Les vingt dernières années ont vu l’émergence de systèmes sans fil dans la vie de tous les jours. Ils ont rendu possible la création de technologies telles que les téléphones portables, le WiFi ou l’internet mobile qui sont maintenant tenus pour acquis dans la société actuelle. L’impact environnemental des technologies de l’information et des communications connaît une croissance exponentielle et a atteint l’impact de l’industrie du transport aérien. L’initiative d’informatique verte a été lancée en réponse à cette observation pour réduire de 15 à 30% les émissions de gaz à effet de serre en 2020 comparé aux prédictions faites en 2002 afin de garder le réchauffement climatique inférieur à 2°C. Dans cette thèse, nous avons étudié des techniques d’économie d’énergie dans les réseaux sans fil et comment elles interagissent entre elles afin de donner une vue holistique des réseaux verts. Nous prenons également en compte l’usage du spectre radio fréquence qui est le moyen le plus utilisé pour les communications entre systèmes sans fil et qui devient une ressource rare à cause du besoin grandissant de notre société pour de la bande passante en mobilité. Cette thèse suit les couches réseaux avant de remonter les piles matérielleset logicielles. Des contributions ont été apportées à la plupart des couches afin de proposer un réseau sans fil autonome où les noeuds peuvent collaborer pour améliorer les performances du réseau, réduire de façon globale l’utilisation du spectre radio tout en limitant la consommation énergétique du réseau. / The last twenty years saw the emergence of wireless systems in everyday’s life. They made possible technologies such as mobile phones, WiFi or mobile Internet which are now taken for granted in today’s society. The environmental impact of Information and Communications Technology (ICT) has been raising exponentially to equate the impact of the airline industry. The green computing initiative has been created in response to this observation in order to meet the 15%-30% reduction in green-house gases by 2020 compared to estimations made in 2002 to keep the global temperature increasebelow 2°C. In this thesis, we studied power-saving techniques in wireless networks and how they interact with each others to provide a holistic view of green networking. We also take into account the radio frequency resource which is the most commonly usedcommunication medium for wireless systems and is becoming a scarce resource due to our society’s ever-increasing need for mobile bandwidth. This thesis goes down the network stacks before going up the hardware and software stack. Contributions have been madeat most layers in order to propose an autonomic wireless network where nodes can work collaboratively to improve the network’s performance, globally reduce the radio frequency spectrum usage while also increasing their battery life.

Les systèmes de cogénération (SC) sont largement définis par la production simultanée ou coïncidente de la production combinée de chaleur et d'électricité. L’idée de la cogénération revêt une importance particulière puisqu’elle est un outil de réduction des émissions à effet de serre. Comme les systèmes électriques ont été développés selon les carburants et leur utilisation énergétique, de même, les SC ont été développés afin d'utiliser l'énergie possible du carburant pour produire de l’électricité et de la chaleur. La décentralisation de la production électrique est désormais un événement existant. La favorisation maximale de l’électricité d’origine renouvelable ou des systèmes de
cogénération, a abouti à cette décentralisation formant une partie de la production électrique.
Cette thèse est appliquée au cas du système électrique libanais. Elle sert à évaluer la puissance optimale de cogénération qui doit être installée par le secteur public ou le secteur privé, ainsi que la mise en évidence des impacts économiques et environnementaux dus à l’intégration des SC et des énergies renouvelables dans le réseau. Dans ce travail de thèse, nous nous sommes intéressés à l’intégration des systèmes de cogénération dans un réseau électrique. Nous avons travaillé sur deux thèmes principaux et les avons appliqués au cas du réseau électrique libanais. Le premier thème principal est l’innovation d’une stratégie de prise de décision qui sert à trouver une puissance de cogénération respectant l’économie et l’environnement. Le second thème principal est l’optimisation et le contrôle du réseau électrique en fonction des énergies renouvelables (ER) et des SC intégrés. Les deux thèmes cités sont ensuite appliqués au cas du réseau électrique libanais pour montrer les avantages de l’intégration des SC et des ER dans ce réseau. / Cogeneration systems (CS) are largely defined by the simultaneous or coincident production of combined heat and power. The idea of cogeneration is of particular importance since it is a tool for reducing greenhouse gases emissions. As electrical systems have been developed according to the fuel and energy use, the CS have been developed to profit from the possible potential of the fuel energy to produce electricity and heat. Decentralization of power generation is considered an important fact. The maximum use of electricity from renewable sources or cogeneration systems, has leaded to the decentralization of power generation.This thesis is applied to the Lebanese electrical system. It is used to assess the optimum cogeneration power to be installed by the public sector or the private sector, as well as highlighting the economic and environmental impacts due to the integration of the CS and renewables into the grid. In this thesis, we focused on the integration of cogeneration systems into a grid. We worked on two major themes and have applied them to the case of the Lebanese electrical grid. The first main theme is the innovation of a new decision making strategy to find the cogeneration power respecting the economy and the environment. The second main theme is the optimization and the control of the electrical grid due to the integration of renewable energy (RE) and CS. The two themes cited are then applied to the case of the Lebanese electrical grid to show the benefits of the integration of RE and CS into this grid.

