Le sujet de ce travail de thèse s'inscrit dans la récupération d'énergie thermique à l'échelle microscopique pour proposer une alternative aux matériaux thermoélectriques. L'objectif est de concevoir, fabriquer et caractériser un récupérateur microscopique pour tirer profit de l'augmentation des échanges thermiques et des fréquences d'oscillations avec la réduction d'échelle. Il est basé sur une double transduction, thermo-mécanique grâce au flambage d'une poutre bi-couche initialement courbe, et piézoélectrique.Des structures rectangulaires de différents tailles à base d'AlN et d'Al ont été fabriquées et caractérisées. La courbure transverse des plaques rectangulaires étant trop importante, des structures optimisées en forme de papillons ont par ailleurs été fabriquées et caractérisées. / This PhD thesis focuses on the thermal energy harvesting at microscale to propose an alternative to thermoelectric materials. The aim is to conceive, fabricate and characterize a microscopic harvester to take profit of the increase of thermal exchanges and oscillation frequencies with the downscaling. It is based on a double-step transduction: thermo-mecanical one thanks to the thermal buckling of a bilayer plate initially curved, and piezoelectric.Rectangular structures of different sizes composed of AlN and Al have been fabricated and characterized. The transverse curvature of the rectangular plate being to high, optimized structures having a butterfly shape have also been fabricated and characterized.

Neste trabalho, é apresentado um estudo sobre um sistema de micro geração de energia a partir da vibração de uma viga em balanço utilizando um transdutor piezoelétrico. A análise é feita levando-se em consideração as dimensões da viga utilizada, tipo de gerador piezoelétrico e diferentes tipos de cargas acopladas a este. O sistema de geração tem sua excitação realizada por um atuador piezoelétrico, que é alimentado por uma fonte de tensão com amplitude, frequência e forma de onda ajustáveis. A avaliação da potência de saída e influência dos diferentes tipos de carga acoplados a saída são analisados. As cargas utilizadas são: puramente resistiva, resistiva-capacitiva e não linear, por meio de um retificador de onda completa. Para avaliar experimentalmente os resultados analíticos foi utilizado um protótipo de uma viga em balanço construída com uma barra de alumínio exposta a uma excitação, induzida por um outro transdutor piezoelétrico ligado a uma placa dSpace controlada por um computador. Os parâmetros do sistema são identificados sendo possível determinar sua influência na saída e realizando assim uma análise pontual do micro gerador piezoelétrico quando submetido a uma carga qualquer. Os resultados da geração com os diferentes tipos de cargas são comparados, bem como a influência destas na dinâmica do sistema. As potências máximas são apresentadas em diferentes modos de vibração depois de otimizadas. Foram obtidos os seguintes resultados: 3;357mW com uma resistência de 200k no primeiro modo; 13;17mW com uma resistência de 50k no segundo modo; para o terceiro e quarto modos de vibração a máxima potência é obtida com a resistência de 10k, sendo 10;22mW e 15;63mW, respectivamente. A alteração da frequência de vibração é de aproximadamente 0;2% para os modos de vibração em função da resistência máxima e mínima. Para a carga resistiva-capacitiva, o comportamento da geração não é afetado significativamente para os valores de resistência de 1M e 100k. Com os valores de 10k e 1k a potência ativa se eleva em 30%, aproximadamente. O comportamento da carga não linear é aproximado por uma impedância com característica capacitiva. Sendo que, com a elevação da frequência, a impedância vista pelo gerador piezoelétrico é diminuída. A energia armazenada é de 0;8039mJ, 2;5245mJ e 1;3041mJ para o primeiro, segundo e terceiro modos de vibração, respectivamente. / This work presents a study of a energy harvesting system based on vibration from a cantilever beam utilizing a piezoelectric generator. The analysis considers the dimensions of the beam, type of piezoelectric generator and di erent types of loads coupled. A piezoelectric actuator is handles for the system excitement, powered by a voltage source with adjustable amplitude, frequency and shape. Are evaluate the output power and the in uence of di erent charge types coupled to the piezoelectric generator. The loads are purely resistive, resistive-capacitive and non-linear, by a full-wave bridge recti er. To check experimentally the analytical results, are used a prototype of a cantilever beam constructed with an aluminum bar exposed to an excitation induced by another piezoelectric transducer attached to a dSpace board controlled by a computer. The system parameters are individually identi ed to determine their in uence on output, allowing the punctual analysis of the piezoelectric harvesting when subjected to any load. The results of power generation are compare with di erent types of loads as well as its in uence on the dynamic of the system. After a optimization, the greatest power delivered to the load happen in di erent vibrational modes. We obtain the following results: 3:357mW with a 200k resistance in the rst mode; 13:17mW with a 50k resistance in the second mode, for the third and fourth vibration modes greatest power is obtained with the 10k resistance, being 10:22mW and 15:63mW, respectively. The modi cation of the vibration frequency are approximately 0:2% for all vibration modes depending on the largest and smallest resistance. For the resistive-capacitive load, the generation behavior are not a ect to the 1M and 100k resistance. With the 10k and 1k values, the active power increases by approximately 30%. The nonlinear load behavior are approach by an impedance with capacitive characteristics. With increasing of frequency, the impedance seen by the piezoelectric harvester is decreased. The energy stored is 0:8039mJ, 2:5245mJ and 1:3041mJ for the rst, second and third vibration modes, respectively.

