Fred D. Lang

ASME 2009 Power Conference • 2008

This paper presents both criticism and suggested changes to boiler efficiency standards associated with fossil-fired steam generators. These standards include the widely used ASME PTC 4.1, PTC 4 and DIN 1942, and others. The chief criticism is inconsistent application of thermodynamic principles. Specifically, conceptual errors are made with application of reference temperatures and the treatment of shaft powers. When using computed fuel flow as a touchstone, it becomes obvious that arbitrary use of reference temperatures and/or use of capricious energy credits cannot dictate a system’s computed fuel flow. Efficiency, calorific value and fuel flow must have fixed definitions concomitant with a system’s useful energy flow. Thermodynamics is not an arbitrary discipline, the computed fuel needs of a system must describe the actual. Boiler efficiency requires the same treatment, as an absolute value, as actual fuel feed and emission flow. Boiler efficiencies and associated calorific values have obvious standing when judging contractual obligations, for thermal performance monitoring, and for confirming carbon emissions. Note that a 0.5 to 1% change in efficiency may well have significant financial consequences when testing a new unit, or the on-going costs associated with fuel and carbon taxes. This paper demonstrates that errors greater than 2% are entirely possible if following the current standards. This paper appeals to the resolution of efficiency at the 0.1% level. The power plant engineer is encouraged to read the Introduction and Summary & Recommendations sections while the thermodynamicist is requested to throughly review and critique the mid-sections. The author hopes such reviews will advocate for improvement of these important industrial standards.

Shahin S. Lotfabadi

• 2021

Power is a significant design constraint for implementing portable applications. Operating transistors in the subthreshold region can significantly reduce power consumption while reducing performance. The low frequency nature of biosignals makes a FPGA operating subthreshold region a good candidate. In this work, I investigate the feasibility of desinging such a device and the trade-off between power consumpation and performance for FPGA routing resources operating in the subthreshold region. For the 32nm Predictive Technology Model studied in this work, it was observed a power reduction of 197.7 times (or power-delay-product reduction of 3.3 times) for operating under a supply voltage of 0.4 volts (as compared to normal operation in the saturation region using a 0.9V). Under a supply voltage of 0,4 volts, FPGA can operate at 2.0 MHz while allowing signals to propagate unregistered through 20 routing tracks which meets the real-time requirement for processing 20000 samples per second.

Tomohiro Asai, Satoschi Dodo, Mitsuhiro Karishuku et al.

Journal of Engineering for Gas Turbines and Power • 2015

The successful development of coal-based integrated gasification combined cycle (IGCC) technology requires gas turbines capable of achieving the dry low nitrogen oxides (NOx) combustion of hydrogen-rich syngas fuels for low emissions and high plant efficiency. Mitsubishi Hitachi Power Systems, Ltd. (MHPS) has been developing a “multiple-injection burner” to achieve the dry low-NOx (DLN) combustion of hydrogen-rich syngas fuels. The purposes of this paper are to present the test results of a multican combustor equipped with multiple-injection burners in an IGCC pilot plant, and evaluate combustor performance by focusing on the effects of flame shapes. The syngas fuel produced in the plant contained approximately 50% carbon monoxide, 20% hydrogen, and 20% nitrogen by volume. In the tests, the combustor with slenderer flames achieved lower NOx emissions of 10.9 ppm (at 15% oxygen), reduced combustor liner and burner plate metal temperatures, and lowered combustion efficiency at the maximum gas turbine load. The test results showed that the slenderer flames were more effective in reducing NOx emissions and liner/burner plate metal temperatures. A comparison with the diffusion-flame combustor demonstrated that the multiple-injection combustors achieved the dry low-NOx combustion of the syngas fuel in the plant.

Eric Bermudez, Andrew McDaniel, Terrence Dickerson et al.

Journal of Engineering for Gas Turbines and Power • 2016

A new hydroprocessed depolymerized cellulosic diesel (HDCD) fuel has been developed using a process which takes biomass feedstock (principally cellulosic wood) to produce a synthetic fuel that has nominally ½ cycloparaffins and ½ aromatic hydrocarbons in content. This HDCD fuel with a low cetane value (derived cetane number from the ignition quality tester, DCN = 27) was blended with naval distillate fuel (NATO symbol F-76) in various quantities and tested in order to determine how much HDCD could be blended before diesel engine operation becomes problematic. Blends of 20% HDCD (DCN = 45), 30%, 40% (DCN = 41), and 60% HDCD (DCN = 37) by volume were tested with conventional naval distillate fuel (DCN = 49). Engine start performance was evaluated with a conventional mechanically direct injected (DI) Yanmar engine and a Waukesha mechanical indirect injected (IDI) Cooperative Fuels Research (CFR) diesel engine and showed that engine start times increased steadily with increasing HDCD content. Longer start times with increasing HDCD content were the result of some engine cycles with poor combustion leading to a slower rate of engine acceleration toward rated speed. A repeating sequence of alternating cycles which combust followed by a noncombustion cycle was common during engine run-up. Additionally, steady-state engine testing was also performed using both engines. HDCD has a significantly higher bulk modulus than F76 due to its very high aromatic content, and the engines showed earlier start of injection (SOI) timing with increasing HDCD content for equivalent operating conditions. Additionally, due to the lower DCN, the higher HDCD blends showed moderately longer ignition delay (IGD) with moderately shorter overall burn durations. Thus, the midcombustion metric (CA50: 50% burn duration crank angle position) was only modestly affected with increasing HDCD content. Increasing HDCD content beyond 40% leads to significantly longer start times.

, Moradmand Jazi Hamed

• 2025

(English) Nowadays, high step-up converters with fast-dynamic response are demanded for many applications such as uninterruptible power supplies which are used to feed sensitive loads and DC-DC converters in grid connected micro inverters to absorb the maximum power from the PV panels. Several studies have been carried out on high step-up converters to increase voltage gain and efficiency as well as reduce the voltage stress of semiconductors while less attention has been paid to their dynamic response. A converter which can compensate load variations rapidly would have faster dynamic response and lower undershoot and overshoot output voltage and current. In this research, various switching converters will be investigated to achieve new topologies having the capability of faster dynamic response and obtaining higher voltage gain for the above-mentioned applications. Merging some converters has the potential of removing right half plane zero and making converters respond load variations at a faster pace without making any changes in the control circuit and filters. If the integrated converter can deliver power form the input to the load in all operating modes whether the switch is on or not, the converter would compensate load variations with lower interruption. This theory can be evaluated and proved by doing some theoretical and mathematical calculations on the control response and the situation of Zeros and Poles of the closed loop transfer function of the converter. To rate the achievements of this research, the dynamic quantities in the step response of the converters (e. g. overshoot, rise time, and settling time) can be investigated. Also, the voltage gain and efficiency of the converters are important qualities which have to be considered in comparisons. A time table is considered for each stage to ensure that this research can be finished through the next three years. (Català) Actualment, els convertidors elevadors amb una resposta dinàmica ràpida són molt demandats per un gran nombre d’aplicacions, com ara els sistemes d’alimentació ininterrompuda, que s’utilitzen per alimentar càrregues sensibles, i els convertidors DC-DC en microinversors fotovoltaics connectats a la xarxa, que extreuen la màxima potència dels panells fotovoltaics. S’han realitzat diversos estudis sobre convertidors elevadors per augmentar el guany de tensió i l’eficiència, així com per reduir l’estrès de tensió en els semiconductors, tot i que en una primera instància s’ha prestat menys atenció a la seva resposta dinàmica. Un convertidor capaç de compensar ràpidament les variacions de càrrega tindria una resposta dinàmica més ràpida i uns menors sobreimpuls i subimpuls en la tensió i el corrent de sortida. En aquesta investigació, s’estudiaran diversos convertidors commutats per desenvolupar noves topologies amb la capacitat d’oferir una resposta dinàmica més ràpida i un guany de tensió més alt per a les aplicacions esmentades. La combinació d’alguns convertidors té el potencial d’eliminar el zero al semiplà dret i permetre que els convertidors responguin a les variacions de càrrega de manera més ràpida sense fer canvis al circuit de control ni als filtres. Si el convertidor integrat pot transferir energia de l’entrada a la càrrega en tots els modes d’operació, independentment de si l’interruptor està activat o no, el convertidor podria compensar les variacions de càrrega amb menys interrupcions. Aquesta teoria es pot avaluar i demostrar mitjançant càlculs teòrics sobre la resposta de control i la situació dels zeros i pols de la funció de transferència en llaç tancat del convertidor. Per valorar els avenços d’aquesta investigació, es poden analitzar les magnituds dinàmiques en la resposta a un esglaó dels convertidors (com ara el sobreimpuls, el temps de pujada i el temps d’establiment). A més, el guany de tensió i l’eficiència dels convertidors són qualitats importants que cal tenir en compte en les comparacions que es realitzaran. (Español) En la actualidad, los convertidores elevadores con respuesta dinámica rápida son demandados en gran número de aplicaciones, como son los sistemas de alimentación ininterrumpida, utilizados para alimentar cargas sensibles, y los convertidores DC-DC en microinversores fotovoltaicos conectados a la red, que garantizan la extracción de la máxima potencia de los paneles fotovoltaicos. Se han realizado varios estudios sobre convertidores elevadores con el fin de aumentar la ganancia en tensión y la eficiencia, así como para reducir el estrés de voltaje en los semiconductores, mientras que en una primera instancia se ha prestado menos atención a su respuesta dinámica. Un convertidor que pueda compensar rápidamente las variaciones de carga tendría una respuesta dinámica más rápida y unos menores sobreimpulso y subimpulso en el voltaje y la corriente de salida. En esta investigación, se estudiarán diversos convertidores conmutados para lograr nuevas topologías que tengan la capacidad de ofrecer una respuesta dinámica más rápida y una mayor ganancia en tensión para las aplicaciones mencionadas. La combinación de algunos convertidores tiene el potencial de eliminar el cero en el semiplano derecho y permitir que los convertidores respondan a las variaciones de carga a un ritmo más rápido sin realizar cambios en el circuito de control ni de filtrado. Si el convertidor integrado puede transferir energía desde la entrada hasta la carga en todos los modos de operación, independientemente de si el interruptor está activado o no, el convertidor podría compensar las variaciones de carga con una menor interrupción. Esta teoría puede evaluarse y demostrarse mediante cálculos teóricos sobre la respuesta del control y la situación de los ceros y polos de la función de transferencia en lazo cerrado del convertidor. Para evaluar los logros de esta investigación, se pueden analizar las magnitudes dinámicas en la respuesta a un escalón de los convertidores (como el sobreimpulso máximo, el tiempo de subida y el tiempo de establecimiento). Además, la ganancia en tensión y la eficiencia de los convertidores son cualidades importantes que deben considerarse en las comparaciones que se realizarán.

