41 research outputs found

    Evaluation of the PCB-embedding technology for a 3.3 kW converter

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    International audienceThis paper presents a converter fully made using PCB embedding technology (including the semiconductor devices , but also their gate driver circuits as well as the passive components). This converter is rated at a high-power (3.3 kW) considering the PCB technology. Here, the focus is given to the experimental validation of the embedding process, with the characterization of many of the embedded devices (SiC MOS-FETs, diodes, capacitors). These results show that most of the components were unaffected by the process, with the noticeable exception of the large inductors which exhibit variations in the inductance values as well as a large ac resistance. Finally, the converter is successfully assembled an tested at low power

    Thermal Considerations of a Power Converter with Components Embedded in Printed Circuit Boards

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    International audiencePrinted-Circuit-Board (PCB) technology is attractive for power electronic systems as it offers a low manufacturing cost for mass production. Integration technologies such as device embedding have been developed to take advantage of the inter-layer space in multi-layer PCBs and to increase the performances (Electrical, Thermal). However, the PCB technology offers limited power dissipation due to the low thermal conductivity (≈0.3 W/(m·K)) of its composite substrate. In this paper, we consider PCB embedding for a 3.3 kW AC/DC bidirectional converter. We describe the integration of not only the power dies, but also the gate drive circuits and the power inductor, with a special focus on the thermal management. The manufacturing processes of the boards are presented. Two thermal models based on finite elements (FE) of this converter stage are introduced. The accuracy of these models is validated against experiments. The results show that a simplified FE model offers satisfying accuracy and fast simulation, even considering the relatively complex structure and layout of the PCBs