Le but de cette thèse était d’étudier des solutions innovantes pour la récupération d’énergie pour pouvoir alimenter de manière autonome les futurs capteurs et nœuds communicants sans fil de l’Internet des Objets (IoT pour Internet of Things). Le travail s’est focalisé sur des matériaux piézoélectriques souples et sur une approche composite et multiphysique. L’objectif est de récupérer de l’énergie à partir de déformations directes ou induites provenant de sources à la fois mécaniques et thermiques et en particulier de sources négligées jusqu’alors (lentes et de faibles intensités). L’idée maitresse est l’hybridation de plusieurs matériaux fonctionnels avec un cœur du système constitué par des microgénérateurs piézoélectriques (et pyroélectriques) imprimés nécessaires à la génération de charges électriques. L’originalité de ce travail est d’avoir réalisé un système de récupération d’énergie entièrement flexible, au format d’une carte de crédit et compatible avec de plus grandes dimensions, en utilisant des copolymères piézoélectriques de P(VDF-TrFE) sous forme d’encres. Ce matériau est flexible et particulièrement résistant, ce qui le rend attractif pour desapplications mettant en jeu formes complexes, notamment, courbes. Un autre avantage du copolymère de P(VDF-TrFE) est qu’il ne nécessite pas de pré-déformation mécanique comme pour le polymère PVDF et il commence à être aujourd’hui disponible sous forme d’encres pour l’électronique imprimée, ce qui simplifiera et réduira les coûts de fabrication à termes.En premier, nous décrivons le procédé de fabrication par sérigraphie des microgénérateurs en P(VDF-TrFE), suivi par les caractérisations ferroélectriques puis piézoélectriques des dispositifs. A cet effet, nous avons développé des techniques de mesures originales en circuit ouvert qui ont été testées et validées au préalable avec des échantillons dePVDF commercial. La dernière étape a été de réaliser un prototype de récupération d’énergie thermique flexible de faible encombrement (sans radiateur). Cela a été réalisé en hybridant les microgénérateurs précédemment fabriqués avec des feuilles d’alliages à mémoire de forme thermique à base de NiTi, qui est un matériau sensible à un seuil de température donnée.Les résultats phares de cette étude sont : 1) le dépôt multicouches de P(VDF-TrFE)combiné au dépôt d’une électrode souple en PEDOT:PSS, β) l’établissement des caractéristiques ferroélectriques et piézoélectriques en fonction de l’épaisseur de P(VDFTrFE) et enfin γ) la détermination d’un coefficient g31 supérieur à la normale avec0.15 V·m/N. Aussi, nous avons démontré la capacité de ces microgénérateurs à délivrer des tensions utiles de l’ordre de 10 V avec ici une densité d’énergie de proche de 500 μJ/cm3, ces valeurs étant limitées aux conditions de test utilisées.Nous concluons ce travail sur une preuve de concept fonctionnelle de récupérateur d’énergie thermique flexible apte à détecter ou utiliser des variations lentes et faibles de température à partir de sources élémentaires, produisant pour l’instant γ7 V (correspondant à95 μJ) à 65 ºC, et qui à termes pourront être l’air ambiant (chaud ou froid) ou la chaleur de la peau. / This work aims to study innovative solutions for energy harvesting applicable toautonomous wireless sensors for IoT (Internet of Things). It is focused on flexiblepiezoelectric composite materials and a multi-physical approach. The objective is to harvestenergy via strain-induced phenomena from both mechanical and thermal sources, andparticularly sources neglected so far (slow and low). The main idea is the hybridization ofdifferent functional materials with the core of the system being screen printed piezo/pyroelectricmicrogenerators, mandatory to generate electrical charges. The originality of thiswork is to realize large area flexible energy harvesting systems by using ink-basedpiezoelectric copolymers of polyvinylidene fluoride P(VDF-TrFE). This material is veryflexible and durable which makes it attractive for applications in systems with complexshapes. Another benefit of P(VDF-TrFE) is that it does not need to be pre-stretched as PVDFand it is