Sai Krishna, Sweta Lal, Suyash Shrivastava et al.

Research Square • 2023

Abstract This work demonstrates the application of a urea-powered paper-based fuel cell (PFC) with Hydrogen Peroxide (H 2 O 2 ) as the oxidant to drive a flexible electronic circuit (ring oscillator (RO)), for the first time. Herein, the electrochemical performance of membraneless PFCs is studied by employing different non-precious electrodes, such as, Nickel-mesh, Toray carbon paper(CP) and Nickel Cobalt nanoparticles supported on reduced Graphene Oxide loaded on the CP (NiCo@rGo@CP). A single-PFC with Ni-Co@rGo@CP as electrodes delivers a peak power density (P max ) of 55 µW cm − 2 , maximum current density (J max ) of 371 µA cm − 2 and an open-circuit voltage (OCV) of 0.7 V at 3 M urea. A membrane-based PFC assembled onto an anion exchange membrane with Ni-Co@rGo@CP electrodes, delivers a P max of approx 70 µW cm − 2 , J max of ≈ 500 µA cm − 2 and an OCV of 0.7 V at 3 M urea. Subsequently, a stack of two membrane-based PFCs delivers an OCV of ≈ 1.4 V for 400 seconds. Finally, this stack is employed as a power source to drive a RO. The measured frequency and peak-to-peak voltage are 37.52 kHz and 1.04 V, respectively. This demonstration opens a window to implement self-contained flexible electronic system using PFC as power source with minimal e-waste.

Jean-Philippe Poirot-Crouvezier, Arnaud Morin, Pierrick Balestriere et al.

ECS Meeting Abstracts • 2023

In this work, experimental and numerical analyses of Proton Exchange Membrane Fuel Cell stacks for automotive application are proposed. Performance and durability of PEMFC stacks strongly rely on an optimized water management. An adequate balance has to be found between a sufficient membrane hydration enhancing electrical conductivity and a limited liquid water presence avoiding water flooding. This requires investigations at a local scale inside the cells, because the location of water condensation is not distributed homogeneously in the active area, due to spatial variations of temperature, gas composition or current density. Allowing the quantification of liquid water locally inside PEMFCs, neutron imaging is a powerful tool for the analysis of fuel cell operation at a local scale. It is generally used with single cells and not with stacks, due to the complexity of such experiments. A quantification of liquid water over the active area is obtained through neutron imaging of stacks for several operating conditions. Specific segmented high surface sensors are placed inside stacks to map the current density and temperature distribution in the same area. A multi-physics pseudo-3D two-phase flow model coupling all the electrochemical and transport phenomena supports the understanding of the relationship between all these parameters. The comparison with experimental mappings validates the model, which is able to predict both the current density and the amount of liquid water at a local scale. Unlike experimental measurements that gives a total amount of liquid water in the cell, the model allows to distinguish between anode and cathode sides, or between channels and GDLs, providing crucial information regarding flooding phenomena. Moreover, the flowing direction of the fluids inside the stack have a major influence on liquid water distribution. As a general trend, it is observed that the average total water thickness always decreases when current density increases, in all tested stack flow configurations. Furthermore, a clear relationship appears between flooding, cathode pressure drop and cathode liquid water content. Finally, a detailed analysis is proposed to explain the flooding phenomena, in order to improve the fuel cell stack control. Figure 1

Olabanji Benjamin Awodumi

Research Square • 2021

Abstract The quest for sustainability and greener economies has intensified the call for more stringent environmental regulation, hence environmental efficiency of production processes that produce growth. Since trade activities represent a huge part of economic growth, while countries are becoming increasingly cautious of their imports, environmental efficiency becomes an integral consideration for trade. This study investigates the link between environmental efficiency and export performance among the top 20 countries on the environmental performance scale utilizing annual data between 1980 and 2019. The classic comparative advantage theory of international trade provides the theoretical basis for the study. Environmental efficiency scores were generated using the slack-based data envelopment analysis while the nature of causality between environmental efficiency and export performance is established using the Pairwise Dumitrescu Hurlin Panel Causality Tests and VECM Granger causality approaches. The export models are estimated using the fully modified and dynamic ordinary least squares approaches.Bidirectional causality is found between export per capita (and export intensity) and environmental efficiency for the panel analysis. Causality results is however mixed at country level with significant unidirectional causal links running from either export to environmental efficiency or otherwise. The FMOLS and DOLS analysis provides evidence of significant positive effect of environmental efficiency on export per capita and export intensity for the panel of the top EPI countries, and confirmed in most of the countries. The study therefore provides strong evidence for the role of environmental efficiency in countries’ efforts to improve their global competitiveness in trade-related activities. Thus, the study emphasizes increased global investment in environmental efficiency as the global economies grow. JEL: F18; Q56; Q58; N40

Tien Q. Nguyen, Daniel Minami, Chau Hua et al.

Journal of Fuel Cell Science and Technology • 2015

Several reports have been made recently of the direct formate fuel cell (DFFC) operating at high-temperature and using Pt cathode catalyst. In the present work, we demonstrate a Pt-free DFFC employing ACTA HypermecTM 4020 Fe–Co second-generation cathode catalyst operating at low-temperature. We report a maximum power density (PD) of 45 mW cm−2 at ambient temperature (20 °C), when the fuel stream was 1 M HCOOK and 2 M KOH with oxygen used at the cathode. When air was used at the cathode, the maximum PD was 35 mW cm−2. When hydroxide was removed from the fuel stream and oxygen used at the cathode, the maximum PD at 20 °C was 18 mW cm−2. This low-temperature, KOH-free operation is important to development of a practical DFFC.

Petroleum and Chemical Industry International • 2021

Hydrogen enrichment in internal combustion engines has been a topic of research interest to improve engine efficiencies and reduce carbon emissions. Hydrogen enrichment has garnered more interest than the pure hydrogen powered engines due to less complexity involved with the modifications of the engine and fuel system as well as the infrastructure required for it. Similarly, accurate chemical kinetics has proved to provide accurate results in terms of engine performance parameters, such as, in-cylinder pressure. The present study is an extension of study performed earlier with hydrogen enrichment in gasoline direct injection engine while using C8 H17 as a surrogate fuel for gasoline and assumes that an on-board electrolysis system installed on the vehicle produces hydrogen for the enrichment purposes. A mesh independent study is performed using 90% iso-octane (iC8 H18) and 10% n-heptane (nC7 H16) blend as a gasoline surrogate with hydrogen enrichment of 0%, 1%, 2% and 3% at equivalence ratios of 0.98 and 1.3, in a premixed spark ignition engine. Numerical simulations are performed to calculate and compare the thermal and combustion efficiencies of the engine using hydrogen-enriched fuel versus iso-octane and n-heptane blend. The study also predicts and measures the engine performance parameter of in-cylinder pressure, while comparing the iso-octane and n-heptane blend against the blend enriched with hydrogen. Based on the results obtained from smaller hydrogen enrichment concentrations, the study increases the hydrogen-enrichment of the fuel to 5%, 10% and 15% to analyse the effects of enrichment on the thermal and combustion efficiencies, as well as the in-cylinder pressure.

Noshin Birjandi, Habibollah Younesi, Ali Asghar Ghoreyshi et al.

Journal of Chemical Technology & Biotechnology • 2015

Abstract BACKGROUND In the present study, the performance of ethanol fermentation by Saccharomyces cerevisiae and glucose degradation in a bio‐electro‐Fenton ( BEF ) system was investigated. This system contained a dual‐chamber microbial fuel cell ( MFC ) with Nafion® membrane as a separator and is equipped with an Fe@ Fe 2 O 3 /graphite electrode. The performance of MFCs under different operational conditions was evaluated in terms of glucose removal, ethanol production and electrical power output. RESULTS The maximum ethanol production in an anaerobic condition was 11.52 g L −1 . The glucose removal was 34.15 and 68.81% and the measured maximum power densities were 13.51 and 30.46 mW m −2 with graphite and Fe@ Fe 2 O 3 /graphite systems, respectively. CONCLUSION The energy production, glucose degradation and fermentation process for ethanol production from glucose by S. cerevisiae was successfully carried out in a BEF system. This study demonstrates that the BEF system, without the requirement for an external electrical energy supply and any addition of H 2 O 2 , is an effective and economical system for wastewater treatment. © 2015 Society of Chemical Industry

SONAM PAL A -, J.C Narayana Swamy -

International Journal For Multidisciplinary Research • 2023

The development of high-efficiency capacitance multipliers and precision rectifiers for VLSI (Very Large-Scale Integration) systems is examined in this work, with a focus on low voltage operation. The major goal is to reduce supply voltage in order to consume energy as little as possible. It has been successfully created for the capacitance multiplier to work properly even with extremely low voltage supply, as low as 0.25 V. Class-AB current mirrors, which are renowned for their outstanding current efficiency, are used in the design. Experimental measurements were made on a 180-nm CMOS-based capacitance multiplier that obtained a multiplication factor of 11 in order to assess performance. The same class-AB current mirrors were also used in the same CMOS technology to construct low-voltage precision rectifiers. Over a hundred times more output current than quiescent current is produced by these rectifiers. Notably, both circuits function with 0.25 V supply and dissipate static power at a rate of only 100 nW. The work shows that low-voltage designs and class-AB current mirrors can be used to produce great performance and efficient power usage in VLSI systems.

