by ETSI and mobile operators for our system models. Firstly, we investigate energy-saving strategies within a remote site fully powered by only green/renewable energy (solar and wind). Here, we consider a single Base Station (BS) co-located with the MEC server, i.e., the BS is empowered with computing capabilities. To address the energy consumption problem within the remote site, we propose an online algorithm for edge network management. The algorithm make use of a Long Short-Term Memory (LSTM) neural network for estimating the short-term future traffic load and harvested energy, and control theory, specifically the Limited Lookahead Control (LLC) principles, for foresighted optimization. It also make use of energy management procedures, i.e., BS sleep modes and Virtual Machine (VM) soft-scaling (the reduction of computing resources per time instance). To obtain the energy savings and guarantee QoS, per time instance, the algorithm considers the future BS loads, onsite green energy available and then provisions edge network resources based on the learned information. Secondly, we study the energy consumption problem within an environment where BSs are densely-deployed, i.e., similar to an urban or semi-urban scenario. This work extend the energy consumption problem from a single BS case to multiple BSs. Here, each BS is powered by hybrid energy supplies (solar and power grid) and also empowered with computation capabilities (each BS is co-located with a MEC server). Towards edge system management, we propose a controller-based network architecture for managing energy harvesting (EH) BSs empowered with computation capabilities where on/off switching strategies allow BSs and VMs to be dynamically switched on/off, depending on the traffic load and the harvested energy forecast, over a given look-ahead prediction horizon. To solve the energy consumption minimization problem in a distributed manner, the controller partitions the BSs into clusters based on their location; then, for each cluster, it minimizes a cost function capturing the individual communication site energy consumption and the users’ QoS. To manage the communication sites, the controller performs online supervisory control by forecasting the traffic load and the harvested energy using a LSTM neural network, which is utilized within a LLC policy to obtain the system control actions that yield the desired trade-off between energy consumption and QoS. Finally, we investigate the energy consumption problem within a virtualized MEC server placed in proximity to a group of BSs. To address this challenge, we consider a computing-plus-communication energy model, within the MEC paradigm, where we focus on the communication-related energy cost in addition to the energy drained due to computing processes. Towards server management, an online algorithm based on traffic engineering and MEC Location Service is proposed. To obtain the energy savings and QoS guarantee, we jointly launch an optimal number of VMs for computing and transmission drivers coupled with the location-aware traffic routing for real-time data transfers. In order to efficiently provisioned edge system resources, we forecast the server workloads and harvested energy by using a LSTM neural network and the output is then used within the LLC-based algorithm. Our numerical results, obtained through trace-driven simulations, show that the proposed optimization strategies (algorithms) leads to a considerable reduction in the energy consumed by the edge computing and communication facilities, promoting energy self-sustainability within the MN through the use of green energy.

Une grande partie des nouvelles générations d'objets connectés ne pourra se développer que s'il est possible de les rendre entièrement autonomes sur le plan énergétique. Même si l'utilisation de batteries ou de piles résout une partie de ce problème en assurant une autonomie qui peut-être importante avec des coûts relativement faibles, elle introduit non seulement des contraintes de maintenance incompatibles avec certaines applications, mais aussi des problèmes de pollution. La récupération de l'énergie thermique, mécanique, électromagnétique, solaire ou éolienne est une solution très prometteuse. Dans ce cas, la vie de l'objet connecté peut-être prolongée. Cependant, l'énergie récupérée dépend fortement des conditions au voisinage du dispositif et peut donc varier de façon périodique ou aléatoire. Il parait alors important d'adapter le système (mesure et transmission de données) aux contraintes de la récupération d'énergie. L'objectif de la thèse est de proposer une solution de capteur autonome basée sur un système de récupération et de gestion multisources d'énergies (solaire et éolienne) et pouvant-être mis en oeuvre dans différentes classes d'applications IoT. On s'intéresse, dans un premier temps, à la modélisation de la consommation du noeud capteur. Ensuite, on modélise le système de récupération multisources. Puis, on se focalise sur le management de puissance du système autonome. Ce management est basé sur des prédictions de l'énergie disponible et de celle consommée. Enfin, le travail de modélisation et d'optimisation est validé par des expérimentations afin d’avoir un démonstrateur de Capteur Communicant Autonome en Énergie pour les applications IoT
Researchers aim to develop entirely autonomous sensors. By ensuring an important autonomy, the use of batteries solves part of the energy problem with relatively low costs. However, batteries introduce different problems such as maintenance and environmental pollution. Harvesting thermal, mechanical, electromagnetic, solar or wind energy present in the environment is an attractive solution. Using harvested energy from their surroundings, wireless sensor nodes can significantly increase their typical lifetime. Nevertheless, the harvested energy depends on the surrounding conditions of the device and can vary periodically or randomly. It seems important to adapt the system (measurement and data transmission) to the harvesting energy constraints. The thesis objective is to provide an autonomous sensor solution based on a multisources energy harvesting and management system (solar and wind energies), which can be used in different IoT applications. First, we are interested in modeling and optimizing the sensor node energy consumption. Then, the multiple harvesting system is modeled according to the energy needs of the sensor node. Besides, we focus on the power management of the autonomous system. This management part is based on predictions of both available and consumed energies. Finally, the proposed modeling and optimization studies are validated with experimental works in order to develop an Autonomous Communicating Sensor platform for IoT applications