now available in inks for printable electronics which can simplify and reduce theprice of the fabrication process.We first describe the fabrication process of the screen printed P(VDF-TrFE)microgenerators, followed by ferroelectric and piezoelectric characterizations. For thispurpose we have developed optimized methods in open-circuit conditions adapted for flexiblesystems tested and validated on commercial bulk PVDF. The last step was to realize a lowprofile thermal flexible energy harvester prototype (no radiator). It was done by hybridizationof the fabricated microgenerators and foils of shape memory NiTi-based alloy, which is afunctional material sensitive to a given temperature threshold.The key outcomes of this work are: 1) the successful deposition of multilayers ofP(VDF-TrFE) and organic PEDOT:PSS electrode, 2) dielectric, ferroelectric and directpiezoelectric constants reported as a function of film thickness, and 3) the g31 direct voltagecoefficient, measured for the first time, and showing the record value of 0.15 V·m/N. Also,we have demonstrated that in open-circuit conditions, the microgenerators can produce auseful strain-induced voltage of 10 V with an energy density close to 500 μJ/cm3, these valuesbeing limited by the experimental set-up.The concept of thermal energy harvesting composite based on thin film screen printedP(VDF-TrFE) microgenerators was realized and demonstrated to be effective. We concludewith a functional prototype of flexible energy harvester, able to detect non-continuous slowthermal events and producing 37 V (corresponding to 95 μJ) at 65 ºC.

The development of a complete thermoelectric generator and its application on a display polarizer film was successfully accomplished in this thesis. A systematic study of the prospective thermoelectric materials, PEDOT:PSS-based and ${ZnON}$, used for the present application is presented. To the best of our knowledge, this is the first exploration of the thermoelectric parameters of ${ZnON}$ reported here. Thin-film deposition of these materials was performed via both solution- and vacuum-based techniques. In addition, certain doping mechanisms were tested in an attempt to further understand the correlation between electrical conductivity and Seebeck coefficient. A maximum power factor of $42{\mu}Wm^{-1}K^{-2}$ was achieved for the PEDOT:PSS-based thin film at room temperature. It was initially doped via 5vol% of DMSO and sequentially treated with ethylene glycol. Specifically, its electrical conductivity displayed a 2-fold increase after EG treatment, reaching a value of about 1632 Scm$^{-1}$. Systematic studies performed on the association between thin-film thickness and its Seebeck coefficient shows a decrease in the latter as the number of multilayers printed increases. Among the different $O_{2}/N_{2}$ ratios that were tested for ${ZnON}$ thin films, a maximum power factor value of 163${\mu}Wm^{-1}K{-2}$ was achieved with the lowest $O_{2}$ flow rate configuration. In contrast to PEDOT:PSS-based thin films, the ${ZnON}$ displayed the opposite effect on the relation of the Seebeck coefficient with respect to thin-film thickness. Furthermore, a heterostructure was also developed by implementing ${ZnO}$ nanowires into the ${ZnON}$ thin film. ${ZnO}$ nanowires have been fabricated through the hydrothermal method on inkjet-printed patterns of zinc acetate dihydrate. It has been demonstrated that with the right inkjet-printing parameters and substrate temperature, ${ZnO}$ nanowires can be effortlessly fabricated in accordance with the desired pattern variations under low temperature and mild conditions. Finally, a complete device of the thermoelectric generator was fabricated using the above materials and a special set-up developed in order to test the device on the polarizer. The power output achieved from a 1-thermoelectric couple under normal backlight illumination and ambient conditions was 23pW. Overall, it is thought that the particular design and proof of concept presented here can be the basis of a prospective energy harvesting scheme via thermoelectrics in future display-based handheld devices.