Pablo A. Garcia-Salaberri, Hasan Shahzad, Luis Duque et al.

ECS Transactions • 2024

Air-breathing polymer electrolyte fuel cells (PEMFCs) are expected to play an important role in the development of sustainable portable and mobile devices, such as unnamed aerial vehicles, motorbikes or laptops. In this work, the performance of air-breathing PEMFCs with a columnar cathode plate design is examined by means of a 3D two-phase, non-isothermal model, and compared against experimental data. The results show that the performance is highly influenced by the cell orientation, namely horizontal (material plane perpendicular to gravity) versus vertical (material plane parallel to gravity). Oxygen transport in horizontal cells is mainly dominated by diffusion, leading to oxygen shortage toward the cell center and an inhomogeneous current density distribution. In contrast, oxygen transport in vertical cells is assisted by natural convection, enhancing oxygen transport throughout the cell and increasing the current density homogeneity. Water saturation is preferentially accumulated close to the cell center, being larger in horizontal cells due to the lower water removal rate of the cathode plate.

, Mehran Yahyavi

• 2016

Power amplifiers (PAs) are one of the most crucial elements in wireless standards becasue they are the most power hungry subsystems. These elements have to face an important issue, which is the power efficiency, a fact related with the output back-off (OBO). But the OBO depends on the kind of modulated signal, in proportion to the modulated signal peak-to-average power ratio (PAPR). The higuer is the data rate, the higer is the OBO, and consequently the lower is the efficiency. A low efficiency of PAs causes the waste of energy as heat. Furthermore, the trade-off between linearity and efficiency in PAs is another major issue. To cope with the undesired circumstances producing efficiency degradation, the Doherty power amplifier (DPA) is one of the useful techniques which provide high efficiency for high PAPR of modern communication signals. Nevertheless, the limited bandwidth (BW) of this kind of PAs (about 10% of fractional bandwidth) and its importance (in modern wireless systems such as LTE, WiMAX, Wi-Fi and satellite systems) have encouraged the researchers to improve this drawback in recent years. Some typical BW limiting factors effect on the performance of DPAs: i) quarter-wave length transformers, ii) phase compensation networks in/output matching circuits, iii) offset lines and device non-idealities; The quarter-wave length transformers performs as an inverter impedance in the load modulation technique of DPAs. The future objective in designing DPAs is to decrease the impact of these issues. In this context, this PhD-thesis is focused on improving fractional bandwidth of DPAs using the new methods that are related to impedance transformers instead of impedance inverters in the load modulation technique. This study is twofold. First, it is presented a novel DPA where a wideband GaN DPA in the 2.5 GHz band with an asymmetrical Wilkinson splitter. The impedance transformer of the proposed architecture is based on a matching network including a tapered line with multi-section transformer in the main stage. The BW of this DPA has ranged from 1.8 to 2.7 GHz. Plus, the obtained power efficiency (drain) is higher than 33% in the whole BW at both maximum and OBO power levels. Second, based on the benefits of the Klopfenstein taper, a promising DPA design is proposed where a Klopfenstein taper replaces the tapered line. In fact, this substitution results on reducing the reflection coefficient of the transformer. From a practical prototype realization of this novel Doherty-like PA in the 2.25 GHz band, this modification has demonstrated that the resulting DPA BW is increased in comparison to the conventional topology while keeping the efficiency figures. Moreover, this study also shows that the Klopfenstein taper based design allows an easy tuning of the group delay through the output reactance of the taper, resulting in a more straightforward adjustments than other recently published designs where the quarter-wave transformer is replaced by multi-section transmission lines (hybrid or similar). Experimental results have shown 43-54% of drain efficiency at 42 dBm output power, in the range of 1.7 to 2.75 GHz. Concretely, the results presented in this novel Doherty-like PA implies an specific load modulation technique that uses the mixed Klopfenstein tapered line together with a multi-section transformer in order to obtain high bandwidth with the usual efficiency in DPAs. Los amplificadores de potencia (PAs) son uno de los elementos más importantes para los transmisores inalámbricos desde el punto de vista del consumo energético. Un aspecto muy importante es su eficiencia energética, un concepto relacionado con el back-off de salida (OBO), que a su vez viene condicionadpo por el PAPR de la señal modulada a amplificar. Una baja eficiencia de los PA hace que la pérdida de energía se manifieste en forma de calor. De hecho, esta cuestión conduce al incremento de los costes y tamaño, esto último por los radiadores. Además, el compromiso entre la linealidad y la eficiencia en los PA es otro problema importante. Para hacer frente a las circunstancias que producen la degradación de la eficiencia, el amplificador de potencia tipo Doherty (DPA) es una de las técnicas más útiles que proporcionan una buena eficiencia incluso para los altos PAPR comunes en señales de comunicación modernos. Sin embargo, el limitado ancho de banda (BW) de este tipo de PA (alrededor del 10% del ancho de banda fraccional) y su importancia (en los sistemas inalámbricos modernos, tales como LTE, WiMAX, Wi-Fi y sistemas de satélites) han animado a los investigadores para mejorar este inconveniente en los últimos años. Algunos aspectos típicos que limitan el BW en los DPA son: i) transformadores de longitud de cuarto de onda, ii) redes de compensación de fase y circuitos de adaptación de salida, iii) compensación de las líneas y los dispositivos no ideales. Los transformadores de cuarto de onda actuan como un inversor de impedancia en la técnica de modulación de carga de la DPA "("load modulation"). Concretamente, el objetivo futuro de diseño de DPA es disminuir el impacto de estos problemas. En este contexto, esta tesis doctoral se centra en mejorar el ancho de banda fraccional de DPA utilizando los nuevos métodos que están relacionados con el uso de transformadores de impedancias en vez de inversores en el subcircuito de modulación de carga. Este estudio tiene dos niveles. En primer lugar, se presenta una novedosa estructura del DPA de banda ancha usándose dispositivos de GaN en la banda de 2,5 GHz con un divisor Wilkinson asimétrico. El transformador de impedancias de la arquitectura propuesta se basa en una red de adaptación, incluyendo una línea cónica con múltiples secciones del transformador en la etapa principal. El BW de este DPA ha sido de 1,8 a 2,7 GHz. Además, se obtiene una eficiencia de drenador de más del 33% en todo el BW, tanto a nivel de potencia máxima como a nivel del OBO. En segundo lugar, aprovechando los beneficios de un adaptador de Klopfenstein, se propone un nuevo diseño del DPA. Con la sustitución de la lina conica por el Klopfenstein se reduce el coeficiente de reflexión de transformador de impedancias. Sobre un prototipo práctico de esta nueva estructura del Doherty, en la banda de 2,25 GHz, se ha demostrado que el BW resultante se incrementa en comparación con la topología convencional mientras se mantienen las cifras de eficiencia. Por otra parte, en este estudio se demuestra que el diseño basado en el Klopfenstein permite una afinación fácil del retardo de grupo a través de la reactancia de salida del taper, lo que resulta en un ajuste más sencillo que otros diseños publicados recientemente en el que el transformador de cuarto de onda se sustituye por multi-líneas de transmisión de la sección (híbridos o similar). Los resultados experimentales han mostrado un 43-54% de eficiencia de drenador sobre 42 dBm de potencia de salida, en el intervalo de 1,7 a 2,75 GHz. Concretamente, los resultados presentados en esta nueva estructura tipo-Doherty implican una técnica de modulación de carga que utiliza una combinación de un Klopfenstein junto con un transformador de múltiples secciones con el fin de obtener un alto ancho de banda con la eficiencia habitual en DPAs. Els amplificadors de potència (PA) són un dels elements més importants per els sistemes ràdio ja que sone ls principals consumidors d'energía. Un aspecte molt important és l'eficiència de l'amplificador, aspecte relacionat amb el back-off de sortida (OBO) que a la seva vegada ve condicionat pel PAPR del senyal modulat. Una baixa eficiència dels PA fa que la pèrdua d'energia en manifesti en forma de calor. De fet, aquesta qüestió porta a l'increment dels costos i grandària, degut als dissipadors de calor. A més, el compromís entre la linealitat i l'eficiència en els PA es un altre problema important. Per fer front a les circumstàncies que porten a la degradació de l'eficiència, l'amplificador de potència Doherty (DPA) és una de les tècniques més útils i que proporcionen una bona eficiència per als alts PAPR comuns en senyals de comunicació moderns. No obstant això, l'ample de banda limitat (BW) d'aquest tipus de PA (al voltant del 10% de l'ample de banda fraccional) i la seva importància (en els sistemes moderns, com ara LTE, WiMAX, Wi-Fi i sistemes de satèl·lits) han animat els investigadors per millorar aquest inconvenient en els últims anys. Alguns aspectes tipicament limitadors del BW en els DPA son: i) transformadors de longitud d'quart d'ona, ii) xarxes de compensació de fase en circuits / adaptacions de sortida, iii) compensació de les línies i els dispositius no ideals. Els transformadors de quart d'ona s'utilitzen com a inversors d'impedàncies en la tècnica de modulació de càrrega del DPA ("load modulation"). Concretament, l'objectiu futur de disseny d'DPA és disminuir l'impacte d'aquests problemes. En aquest context, aquesta tesi doctoral es centra en millorar l'ample de banda fraccional dels DPA utilitzant nous mètodes que estan relacionats amb l'ús de transformadors d'impedàncies, en comptes d'inversors, en el subcircuit de modulació de càrrega. Aquest treball té dos nivells. En primer lloc, es presenta un DPA novedós que fa servir dispositus GaN DPA a la banda de 2,5 GHz amb un divisor Wilkinson asimètric. El transformador d'impedàncies de l'arquitectura proposada es basa en una xarxa d'adaptació, incloent una línia cònica amb múltiples seccions del transformador en l'etapa principal. El BW d'aquest DPA ha mostrat ser d'1,8 a a 2,7 GHz. A més, s'obté una eficiència de drenador de més del 33% en tot el BW, tant a nivell de potència màxima com de OBO. En segon lloc, sobre la base dels beneficis del adaptador de Klopfenstein, un proposa un nou disseny on un Klopfenstein substitueix la anterior línia cònica. Aquesta substitució repercuteix en la reducció del coeficient de reflexió de transformador d'impedàncies.Des d'una realització pràctica (prototipus) d'aquest nou amplificador tipus Doherty a la banda de 2,25 GHz, s'ha demostrat que el BW resultant s'incrementa en comparació amb la topologia convencional mentre es mantenen les xifres d'eficiència. D'altra banda, en aquest estudi es demostra que el disseny basat en el Klopfenstein permet una afinació fàcil del retard de grup a través de la reactància de sortida de la forma cònica, el que resulta en un ajust més senzill que altres dissenys publicats recentment en què el transformador de quart d'ona es substitueix per multi-línies de transmissió de la secció (híbrids o similar). Els resultats experimentals han mostrat un 43-54% d'eficiència de drenador en 42 dBm de potència de sortida, en l'interval de 1,7-2,75 GHz. Concretament, els resultats presentats en aquest nou amplificador tipus Doherty impliquen una tècnica de modulació de càrrega específic que utilitza una combinació del Klopfenstein juntament amb un transformador de múltiples seccions per tal d'obtenir un alt ample de banda amb la usual eficiència en DPAs.