Doctor of Philosophy
Department of Electrical and Computer Engineering
Balasubramaniam Natarajan
In recent years, there has been a rapid expansion in the development and use of low-power, low-cost wireless modules with sensing, computing, and communication functionality. A wireless sensor network (WSN) is a group of these devices networked together wirelessly. Wireless sensor networks have found widespread application in infrastructure, environmental, and human health monitoring, surveillance, and disaster management. While there are many interesting problems within the WSN framework, we address the challenge of energy availability in a WSN tasked with a cooperative objective. We develop approximation algorithms and execute an analysis of concave utility maximization in resource constrained systems. Our analysis motivates a unique algorithm which we apply to resource management in WSNs. We also investigate energy harvesting as a way of improving system lifetime. We then analyze the effect of using these limited and stochastically available communication resources on the convergence of decentralized optimization techniques. The main contributions of this research are: (1) new optimization formulations which explicitly consider the energy states of a WSN executing a cooperative task; (2) several analytical insights regarding the distributed optimization of resource constrained systems; (3) a varied set of algorithmic solutions, some novel to this work and others based on extensions of existing techniques; and (4) an analysis of the effect of using stochastic resources (e.g., energy harvesting) on the performance of decentralized optimization methods. Throughout this work, we apply our developments to distribution estimation and rate maximization. The simulation results obtained help to provide verification of algorithm performance. This research provides valuable intuition concerning the trade-offs between energy-conservation and system performance in WSNs.

La quantité d'énergie disponible dans les batteries et le nombre limité de cycles de recharge compliquent singulièrement la conception de réseaux de capteurs sans fil (WSN) autonomes. La récupération d'énergie dans l'environnement direct des nœuds et un stockage d'énergie à base de supercondensateurs sont aujourd'hui considérés comme solutions potentielles pour atteindre une durée de vie du réseau théoriquement infinie. Un gestionnaire d'énergie (PM pour ''Power Manager'') est embarqué dans chaque nœud afin de permettre un fonctionnement en neutralité énergétique (ENO), ce qui veut dire que les énergies récupérées et consommées par un nœud sont équivalentes sur le long terme. Dans cette thèse, nous proposons de nouveaux PMs qui adaptent dynamiquement l'intervalle de réveil des nœuds en fonction de l'énergie récupérée. La faible complexité de nos PMs, leur indépendance vis-à-vis du type de source d'énergie récupérée et leur faible empreinte mémoire facilitent leur implantation sur une plate-forme réelle de réseaux de capteurs sans fil. Par ailleurs, lorsque l'on considère un réseau multi-sauts, une variation trop fréquente de l'intervalle de réveil peut s'avérer pénalisante pour l'établissement de rendez-vous entre les nœuds et risque de fortement dégrader la qualité de services globale. Nous proposons donc un gestionnaire d'énergie (WVR-PM) qui limite autant que possible ces variations et qui permet d'améliorer le débit de près de 60% par rapport aux PMs de l'état de l'art tout en diminuant de 45% l'énergie consommée par une communication réussie
The limited energy and recharge cycles of batteries are crippling the design of autonomous Wireless Sensor Networks (WSNs). To overcome this issue, everlasting harvested energy and supercapacitor-based energy storage are considered as potential solutions to achieve a theoretically infinite lifetime. A Power Manager (PM) is embedded in each WSN node to respect the Energy Neutral Operation condition (ENO), which means harvested energy is equal to consumed energy for a long period. In this thesis, a set of PMs are proposed for energy harvesting WSN nodes to adapt their average consumed energy by changing the wake-up interval according to the available harvested energy. Our PMs are low complexity, independent of energy sources, small memory footprint and therefore, can be easily implemented on a real EH-WSN node. Another issue addressed in this thesis when considering a multi-hop EH-WSN is the effect of wake-up interval variations to the global QoS. Due to its low harvested energy, a relay node is impractical to synchronize with a transmitter if its wake-up interval regularly changes, therefore degrading the global QoS. A new power manager, named Wake-up Variation Reduction power manager (WVR-PM) is proposed to reduce the variations of the wake-up interval. By using WVR-PM, the throughput of a multi-hop EH-WSN can be improved up to 59% compare to state-of-the-art PMs while the average consumed energy for one successful communication is reduced by 45%