Wireless backhaul communication and power transfer can make the deployment of outdoor small cells (SCs) more cost effective; thus, their rapid densification can be enabled. For the first time, solar cells can be leveraged for the two-fold function of energy harvesting (EH) and high speed optical wireless communication. In this thesis, two complementary concepts for power provision to SCs are researched using solar cells – the optical wireless power transfer (OWPT) in the nighttime and solar EH during daytime. A harvested power of 1W is considered to be required for an autonomous SC operation. The conditions of darkness – worst case scenario – are initially selected, because the SC needs to harvest power in the absence of ambient light. The best case scenario of daytime SC EH from sunlight is then explored to determine the required battery size and the additional power from optical sources. As a first approach, an indoor 5m experimental link is created using a white light-emitting diode for OWPT to an amorphous silicon (Si) solar panel. Despite the use of a large mirror for collimation, the harvested power and energy efficiency of the link are measured to be only 18:3mW and 0:1%, respectively. Up to five red laser diodes (LDs) with lenses and crystalline Si (c-Si) cells are used in a follow-up study to increase the link efficiency. A maximum power efficiency of 3:2% is measured for a link comprising two LDs and a mono-c-Si cell, and the efficiency of all of its components is determined. Also, the laser system is shown to achieve an improvement of the energy efficiency by 2:7 times compared with a state-of-the-art inductive power transfer system with dipole coils. Since the harvested power is only 25:7mW, an analytical model for an elliptical Gaussian beam is developed to determine the required number of LDs for harvesting 1W; this shows an estimated number of 61 red LDs with 50mW of output optical power per device. However, a beam enclosure of the developed Class 3B laser system of up to a 3:6m distance is required for eye safety. A simulation study is conducted in Zemax for the design of an outdoor 100m infrared wireless link able to harvest 1W under clear weather conditions. Harvesting 1:2W and meeting eye safety regulations for Class 1 are shown to be feasible by a 1550 nm laser link. The required number of laser power converters is estimated to be 47 with an area of 5 5mm2 per device. Also, the dimensions of the transmitter and receiver are considered to be acceptable for the practical application of SC EH. In the last part of this thesis, two multi-c-Si solar panels are initially used for EH in an outdoor environment during daytime. The power supply of at least 1W is shown to be achievable during hour periods under sunny and cloudy conditions. A maximum average power of 4:1W is measured in the partial presence of clouds using a 10W solar panel. Since the variability of weather conditions induces the harvested power to fluctuate with values of mW, the use of optical sources is required in periods of insufficient solar EH for SCs. Therefore, a hybrid solar/laser based EH design is proposed for a continuous annual SC provision of 1Win ‘darker’ places on earth such as Edinburgh, UK. The 10W multi-c-Si solar panel and the 1550 nm laser link are considered; thus, the feasibility of supplying the SC with at least 1Wper hour monthly using a battery with energy content of only 60Wh is shown through simulations. A maximum monthly average harvested power of 824mW is shown to be required by the 1550 nm laser system that has already been overachieved through simulations in Zemax.

This thesis presents ambient energy data obtained from a measurement campaign carried out at an automobile plant. At the automobile plant, ambient light, ambient temperature and ambient radio frequency were measured during the day time over two days. The measurement results showed that ambient light generated the highest DC power. For plant and operation managers at the automobile plant, the measurement data can be used in system design considerations for future energy harvesting wireless sensor nodes at the plant. In addition, wideband measurements obtained from a machine workshop are presented in this thesis. The power delay profile of the wireless channel was obtained by using a frequency domain channel sounding technique. The measurements were compared with an equivalent ray tracing model in order to validate the suitability of the commercial propagation software used in this work. Furthermore, a novel technique for mathematically recreating the time dispersion created by factory inventory in a radio frequency channel is discussed. As a wireless receiver design parameter, delay spread characterizes the amplitude and phase response of the radio channel. In wireless sensor devices, this becomes paramount, as it determines the complexity of the receiver. In reality, it is sometimes difficult to obtain full detail floor plans of factories for deterministic modelling or carry out spot measurements during building construction. As a result, radio provision may be suboptimal. The method presented in this thesis is based on 3-D fractal geometry. By employing the fractal overlaying algorithm presented, metallic objects can be placed on a floor plan so as to obtain similar radio frequency channel effects. The environment created using the fractal approach was used to estimate the amount of energy a harvesting device can accumulate in a University machine workshop space.