    Gestion de l'Ă©nergie des piles Ă  combustible microbiennes

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    Microbial fuel cells (MFCs) harness the metabolism of micro-organisms and utilize organic matter to generate electrical energy. They are interesting because they accept a wide range of organic matter as a fuel. Potential applications include autonomous wastewater treatment, bio-batteries, and ambient energy scavenging. MFCs are low-voltage, low-power devices that are influenced by the rate at which electrical energy is harvested at their output. In this thesis, we study methods to harvest electrical energy efficiently. The voltage at which energy is harvested from MFCs influences their operation and electrical performance. The output power is maximum for a certain voltage value (approx. 1/3rd the open-circuit voltage). This noteworthy operating point is favorable in some applications where MFCs are used as a power supply. MFCs can be tested at this point using an automatic load adjuster which includes a maximum power point tracking algorithm. Such a tool was used to evaluate the maximum power, the fuel consumption rate, the Coulombic efficiency and the energy conversion efficiency of ten similarly built 1.3 L single-chamber MFCs. Although structural and operating condition choices will lead to improved performance, these results investigate for the first time the performance of MFCs in continuous maximum power point condition and characterize MFCs in realistic energy harvesting conditions. Harvesting energy at maximum power point is the main thread of the manuscript. This is made possible with dedicated energy processing circuits embedding control feedback to regulate the MFC voltage to a fraction of its open-circuit voltage. Two typical scenarios are developed as outlined below. One critical application concerns autonomous low-power energy scavenging, to supply remote low-power electronic devices (e.g. wireless sensors). In this case, the low-power and low-voltage constraints imposed by MFCs require dedicated self start-up features. The Armstrong oscillator, composed of high turn-ratio coupled inductors and of a normally-on switch, permits to autonomously step-up voltages from a low DC source like MFCs. Although the circuit requires few components, its operation is not trivial because it partly relies on the parasitic elements of the inductors and the switch. Proper sizing of the inductors enables an optimized operation. This circuit can be associated with power electronic AC/DCand DC/DC converters to realize a voltage-lifter and a fly back-based self-starting Power Management Unit (PMU) respectively. The former is suitable for powering levels below 1mW, while the latter can be scaled for power levels of a few units of mW and facilitates implementation of maximum power point control. A second application of interest concerns the case where energy is harvested from several MFCs.Serial association can be used to step-up voltage but may lead to detrimental consequences in terms of performances because of hydraulic couplings between MFCs sharing the same electrolyte (e.g. if the MFCs are running in continuous flow) or because of electrical non-uniformities between cells. Whereas the former issue can be addressed with galvanically insulated PMUs, the latter can be solved with voltagebalancing circuits. Three of these latter circuits were analyzed and evaluated. The “complete disconnection” circuit isolates a faulty cell from the configuration to ensure it does not impede the overall efficiency. The “switched-capacitor” circuit transfers energy from the strong to the weak MFCs to equilibrate the voltages of the individual cells in the stack. The “switched-MFC” circuit alternatively connects MFCs in parallel and in series. Each of the three methods can be implemented at low-cost and at high efficiency, the most efficient one being the “switched-capacitor”, that permits to harvest more that 85% of the ideal maximum energy of a strongly-non-uniform MFC association.Les Piles Ă  