<p>This doctoral thesis presents new ideas and research results on control of marine electric power system.</p><p>The main motivation for this work is the development of a control system, power management system (PMS) capable to improve the system robustness to blackout, handle major power system faults, minimize the operational cost and keep the power system machinery components under minimal stress in all operational conditions.</p><p>Today, the electric marine power system tends to have more system functionality implemented in integrated automation systems. The present state of the art type of tools and methods for analyzing marine power systems do only to a limited extent utilize the increased knowledge available within each of the mechanical and electrical engineering disciplines.</p><p>As the propulsion system is typically consisted of the largest consumers on the vessel, important interactions exists between the PMS and vessel propulsion system. These are interacted through the dynamic positioning (DP) controller, thrust allocation algorithm, local thruster controllers, generators' local frequency and voltage controllers. The PMS interacts with the propulsion system through the following main functions: available power static load control, load rate limiting control and blackout prevention control (i.e. fast load reduction). These functions serve to prevent the blackout and to ensure that the vessel will always have enough power.</p><p>The PMS interacts with other control systems in order to prevent a blackout and to minimize operational costs. The possibilities to maximize the performance of the vessel, increase the robustness to faults and decrease a component wear-out rate are mainly addressed locally for the individual control systems. The solutions are mainly implicative (for e.g. local thruster control, or DP thrust allocation), and attention has not been given on the interaction between these systems, the power system and PMS. Some of the questions that may arise regarding the system interactions, are as follows: how the PMS functionality may affect a local thruster control, how the local thruster control may affect the power system performance, how some consumers may affect the power system performance in normal operations and thus affect other consumers, how the power system operation may affect the susceptibility to faults and blackout, how various operating and weather conditions may affect the power system performance and thus propulsion performance though the PMS power limiting control, how propulsion performance may affect the overall vessel performance, which kind of faults can be avoided if the control system is re-structured, how to minimize the operational costs and to deal with the conflicting goals. This PhD thesis aims to provide answers to such questions.</p><p>The main contributions of this PhD thesis are:</p><p>− A new observer-based fast load reduction system for the blackout prevention control has been proposed. When compared to the existing fast load reduction systems, the proposed controller gives much faster blackout detection rate, high reliability in the detection and faster and more precise load reduction (within 150 miliseconds).</p><p>− New advanced energy management control strategies for reductions in the operational costs and improved fuel economy of the vessel.</p><p>− Load limiting controllers for the reduction of thruster wear-out rate. These controllers are based on the probability of torque loss, real-time torque loss and the thruster shaft</p><p>accelerations. The controllers provide means of redistributing thrust from load fluctuating thrusters to less load fluctuating ones, and may operate independently of the thrust allocation system. Another solution is also proposed where the load limiting controller based on thrust losses is an integrated part of DP thrust allocation algorithm.</p><p>− A new concept of totally integrated thrust allocation system, local thruster control and power system. These systems are integrated through PMS functionality which is contained within each thruster PLC, thereby distributed among individual controllers, and independent of the communications and dedicated controllers.</p><p>− Observer-based inertial controller and direct torque-loss controller (soft anti-spin controller) with particular attention to the control of machine wear-out rate. These controller contribute to general shaft speed control of electrical thrusters, generators and main propulsion prime movers.</p><p>The proposed controllers, estimators and concepts are demonstrated through time-domain simulations performed in MATLAB/SIMULINK. The selected data are typical for the required applications and may differ slightly for the presented cases.</p>

