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Energy harvesting from human passive powerMateu Sáez, Maria Loreto 05 June 2009 (has links)
Las tendencias en la tecnología actual permiten la reducción tanto en tamaño como en potencia
consumida de los sistemas digitales complejos. Esta disminución en el tamaño y el consumo da
lugar al concepto de dispositivos portátiles que se integren en la vida pertenencias personales y
cotidianas como ropa, relojes, gafas, etc. La fuente de alimentación es un factor limitante en la
movilidad de los dispositivos portátiles que se ve reducida por la duración de la batería.
Además, debido a los costos y difícil accesibilidad, la sustitución o recarga de las baterías a
menudo no es viable para los dispositivos portátiles integrados en ropa inteligente. Los
dispositivos vestibles están distribuidos en las pertenencias personales y, por tanto, la
recolección de energía del usuario es una alternativa para su alimentación. Dispositivos
vestibles pueden crear, al igual que los sensores de una red de sensores inalámbricos (WSN),
una red de área corporal. El principal objetivo de esta tesis es el estudio de generadores
piezoeléctricos, inductivos y termoeléctricos que recolectan energía del cuerpo humano de
forma pasiva.
El principio físico de un transductor es el mismo independientemente de si la fuente proviene
del entorno o del cuerpo humano. Sin embargo, las limitaciones relacionadas con la baja
tensión, corriente y niveles de frecuencia conllevan nuevos requerimientos que no están
presentes en el caso de la utilización de las fuentes que ofrece el entorno y que suponen el
principal desafío de esta tesis.
El tipo de energía entrada y transductor a utilizar forman un tándem donde la elección de uno
impone el otro. Es importante que las mediciones se realicen diferentes partes del cuerpo
humano, mientras se realizan diferentes actividades físicas para localizar las posiciones y las
actividades que producen más energía. El acoplamiento mecánico entre transductor y cuerpo
humano depende de la ubicación del transductor y la actividad que se realiza. Un diseño
específico, teniendo esto en cuenta puede aumentar más de un 200% la eficiencia del
transductor como se ha demostrado con láminas piezoeléctricas situadas en plantillas de
zapatos.
Se han realizado mediciones de aceleraciones en diferentes partes del cuerpo y diferentes
actividades para cuantificar la cantidad de energía disponible en actividades cotidianas.
Se ha realizado una simulación a nivel de sistema, modelando los elementos de un sistema de
energía autoalimentado. El transductor se ha modelado usando las ecuaciones físicas que lo
describen con el objetivo de incluir la parte mecánica del sistema. Se han utilizado modelos
eléctricos y de comportamiento para el resto de los componentes. De esta manera, el proceso
de diseño de la aplicación en su conjunto (incluyendo la carga y un elemento de
almacenamiento de energía cuando es necesario) se simplifica a la hora de lograr los requisitos
planteados. Obviamente, la carga debe ser un dispositivo de bajo consumo como por ejemplo
un transmisor RF. En este caso, es preferible alimentar la carga de forma discontinua, sin una
batería, como se deduce de los resultados obtenidos mediante simulación. Sin embargo, la
evolución de los transmisores RF de baja potencia puede cambiar esta conclusión en función
sobre todo de la evolución del consumo de energía en stand-by y el tiempo de configuración
para la operación de transmisión.
Se ha deducido a partir del análisis de los generadores inductivos que el análisis en el dominio
temporal permite calcular algunas magnitudes que no están disponibles en el dominio
frecuencial. Por ejemplo, la potencia máxima se puede calcular en el dominio frecuencial, pero
para aplicaciones de recolección de energía es más interesante saber el valor de la energía
recuperada durante un cierto tiempo o la potencia media ya que la potencia generada por las
actividades humanas pueden ser muy discontinua.
Se ha demostrado que los transductores recolectores de energía son capaces de suministrar
alimentación a dispositivos electrónicos de baja potencia, como quedó demostrado con un
transmisor RF alimentado por una termogenerador que emplea el gradiente de temperatura
existente entre el cuerpo humano y el entorno (3-5 K) y que es capaz de realizar medidas y
transmitirlas una vez cada segundo / The trends in technology allow the decrease in both size and power consumption of complex digital
systems. This decrease in size and power gives rise to the concept of wearable devices which are
integrated in everyday personal belongings like clothes, watch, glasses, et cetera. Power supply is a
limiting factor in the mobility of the wearable device which gets restricted to the lifetime of the battery.
Furthermore, due to the costs and inaccessible locations, the replacement or recharging of batteries is
often not feasible for wearable devices integrated in smart clothes. Wearable devices are devices
distributed in personal belongings and thus, an alternative for powering them is to harvest energy from the
user. Therefore, the energy can be harvested, distributed and supplied over the human body. Wearable
devices can create, like the sensors of a Wireless Sensor Network (WSN), a Body Area Network. A study
of piezoelectric, inductive and thermoelectric generators that harvest passive human power is the main
objective of this thesis.
The physical principle of an energy harvesting generator is obviously the same no matter whether it is
employed with an environmental or human body source. Nevertheless, the limitations related to low
voltage, current and frequency levels obtained from human body sources bring new requirements to the
energy harvesting topic that were not present in the case of the environment sources. This analysis is the
motivation for this thesis.