Combustible Microbiennes (PCMs) mettent en Ɠuvre le mĂ©tabolisme de micro-organismes et utilisent de la matiĂšre organique pour gĂ©nĂ©rer de l’énergie Ă©lectrique. Les applications potentielles incluent le traitement de l’eau autonome en Ă©nergie, les bio-batteries, et le grappillage d’énergie ambiante. Les PCMs sont des Ă©quipements basse-tension et basse-puissance dont le comportement est influencĂ© par la vitesse Ă  laquelle l’énergie Ă©lectrique est rĂ©cupĂ©rĂ©e. Dans cette thĂšse, on Ă©tudie des mĂ©thodes pour rĂ©cupĂ©rer l’énergie Ă©lectrique de façon efficace. La tension Ă  laquelle l’énergie est rĂ©cupĂ©rĂ©e des PCMs influence leur fonctionnement et leurs performances Ă©lectriques. La puissance dĂ©livrĂ©e est maximum pour une tension spĂ©cifique (environ 1/3 de la tension en circuit-ouvert). Les PCMs peuvent ĂȘtre testĂ©es Ă  ce point en utilisant une charge contrĂŽlĂ©e automatiquement qui inclut un algorithme de recherche de puissance maximale. Un tel outil a Ă©tĂ© utilisĂ© pour Ă©valuer la puissance maximum, la vitesse de consommation du combustible, le rendement Coulombic et le rendement de conversion de 10 PCMs Ă  chambre unique de 1.3 L construites de façon similaire. Bien que d’autres choix structurels et opĂ©ratoires peuvent permettre d’amĂ©liorer ces performances, ces rĂ©sultats ont Ă©tudiĂ© pour la premiĂšre fois les performances des PCMs en condition de production d’énergie de point de puissance maximal et testĂ© les PCMs avec des conditions de rĂ©cupĂ©ration d’énergie rĂ©alistes. RĂ©cupĂ©rer un maximum d’énergie des PCMs est la ligne directrice de ce rapport. C’est rendu possible par des circuits dĂ©diĂ©s de gestion de l’énergie qui embarquent un contrĂŽle contre-rĂ©actif pour rĂ©guler la tension des PCMs Ă  une valeur de rĂ©fĂ©rence qui est Ă©gale Ă  une fraction de leur tension en circuit ouvert. Deux scĂ©narios typiques sont dĂ©veloppĂ©s dans la suite. Une application critique des PCMs concerne le grappillage autonome de petites Ă©nergies, pour alimenter des Ă©quipements Ă©lectroniques basse-puissance (e.g. capteurs sans fil). Dans ce cas, les contraintes basse-puissance et basse-tension imposĂ©es par les PCMs nĂ©cessitent des fonctionnalitĂ©s de dĂ©marrage autonomes. L’oscillateur d’Armstrong, composĂ© d’inductances couplĂ©es Ă  fort rapport d’enroulement et d’un interrupteur normalement-fermĂ© permet d’élever des tensions de façon autonome Ă  partir de sources basse-tension continue comme les PCMs. Ce circuit a Ă©tĂ© associĂ© Ă  des convertisseurs d’électronique de puissance AC/DC et DC/DC pour rĂ©aliser respectivement un Ă©lĂ©vateur-de-tension et une unitĂ© de gestion de l’énergie (UGE) auto-dĂ©marrante basĂ©e sur une architecture flyback. La premiĂšre est adaptĂ©e pour les puissances infĂ©rieures Ă  1mW, alors que la seconde peut ĂȘtre dimensionnĂ©e pour des niveaux de puissance de quelques mW et permet de mettre en Ɠuvre une commande qui recherche le point de puissance maximale du gĂ©nĂ©rateur. Une seconde application d’intĂ©rĂȘt concerne le cas oĂč de l’énergie est rĂ©cupĂ©rĂ©e depuis plusieurs PCMs. L’association sĂ©rie peut ĂȘtre utilisĂ©e pour Ă©lever la tension de sortie mais elle peut avoir des consĂ©quences nĂ©gatives en terme de performances Ă  cause des non-uniformitĂ©s entre cellules. Cet aspect peut ĂȘtre rĂ©solu avec des circuits d’équilibrage de tension. Trois de ces circuits ont Ă©tĂ© analysĂ©s et Ă©valuĂ©s. Le circuit “complete disconnection” dĂ©connecte une cellule dĂ©fectueuse de l’association pour s’assurer qu’elle ne diminue pas le rendement global. Le circuit “switched-capacitor” transfĂšre de l’énergie depuis les MFCs fortes vers les faibles pour Ă©quilibrer les tensions de toutes les cellules de l’association. Le circuit “switched-MFCs” connecte les PCMs en parallĂšle et en sĂ©rie de façon alternĂ©e. Chacune des trois mĂ©thodes peut ĂȘtre mise en Ɠuvre Ă  bas prix et Ă  haut rendement, la plus efficace Ă©tant la “switchedcapacitor”qui permet de rĂ©cupĂ©rer plus de 85% de la puissance maximum idĂ©ale d’une association trĂšs largement non uniforme