The wireless sensor network (WSN) is increasingly used in many areas nowadays. It can be applied to provide the solutions to environmental problems, help increasing security and safety systems, and make the detection of the problems more efficient, e.g. the earthquake or tidal wave, which will harmful to humans. The WNS is durable and resistant to all types of terrain and climate, but while the WSN system is more and more widespread, one of the obstacles hindering the growth of this technology and the demand for WSN applications is the limited battery lifespan. Consequently, there is a significant requirement for techniques for prolonging the battery’s lifespan. Therefore, one potential solution is to use alternative energy sources combined with the sensor nodes in WSN, specifically energy harvesting from existing environmental sources. This research project reviews the characteristics of each kind of energy harvesting, understanding the various energy sources (solar energy, vibration energy and wind power), including wireless power transfer (WPT) by using electromagnetic (EM) radiation energy transfer or RF radio-frequency emission and magnetic coupled energy transfer. They are adopted for extending node’s life in the WSN, based on published information. Then it compares these diverse alternative energy methods and identifies for the most suitable energy harvesting method for application to wireless sensor nodes in order to prolong the lifespan of the battery. The major findings from the researcher include that wireless power transfer energy harvesting (WPT) using the magnetic field is the most appropriate tool for extending the lifespan of the WSN system. In addition, the author also designed an experiment to test this alternative energy, achieving by modelling the wireless power transfer with four coils. From the experimental results, it can be seen that the WPT technique using energy harvesting with magnetic inductive source can be applied to prolong the lifespan of the WSN system.

Le développement des réseaux de capteurs sans fil (WSN) profite des progrès récents en consommation énergétique dans les systèmes électroniques et des progrès en technologies de récupération d'énergie pour construire des entités de contrôle intelligentes utilisées dans des domaines variés comme la santé ou l'agriculture. Grâce aux consommations toujours plus faibles des circuits de communication radiofréquence, il est possible de créer des réseaux de systèmes de capteurs capables d'extraire des données de l'environnement et de les transmettre à une entité maîtresse. Les durées de vie limitées des batteries sont un frein au développement de tels réseaux pour des raisons de coût et de difficulté de maintenance. Grâce à la récupération d'énergie dans l'environnement, qu'elle soit solaire, thermique ou mécanique, il est alors envisageable d'alimenter un système de capteurs et sa communication sans fil afin d'accroitre l'autonomie globale du réseau. Les travaux réalisés dans le cadre de cette thèse visent à étudier la gestion d'énergie au sein d'un nœud de capteurs communicant sans fil. Grâce à l'utilisation d'une architecture d'alimentation avancée à chemins de puissance multiples, basée notamment sur un chemin direct à haut rendement entre les récupérateurs d'énergie et les charges consommantes, le système peut optimiser son rendement énergétique lorsque l'énergie est récupérée dans l'environnement. Cette architecture d'alimentation requiert néanmoins un contrôle numérique fin afin de déterminer à tout moment le chemin de puissance optimal entre les récupérateurs, les capacités et batterie de stockage, et les charges consommantes. Un contrôleur intégré asynchrone réalise une gestion événementielle de ces chemins de puissance et permet au système d'être robuste face aux variations énergétiques environnementales. Après une modélisation et une analyse des gains de l'architecture avancée de gestion de puissance, un contrôleur événementiel adapté aux systèmes de capteurs communicants est proposé. Ce contrôleur est implémenté en logique asynchrone quasi insensible aux délais (QDI) et offre au système une robustesse intrinsèque forte aux variations environnementales en addition à sa très faible consommation. Un circuit de gestion d'alimentation pour nœud de capteurs communicant est ainsi fabriqué en technologie CMOS 180nm et intègre des innovations tant architecturales que de gestion numérique applicative. Sa consommation globale proche d'1µW permet ainsi la réalisation de systèmes de capteurs fonctionnels pour des applications mettant en jeu des puissances de l'ordre du microwatt, autorisant en conséquence la mise en place de réseaux de capteurs ultra faible consommation
Wireless Sensor Networks (WSN) development leverages recent progress in electronic devices power consumption and in energy harvesting technologies in order to create smart sensing structures useful for improvements in various topics such as health monitoring or farming. Thanks to wireless communication circuits lower power consumption, it becomes possible to create networks of sensing systems capable of extracting information from the environment and of transmitting data through the network to the global intelligence. Because of hard and costly maintenance requirements, limited lifespans batteries are a brake on such networks development. Thanks to environmental energy harvesting on solar, thermal or mechanical sources, a system containing sensors and a wireless communication circuit can be powered. Global energy autonomy is thus improved and the node's life is enhanced. Works done during this PhD aim to study energy management within a sensing wireless communicating node. Thanks to the use of advanced multiple power paths architecture leveraging direct power path between the sources and the power loads, the power management system can optimize its energy efficiency when energy is harvested in the environment. Nevertheless, a precise digital control is mandatory to continuously determine the best power path between the energy harvesters, the energy storing capacitors and batteries, and the power loads. An integrated asynchronous controller implements an event-driven management of the power paths and gives the system robustness to environmental energy variations. After modeling and analyzing the power efficiency gain granted by the advanced architecture, an event-driven controller is proposed to ease implementation of wireless sensing applications. The controller is implemented in asynchronous quasi delay insensitive (QDI) logic and presents high intrinsic robustness to environemental variations while maintaining ultra low power consumption. A power management circuit suited for wireless sensing systems is thus fabricated using 180nm CMOS process and includes both architecture and digital management innovations. Its global power consumption close to 1µW allows considering the creation of wireless sensing nodes running for applications in the range of microwatts, consequently enabling development of ultra low power wireless sensor networks