Tadahiro Hyakudome, Hiroshi Yoshida, Satoshi Tsukioka et al.

ECS Transactions • 2010

In 2007, we started research and development of a demonstration long-range vehicle to cruise 3000 kilometers. It is important to improve a system performance of a fuel cell system and to improve storage methods of the pure hydrogen and the pure oxygen to achieve this aim. It is necessary to install an oxygen tank on the vehicle because the oxygen is not taken from environment in the sea. A large quantity of hydrogen and oxygen need to let the fuel cell system generate electricity for a long time to cruise at 3,000 kilometers. Because energy efficiency becomes worse if the body of the vehicle becomes big, the gases must storage compactly. We are developing a pressure vessel for the hydrogen storage, metal hydrides and an oxygen storage system.

Beate Christgen, Martin Spurr, Edward M. Milner et al.

Frontiers in Microbiology • 2023

Many factors affect the performance of microbial fuel cells (MFCs). Considerable attention has been given to the impact of cell configuration and materials on MFC performance. Much less work has been done on the impact of the anode microbiota, particularly in the context of using complex substrates as fuel. One strategy to improve MFC performance on complex substrates such as wastewater, is to pre-enrich the anode with known, efficient electrogens, such as Geobacter spp. The implication of this strategy is that the electrogens are the limiting factor in MFCs fed complex substrates and the organisms feeding the electrogens through hydrolysis and fermentation are not limiting. We conducted a systematic test of this strategy and the assumptions associated with it. Microbial fuel cells were enriched using three different substrates (acetate, synthetic wastewater and real domestic wastewater) and three different inocula (Activated Sludge, Tyne River sediment, effluent from an MFC). Reactors were either enriched on complex substrates from the start or were initially fed acetate to enrich for Geobacter spp. before switching to synthetic or real wastewater. Pre-enrichment on acetate increased the relative abundance of Geobacter spp. in MFCs that were switched to complex substrates compared to MFCs that had been fed the complex substrates from the beginning of the experiment (wastewater-fed MFCs - 21.9 ± 1.7% Geobacter spp.; acetate-enriched MFCs, fed wastewater - 34.9 ± 6.7% Geobacter spp.; Synthetic wastewater fed MFCs – 42.5 ± 3.7% Geobacter spp.; acetate-enriched synthetic wastewater-fed MFCs - 47.3 ± 3.9% Geobacter spp.). However, acetate pre-enrichment did not translate into significant improvements in cell voltage, maximum current density, maximum power density or substrate removal efficiency. Nevertheless, coulombic efficiency (CE) was higher in MFCs pre-enriched on acetate when complex substrates were fed following acetate enrichment (wastewater-fed MFCs – CE = 22.0 ± 6.2%; acetate-enriched MFCs, fed wastewater – CE =58.5 ± 3.5%; Synthetic wastewater fed MFCs – CE = 22.0 ± 3.2%; acetate-enriched synthetic wastewater-fed MFCs – 28.7 ± 4.2%.) The relative abundance of Geobacter ssp. and CE represents the average of the nine replicate reactors inoculated with three different inocula for each substrate. Efforts to improve the performance of anodic microbial communities in MFCs utilizing complex organic substrates should therefore focus on enhancing the activity of organisms driving hydrolysis and fermentation rather the terminal-oxidizing electrogens.

M. Meiler, E. P. Hofer, A. Nuhic et al.

Journal of Fuel Cell Science and Technology • 2012

New technologies for efficient operation of fuel cells require modern techniques in system modeling. Such fuel cell models do not require giving any information about physical mechanisms or internal states of the system. They must be rather precise and should consume less computing time. From the point of view of system theory, polymer electrolyte membrane fuel cells (PEMFC) are multiple input and single output (MISO) systems. The inputs of a fuel cell are the drawn current, the gas pressures at anode and cathode side, and the humidity of these gases which influence the system output, namely the cell voltage, in a nonlinear way. The state of the art in the industry is to describe such nonlinear systems by the usage of lookup tables with a large amount of data. An alternative way to model the input-output behavior of nonlinear systems is the usage of so called black-box and gray-box model approaches. In the last decade, artificial neuronal networks (ANN) became more popular in black-box modeling of nonlinear systems with multiple inputs. Further, if some of the internal processes of a nonlinear system can be mathematically described, a gray-box model is more preferred. In the first part of this paper, the suitability of ANN's in the form of a multilayer perceptron (MLP) network with different numbers of hidden neurons is investigated. A way to confirm the validity for the identified network was worked out. In the second part of this contribution, a gray-box model, valid for a large operating area, based on published semi-empirical models is introduced. Six experimental campaigns for parameter identification and model validation were carried out. The five inputs previously described were varied in a wide range to cover a large operating range. In the last part of this paper, both modeling approaches are investigated with respect to their ability to identify model parameters using a limited number of experimental data.

Subha Ranjan Paul, Sumantra Bhattacharya

Research Square • 2021

Abstract Separation efficiency of coal cleaning equipment is typically assessed by Probable Error in Separation (E p ) and Organic Efficiency (E org ). The first one is determined on the basis of precise cut point density of separation and implies that for ideal separation the error is zero. The second one is calculated on the basis of yield of clean coal/ middling at the target ash and implies that for ideal separation the efficiency is 100%. Plant operators worldwide being accountable for the tonnage of the clean coal and middling produced regularly monitor E org with some application in plant design in India. E p is universally used as an equipment selection criterion from among the vendors, in commercial contracts and sometimes for performance analysis of coal cleaning equipment carried out at the plants. Since both are performance measures there should possibly be a relationship between the two for specific cleaning equipment or for a particular type of density separators. Such relationships are however rarely observed. Moreover there are many instances where high to very high E org does not translate into low to very low E p . Therefore, is there a dichotomy between the two performance measures?

Arun C. A., Ajil C. Abhimannue, Sanchu Sukumaran

Current Journal of Applied Science and Technology • 2023

Renewable energy is the most promising energy-saving and environmentally friendly option. The concentrating type solar collector like parabolic trough collectors can be utilized for solar thermal energy collection due to low cost and high-temperature output. The paper is an experimental study of a solar parabolic trough collector with manual sun tracking. A parabolic trough with an area of 2.5´1.75 m² was constructed for the present study. A highly polished aluminum sheet for concentrating the reflecting sunlight to the focal line contains the receiver tube. The parabolic trough was tracked at regular interval of one hour concerning the sun position and focused the sunlight into the receiver tube to ensure sound performance. Water is used as a working fluid inside the receiver tube, and experiments were done with three different mass flow rates of 0.0072,0.0112 and 0.0158 kg/s. Two heat-collecting elements, such as a stainless-steel receiver tube and a glass-coated copper receiver tube, were tested with a parabolic trough. The performance was analyzed based on the difference in the inlet and outlet temperature of the working fluid at the ends of the receiver tubes of the parabolic trough. The instantaneous efficiency of the parabolic trough with two different materials of receiver tube at three different flow rates were evaluated. The results showed that the glass coated copper tube surpassed in performance compared with stainless steel receiver tubes. The instantaneous efficiency of the glass coated copper tube is found to be 71.17% at a flow rate of 0.0158 kg/s which was significantly high when compared with that of the stainless-steel receiver tube. The glass coated copper tube prevents the convective heat transfer loss and thereby increases the efficiency. The experiment shows that the performance of the parabolic trough solar collector strongly depends upon solar light tracking and the focal line containing the receiver tube.