The type of input energy and transducer form a tandem since the election of one imposes the other. It is
important that measurements are done in different parts of the human body while doing different physical
activities to locate which positions and activities produce more energy. The mechanical coupling between
the transducer and the human body depends on the location of the transducer and the activity that is
done. A specific design taking this into account can increase more than a 200% the efficiency of the
transducer as has been demonstrated with piezoelectric films located in the insoles of shoes.
Acceleration measurements have been performed in different body locations and different physical
activities, in order to quantify the amount of available energy associated with usual human movements.
A system-level simulation has been implemented modeling the elements of an energy self-powered
system. Physical equations have been used for the transducer in order to include the mechanical part of
the system and electrical and behavioral models for the rest of the components. In this way, the process
of the design of the complete application (including the load and an energy storage element when it is
necessary) is simplified to achieve the expected requirements. Obviously, the load must be a low power
consumption device as for example a RF transmitter. In this case, it is preferable to operate it in a
discontinuous way without a battery as it is deduced from simulation results obtained. However, the
evolution in low power transmission modules can change this conclusion depending mostly on the
evolution of the power consumption in stand-by mode and the configuration time in transmission
operation.
It has been deduced from the analysis of inductive generators that time-domain analysis allows to
calculate some magnitudes that are not available in frequency domain. For example, the maximum power
can be calculated in frequency domain, but for energy harvesting applications it is more interesting to
know the value of the recovered energy during a certain time, or the average power since the power
generated by human activities can be highly discontinuous.
It has been demonstrated that energy harvesting transducers are able to supply power to present-day low
power electronic devices as was demonstrated with a RF transmitter powered by a thermogenerator that
employs the temperature gradient between human body and the environment (3-5 K) and that it is able to
sense and transmit data once every second.
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Microfabricated Fuel Cells To Power Integrated CircuitsMoore, Christopher Wayne 12 May 2005 (has links)
Microfabricated fuel cells have been designed and constructed on silicon integrated circuit wafers using many processes common in integrated circuit fabrication, including sputtering, polymer spin coating, reactive ion etching, and photolithography. Fuel delivery microchannels were made through the use of sacrificial polymers. The characteristics of different sacrificial polymers were studied to find the most suitable for this work. A polypropylene carbonate solution containing a photo-acid generator could be directly patterned with ultraviolet exposure and thermal decomposition. The material that would serve as the fuel cells proton exchange membrane (PEM) encapsulated the microchannels. Silicon dioxide deposited by plasma enhanced chemical vapor deposition (PECVD) at relatively low temperatures exhibited material properties that made it suitable as a thin-film PEM in these devices. By adding phosphorous to the silicon dioxide recipe during deposition, a phosphosilicate glass was formed that had an increased ionic conductivity. Various polymers were tested for use as the PEM or in combination with oxide to form a composite PEM. While it did not work well alone, using Nafion on top of the glass layer to form a dual-layer PEM greatly enhanced the fuel cell performance, including yield and long-term reliability. Platinum and platinum/ruthenium catalyst layers were sputter deposited. Experiments were performed to find a range of thicknesses that resulted in porous layers allowing contact between reactants, catalyst, and the PEM. When using the deposited glasses, multiple layers of catalyst could be deposited between thin layers of the electrolyte, resulting in higher catalyst loading while maintaining porosity. The current and power output were greatly improved with these additional catalyst layers.
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Conception et caractérisation de microgénérateurs piézoélectriques pour microsystèmes autonomes / Design and characterization of MEMS micro power generators for autonomous systems on chipDefosseux, Maxime 04 October 2011 (has links)
Le contexte de cette thèse est la récupération d'énergie afin de rendre des capteurs autonomes. L'objectif de ce travail est de répondre à la problématique du couplage des microgénérateurs piézoélectriques résonants à la source de vibration mécanique. Cela nécessite de travailler à plus basse fréquence et sur des gammes de fréquences plus importantes. Pour travailler à plus basses fréquences, des poutres encastrées libres utilisant l'AlN comme matériau piézoélectrique ont été conçues, fabriquées et caractérisées. La possibilité de récupérer 0.6µW à 214Hz pour un volume de moins de 3mm3 a été prouvée. Comparées à la littérature, de très bonnes figures de mérite ont été démontrées. Pour travailler sur des gammes de fréquences plus importantes, une méthode innovante de raidissement non linéaire de la structure a été proposée et prouvée expérimentalement, avec une adaptation de la fréquence de résonance de plus de 50% en dessous de 500Hz / This PhD thesis context is about energy harvesting in order to have autonomous sensors. The problematic of the coupling of piezoelectric mechanical energy harvesters with the mechanical vibration source has been studied. To be efficient, the harvesters have to work at lower frequencies and on larger frequency ranges. To work at lower frequencies, we designed, fabricated and characterized AlN piezoelectric clamped free beams. We proved that it was possible to harvest 0.6µW for a volume of less than 3mm3. Our devices have very good figures of merit compared to literature. To work on wider frequency ranges, we propose an innovative nonlinear hardening method. It has been proven experimentally, with an adaptability of the resonance frequency of more than 50% under 500Hz.
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