The objective of this dissertation is to develop task scheduling guidelines and algorithms for wireless sensor nodes that harvest energy from ambient environment and use supercapacitor based storage systems to buffer the harvested energy. This dissertation makes five contributions. First, a physics based equivalent circuit model for supercapacitors is developed. The variable leakage resistance (VLR) model takes into account three mechanisms of supercapacitors: voltage dependency of capacitance, charge redistribution, and self-discharge. Second, the effects of time and supercapacitor initial state on supercapacitor voltage change and energy loss during charge redistribution are investigated. Third, the task scheduling problem in supercapacitor based environmentally powered wireless sensor nodes is studied qualitatively. The impacts of supercapacitor state and energy harvesting on task scheduling are examined. Task scheduling rules are developed. Fourth, the task scheduling problem in supercapacitor based environmentally powered wireless sensor nodes is studied quantitatively. The modified earliest deadline first (MEDF) algorithm is developed to schedule nonpreemptable tasks without precedence constraints. Finally, the modified first in first out (MFIFO) algorithm is proposed to schedule nonpreemptable tasks with precedence constraints. The MEDF and MFIFO algorithms take into account energy constraints of tasks in addition to timing constraints. The MEDF and MFIFO algorithms improve the energy performance and maintain the timing performance of the earliest deadline first (EDF) and first in first out (FIFO) algorithms, respectively.

Significant advances in wind turbine technology have increased the need for maintenance through condition monitoring. Indeed condition monitoring techniques exist and are deployed on wind turbines across Europe and America but are limited in scope. The sensors and monitoring devices used can be very expensive to deploy, further increasing costs within the wind industry. The work outlined in this thesis primarily investigates potential low-cost alternatives in the laboratory environment using vibration-based and modal testing techniques that could be used to monitor the condition of wind turbine blades. The main contributions of this thesis are: (1) the review of vibration-based condition monitoring for changing natural frequency identification; (2) the application of low-cost piezoelectric sounders with proof mass for sensing and measuring vibrations which provide information on structural health; (3) the application of low-cost miniature Micro-Electro-Mechanical Systems (MEMS) accelerometers for detecting and measuring defects in micro wind turbine blades in laboratory experiments; (4) development of an in-service calibration technique for arbitrarily positioned MEMS accelerometers on a medium-sized wind turbine blade. This allowed for easier aligning of coordinate systems and setting the accelerometer calibration values using samples taken over a period of time; (5) laboratory validation of low-cost modal analysis techniques on a medium-sized wind turbine blade; (6) mimicked ice-loading and laboratory measurement of vibration characteristics using MEMS accelerometers on a real wind turbine blade and (7) conceptualisation and systems design of a novel embedded monitoring system that can be installed at manufacture, is self-powered, has signal processing capability and can operate remotely. By applying the conclusions of this work, which demonstrates that low-cost consumer electronics specifically MEMS accelerometers can measure the vibration characteristics of wind turbine blades, the implementation and deployment of these devices can contribute towards reducing the rising costs of condition monitoring within the wind industry.

This thesis entails the design and fabrication of a smartphone charger that is powered by a bicycle dynamo hub. In addition to the design and validation of the charger prototype, this thesis involves the testing and characterization of the dynamo hub power source, the design and construction of specialized test equipment, and the design and prototyping of a handlebar-mounted case for the smartphone and charging electronics. With the intention of making the device a commercial product, price, aesthetics, and marketability are of importance to the design. An appropriate description of the charger circuit is a microcontroller-based energy management system, tailored to meet strict power demands of current smartphones. The system incorporates a switched-mode power supply, lithium polymer battery, microcontroller, and specialized protection circuitry. Prototype testing confirms that the circuit meets the charging requirements of the smartphone at bicycle speeds ranging from 7 miles per hour to as high as 55 miles per hour.