This doctoral thesis presents new ideas and research results on control of marine electric power system. The main motivation for this work is the development of a control system, power management system (PMS) capable to improve the system robustness to blackout, handle major power system faults, minimize the operational cost and keep the power system machinery components under minimal stress in all operational conditions. Today, the electric marine power system tends to have more system functionality implemented in integrated automation systems. The present state of the art type of tools and methods for analyzing marine power systems do only to a limited extent utilize the increased knowledge available within each of the mechanical and electrical engineering disciplines. As the propulsion system is typically consisted of the largest consumers on the vessel, important interactions exists between the PMS and vessel propulsion system. These are interacted through the dynamic positioning (DP) controller, thrust allocation algorithm, local thruster controllers, generators' local frequency and voltage controllers. The PMS interacts with the propulsion system through the following main functions: available power static load control, load rate limiting control and blackout prevention control (i.e. fast load reduction). These functions serve to prevent the blackout and to ensure that the vessel will always have enough power. The PMS interacts with other control systems in order to prevent a blackout and to minimize operational costs. The possibilities to maximize the performance of the vessel, increase the robustness to faults and decrease a component wear-out rate are mainly addressed locally for the individual control systems. The solutions are mainly implicative (for e.g. local thruster control, or DP thrust allocation), and attention has not been given on the interaction between these systems, the power system and PMS. Some of the questions that may arise regarding the system interactions, are as follows: how the PMS functionality may affect a local thruster control, how the local thruster control may affect the power system performance, how some consumers may affect the power system performance in normal operations and thus affect other consumers, how the power system operation may affect the susceptibility to faults and blackout, how various operating and weather conditions may affect the power system performance and thus propulsion performance though the PMS power limiting control, how propulsion performance may affect the overall vessel performance, which kind of faults can be avoided if the control system is re-structured, how to minimize the operational costs and to deal with the conflicting goals. This PhD thesis aims to provide answers to such questions. The main contributions of this PhD thesis are: − A new observer-based fast load reduction system for the blackout prevention control has been proposed. When compared to the existing fast load reduction systems, the proposed controller gives much faster blackout detection rate, high reliability in the detection and faster and more precise load reduction (within 150 miliseconds). − New advanced energy management control strategies for reductions in the operational costs and improved fuel economy of the vessel. − Load limiting controllers for the reduction of thruster wear-out rate. These controllers are based on the probability of torque loss, real-time torque loss and the thruster shaft accelerations. The controllers provide means of redistributing thrust from load fluctuating thrusters to less load fluctuating ones, and may operate independently of the thrust allocation system. Another solution is also proposed where the load limiting controller based on thrust losses is an integrated part of DP thrust allocation algorithm. − A new concept of totally integrated thrust allocation system, local thruster control and power system. These systems are integrated through PMS functionality which is contained within each thruster PLC, thereby distributed among individual controllers, and independent of the communications and dedicated controllers. − Observer-based inertial controller and direct torque-loss controller (soft anti-spin controller) with particular attention to the control of machine wear-out rate. These controller contribute to general shaft speed control of electrical thrusters, generators and main propulsion prime movers. The proposed controllers, estimators and concepts are demonstrated through time-domain simulations performed in MATLAB/SIMULINK. The selected data are typical for the required applications and may differ slightly for the presented cases.