    Power Management for Microbial Fuel Cells

    No full text
    Microbial fuel cells (MFCs) harness the metabolism of micro-organisms and utilize organic matter to generate electrical energy. They are interesting because they accept a wide range of organic matter as a fuel. Potential applications include autonomous wastewater treatment, bio-batteries, and ambient energy scavenging. MFCs are low-voltage, low-power devices that are influenced by the rate at which electrical energy is harvested at their output. In this thesis, we study methods to harvest electrical energy efficiently. The voltage at which energy is harvested from MFCs influences their operation and electrical performance. The output power is maximum for a certain voltage value (approx. 1/3rd the open-circuit voltage). This noteworthy operating point is favorable in some applications where MFCs are used as a power supply. MFCs can be tested at this point using an automatic load adjuster which includes a maximum power point tracking algorithm. Such a tool was used to evaluate the maximum power, the fuel consumption rate, the Coulombic efficiency and the energy conversion efficiency of ten similarly built 1.3 L single-chamber MFCs. Although structural and operating condition choices will lead to improved performance, these results investigate for the first time the performance of MFCs in continuous maximum power point condition and characterize MFCs in realistic energy harvesting conditions. Harvesting energy at maximum power point is the main thread of the manuscript. This is made possible with dedicated energy processing circuits embedding control feedback to regulate the MFC voltage to a fraction of its open-circuit voltage. Two typical scenarios are developed as outlined below. One critical application concerns autonomous low-power energy scavenging, to supply remote low-power electronic devices (e.g. wireless sensors). In this case, the low-power and low-voltage constraints imposed by MFCs require dedicated self start-up features. The Armstrong oscillator, composed of high turn-ratio coupled inductors and of a normally-on switch, permits to autonomously step-up voltages from a low DC source like MFCs. Although the circuit requires few components, its operation is not trivial because it partly relies on the parasitic elements of the inductors and the switch. Proper sizing of the inductors enables an optimized operation. This circuit can be associated with power electronic AC/DC and DC/DC converters to realize a voltage-lifter and a flyback-based self-starting Power Management Unit (PMU) respectively. The former is suitable for powering levels below 1 mW, while the latter can be scaled for power levels of a few units of mW and facilitates implementation of maximum power point control. A second application of interest concerns the case where energy is harvested from several MFCs. Serial association can be used to step-up voltage but may lead to detrimental consequences in terms of performances because of hydraulic couplings between MFCs sharing the same electrolyte (e.g. if the MFCs are running in continuous flow) or because of electrical non-uniformities between cells. Whereas the former issue can be addressed with galvanically insulated PMUs, the latter can be solved with voltage balancing circuits. Three of these latter circuits were analyzed and evaluated. The "complete disconnection" circuit isolates a faulty cell from the configuration to ensure it does not impede the overall efficiency. The "switched-capacitor" circuit transfers energy from the strong to the weak MFCs to equilibrate the voltages of the individual cells in the stack. The "switched-MFC" circuit alternatively connects MFCs in parallel and in series. Each of the three methods can be implemented at low-cost and at high efficiency, the most efficient one being the "switched-capacitor", that permits to harvest more that 85 % of the ideal maximum energy of a strongly-non-uniform MFC association.Les Piles Ă  Combustible Microbiennes (PCMs) mettent en oeuvre