Neste trabalho, é apresentado um estudo sobre um sistema de micro geração de energia a partir da vibração de uma viga em balanço utilizando um transdutor piezoelétrico. A análise é feita levando-se em consideração as dimensões da viga utilizada, tipo de gerador piezoelétrico e diferentes tipos de cargas acopladas a este. O sistema de geração tem sua excitação realizada por um atuador piezoelétrico, que é alimentado por uma fonte de tensão com amplitude, frequência e forma de onda ajustáveis. A avaliação da potência de saída e influência dos diferentes tipos de carga acoplados a saída são analisados. As cargas utilizadas são: puramente resistiva, resistiva-capacitiva e não linear, por meio de um retificador de onda completa. Para avaliar experimentalmente os resultados analíticos foi utilizado um protótipo de uma viga em balanço construída com uma barra de alumínio exposta a uma excitação, induzida por um outro transdutor piezoelétrico ligado a uma placa dSpace controlada por um computador. Os parâmetros do sistema são identificados sendo possível determinar sua influência na saída e realizando assim uma análise pontual do micro gerador piezoelétrico quando submetido a uma carga qualquer. Os resultados da geração com os diferentes tipos de cargas são comparados, bem como a influência destas na dinâmica do sistema. As potências máximas são apresentadas em diferentes modos de vibração depois de otimizadas. Foram obtidos os seguintes resultados: 3;357mW com uma resistência de 200k no primeiro modo; 13;17mW com uma resistência de 50k no segundo modo; para o terceiro e quarto modos de vibração a máxima potência é obtida com a resistência de 10k, sendo 10;22mW e 15;63mW, respectivamente. A alteração da frequência de vibração é de aproximadamente 0;2% para os modos de vibração em função da resistência máxima e mínima. Para a carga resistiva-capacitiva, o comportamento da geração não é afetado significativamente para os valores de resistência de 1M e 100k. Com os valores de 10k e 1k a potência ativa se eleva em 30%, aproximadamente. O comportamento da carga não linear é aproximado por uma impedância com característica capacitiva. Sendo que, com a elevação da frequência, a impedância vista pelo gerador piezoelétrico é diminuída. A energia armazenada é de 0;8039mJ, 2;5245mJ e 1;3041mJ para o primeiro, segundo e terceiro modos de vibração, respectivamente. / This work presents a study of a energy harvesting system based on vibration from a cantilever beam utilizing a piezoelectric generator. The analysis considers the dimensions of the beam, type of piezoelectric generator and di erent types of loads coupled. A piezoelectric actuator is handles for the system excitement, powered by a voltage source with adjustable amplitude, frequency and shape. Are evaluate the output power and the in uence of di erent charge types coupled to the piezoelectric generator. The loads are purely resistive, resistive-capacitive and non-linear, by a full-wave bridge recti er. To check experimentally the analytical results, are used a prototype of a cantilever beam constructed with an aluminum bar exposed to an excitation induced by another piezoelectric transducer attached to a dSpace board controlled by a computer. The system parameters are individually identi ed to determine their in uence on output, allowing the punctual analysis of the piezoelectric harvesting when subjected to any load. The results of power generation are compare with di erent types of loads as well as its in uence on the dynamic of the system. After a optimization, the greatest power delivered to the load happen in di erent vibrational modes. We obtain the following results: 3:357mW with a 200k resistance in the rst mode; 13:17mW with a 50k resistance in the second mode, for the third and fourth vibration modes greatest power is obtained with the 10k resistance, being 10:22mW and 15:63mW, respectively. The modi cation of the vibration frequency are approximately 0:2% for all vibration modes depending on the largest and smallest resistance. For the resistive-capacitive load, the generation behavior are not a ect to the 1M and 100k resistance. With the 10k and 1k values, the active power increases by approximately 30%. The nonlinear load behavior are approach by an impedance with capacitive characteristics. With increasing of frequency, the impedance seen by the piezoelectric harvester is decreased. The energy stored is 0:8039mJ, 2:5245mJ and 1:3041mJ for the rst, second and third vibration modes, respectively.