Muhammad Habib Ur Rehman, Luigi Coppola, Ernestino Lufrano et al.

Energies • 2023

The synergistic combination of Nafion and sulfonated graphene oxide (GOsulf) in nanocomposite membranes emerged as a promising strategy for advancing proton exchange membrane fuel cell (PEMFC) technology. In the pursuit of elucidating the effect of GOsulf introduction on transport properties and electrochemical performance of Nafion, this work provides a systematic study combining swelling tests, water release tests, 1H NMR characterization, and Electrochemical Impedance Spectroscopy (EIS) investigation. The incorporation of organomodified GO nanolayers alters the distribution of water molecules within the hydrophilic domains of Nafion and produces a considerable increase in the “bound-water” fraction. This increases its water retention capability while ensuring very high diffusivity even under high temperatures, i.e., 1.5 × 10−5 cm2 s−1 at 130 °C. These peculiar features enable Naf-GOsulf to successfully operate under a dehydrating environment, yielding a proton conductivity of 44.9 mS cm−1 at 30% RH.

Adam Phillips, Jocelyn Mackay, Naveen Shrivastava et al.

ECS Meeting Abstracts • 2017

The polymer electrolyte membrane fuel cell (PEMFC) is a clean alternative to petroleum-based technologies such as the internal combustion engine (ICE). In order to be competitive with the ICE in transportation applications, fuel cell systems must have less than a 10% performance loss after 5,000 hours of operation while reaching cost targets of $40/kW [1,2]. The membrane electrode assembly (MEA), a proton conducting polymer electrolyte membrane (PEM) with attached platinum-containing catalyst layers and gas diffusion layers (GDLs), may possess non-uniformities in any of its constituent components, which could lead to performance losses [3,4]. This work studies a subset of casting irregularities located within the PEM to understand their potential impacts on PEMFC initial performance. If the MEA experiences statistically significant lower initial performance as a result of a casting irregularity, then this irregularity should be classified as a defect. Classification of irregularities as defects will ultimately assist the industry by developing threshold detection limits for in-line quality control diagnostics. Membrane material was cast on a web-line operating within and at the boundaries of the process window by controlling process parameters such as slot and coating gap, flow rate, and substrate speed. The resulting membrane material was either pristine or contained air bubbles, cracks, and contamination, ranging from 0.6 to 3 mm. Gas-diffusion electrodes (GDEs) were fabricated using an ultrasonic spray system. The active area and nominal loading of these GDEs were 50 cm 2 and 0.2/0.2 mg Pt/cm 2 , respectively. MEAs were assembled in the cell by placing a sheet of fabricated membrane material in between two pristine GDEs. Operating conditions for all samples were T cell : 80°C, anode/cathode relative humidity (RH) at 32/32 and 100/50%, 1.5/2 stoichiometric flow rates of H 2 /Air, and 150/150 kPa backpressure. Voltage controlled polarization (VI) curves were conducted using a 121 channel segmented fuel cell system. To quantify performance impacts the VI performance of the MEAs containing casting irregularities was subtracted from that of pristine reference MEAs. Thermal imaging was performed subsequent to the performance experiments to map hydrogen crossover to spatial performance [5]. Figure A shows initial VI curves performed at 32/32% RH for four pristine reference samples as well as two samples with casting irregularities. The VI curve data indicate that the samples with irregularities have statistically lower OCV values than the pristine samples. Figure B illustrates the experimental method using GT118 as a representative sample. Prior to the experiment the morphology and size of the casting irregularities were determined using optical microscopy. Sample GT118 contained two air bubbles with sizes of approximately 660 and 1416 µm as shown on the left of Figure B. Then spatial current density distributions were measured with the segmented cell to determine to what extent the casting irregularities caused localized performance losses. The red regions in the spatial current density distribution, shown in the center of Figure B, indicated the lowest local performances in the cell. Subsequent to the performance experiment, a spatial thermal imaging diagnostic was applied to determine regions of increased hydrogen crossover. In the thermal imaging map for GT118 as shown on the right of Figure B, the red boxes indicate air bubble locations and the white regions denote areas of increased hydrogen crossover. These data show the correlation between casting irregularity location, local performance decrease, and increased local hydrogen crossover. In this presentation, we will discuss the impacts of the various casting irregularities in the membrane, and how certain experimental methodologies can be potentially used as defect classification tools. References Marcinkoski, Jason et al. “Fuel Cell System Cost – 2015”. September 30, 2015. James, Brian et al. “Mass Production Cost Estimation of Direct H2 PEM Fuel Cell Systems for Transportation Applications: 2015 Update”. December 2015. Kundu, S., et al. Journal of Power Sources 157.2 (2006): 650-656. Benchmarking and Best Practices Center of Excellence. Manufacturing Fuel Cell Manhattan Project , November 2011 Bender, Guido, et al. Journal of Power Sources 253 (2014): 224-229. Figure 1

Carla Sophie Harzer, Roberta Karla Francesca Della Bella, Hubert Andreas Gasteiger

ECS Meeting Abstracts • 2023

In order to reach the target of carbon neutrality by the end of 2050 set by the European Union, hydrogen technologies will play an important role in supporting the transition to a renewable energy economy, especially for heavy duty applications, such as trucks and airplanes. 1 For the latter, hydrogen is a viable alternative fuel compared to kerosene, offering a higher specific energy density as well as zero in-flight CO 2 emissions. 2 However during operation, proton exchange membrane fuel cells (PEMFCs) suffer from significant performance losses due to the instability of Pt-based catalysts for the oxygen reduction reaction (ORR) via the loss of electrochemically active surface area ( ECSA ). 3 This induces substantial decay in the H 2 /air performance mainly due to the increasing impact of the local O 2 transport resistance (R O2,local ) with decreasing cathode roughness factor ( rf , in units of cm 2 Pt cm -2 MEA ), which is especially pronounced for low Pt-loadings. 4 Thus, for heavy duty applications requiring long-term durability, higher Pt loadings are required to reduce the impact of R O2,local . In this study, we analyse the H 2 /air performance loss contributions during voltage cycling based accelerated stress tests (ASTs) using cathodes with different Pt-loadings. ASTs were performed using 5 cm 2 MEAs with cathode Pt loadings of 0.2, 0.4, and 0.8 mg Pt cm MEA -2 (48.6 wt%, TEC10V50E, Tanaka Kikinzoku K.K. (TKK)). Full characterization of the MEA performance characteristics after different numbers of voltage cycles, was performed by measuring: i) H 2 /O 2 and H 2 /air polarization curves; ii) cathode rf , determined by cyclic voltammetry and CO stripping; iii) O 2 transport resistances (R O2,total ) via limiting current measurements; and, iv) proton conduction resistances in the cathode catalyst layer (R H+,cath ) via electrochemical impedance spectroscopy (EIS). Voltage cycling was performed under H 2 /N 2 (200/75 nccm) at 80 °C, 95% RH, and ambient pressure using square wave profiles with lower and upper potential limits of 0.60 and 0.95 V, respectively, with hold times of 1 s at each potential. A strong H 2 /air performance dependency on the cathode rf is visible for the same Pt/C cathode catalyst with varying Pt loading. As shown in Figure 1, the same H 2 /air performance is reached at similar cathode rf values, independent of number of voltage cycles. This is due to the observation that the R O2,local values only depend on the cathode rf and not on the electrode’s history. Finally, when choosing an end-of-life (EoL) criterion of a more than 20 mV deviation of the measured cell voltages at a given current density from the theoretical ORR kinetics losses (c.f. red line in Figure 1 and gray areas for accepted cell voltage range), this EoL criterion is reached for the differently loaded MEAs at the same cathode rf but after different amounts of aging cycles. For example, at 1.5 A cm 2 MEA this 20 mV deviation is reached at a cathode rf of 50-70 mg Pt 2 cm MEA -2 . However, for the 0.8 mg Pt cm MEA -2 Pt/C cathode more than 200.000 cycles are needed to reach this value, compared to only 5.000 cycles for the 0.2 mg Pt cm MEA -2 loaded cathode. Consequently, a 4-fold increase of the the cathode Pt loading increases its voltage cycling stability by »40-fold. References: "A European Green Deal - Striving to be the first climate-neutral continent", European Commission, (accesssed: 06/03/2023). C. Koroneos, A. Dompros, G. Roumbas, and N. Moussiopoulos, Resour Conserv Recycl, 44 (2), 99-113 (2005). G. S. Harzer, J. N. Schwämmlein, A. M. Damjanović, S. Ghosh, and H. A. Gasteiger, J. Electrochem. Soc., 165 (6), F3118-F3131 (2018). R. K. F. Della Bella, B. M. Stühmeier, and H. A. Gasteiger, Journal of The Electrochemical Society, 169 (4), 044528 (2022). Acknowledgement: We gratefully acknowledge funding from the German Federal Ministry for Digital and Transport (BMDV) under the funding scheme H2Sky (funding code 03B10706). R.K.F.D.B. also gratefully acknowledges funding from the German Federal Ministry for Economic Affairs and Energy (BMWi) under the funding scheme POREForm (funding number 03ET B027C). Figure 1: Correlation between the cathode roughness factor (rf) and the H 2 /air performance at different current densities over the course of a voltage cycling AST for MEAs using Pt/C cathodes with different Pt-loadings: 20,000 voltage cycles for 0.2 mg Pt cm MEA -2 loadings, 200,000 voltage cycles for 0.4 mg Pt cm MEA -2 loadings, and 500,00 voltage cycles for 0.8 mg Pt cm MEA -2 loadings. Voltage cycling was done between 0.6 V and 0.95V using square wave modulation with 1s hold time. The red line describes the theoretical ORR kinetic induced losses based on DE = 70 mV×log(rf/rf initial ). The gray shaded areas visualize a 20 mV deviation from the theoretical ORR kinetics. Figure 1

Zuhui Li, Ran Ge, Ling Tan et al.