Da substituição da colheita manual de cana queimada pela mecanizada de cana crua, decorre grande demanda por pesquisas relacionadas aos efeitos do palhiço, residual da colheita, sobre a cana soca e sobre o ambiente de produção. O presente trabalho teve por objetivo estudar os efeitos do sistema de colheita e do manejo do palhiço residual sobre o desenvolvimento das soqueiras de cana-de-açúcar e sobre algumas propriedades físicas e químicas do solo. O experimento foi instalado em área de colheita mecanizada de cana-de-açúcar, variedade SP91- 1049, conduzido ao longo do ciclo da primeira soca, delineado em blocos completos casualizados, com quatro repetições e os seguintes quatro tratamentos: palhiço em área total (não manejado); remoção do palhiço de sobre as linhas de cana (desaleiramento); palhiço aleirado; e palhiço queimado. Uma medida mensal de temperatura do solo foi feita até o 9º mês após o corte. A biometria foi feita mensalmente até 8 meses após o corte, avaliando-se o perfilhamento da cana e o crescimento inicial da parte aérea. Próximo ao final do ciclo foram feitas análises químicas de solo e de folhas de cana, análises físicas de solo não deformado, avaliação da distribuição da umidade e do sistema radicular no perfil do solo, e análises tecnológicas de amostras de cana para avaliação da maturação. Por ocasião da colheita, pesou-se a produção. O maior efeito do palhiço sobre a cana-de-açúcar foi reduzir o perfilhamento inicial, sendo que o desaleiramento mostrou-se a forma de manejo do palhiço mais eficaz em mitigar o efeito negativo do mesmo sobre o perfilhamento inicial. O aleiramento, além de ser menos eficaz nesse sentido, induziu um perfilhamento inicial deveras heterogêneo. Quanto às propriedades químicas do solo, o palhiço não causou efeito significativo sobre os teores de MO, CTC, Al e pH; entre os nutrientes, apenas o manganês sofreu efeito significativo dos tratamentos, apresentando menor teor sob palhiço em área total do que onde o palhiço foi queimado. Quanto às propriedades físicas do solo, o palhiço favoreceu uma pequena compactação, indicada por redução da aeração do solo na capacidade de campo; além da redução da temperatura do solo, significativa só nos primeiros 6 meses após o corte. Sobre a distribuição da água no perfil do solo, avaliada no 11º mês após o corte e depois 2 semanas sem chuva, na camada de 0-20 cm a umidade foi significativamente maior sob palhiço em área total do que onde o palhiço foi queimado; e em profundidades maiores não houve diferença significativa devida aos tratamentos. Não obstante, sobre a distribuição do sistema radicular no perfil do solo, os tratamentos não produziram nenhuma diferença significativa.
Replacing the manual harvesting of burnt sugarcane for green sugarcane mechanical harvesting, follows a great demand for research about the effects of straw on sugarcane ratoon and on the production environment. This work aimed to study the effects of the harvest and of straw management on the development of the sugarcane ratoon and on some physical and chemical properties of soil. The experiment was conducted on an area of mechanical harvesting of sugarcane, variety SP91-1049, conducted during the first cycle of ratoon, the experimental design was randomized blocks with four repetitions and the following four treatments: straw in total area; straw removed from the sugarcane lines; with the straw between four lines moved to a ridge between two lines (straw tilling); and burnt straw. Measurements of soil temperature were made monthly, until the 9th month after the harvest. Biometric measurements were performed monthly until 8 months after harvesting, evaluating the sugarcane tillering and the initial growth of the tillers. Near the end of the cycle, chemical analyses of soil and of sugarcane leaves, and physical analyses of not deformed soil samples were performed; the distribution of moisture and of root system into the soil profile were evaluated; and technological analysis of sugarcane samples were made to evaluate the maturity stage of sugarcane. At the harvest, the production was weighed. The biggest effect of straw on sugarcane was reducing the initial tillering, and the removal of straw from sugarcane lines proved to be the more effective management to mitigate the negative effect of straw on the tillering. The straw tilling, less effective in this sense, also induced a very heterogeneous initial tillering. Regarding the soil chemical properties, straw did not cause significant effect on the levels of organic matter, capacity of cations exchange, Al and pH; among the nutrients, only Mn had a significant effect of the treatments, with lower content under straw in total area than where straw was burned. Regarding the physical properties of soil, straw provided a little compaction, indicated by reduction of the soil aeration at field capacity; as well as significant reducing of soil temperature only in the first 6 months after harvest. On the distribution of water in the soil profile, measured 11 months after harvest and after 2 weeks without rain, in the depth of 0 to 20 centimeters, moisture was significantly higher under straw in total area than where straw was burned, and in bigger depths there were no significant difference due to treatments. However, on the distribution of root system in the soil profile, the treatments produced no significant difference.