le mĂ©tabolisme de micro-organismes et utilisent de la matiĂšre organique pour gĂ©nĂ©rer de l'Ă©nergie Ă©lectrique. Les applications potentielles incluent le traitement d'eau usĂ©e autonome en Ă©nergie, les bio-batteries, et le grappillage d'Ă©nergie ambiante. Les PCMs sont des Ă©quipements basse-tension et basse-puissance dont le comportement est influencĂ© par la vitesse Ă  laquelle l'Ă©nergie Ă©lectrique est rĂ©cupĂ©rĂ©e. Dans cette thĂšse, on Ă©tudie des mĂ©thodes pour rĂ©cupĂ©rer l'Ă©nergie Ă©lectrique de façon efficace. La tension Ă  laquelle l'Ă©nergie est rĂ©cupĂ©rĂ©e des PCMs influence leur fonctionnement et leurs performances Ă©lectriques. La puissance dĂ©livrĂ©e est maximum pour une tension spĂ©cifique (environ 1/3 de la tension en circuit-ouvert). Les PCMs ont Ă©tĂ© testĂ©es Ă  ce point en utilisant une charge contrĂŽlĂ©e automatiquement qui inclut un algorithme de recherche de puissance maximale. Un tel outil a Ă©tĂ© utilisĂ© pour Ă©valuer la puissance maximum, la vitesse de consommation du combustible, le rendement Coulombic et le rendement de conversion de 10 PCMs Ă  chambre unique de 1.3 L, construites de façon similaire. Bien que d'autres choix structurels et opĂ©ratoires peuvent permettre d'amĂ©liorer ces performances, ces rĂ©sultats ont Ă©tudiĂ© pour la premiĂšre fois les performances des PCMs en condition de production d'Ă©nergie de point de puissance maximal et les PCMs ont Ă©tĂ© testĂ©es avec des conditions de rĂ©cupĂ©ration d'Ă©nergie rĂ©alistes. RĂ©cupĂ©rer un maximum d'Ă©nergie des PCMs est la ligne directrice de ce rapport. Cela est rendu possible par des circuits dĂ©diĂ©s de gestion de l'Ă©nergie qui embarquent un contrĂŽle contre-rĂ©actif pour rĂ©guler la tension des PCMs Ă  une valeur de rĂ©fĂ©rence qui est Ă©gale Ă  une fraction de leur tension en circuit ouvert. Deux scĂ©narios typiques sont dĂ©veloppĂ©s dans la suite. Une application critique des PCMs concerne le grappillage autonome de petites Ă©nergies, pour alimenter des Ă©quipements Ă©lectroniques basse-puissance (e.g. capteurs sans fil). Dans ce cas, les contraintes basse-puissance et basse-tension imposĂ©es par les PCMs nĂ©cessitent des fonctionnalitĂ©s de dĂ©marrage autonomes. L'oscillateur d'Armstrong, composĂ© d'inductances couplĂ©es Ă  fort rapport d'enroulement et d'un interrupteur normalement-fermĂ© permet d'Ă©lever des tensions de façon autonome Ă  partir de sources basse-tension continues comme les PCMs. Ce circuit a Ă©tĂ© associĂ© Ă  des convertisseurs d'Ă©lectronique de puissance AC/DC et DC/DC pour rĂ©aliser respectivement un Ă©lĂ©vateur-de-tension et une unitĂ© de gestion de l'Ă©nergie (UGE) auto-dĂ©marrante basĂ©e sur une architecture flyback. La premiĂšre est adaptĂ©e pour les puissances infĂ©rieures Ă  1 mW, alors que la seconde peut ĂȘtre dimensionnĂ©e pour des niveaux de puissance de quelques mW et permet de mettre en oeuvre une commande qui recherche le point de puissance maximal du gĂ©nĂ©rateur. Une seconde application d'intĂ©rĂȘt concerne le cas oĂč de l'Ă©nergie est rĂ©cupĂ©rĂ©e depuis plusieurs PCMs. L'association sĂ©rie peut ĂȘtre utilisĂ©e pour Ă©lever la tension de sortie mais elle peut avoir des consĂ©quences nĂ©gatives en terme de performances Ă  cause des non-uniformitĂ©s entre cellules. Cet aspect peut ĂȘtre rĂ©solu avec des circuits d'Ă©quilibrage de tension. Trois de ces circuits ont Ă©tĂ© analysĂ©s et Ă©valuĂ©s. Le circuit " complete disconnection " dĂ©connecte une cellule dĂ©fectueuse de l'association pour s'assurer qu'elle ne diminue pas le rendement global. Le circuit " switched-capacitor " transfĂšre de l'Ă©nergie depuis les MFCs fortes vers les faibles pour Ă©quilibrer les tensions de toutes les cellules de l'association. Le circuit " switched-MFCs " connecte les PCMs en parallĂšle et en sĂ©rie de façon alternĂ©e. Chacune des trois mĂ©thodes peut ĂȘtre mise en oeuvre Ă  bas prix et Ă  haut rendement, la plus efficace Ă©tant la " switched-capacitor " qui permet de rĂ©cupĂ©rer plus de 85 % de la puissance maximum idĂ©ale d'une association trĂšs largement non uniform