ChemCatChem • 2023

Abstract Surface display technology has emerged as a powerful tool for enhancing the stability, accessibility, and reusability of enzymes. Fatty acid photodecarboxylase from Chlorella variabilis NC64A ( Cv FAP) is capable of catalyzing decarboxylation reactions from free fatty acids to alkanes under blue light, however, its stability and reusability in catalytic cycles remain to be improved. Herein, we successfully displayed Cv FAP on the surface of Escherichia coli cells utilizing full‐length ice nucleation protein as the anchor protein. By comparing the performance of the surface displayed Cv FAP with whole‐cells harboring Cv FAP, it was found that surface displaying of Cv FAP significantly reduces the reaction time and enhances substrate accessibility, resulting in a turnover number of 9972. Also, compared to soluble enzymes, the surface displayed Cv FAP exhibits enhanced stability and reusability in the decarboxylation reaction. Furthermore, the broad substrate scope of surface displayed Cv FAP suggests its potential for large‐scale hydrocarbon and fatty chemicals production. Overall, our results highlight the value of surface display approach in broadening the application of photodecarboxylase.

Vinicius Andrea, Patricia da Silva Pagetti Oliveira, Elisabete I. Santiago et al.

ECS Transactions • 2016

Durability still represents one of the major barriers to the commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs) in the market. Therefore, it is important to understand the main phenomena involving the long-term operation of PEMFCs in order to elucidate the degradation issues of these devices. Thus, in this work long-term experiments of 500 hours at steady state were performed with variations of the operational parameters such as relative humidity, cell temperature and the reactant flow rates. According to the results obtained, the test which presented the lowest global loss of performance (132μV.h -1 , with reversible and irreversible losses measured all together) was the one with the temperatures of the humidifiers and cell set all at 75°C and the reactants flow rates set as 300 ml.min -1 and 200 ml.min -1 for the H 2 and O 2 , respectively. For this test, the irreversible loss of performance was assessed as 38μV.h -1 . On the other hand, the test performed with higher humidification degree presented much higher global and irreversible losses of performance (318 and 52μV.h -1 , respectively), showing that the degree of humidification, which is a function of the operational parameters, strongly influence on the long-term performance. Therefore, the water management is a key point to obtain better performances in long-term operation of PEMFCs.

Eko Supriyanto, Nur Cahyo, Ruly Sitanggang et al.

IOP Conference Series: Earth and Environmental Science • 2021

Abstract In a coal steam power plant, changes in coal quality significantly affect plant performance, especially in its boiler. A coal-fired power plant with a capacity of 400 MWe had been commissioned using coal with a calorific value of 5,242 kCal/kg. This study aims to determine the effect on unit performance and boiler efficiency due to changes in fuel use with the typical calorific value of 3,520 kCal/kg, 34,17% lower than the initial design. The performance tests were conducted using the heat loss method at loads: 50%, 65%, 75%, and 100%. The test result showed that using low-grade coal reduces boiler efficiency by 6.26%. There were four dominant boiler losses: heat loss due to moisture in dry flue gas, heat loss due to combustible in refuse, heat loss due to moisture in fuel, and heat loss due to hydrogen burning. Furthermore, the gross plant heat rate using low-grade coal was increased from 2,120 kCal/kWh to 2,718 kCal/kWh; however, the electric price becomes cheaper from 1.99 cent-USD/kWh becomes 1.31 cent-USD/kWh.

Xiao‐Zhou Zhang, Y.‐H. Percival Zhang

Microbial Biotechnology • 2010

Summary Bacillus subtilis can serve as a powerful platform for directed evolution, especially for secretory enzymes. However, cloning and transformation of a DNA mutant library in B. subtilis are not as easy as they are in Escherichia coli . For direct transformation of B. subtilis , here we developed a new protocol based on supercompetent cells prepared from the recombinant B. subtilis strain SCK6 and multimeric plasmids. This new protocol is simple (restriction enzyme‐, phosphatase‐ and ligase‐free), fast (i.e. 1 day) and of high efficiency (i.e. ∼10 7 or ∼10 4 transformants per µg of multimeric plasmid or ligated plasmid DNA respectively). Supercompetent B. subtilis SCK6 cells were prepared by overexpression of the competence master regulator ComK that was induced by adding xylose. The DNA mutant library was generated through a two‐round PCR: (i) the mutagenized DNA fragments were generated by error‐prone PCR and linearized plasmids were made using high‐fidelity PCR, and (ii) the multimeric plasmids were generated based on these two DNA templates by using overlap PCR. Both protein expression level and specific activity of glycoside hydrolase family 5 endoglucanse on regenerated amorphous cellulose were improved through this new system. To our limited knowledge, this study is the first report for enhancing secretory cellulase performance on insoluble cellulose.

HUNG-YI TENG, HUNG-CHI LAI, REN-HUNG HWANG

Journal of Interconnection Networks • 2012

In this paper, a load balancing mechanism based on cell breathing was proposed for the hybrid EPON-WiMAX network. The hybrid EPON-WiMAX network integrates the emerging Ethernet Passive Optical Network (EPON) and Worldwide Interoperability for Microwave Access (WiMAX) technologies to support high bandwidth, broadband access, mobility, and Quality of Service (QoS) guarantee. Load balancing is required due to uneven distribution of traffic among different WiMAX base stations (BS) as well as mobility of WiMAX Subscriber Station (SS). Cell breathing is a well-known load balancing technique adopted in wireless networks. By changing the transmission powers of the base stations, the cell breathing technique is able to adjust the traffic, both uplink and downlink, load of base stations. In the integrated EPON-WiMAX network, transmission powers of WiMAX base stations can be optimally allocated at the EPON optical networking unit (ONU). In this paper, we formulate the cell breathing-based load balancing problem into a linear programming problem. Our goal is to find the best power adjustment that maximizes system throughput. To alleviate the time complexity of solving the linear programming problem, we propose a Heaviest Load First Algorithm (HLFA) to obtain the near optimal solution. The solution obtained by the HLFA algorithm will not waste any transmission power to make the entire system energy-efficiency. We demonstrate the performance of HLFA via extensive simulations. The simulation results show that the HLFA can provide the best solution to achieve load balancing and enhance the system throughput as compared to existing solutions. Furthermore, HLFA maintains good performance even when the system has multiple overloaded ONU-BSs.

Walid Matar

Energy Efficiency • 2015

Abstract Energy efficiency in buildings has garnered significant attention in Saudi Arabia. This paper outlines the potential effects of higher residential efficiency on electricity load profiles in the Kingdom. It further presents the associated benefits that could have been realized by the local utilities in 2011. To perform the analysis, we designed an integrated methodology in which an engineering-based residential electricity demand model is used within an economic equilibrium framework. The modeling approach allows us to capture the physical interactions arising from higher efficiency and the structural changes that could occur in the economy beyond the end-consumers. Raising the average air-conditioner energy efficiency ratio (EER) to 11 British thermal unit (BTU)/(Wh) from its 2011 average would have saved 225,000 barrels/day of crude oil in electricity generation. Alternatively, increasing the share of insulated homes from 27 to 64 % would have allowed the power sector to lower its use of the fuel by 158,000 barrels/day. Combining both measures in a single simulation yields incremental yet not additive reductions. All alternative scenarios reduce costs to the utilities and improve the average thermal efficiency for the electricity generated. The studied efficiency options shift the load curve downward during the peak load segment when the least efficient turbines would be used. We additionally show how efficiency improvements in end-uses can affect the decisions of other sectors in the economy.

Yu-shin Fang, Peter Po-jen Chu

ECS Meeting Abstracts • 2016

Traditional fuel cell membrane suffers from fuel cross over and high degree of swelling after extensive operation. To circumvent these deficiencies, we disclose in this study proton conducting membrane by incorporating poly(ether sulfones)(PES) with sulfonated poly(ether ether ketone)(sPEEK, degree of sulfonation=50%) prepared under electric field poling condition. The external field enhanced the aromatic chain ordering from both sPEEK and PES and improved the miscibility. This external force is conducive to the formation of more densely packed and ordered hydrophobic domain that eventually leads to long range ordered hydrophilic proton conducting channels. The averaged hydrophilic dimension is smaller than that in generic sPEEK, thus displayed much lower methanol permeability (3.17x10 -7 cm 2 /s), and lower swelling ratio (31.20%). However, the conductivity (7.43x10 -2 S/cm) is higher compared to sPEEK at 64% degree of sulfonation, and comporable with Nafion. The binary composite is highly durable; and shows improved membrane mechanical strength, possibly due to the densification of amorphous domain. Nearly 50% increase of DMFC power output is observed using this membrane, and the best power density is recorded at 150mA/cm 2 (80 o C, 1M Methanol).