Ces travaux portent sur la question de l’autonomie énergétiquedes capteurs sans fil dans un contexte aéronautique, à laquelle la récupérationet le stockage d’énergie ambiante sont susceptibles d’apporter uneréponse. Nous étudions dans un premier temps la génération thermoélectrique,destinée à être appliquée au suivi du vieillissement structurelprès de la zone moteur, et débouchant sur la réalisation d’un démonstrateur.Nous proposons ensuite une architecture de stockage capacitif qui,en s’adaptant à son état de charge, vise à améliorer la performance de cettesolution de stockage en termes de temps de démarrage, de taux d’utilisationd’énergie et sous certaines conditions, de transfert d’énergie. Finalement,nous rapportons les résultats d’une étude prospective sur la récupérationd’énergie du vent relatif grâce au phénomène aéroacoustique. Nousmontrons que cette méthode présente un potentiel énergétique intéressant,puis nous présentons la conception et la réalisation d’un circuit optimiséde gestion de l’énergie, permettant d’alimenter grâce à cette technique uncapteur sans fil de température
This work adresses the issue of energy autonomy within wirelesssensor networks embedded in aircrafts, which may be solved throughambient energy harvesting and storage. In a first study, we develop a demonstratorbased on thermal gradients energy harvesting, which is designedto supply power to a structural health monitoring system implementednear the engine zone. Thereafter, we introduce a capacitive storagearchitecture which self-adapts to its own state of charge, aiming at improvingits performance in terms of startup time, the energy utilization ratioand under some conditions, the energy transfer. Finally, we report the resultsof a prospective study on aeroacoustic energy harvesting appliedto the relative wind. It is shown that this method exhibits an interestingpotential in terms of generated power, then we introduce the design andthe realization of an optimized energy management circuit, allowing ourtechnique to supply power to a wireless temperature sensor

Augmenter la durée de vie d'une pile, voire s'en passer est aujourd'hui devenu une obligation pour les microsystèmes. En effet, à cette échelle, le remplacement des piles et leur rejet dans l'environnement sont problématiques. La voie préconisée pour répondre à cet enjeu est d'utiliser des sources d'énergie renouvelables (solaire, thermique et mécanique). Pour cela, nous proposons de développer une plateforme de récupération d'énergie multi-sources/multi-charges (MANAGY) capable de s'adapter à son environnement pour en extraire le maximum d'énergie et répondre à des applications diverses. L'architecture est constituée de chemins directs et de chemins indirects où l'énergie provenant des sources est d'abord transférée dans une unité de stockage avant d'être réutilisée par les charges du microsystème. L'utilisation de cette nouvelle architecture permet d'optimiser le transfert d'énergie entre sources et charges et améliore le rendement du système de 33%. Avant de développer une architecture multi-sources, nous avons cherché à améliorer le rendement de la source photovoltaïque (PV) qui, au vu de l'état de l'art, a la densité de puissance la plus élevée. La recherche du rendement maximum de la source PV revient à la recherche du point de puissance maximum (MPPT). Il existe pour chaque condition d'irradiance, de température, et d'énergie extraites un couple tension-courant permettant à la source de fournir un maximum de puissance (MPP). Grâce à l'utilisation de deux chemins de puissance, nous arrivons simultanément à créer une boucle de régulation faible puissance agissant sur le rapport cyclique du système de gestion d'énergie (MPPT) et une boucle de régulation de la tension de sortie agissant sur le transfert de l'énergie. La modélisation du système nous a permis de spécifier ses performances. Pour atteindre les performances requises, des architectures innovantes ont été réalisées qui ont fait l'objet de trois brevets. De plus, des blocs ne sont activés qu'aux instants de changement d'état du système et sont conçus, quand cela a été possible, avec des transistors fonctionnant en mode faible inversion. Toutes ces optimisations permettent au système de fonctionner sur une large plage de variation de l'éclairement (de conditions intérieures supérieures à 500 lux à extérieures) avec un rendement proche de 90%.