The need for high performance circuits in systems with low-voltage and low-power requirements has exponentially increased during the few last years due to the sophistication and miniaturization of electronic components. Most of these circuits are required to have a very good efficiency behavior in order to extend the battery life of the device. This dissertation addresses two important topics concerning very high efficiency circuits with very high performance specifications. The first topic is the design and implementation of class D audio power amplifiers, keeping their inherent high efficiency characteristic while improving their linearity performance, reducing their quiescent power consumption, and minimizing the silicon area. The second topic is the design and implementation of switching voltage regulators and their controllers, to provide a low-cost, compact, high efficient and reliable power conversion for integrated circuits. The first part of this dissertation includes a short, although deep, analysis on class D amplifiers, their history, principles of operation, architectures, performance metrics, practical design considerations, and their present and future market distribution. Moreover, the harmonic distortion of open-loop class D amplifiers based on pulse-width modulation (PWM) is analyzed by applying the duty cycle variation technique for the most popular carrier waveforms giving an easy and practical analytic method to evaluate the class D amplifier distortion and determine its specifications for a given linearity requirement. Additionally, three class D amplifiers, with an architecture based on sliding mode control, are proposed, designed, fabricated and tested. The amplifiers make use of a hysteretic controller to avoid the need of complex overhead circuitry typically needed in other architectures to compensate non-idealities of practical implementations. The design of the amplifiers based on this technique is compact, small, reliable, and provides a performance comparable to the state-of-the-art class D amplifiers, but consumes only one tenth of quiescent power. This characteristic gives to the proposed amplifiers an advantage for applications with minimal power consumption and very high performance requirements. The second part of this dissertation presents the design, implementation, and testing of switching voltage regulators. It starts with a description and brief analysis on the power converters architectures. It outlines the advantages and drawbacks of the main topologies, discusses practical design considerations, and compares their current and future market distribution. Then, two different buck converters are proposed to overcome the most critical issue in switching voltage regulators: to provide a stable voltage supply for electronic devices, with good regulation voltage, high efficiency performance, and, most important, a minimum number of components. The first buck converter, which has been designed, fabricated and tested, is an integrated dual-output voltage regulator based on sliding mode control that provides a power efficiency comparable to the conventional solutions, but potentially saves silicon area and input filter components. The design is based on the idea of stacking traditional buck converters to provide multiple output voltages with the minimum number of switches. Finally, a fully integrated buck converter based on sliding mode control is proposed. The architecture integrates the external passive components to deliver a complete monolithic solution with minimal silicon area. The buck converter employs a poly-phase structure to minimize the output current ripple and a hysteretic controller to avoid the generation of an additional high frequency carrier waveform needed in conventional solutions. The simulated results are comparable to the state-of-the-art works even with no additional post-fabrication process to improve the converter performance.

Components used in mobile hand-held devices (smart phones and tablets) vary greatly in performance and power consumption. The microprocessors used in these devices also have vastly different capabilities and manufacturing limitations leading to significant variation effects. Battery life is a significant concern to the end users of these products. A stand-alone Android application capable of benchmarking a device's performance and power consumption is introduced. The application does not require the end user to have any analytic equipment or to have a technical background. This enables individual end users to better understand their particular device's performance and battery life interaction. They may also use the application to determine if their device's performance or battery life has degraded over time. Data is also uploaded to a central location so that devices can be compared against each other. The benchmarking application is capable of resolving variation effects caused by device, environmental changes and power management actions. This application demonstrates the feasibility of creating a low cost ecosystem where thousands of devices can be quantitatively compared. / text

What are the elementary particles and how did the universe originate are the main driving forces in the high energy physics. In order to further demonstrate the standard model and discover new physics, several detectors are built for the high energy physics experiments. CMOS pixel sensors (CPS) can achieve an attractive tradeoff among many performance parameters, such as readout speed, granularity, material budget, power dissipation, radiation tolerance and integrating readout circuitry on the same substrate, compared with the hybrid pixel sensors and charge coupled devices. Thus, the CPS is a good candidate for tracking the charged particles in vertex detectors and beam telescopes.The power distribution becomes an important issue in the future detectors, since a considerable amount of sensors will be installed. Unfortunately, the independent powering has been proved to fail. In order to solve the power distribution challenges and to provide noiseless voltages, this thesis focuses on the design of a low noise, limited area, low power consumption and full on-chip power management in CPS chips. The CPS are firstly introduced drawing the design requirements of the power management. The power distribution dedicated to CPS chips is then proposed, in which the power management is utilized as the second power conversion stage. Two full on-chip regulators are proposed to generate the analog power supply voltage and the reference voltage required by correlated double sampling operation, respectively. Two prototypes have verified these regulators. They can meet the requirements of CPS. Moreover, the power management techniques and the radiation tolerance design are also presented in this thesis.