    Power management for microbial fuel cells

    No full text
    Les Piles Ă  Combustible Microbiennes (PCMs) mettent en Ɠuvre le mĂ©tabolisme de micro-organismes et utilisent de la matiĂšre organique pour gĂ©nĂ©rer de l Ă©nergie Ă©lectrique. Les applications potentielles incluent le traitement de l eau autonome en Ă©nergie, les bio-batteries, et le grappillage d Ă©nergie ambiante. Les PCMs sont des Ă©quipements basse-tension et basse-puissance dont le comportement est influencĂ© par la vitesse Ă  laquelle l Ă©nergie Ă©lectrique est rĂ©cupĂ©rĂ©e. Dans cette thĂšse, on Ă©tudie des mĂ©thodes pour rĂ©cupĂ©rer l Ă©nergie Ă©lectrique de façon efficace. La tension Ă  laquelle l Ă©nergie est rĂ©cupĂ©rĂ©e des PCMs influence leur fonctionnement et leurs performances Ă©lectriques. La puissance dĂ©livrĂ©e est maximum pour une tension spĂ©cifique (environ 1/3 de la tension en circuit-ouvert). Les PCMs peuvent ĂȘtre testĂ©es Ă  ce point en utilisant une charge contrĂŽlĂ©e automatiquement qui inclut un algorithme de recherche de puissance maximale. Un tel outil a Ă©tĂ© utilisĂ© pour Ă©valuer la puissance maximum, la vitesse de consommation du combustible, le rendement Coulombic et le rendement de conversion de 10 PCMs Ă  chambre unique de 1.3 L construites de façon similaire. Bien que d autres choix structurels et opĂ©ratoires peuvent permettre d amĂ©liorer ces performances, ces rĂ©sultats ont Ă©tudiĂ© pour la premiĂšre fois les performances des PCMs en condition de production d Ă©nergie de point de puissance maximal et testĂ© les PCMs avec des conditions de rĂ©cupĂ©ration d Ă©nergie rĂ©alistes. RĂ©cupĂ©rer un maximum d Ă©nergie des PCMs est la ligne directrice de ce rapport. C est rendu possible par des circuits dĂ©diĂ©s de gestion de l Ă©nergie qui embarquent un contrĂŽle contre-rĂ©actif pour rĂ©guler la tension des PCMs Ă  une valeur de rĂ©fĂ©rence qui est Ă©gale Ă  une fraction de leur tension en circuit ouvert. Deux scĂ©narios typiques sont dĂ©veloppĂ©s dans la suite. Une application critique des PCMs concerne le grappillage autonome de petites Ă©nergies, pour alimenter des Ă©quipements Ă©lectroniques basse-puissance (e.g. capteurs sans fil). Dans ce cas, les contraintes basse-puissance et basse-tension imposĂ©es par les PCMs nĂ©cessitent des fonctionnalitĂ©s de dĂ©marrage autonomes. L oscillateur d Armstrong, composĂ© d inductances couplĂ©es Ă  fort rapport d enroulement et d un interrupteur normalement-fermĂ© permet d Ă©lever des tensions de façon autonome Ă  partir de sources basse-tension continue comme les PCMs. Ce circuit a Ă©tĂ© associĂ© Ă  des convertisseurs d Ă©lectronique de puissance AC/DC et DC/DC pour rĂ©aliser respectivement un Ă©lĂ©vateur-de-tension et une unitĂ© de gestion de l Ă©nergie (UGE) auto-dĂ©marrante basĂ©e sur une architecture flyback. La premiĂšre est adaptĂ©e pour les puissances infĂ©rieures Ă  1mW, alors que la seconde peut ĂȘtre dimensionnĂ©e pour des niveaux de puissance de quelques mW et permet de mettre en Ɠuvre une commande qui recherche le point de puissance maximale du gĂ©nĂ©rateur. Une seconde application d intĂ©rĂȘt concerne le cas oĂč de l Ă©nergie est rĂ©cupĂ©rĂ©e depuis plusieurs PCMs. L association sĂ©rie peut ĂȘtre utilisĂ©e pour Ă©lever la tension de sortie mais elle peut avoir des consĂ©quences nĂ©gatives en terme de performances Ă  cause des non-uniformitĂ©s entre cellules. Cet aspect peut ĂȘtre rĂ©solu avec des circuits d Ă©quilibrage de tension. Trois de ces circuits ont Ă©tĂ© analysĂ©s et Ă©valuĂ©s. Le circuit complete disconnection dĂ©connecte une cellule dĂ©fectueuse de l association pour s assurer qu elle ne diminue pas le rendement global. Le circuit switched-capacitor transfĂšre de l Ă©nergie depuis les MFCs fortes vers les faibles pour Ă©quilibrer les tensions de toutes les cellules de l association. Le circuit switched-MFCs connecte les PCMs en parallĂšle et en sĂ©rie de façon alternĂ©e. Chacune des trois mĂ©thodes peut ĂȘtre mise en Ɠuvre Ă  bas prix et Ă  haut rendement, la plus efficace Ă©tant la switchedcapacitor qui permet de rĂ©cupĂ©rer