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The poultry Industry has a relevant attribution for agribusiness in Brazil, regarding the economic and social aspect. However, given the high consumption of water and electricity, and the high generation of waste, it becomes aggressive and polluting the environment. The objective of this research is to characterize poultry of broiler chicken in terms of the interfaces of technological innovation, proposing sustainable alternatives. For the elaboration of this research, as methodology, it was based on the qualitative research approach. As for the objectives, these are classified as exploratory, descriptive and applied research. Regarding the procedures, field research was chosen. For the economic viability analysis, the techniques of Net Present Value (NPV), simple payback and discounted payback were used. As a result, the proposed photovoltaic energy installation project presented economic viability in the 18-year period for the simple payback and 19 years for the discounted payback. Since these are third-party resources (Pronaf Mais Alimentos), we opted to use the same rate applied by the Financial Institution (2.5%) as the Average Attractiveness Rate (TMA). The investment showed a Profitability Index (IL) of 17.11% during the project life and Internal Rate of Return (IRR) 3.76% per annum. The rainwater harvesting system presented economic viability in the 15-year period by simple payback and infeasibility for the 18-year period for the discounted payback, with an IRR of 4% per year and IL of (-29%). In this research, it was also identified that rainwater is of satisfactory quality for animal consumption and for human consumption. Regarding solid waste management, the property produces an average of 350 tons of poultry litter per 18 lots (2 years) and the packaging, booties, gloves and rodent poison remains totaled 1,960 kg in the analyzed period. When assessing the perception of the managers of the poultry integrators regarding sustainability and the implementation of "Sustainable Aviaries", it was identified that all managers of the companies questioned believe that Sustainable Aviaries are necessary and should be implemented in the long term. From the results presented, it is understood that rainwater harvesting system, photovoltaic power generation system and solid waste management are mechanisms that can contribute to reduce the environmental impacts caused by the poultry production process, promoting rural development sustainable development.
A avicultura possui uma atribuição relevante para o agronegócio no Brasil, quanto ao aspecto econômico e social. Porém, diante do elevado consumo de água e energia elétrica, e a alta geração de resíduos, torna-se agressora e poluidora do meio ambiente. Esta pesquisa tem por objetivo caracterizar aviário de frango de corte quanto às interfaces da inovação tecnológica, propondo alternativas sustentáveis. Para a elaboração desta pesquisa, como metodologia, baseou-se na abordagem de pesquisa qualitativa. Quanto aos objetivos, estes são classificados como pesquisa exploratória, descritiva e aplicada. Em relação aos procedimentos, optou-se pela pesquisa de campo. Para a análise da viabilidade econômica, utilizou-se as técnicas de Valor Presente Líquido (VPL), payback simples e payback descontado. Como resultado, o projeto proposto de instalação de energia fotovoltaica apresentou viabilidade econômica no período de 18 anos pelo payback simples e de 19 anos pelo payback descontado. Por se tratar de recursos de terceiros (Pronaf Mais Alimentos), optou-se por usar a mesma taxa aplicada pela Instituição Financeira (2,5%) como Taxa Média de Atratividade (TMA). O investimento apontou um Índice de Lucratividade (IL) de 17,11% durante a vida útil do projeto e Taxa Interna de Retorno (TIR) 3,76% ao ano. O sistema de captação da água de chuva apresentou viabilidade econômica no período de 15 anos pelo payback simples e inviabilidade para o período de 18 anos pelo payback descontado, com uma TIR de 4% ao ano e IL de (-29%). Nesta pesquisa, identificou-se também que a água de chuva possui qualidade satisfatória para dessedentação de animais e para o consumo humano. Em relação ao gerenciamento dos resíduos sólidos, a propriedade produz em média 350 toneladas de cama de aviário a cada 18 lotes (2 anos) e as embalagens, botinhas, luvas e restos de veneno para roedores somaram 1,960 kg, no período analisado. Ao avaliar a percepção dos gestores das integradoras avícolas quanto à sustentabilidade e quanto à implantação de “Aviários Sustentáveis”, identificou-se que todos os gestores das empresas questionadas acreditam que Aviários Sustentáveis são necessários e devem ser implantados em longo prazo. A partir dos resultados apresentados, entende-se que sistema de captação de água de chuva, sistema de geração de energia fotovoltaica e gerenciamento de resíduos sólidos são mecanismos que podem contribuir para reduzir os impactos ambientais, causados pelo processo produtivo avícola, promovendo o desenvolvimento rural sustentável.

This thesis presents an optimal method of designing and controlling an oscillating energy harvesting system. Many new and emerging energy harvesting systems, such as the energy harvesting backpack and ocean wave energy harvesting, capture energy normally expelled through mechanical interactions. Often the nature of the system indicates slow system time constants and unsteady AC voltages. This paper reveals a method for achieving maximum energy harvesting from such sources with fast determination of the optimal operating condition. An energy harvesting backpack, which captures energy from the interaction between the user and the spring decoupled load, is presented in this paper. The new control strategy, maximum energy harvesting control (MEHC), is developed and applied to the energy harvesting backpack system to evaluate the improvement of the MEHC over the basic maximum power point tracking algorithm.
M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE

Ubiquitous computing and pervasive networks are prevailing to impact almost every part of our daily lives. Convergence of technologies has allowed electronic devices to become untethered. Cutting of the power-cord and communications link has provided many benefits, mobility and convenience being the most advantageous, however, an important but lagging technology in this vision is the power source. The trend in power density of batteries has not tracked the advancements in electronic systems development. This has provided opportunity for a bridging technology which uses a more integrated approach with the power source to emerge, where a device has an onboard self sustaining energy supply. This approach promises to close the gap between the increased miniaturisation of electronics systems and the physically constrained battery technology by tapping into the ambient energy available in the surrounding location of an application. Energy harvesting allows some of the costly maintenance and environmentally damaging issues of battery powered systems to be reduced. This work considers the characteristics and energy requirements of wireless sensor and actuator networks. It outlines a range of sources from which the energy can be extracted and then considers the conversion methods which could be employed in such schemes. This research looks at the methods and techniques for harvesting/scavenging energy from ambient sources, in particular from the motion of human traffic on raised flooring and stairwells for the purpose of powering wireless sensor and actuator networks. Mechanisms for the conversion of mechanical energy to electrical energy are evaluated for their benefits in footfall harvesting, from which, two conversion mechanisms are chosen for prototyping. The thesis presents two stair-mounted generator designs. Conversion that extends the intermittent pulses of energy in footfall is shown to be the beneficial. A flyback generator is designed which converts the linear motion of footfall to rotational torque is presented. Secondly, a cantilever design which converts the linear motion to vibration is shown. Both designs are mathematically modelled and the behaviour validated with experimental results & analysis. Power, energy and efficiency characteristics for both mechanisms are compared. Cost of manufacture and reliability are also discussed.

Tato diplomová práce se zabývá vývojem autonomního zdroje elektrické energie založeného na MEMS termoelektrickém generátoru. Uvažovaný generátor bude následně použit pro napájení autonomní senzorické jednotky pro letecké aplikace. Systémový pohled na autonomní senzorickou jednotku zahrnuje senzor se zpracováním a přenosem dat, energy harvester (termoelektrický generátor), power management, akumulační prvek a autodiagnostiku. Všechny výše uvedené komponenty jsou v práci podrobně popsány. V úvodu práce je provedena široká rešerše existujících termoelektrických generátorů pro letecké aplikace. Následně jsou popsány základní teoretické poznatky z oblasti DC/DC měničů pro energy harvesting. Zvláštní pozornost je věnována metodám MPPT (Maximum Power Point Tracking). Jako základ pro vývoj napájení autonomní senzorické jednotky bylo provedeno množství simulací za pomoci nástroje MATLAB/Simulink Simscape. Pro identifikaci prametrů modelu posloužilo měření na speciálním přípravku. Praktická implementace teoreticky popsaných problémů je provedena na k tomuto účelu navrženém technologickém demonstrátoru. Závěrem je zhodnocena reálná využitelnost navržené technologie pro finální aplikaci v leteckém průmyslu.

Dissertation thesis is focused on using alternative energy sources called energy harvesting. This thesis offers a solution to problems with autonomous powering of sensor networks if primary power source recovery is impossible. In these cases, energy of the external power (e.g. temperature, light, motion) should be used. Proposed solution should be especially used in the field of medical applications (e.g. cochlear implants, pacemakers, insulin pumps). Long time monitoring of the personal health status is also possible when employing automated sensor systems. In this work, there is state of art review relating to the low power energy sources for an alternative powering of sensor systems. It was observed that existing systems are almost prepared for the implementation of energy harvesting power sources. The energy harvesting power sources have been developed by numerous researcher teams around the world, but there are only a few variants of power management circuits for effective energy gaining, storing and using. This area has a huge potential for the next research. The issues regarding to the distribution of gained energy are solved on the complex level in the thesis. For these purposes, a new simulation model of the whole system (fully implantable artificial cochlea) including its subcircuits was developed in the SPICE environment. It connects independent subcircuits into a single comprehensive model. Using this model, a few novel principles for energy distribution (e.g. Charge Push Through technique) was developed. In the near future, these techniques are also applicable to the design of versatile sensor systems.

Improvements in embedded electronics which have effectively reduced power consumption requirements as well as advancements in IC technology allowing utilization of low power inputs have made Energy Harvesting a popular power solution for low power applications such as WSNs. In many implementation areas, we can see solar, thermal, and vibration energy harvesting techniques have taken the role of batteries as power source. Now that Energy Harvesting is a popular and considerably mature technology, with proper design and installation, any object exposing energy has the ability to be promoted as a power source. We are currently living in Internet age where we connect to the world through network packets. Ethernet, by far, is the most popular LAN technology which allows us to plug and play. Therefore, on an Ethernet link, billions of packets where our data are encapsulated in are traversing every hour. We assume each of these packets exposes some level of energy on an Ethernet link. The challenge here is harvesting the energy available from Ethernet packets and transforming it into useful energy so that it can be used to power devices such as WSNs. In this thesis work, we have revealed how much energy is available from Ethernet packets, and how much of it can be made usable. We have also designed a system where a WSN is generating all of its operating power solely from Ethernet packets and consuming this energy in communication with a base station.