Detta arbete var beställt av Sjöfartshögskolan i Kalmar. Skolan ville ha en enhet som kunde mäta aktiv-, reaktiv- och skenbar effekt, ström, spänning, frekvens och cosϕ på en generator och som kommunicerade vidare dessa värden till en PLC. Detta för att kunna lastfördela lasten mellan ett antal generatorer i kursen Tillämpad elteknik 15 hp där studenterna bygger en generatorinstallation med tre generatorer. Ett funktionsblock för lastfördelning skulle också programmeras. Prototypen som konstruerades baserades på en Arduino Ethernet och kommunikationen löstes med Modbus TCP/IP över Ethernet. Ett lastfördelningsprogram programmerades i form av ett funktionsblock som studenterna kunde importera till CoDeSys v2.3 och använda i sina installationer. Prototypen kunde läsa av värdena med ungefär samma noggrannhet som ett kommersiellt instrument som använder sig av samma mätteknik som prototypen. Uppdateringsfrekvensen var dock lägre än hos ett kommersiellt instrument. Kommunikationen med PLC:n fungerade utan problem. Då ingen undervisning hölls i arbetets slutskede kunde inte lastfördelningen testas på en fullskalig anläggning. Lastfördelningsprogrammet klarade dock av att hålla rätt frekvens på en ensam generator och fungerade som tänkt när programmet testades i en simulator. Prototypen gav fel mätvärden vid kapacitiv last. Vid jämförelse med en kommersiell tångamperemeter visade sig mätfelet bero på mätmetoden då båda gav liknande resultat. Som referens användes en professionell elkvalitetsanalysator. Alla uppdragsgivarens krav blev uppfyllda och arbetet kommer att kunna användas i undervisningen. / This thesis was ordered by Kalmar Maritime Academy. The request was for a device that could measure active, reactive and apparent power, as well as frequency, voltage, current and cosϕ on a generator. The measured values would be communicated to a PLC for use in a load sharing program between a number of generators in the course Tillämpad elteknik, 15 ECTS. In that course the students constructs a three-generator electric power grid. Included in the request was also to program a load sharing program. The prototype being constructed was based on the Arduino Ethernet, and the communication was enabled by means of the Modbus TCP/IP protocol over Ethernet. A load sharing program was created in the form of a function block which the student could import into the CoDeSys for use in the generator systems. The prototype could measure values with close to the same accuracy as a commercial available instrument that were using the same technique for measuring. The refresh rate was however lower than the commercial available instrument. Communication with the PLC worked without any issues. No full-scale testing could be done since no course was held during the final stages of the thesis, however the load sharing program could keep frequency on a single generator alone and worked in a simulated soft environment. Measuring errors occurred when measuring a capacitive load. When comparing to a commercial available clamp meter, the same errors occurred. As a reference a professional power and energy quality analyser was used. All the requests were fulfilled and the result of this thesis will be used in the educational programme at the Academy.

La consommation énergétique est devenue un problème majeur dans la conception des systèmes aussi bien d'un point de vue de la fiabilité des circuits que de l'autonomie d'un équipement embarqué. Cette thèse vise à caractériser et modéliser le coût énergétique du système d'exploitation (OS) embarqué en vue d'explorer des solutions faibles consommation. La première contribution consiste à définir une approche globale de modélisation de la consommation des services de base de l'OS: la stimulation de l'exécution de ces services, tels que le changement de contexte, l'ordonnancement et la communication interprocessus, est effectuée à travers des programmes de test adéquats. Sur la base de mesures de la consommation d'énergie sur la carte OMAP35x EVM, des paramètres pertinents soit matériels soit logiciels ont été identifiés pour en déduire des modèles de consommation. Dans une seconde étape, la prise en compte de ces paramètres doit intervenir au plus haut niveau de la conception. L'objectif sera d'exploiter les fonctionnalités offertes par un langage de modélisation et d'analyse architecturale AADL tout en modélisant les aspects logiciel et matériel en vue d'estimer la consommation d'énergie. Ensuite, les modèles énergétiques de l'OS ont été intégrés dans un simulateur multiprocesseur de politique d'ordonnancement STORM afin d'identifier la consommation de l'OS et ceci pour des politiques d'ordonnancement mettant en œuvre des techniques de réduction de la consommation tel que le DVFS et le DPM. Enfin, la définition et vérification de certaines contraintes temps-réel et énergétiques ont été effectuées avec des langages de spécification de contraintes (QAML, RDAL). / The ever-increasing complexity of embedded systems that are developing their computation performances poses a great challenge for embedded systems designers: power and energy consumption. This thesis focuses on power and energy characterization, modeling, estimation of embedded operating systems (OS) energy consumption. First, an OS energy consumption characterization flow is introduced: a set of benchmarks, which are test programs that stimulate each OS service separately, are implemented. These programs are executed on the hardware platform: OMAP 35x EVM board. Based on hardware measurements, several hardware and software parameters that influence the OS power/energy consumption are identified and energy consumption mathematical models are extracted. The second contribution consists in proposing a high level model of software application, the OS services and hardware platform using an architecture analysis and design language (AADL). Then, AADL and mathematical models of OS services energy consumption are integrated in a multiprocessor scheduling simulator (STORM) in order to evaluate the OS energy overhead when using DPM and DVFS low power techniques. Finally, a flow of definition and verification of system requirements when allocating application tasks to the processors is proposed. Using a set of languages, RDAL and QAML, various real time and energetic constraints are checked when exploring the design.