plus de 85% de la puissance maximum idĂ©ale d une association trĂšs largement non uniforme.Microbial fuel cells (MFCs) harness the metabolism of micro-organisms and utilize organic matter to generate electrical energy. They are interesting because they accept a wide range of organic matter as a fuel. Potential applications include autonomous wastewater treatment, bio-batteries, and ambient energy scavenging. MFCs are low-voltage, low-power devices that are influenced by the rate at which electrical energy is harvested at their output. In this thesis, we study methods to harvest electrical energy efficiently. The voltage at which energy is harvested from MFCs influences their operation and electrical performance. The output power is maximum for a certain voltage value (approx. 1/3rd the open-circuit voltage). This noteworthy operating point is favorable in some applications where MFCs are used as a power supply. MFCs can be tested at this point using an automatic load adjuster which includes a maximum power point tracking algorithm. Such a tool was used to evaluate the maximum power, the fuel consumption rate, the Coulombic efficiency and the energy conversion efficiency of ten similarly built 1.3 L single-chamber MFCs. Although structural and operating condition choices will lead to improved performance, these results investigate for the first time the performance of MFCs in continuous maximum power point condition and characterize MFCs in realistic energy harvesting conditions. Harvesting energy at maximum power point is the main thread of the manuscript. This is made possible with dedicated energy processing circuits embedding control feedback to regulate the MFC voltage to a fraction of its open-circuit voltage. Two typical scenarios are developed as outlined below. One critical application concerns autonomous low-power energy scavenging, to supply remote low-power electronic devices (e.g. wireless sensors). In this case, the low-power and low-voltage constraints imposed by MFCs require dedicated self start-up features. The Armstrong oscillator, composed of high turn-ratio coupled inductors and of a normally-on switch, permits to autonomously step-up voltages from a low DC source like MFCs. Although the circuit requires few components, its operation is not trivial because it partly relies on the parasitic elements of the inductors and the switch. Proper sizing of the inductors enables an optimized operation. This circuit can be associated with power electronic AC/DCand DC/DC converters to realize a voltage-lifter and a fly back-based self-starting Power Management Unit (PMU) respectively. The former is suitable for powering levels below 1mW, while the latter can be scaled for power levels of a few units of mW and facilitates implementation of maximum power point control. A second application of interest concerns the case where energy is harvested from several MFCs.Serial association can be used to step-up voltage but may lead to detrimental consequences in terms of performances because of hydraulic couplings between MFCs sharing the same electrolyte (e.g. if the MFCs are running in continuous flow) or because of electrical non-uniformities between cells. Whereas the former issue can be addressed with galvanically insulated PMUs, the latter can be solved with voltagebalancing circuits. Three of these latter circuits were analyzed and evaluated. The complete disconnection circuit isolates a faulty cell from the configuration to ensure it does not impede the overall efficiency. The switched-capacitor circuit transfers energy from the strong to the weak MFCs to equilibrate the voltages of the individual cells in the stack. The switched-MFC circuit alternatively connects MFCs in parallel and in series. Each of the three methods can be implemented at low-cost and at high efficiency, the most efficient one being the switched-capacitor , that permits to harvest more that 85% of the ideal maximum energy of a strongly-non-uniform MFC association.LYON-Ecole Centrale (690812301) / SudocSudocFranceF