Valery A. Danilov, Joeri F. Denayer

Energy Technology • 2014

Abstract A new concept is proposed for a high‐performance fuel cell design. The concept is based on the intensification of mass transfer processes due to implementing multiple contact zones with jet flow and preventing the intermixing of the reactants and products. A proof of concept was performed by comparing the new fuel cell design with conventional proton‐exchange membrane fuel cell (PEMFC) containing a standard membrane electrode assembly (MEA) and gas diffusion layer (GDL). It is shown that the application of the new concept for flow‐field design provides an increase of the fuel cell performance of up to 40 % without humidification and flooding problems.

SD Febriawan, AP Febriana, A Yuniarto et al.

IOP Conference Series: Earth and Environmental Science • 2023

Abstract Palm oil liquid waste has been successfully developed to produce bio-electricity with a dual chamber-microbial fuel cell system. This study utilized the Lactobacillus bulgaricus bacteria as a support for the substrate samples prepared in the anode chamber. Meanwhile, in the cathode chamber, KMnO 4 electrolyte solution is used as an electroactive species that can capture electrons well. In addition, salt bridges fabricated from agar have a role as ion-exchange media in microbial fuel cells. The test results showed that the best performance was obtained in samples of palm oil wastewater with the addition of 10% Lactobacillus bulgaricus (LS/B-10) bacteria with current, voltage, and power density values of 0.9640 mA, 0.6760 V, and 248.04 mW/m2, respectively. The MFC system has also been proven to be able to reduce COD (Chemical Oxygen Demand) and TSS (Total Suspended Solid) levels, with the results of a reduction percentage of 42.6% and 7.2%, respectively, in the LS/B-10 variable treatment. All test results show that palm oil wastewater with the addition of Lactobacillus bulgaricus bacteria is promising for producing bioelectricity with a microbial fuel cell system.

Mahendiravarman Elangovan, Sangeetha Dharmalingam

Polymers for Advanced Technologies • 2017

Biofouling of anion exchange membranes is a matter of concern in microbial fuel cell. In the present study, we have attempted to improve the antibiofouling potential of anion exchange membrane by using quaternized poly(ether ether ketone) (QPEEK) with surface modification by polydopamine. It is well known that the antiadhesion test tops the list in measuring the antibiofouling potential of the membrane and hence studied. In addition, the effect of dopamine concentration on membrane hydrophilicity and surface roughness was also discussed. From the data, it was clear that power density in all microbial fuel cells showed the highest in the sixth batch and thereafter declined, although at a varying rate. As predicted, QPEEK‐1.0 registered the least. The power density suffered a loss of 918 to 897 mW m −2 in the case of QPEEK‐1.0, which is the minimum and the same for QPEEK; QPEEK‐0.5 and AMI‐7001 were 918 to 869 mW m −2 , 917 to 885 mW m −2 , and 578 to 537 mW m −2 , respectively. A least value of protein content was obtained for QPEEK‐1.0 (0.21 ± 0.05 g cm −2 ), and the same for QPEEK‐0.5, QPEEK, and AMI 7001 were found to be 0.37 ± 0.05 g cm −2 , 0.78 ± 0.09 g cm −2 , and 1.4 ± 0.11 g cm −2 , respectively. In comparison, the antibiofouling potential of modified membranes was found to be higher than that of unmodified QPEEK and commercially available AMI 7001. The internal resistance values also confirmed that modification with PDA prevents bacteria adhesion leading to high antibiofouling potential.

Meirong Ma, Limin Cao, Li Chen et al.

Water Environment Research • 2015

ABSTRACT: A photosynthetic microbial fuel cell (m‐PMFC) is developed for generating electricity by harnessing solar energy using Microcystis aeruginosa . In this m‐PMFC, commensal bacteria can consume the nutrients that Microcystis aeruginosa produces to generate electricity so that no net CO 2 production occurs. A b‐MFC is constructed to confirm the role of commensal bacteria in electric generation. An s‐PMFC is constructed to confirm the contribution of Microcystis aeruginosa as substrates. The power outputs of m‐PMFCs exhibit no significant difference in terms of different inoculation amount of Microcystis aeruginosa or light/dark cycles. The power density of m‐PMFC exhibits similar response to bubbling of N 2 and O 2 as that of b‐MFC, as confirmed by cyclic voltammetry analysis of m‐PMFC and b‐MFC. Scanning electron microscope images demonstrate that the biofilm of m‐PMFC consists mainly of commensal bacteria. These results suggest that commensal bacteria act as the main biocatalysts and Microcystis aeruginosa as the anode substrates in the m‐PMFC.

Deóis Chiaráin Ua Cearnaigh, Joseph H Dumont, Hoon T Chung et al.

ECS Meeting Abstracts • 2015

The direct methanol fuel cell (DMFC) has been of interest due to the absence of a difficult to split carbon-carbon bond in methanol, high energy content of the liquid fuel and facile handling. Other established high energy-density liquid fuels, such as ethanol, are not yet amenable to direct electrochemical oxidation due to the lack of electrocatalysts for an efficient carbon-carbon bond scission. A related fuel to methanol, with strong direct feed fuel cell potential is dimethyl ether (DME). DME possesses many of the same physical advantages that methanol does. 1-3 It is similar to methanol in terms of theoretical open cell voltage (1.18 vs. 1.21 V at 25°C) and does not require a carbon-carbon bond scission. DME is also a clean and, unlike methanol, nontoxic fuel that undergoes facile biodegradation and can be easily synthesized from recycled carbon dioxide and renewable energy. 4 Due to its lower dipole moment, DME is less subject to membrane crossover than methanol; it also has a higher energy content than methanol (8.2 vs. 6.1 kWh/kg). 5,6 Complete electro-oxidation of DME consumes 3 equivalents of water and yields 12 equivalents of electrons: CH 3 OCH 3 +3H 2 O→2CO 2 +12H + +12e - (1) While the direct DME fuel cell (DDMEFC) performance has by now been demonstrated to match that of the state-of-the-art DMFC, 7 DDMEFC still requires development to become fully viable. In addition to the needed improvements in the anode catalyst activity, the catalyst deactivation and its durability continue to pose a challenge. Several aspects of optimization have been explored of which break-in has been one area of attention. 8 In this work, membrane electrode assembly (MEA) preparation and initial break-in were carried out according to standard procedure. 1 Prior to operation in the DDMEFC mode, the fuel cell was operated on humidified hydrogen/air to condition the membrane. When the current at 0.7 V plateaued the break-in was stopped, fuel cell polarization recorded on H 2 /air, and the anode feed switched to preheated, humidified DME under a pressure of approximately 1.75 bar gauge (2.56 bar absolute). 1 Performance at this point reproduced previously observed performance on DME under similar conditions. Several DDMEFC polarization plots were recorded, leading a gradual performance loss. In an attempt to recover lost performance, the cell was switched back to break-in conditions on H 2 /air and after break in, DDMEFC polarization plots were recorded again. With each additional iteration of this procedure, the fuel cell performance increased, up to ~0.3 A cm -2 at 0.5 V after a thirteenth iteration (Figure 1). As a result of this conditioning, the DDMEFC power density achieved reached 0.18 W cm -2 – a 50% increase over the highest power density value reported in the literature with a commercial PtRu catalyst (0.12 W cm -2 ). 7 In this presentation, we will provide details of the procedure used and discuss the causes of such a significant performance improvement. We will also comment on the DDMEFC performance durability in the context of the conditioning approach used in this study. Acknowledgment Financial support from the Office of Energy Efficiency and Renewable Energy of the U.S. Department of Energy through Fuel Cell Technologies Office is gratefully acknowledged. REFERENCES 1 Li, Q., Wu, G., Johnston, C. M., Zelenay, P. "Direct Dimethyl Ether Fuel Cell with Much Improved Performance." Electrocatalysis 5 , 310-317 (2014). 2 Jensen, J. O., Vassiliev, A., Olsen, M., Li, Q., Pan, C., Cleemann, L. N., Steenberg, T., Hjuler, H. A., Bjerrum, N. "Direct dimethyl ether fueling of a high temperature polymer fuel cell." Journal of Power Sources 211 , 173-176 (2012). 3 Li, Q., Wen, X., Wu, G., Chung, H. T., Zelenay, P. "High-Activity PtRuPd/C Catalyst for Direct Dimethyl Ether Fuel Cell." Angewandte Chemie International Edition (In Press). 4 Olah, G. A., Goeppert, A., Prakash, G. S. "Chemical recycling of carbon dioxide to methanol and dimethyl ether: from greenhouse gas to renewable, environmentally carbon neutral fuels and synthetic hydrocarbons." The Journal of Organic Chemistry 74 , 487-498 (2008). 5 Müller, J. T., Urban, P. M., Hölderich, W. F., Colbow, K. M., Zhang, J., Wilkinson, D. "Electro‐oxidation of dimethyl ether in a polymer‐electrolyte‐membrane fuel cell." Journal of the Electrochemical Society 147 , 4058-4060 (2000). 6 Mizutani, I., Liu, Y., Mitsushima, S., Ota, K.-i., Kamiya, N. "Anode reaction mechanism and crossover in direct dimethyl ether fuel cell." Journal of Power Sources 156 , 183-189 (2006). 7 Chung, H. T., Dumont, J. H., Martinez, U., Zelenay, P. Catalyst Development for Dimethyl Ether Electrooxidation. in Meeting abstracts. 929-929p (The Electrochemical Society). 8 Qi, Z., Kaufman, A. "Quick and effective activation of proton-exchange membrane fuel cells." Journal of Power Sources 114 , 21-31 (2003). Figure 1

Maurizio Santini, Manfredo Guilizzoni, Massimo Lorenzi et al.