Recently, massive multiple-input multiple-output (MIMO) systems have gained significant attention as a new network architecture to not only achieving unprecedented spectral and energy efficiencies, but also to alleviating propagation losses and inter-user/inter-cell interference. Therefore, massive MIMO has been identified as one of the key candidate technologies for the 5th generation wireless standard. This dissertation thus focuses on (1) developing a performance analysis framework for cognitive massive MIMO systems by investigating the uplink transmissions of multi-cell multi-user massive MIMO secondary systems, which are underlaid in multi-cell multi-user primary massive MIMO systems, with taking into consideration the detrimental effects of practical transmission impairments, (2) proposing a new wireless-powered underlay cognitive massive MIMO system model, as the secondary user nodes is empowered by the ability to efficiently harvest energy from the primary user transmissions, and then access and utilize the primary network spectrum for information transmission, and (3) developing a secure communication strategy for cognitive multi-user massive MIMO systems, where physical layer secure transmissions are provisioned for both primary and secondary systems by exploiting linear precoders and artificial noise (AN) generation in order to degrade the signal decodability at eavesdropper. The key design feature of the proposed cognitive systems is to leverage the spatial multiplexing strategies to serve a large number of spatially distributed user nodes by using very large numbers of antennas at the base-stations. Moreover, the fundamental performance metrics, the secondary transmit power constraints, which constitute the underlay secondary transmissions subject to a predefined primary interference temperature, and the achievable sum rates of the primary and secondary systems, are characterized under different antenna array configurations. Additionally, the detrimental impact of practical wireless transmission impairments on the performance of the aforementioned systems are quantified. The important insights obtained throughout these analyses can be used as benchmarks for designing practical cognitive spectrum sharing networks.

This report investigates the various methods of harvesting and storing the ambient energies which surround us. The concept and interest of harvesting ambient energy has been prevalent for some time. Mainly seen as an alternative and smarter way of storing energy for instant or later usage for low power devices. Typically to avoid the excess use of pre-stored energy where energy already exists. For this project, various energy harvesting methods will be examined in greater detail and to then be constructed together in a coherent way. Something which has yet to become more ubiquitous which therefore becomes a motivation for this thesis. To explore the possible outcomes of this implementation and if it will further the subject. This device could have many applications in terms of charging other devices in remote or powerless locations. It can also serve as an alternative to traditional charging and by that showing that the charger could be just as good as any other socket charger could be.

Magíster en Ciencias de la Ingeniería, Mención Mecánica. Ingeniero Civil Mecánico / Energy harvesting es la conversión de energía presente en el entorno a energía eléctrica. Dentro de esta clasificación la energía eólica puede ser capturada desde diferentes fuentes: naturales, como flujo de aire en campos libres; pseudo-artificiales, como corrientes de aire en ambientes urbanos; artificiales, como túneles de transporte, autopistas y ductos de ventilación. Este trabajo de Tesis tiene como objetivo principal estudiar la potencia capturable debido a la interacción fluido-estructura de un arreglo de dos cilindros circulares, rectos y paralelos, enfrentado a un flujo de aire perpendicular a su eje. Se estudian la influencia de separaciones, tamaños y velocidad de ataque en un dispositivo de captación de energía eólica, mediante vibraciones del tipo wake galloping. Se realiza un análisis computacional de vibraciones inducidas por vórtices para régimen laminar, en el programa ANSYS Fluent 14.5 y una implementación numérica de interacción fluido estructura, en el programa FORTRAN con el propósito de caracterizar el flujo y movimientos de un generador de vórtices. Posteriormente se construye un montaje experimental en el túnel de viento del Laboratorio de Procesos del Departamento de Ingeniería Mecánica de la Universidad de Chile para analizar la aceleración y potencia en un arreglo de wake galloping. El dispositivo consta de dos cilindros alineados, de diámetros D1 y D2, a una distancia L entre sus centros. Se estudia la razón de tamaño, Y=D2/D1, y razón de distancia, X=L/D1, para velocidades de viento en el rango 1-7[ms-1]. Los resultados experimentales muestran que la aceleración posee una relación directamente proporcional al cuadrado de la velocidad del viento y una potencia RMS máxima de ~4.5[mW], bajo una configuración de tamaño Y=0.7 y distancia X=3, lograda bajo el acoplamiento de la frecuencia natural y de la frecuencia del desprendimiento de vórtices sobre el cilindro aguas abajo. Frente a frecuencias no coincidentes el mayor desempeño se produce para una relación de tamaño Y=1.5 y distancia X=4 con un rango de potencia RMS de 0.1-0.4[mW]. La potencia generada puede ser fácilmente incrementada considerando para todas las razones de tamaño y distancia, excitar el sistema a su resonancia variando la frecuencia natural del sistema, por ejemplo, al modificar su rigidez.