Les Piles à Combustible Microbiennes (PCMs) produisent de l’électricité à partir de la dégradation de matières organiques par des bactéries. Les PCMs sont considérées comme des micro- génératrices à faible tension et faible puissance. Dans le but de récupérer l’énergie électrique produite afin de pouvoir alimenter des capteurs autonomes, des architectures mettant en œuvre plusieurs piles seront préférées. L'association d'un grand nombre de PCMs individuelles offre des perspectives très intéressantes notamment au niveau de la production d'énergie électrique. Cela permet d’atteindre des niveaux de tension acceptables en sortie et permet de mutualiser les puissances électriques de chaque cellule. L’association série d’un grand nombre de PCMs est un défi en soi à cause des couplages hydrauliques (lorsque les PCMs partagent le même substrat) et à cause des non-uniformités entre générateurs qui mènent à une association non-efficace. Les circuits d'équilibrage de tension peuvent être une solution pour compenser ces inhomogénéités. Ils peuvent améliorer l’efficacité de l’association et prévenir le phénomène d'inversion de tension. L’association hydraulique des biopiles permet d’éviter la chute de puissance liée au manque de carburant. Une fuite de charge entre les PCMs va diminuer le rendement global de l’association. Le débit du flux doit être contrôlé pour éliminer ce problème. Un flux de la cathode vers l’anode provoque des pertes supplémentaires dues à la fuite d’oxygène. La récupération d’énergie à partir de PCMs nécessite une unité de gestion d’énergie qui adapte la tension et contrôle le fonctionnement de la PCM. Un convertisseur flyback à faible tension d’entrée, autonome et auto-démarrant a été conçu et optimisé pour la récupération d’énergie à partir des PCMs. La récupération d’énergie à partir des PCMs peut être présentée comme une source alternative pour éliminer les batteries dans les applications de faible puissance (capteur autonome). / Microbial Fuel Cells (MFCs) are bioreactors that convert chemical energy in organic compounds to electrical energy through the metabolism of microorganisms. Organic matters are widely available in the environment that contains a huge amount of energy. This energy could be harvested, converted, by the technology of MFCs, to be used in certain applications. Energy production of a MFC is limited in low voltage value and low-power values what limits the potential applications. To step-up the voltage of MFCs to be suitable for real applications, an efficient power management unit (PMU) is required with a specific design to deal with their characteristics. A flyback converter under discontinuous conduction mode (DCM) is the most adapted to such low-power source like MFCs, offers a simple implementation, and low losses conversion system. The flyback converter has a good efficiency that can reach 75% with one MFC and about 80% when it is supplied by a serial stack of MFCs. Associations of MFCs are very interesting to increase the output power and expand the domain of application. Parallel association is a method to increase the output current but it imposes limitations in conversion efficiency due to the low output voltage of the stack. Contrarily, the serial association steps-up the voltage what leads to better performance of the converter. However the non-uniformities between cells in a serial stack affect negatively the performance of the stack. Voltage balancing circuits are considered as the solution to compensate this phenomenon. In the switched-capacitor method, an external capacitor is used to transfer the energy from the strongest MFC(s) to the weakest one(s). The losses in the switched-capacitor circuit are less than the losses of the switched-MFCs. The switched-capacitor offers an efficient, simple, low consumption method to optimize the performance and prevent the voltage reversal of the weak cells. Integration of this circuit can optimize the efficiency. Continuous operation mode by hydraulically connection between MFCs can continuously refresh the substrate to give an autonomous energy harvesting system. On the other hand, in some applications, e.g. a wastewater treatment plant, MFCs could not be hydraulically isolated. In this configuration, a leakage charge between the associated MFCs will decrease the global efficiency. The flow rate has to be controlled to eliminate this problem. A flow from cathodes to anodes causes additional losses due to the oxygen leakage. A temperature sensor is continuously supplied by alternatively connecting two MFCs. Each MFC supplies the sensor for two days. The flyback converter is able to continuously supply the sensor from the energy harvested from one continuously-fed MFC. This could be a good example, in a wastewater treatment plant (WWTP), to supply monitoring systems or also to supply low power applications of a building from a local WWTP.