    Voltage balancing circuit for energy harvesting from a stack of serially-connected Microbial Fuel Cells

    No full text
    International audienceMicrobial Fuel Cells (MFCs) harness the metabolism of micro-organisms to generate electrical energy from organic matter. MFCs offer great promise for simultaneous wastewater treatment and green energy production. The association of a large number of individual MFCs offers very interesting perspectives for electrical energy generation. It can scale-up the low output voltage of an individual cell to enable output voltages to levels acceptable by commercially-available DC/DC converters and it permits to mutualize the electrical powers of each cell. The serial association of a large number of MFCs is a challenge itself for many reasons. Firstly the hydraulic couplings (when MFCs share the same substrate) witch cause leakage of electrical-charge careers between the connected reactors. Secondly the non-uniformities between generators which lead to a non-optimal energy recovery because the associated cells do not able to operate at Maximum Power Point (MPP). Non-uniformities can be compensated with electronic circuits to prevent voltage reversal or enable voltage equalizing. In this paper a balancing method is studied and adapted for energy harvesting from a stack of serially connected MFCs. The balancing circuit was simulated, realized and tested for energy harvesting. With balancing method the cell voltage of MFCs in a stack can be equalized and the performance of MFCs can be improved and it leads to an optimal energy recovery of the stack

    Electrical energy generation from a large number of microbial fuel cells operating at maximum power point electrical load

    No full text
    International audienceMicrobial fuel cells (MFCs) convert organic matter into electrical power. For most applications, the electrical-load seen from the MFC can advantageously be controlled by a DC/DC inductive converter. Implementation of a so-called maximum power point tracking (MPPT) control permits to set the operating point of the MFC to optimize power harvesting whatever the actual load. This paper studies the electrical performances of MFCs under maximum power point (MPP) load conditions. Ten similar single-chamber 1.3 L MFCs are constructed and simultaneously tested. For an identical amount of injected organic matter (1 g of acetate), the "perturbation and observation" (P&O) algorithm achieves a best electrical energy production of 985 J electrical power, corresponding to 8.6 % global energy conversion efficiency (ECE). A novel algorithm that regulates MFC voltage to one-third its open-circuit voltage is introduced and compared to the state of the art P&O algorithm. It enables a best conversion efficiency of 7.7 % and promises low-cost effective implementation in silicon DC/DC converters

    Progress in Microbial Fuel Cells Energy Production

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    International audienceBiological fuel cells are devices capable of directly transforming chemical to electrical energy via electrochemical reactions involving biochemical pathways. Among others, microbial fuel cells (MFCs) use bacterial metabolism at the anode to produce electricity from a wide range of organic substrate. While the idea of harvesting energy produced by MFCs is sprouting, two major issues need to be addressed: low power densities and high manufacturing cost. A typical 1 liter reactor produces no more than 10mW of electrical power, while the costs of the materials to manufacture it is above 30€. High price is caused by the use of nafion and platinum respectively in the membrane and the cathode. A lowcost (and low power density) MFC was built. Earthen membrane replaced nafion and biocathode replaced platinum cathode. Other more common works investigate single chamber air-cathode reactors where the membrane and the cathode are combined. Recent multidisciplinary works on reactor designs, electrodes, substrate and bacterial communities address price and performance issues altogether. In the near future, electrical engineers will contribute by designing adapted power management modules to capture and make use of the harvested energy. The way is long before MFCs can reach the present competitiveness of other renewable energy sources like photovoltaic modules. First applications of MFCs will most likely be to power micro-sensors in remote areas

    Récupération de l'énergie électrique produite par les piles à combustibles microbiennes

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    Les Piles à Combustibles Microbiennes (PCMs) produisent de l'électricité à partir de la dégradation de matiÚre organique par des bactéries. Pour récupérer l'énergie électrique produite, des architectures mettant en jeux plusieurs piles seront préférées à des architectures basées sur une pile unique de taille importante. Par ailleurs la nécessité d'élever les tensions, de mutualiser les puissances et d'adapter la charge à la source passent par le choix et le dimensionnement d'une chaßne judicieuse de convertisseurs de puissance spécifiques (faible tension d'entrée et basse puissance) au sein d'un réseau de PCMs. Le nombre de micro-sources considérées conduit naturellement à envisager la cellularisation de la conversion avec mise en réseau série et/ou parallÚle des convertisseurs. Une récupération efficace de l'énergie passe également par l'intégration de la fonctionnalité MPPT (Maximum Power Point Tracking) qui permet d'adapter la charge à la pile
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