ECS Meeting Abstracts • 2016

The cathode performances are one of the main limitations related with microbial fuel cell (MFC) that strongly limit the overall output. The low power produced is an important problem that has to be addressed for the scale up of the MFCs. Cathodic overpotential is particularly high at circumneutral pH when carbonaceous or metallic catalysts are used [1]. Overpotentials are much lower for enzymes but enzymatic biocathodes are expensive and not durable [2]. Single chamber membrane-less MFCs are preferred due to the lower cost and higher power output. In membrane-less MFCs, both electrodes (anode and cathode) are exposed directly to the electrolyte or carbon-rich solution. The presence of growing bacteria inside the chamber generates electron acceptor-rich and electron donor-rich zones, which serve as cathode and anode, respectively. In fact, bacteria consume rapidly the oxygen inside the chamber creating anaerobic conditions that are useful for electrogenic bacteria for colonizing the anode electrode and oxidize organics. The cathode used is an air-breathing cathode and it is porous and allows oxygen to penetrate through the anodic solution. A biofilm is formed also on the cathode surface consuming the oxygen and forming a natural and cheap membrane that separate the cathode from the solution and stop the oxygen leaking inside the chamber, thus ensuring anaerobic conditions. Strict anaerobes grow quickly within 1 week of operations as recently showed [3]. It has been showed previously that the biofilm formation on the cathode initially increased the cathodic reduction reaction [4]. In this work, we analyzed the cathode performances and the MFC overall performance along 6 months operations [5]. At the end of the experimentation, the cathode has been examined with X-Ray Micro Computed Tomography (microCT), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) for characterizing the organic/inorganic layer on the cathode surface facing the solution [5]. Single chamber MFC with volume of 125 mL was used and the cell was fed with raw wastewater and sodium acetate. The results obtained showed that cathode reduction reaction increased in the first 15 days but then decreased continuously over time [5]. The initial increase might be due to the formation of an initial biofilm layer that probably enhanced the cathodic reduction reaction. Over time, precipitation of compounds and fouling might take place. It has been speculated that thick biofouling decreased the performances. After 6 months, part of the cathode was dried and analyzed with SEM/EDX and the other part was analyzed as it is using microCT [5]. SEM has the great potential of very high resolution but images have to be taken after treating the sample and consequently change the morphology of the biofilm after drying it. Moreover, SEM is not able to pass through objects and consequently only the surface can be analyzed. The coupling with EDX allowed to identify sodium (Na) on the external part of the cathode and calcium (Ca) on the internal face [5]. Na and Ca were present in form of carbonate. The production of OH- due to the cathodic reaction, caused the alkalinization of solution at the interface with the cathode making the precipitation of carbonate species on the cathode is very probable. MicroCT images allowed making a complete 3D scan of the entire cathode analyzed. Interestingly, the different components (cathode, carbonate and biofilm) were clearly distinguishable (Figure 1). In fact, a compact and continuous thick layer of carbonate was clearly visible between the cathode and the biofilm (Figure 1, white color). Those results obtained using microCT clearly showed that the thick, not porous carbonate layer and not the biofilm itself might increase the proton mass transport resistance from the solution to the catalytic sites and lowering dramatically the cathode output during long terms operation. Reference [1] C. Santoro, F. Soavi, A. Serov, C. Arbizzani, P. Atanassov. Biosensors and Bioelectronics. 2016, 78, 229-235. [2] C. Santoro, S. Babanova, B. Erable, A. Schuler, P. Atanassov. Bioelectrochemistry. 2016, 108, 1-7. [3] M. Grattieri, S. Babanova, C. Santoro, E. Guerrini, S.P.M. Trasatti, P. Cristiani, M. Bestetti, P. Atanassov. Electroanalysis, 2015, 27(2), 327-335. [4] P. Cristiani, M.L. Carvalho, E. Guerrini, M. Daghio, C. Santoro, B. Li. Bioelectrochemistry, 2013, 92, 6-13. [5] M. Santini, M. Guilizzoni, M. Lorenzi, P. Atanassov, E. Marsili, S. Fest-Santini, P. Cristiani, C. Santoro. Biointerphases. 2015, 10, 031009. Figure 1. Cross Section of the cathode analyzed using microCT. Figure 1

Kuei‐Hsiang Chao, Min‐Sen Yang

IET Power Electronics • 2014

This study aims to develop a soft‐switching interleaved converter with a high‐voltage conversion ratio using a single auxiliary switch. As a step‐up voltage converter, it performs zero voltage switching and zero current switching operations on main switches by means of the manipulation of the single auxiliary switch. In this manner, both the switching loss and switching stress of main switches can be reduced, giving rise to an improvement in the conversion efficiency. Placed in parallel with a converter available, merely a single resonant branch is employed in the proposed soft‐switching mechanism, a simple and elegant way to reach the goal. This proposal is further applied to a fuel cell system as a high performance DC voltage booster so as to drive a high‐voltage DC load. PSIM simulations are conducted and subsequent experimental validation is presented at the end of this work.

Nour Bassim Frahat, Abid Ustaoglu, Osman Gencel et al.

Scientific Reports • 2023

Abstract Wood fiber is a great potential supportive material for creating a new composite the phase change materials (PCM) due to its beneficial qualities, including high sorption competency, low density, enviro -friendliness, economic effectiveness, and chemical inertness. The main objective of this paper is to study the effect of using the wood fiber/eutectic mixture of stearic and capric acid on the fuel, cost, and carbon emission-saving potentials for various PCM cases. Which experiences a phase transition within the thermally pleasant temperature range of buildings, used for the building's thermal energy storing purposes and consumption cost saving. The energy performance analysis was carried out for buildings incorporated with stearic and capric acid eutectic mixture of PCM with wood fiber-based insulation material (INS) in different climate regions. The results showed that the largest energy-saving capacity belongs to PCM5. The energy saving reaches 52.7% for PCM5 for a thickness of 0.1 m. The PCM1, PCM2, PCM3, PCM4 can provide energy saving rates of 23.5%, 34.3%, 44.7% and 50.5%, respectively. INS-PCM5 can provide about 1.74-, 1.5-, and 1.33 times larger cost savings than INS in 2nd, 3rd, and 4th regions for all fuels. The payback period varies between 0.37 and 5.81 years regarding the fuel and Region. Finally, the results indicate that the proposed composite provided a promising energy-saving potential in building applications by reducing.

C.‐G. Lee, M.‐B. Song

Fuel Cells • 2012

Abstract Electrically insulated carbon fuel, called cartridge fuel here, was employed in a coin type direct carbon fuel cell, which was assembled using molten carbonate fuel cell technology. The cartridge fuel was comprised of solid carbon and carbonate mixtures filling an alumina tube. Both ends of the tube were sealed with Ni mesh through which gas was able to penetrate. However, the meshes were installed inside the tube, forming an electrically insulated fuel cartridge. The cartridge fuel showed very similar performance to normal powder fuel, indicating that carbon oxidation took place through the intermediate gas species of carbon monoxide. Also, solid carbons were manufactured from oak at 400, 800, and 1,200 °C. The carbon that was carbonized at lower temperature showed higher open circuit voltage and performance. The difference between the carbon species results in a performance variation due to varying generation of CO.

Scott Calabrese Barton

ECS Meeting Abstracts • 2014

Although the 2015 Millennium Development Goal (MDG) for access to safe drinking water has largely been achieved, over 700 million people cannot access safe drinking water [1]. More importantly, the MDG for water sanitation is is far from achieved: 2.5 million people, primarily in sub-saharan Africa, lack access to water sanitization. One solution for these populations is low-cost, mobile water purification based on microbial fuel cells (MFCs). MFCs are capable of producing energy from organic water contamination by oxidizing the contaminants, thereby producing electricity and reducing the chemical oxygen demand (COD) a key measure of water contamination, by more than 90% [2]. However, such a system would need to meet stringent cost and durability requirements; a self-powered purification system would require an approximately 10-fold increase in typical MFC power density and lifetime. Moreover, bench scale MFCs of 0.1 L size would would need to be scaled up to over 10 L for practical applications. These requirements can only be met by through careful engineering design and optimization. Here we describe a numerical model of the the steady-state and transient operation of a microbial fuel cell for water purification. The model is based on laboratory-scale experiments conducted on MFCs using the Dissimilatory metal reducing bacteria Shewanella oneidensis MR-1 [3]. The model accounts for growth of bacterial biofilms, transport of reactants and products within the films, and related consumption of organic contaminants to electricity production. Particular attention is paid to biofilm composition, and electron transport mechanisms with the biofilm, including electron transport via dissolved mediators, pili and nano filaments, and surface exchange. These considerations allow the the model to applied to a variety of metal-reducing species. After calibration with laboratory-scale MFC data, the model is used to predict performance of 10L-scale MFCs, including the relationship between decontamination rate, water flow rate, and power generation. Sensitivity studies may be directly compared with principal component analysis of experimental results, indicating the degree to which the model can be used for design and optimization of real-world devices. "Millennium Development Goal drinking water target met”, http://www.who.int/mediacentre/news/releases/2012/drinking_water_20120306/en/ M. M. Ghangrekar and V. B. Shinde, Bioresour. Technol., 98, 2879 (2007). doi:10.1016/j.biortech.2006.09.050 E. Baranitharan, M. R. Khan, D. M. R. Prasad and J. Bin Salihon, Water, Air, Soil Pollut., 224, 1533 (2013). doi:10.1007/s11270-013-1533-1 S. Babanova, O. Bretschger, J. Roy, A. Cheung, K. Artyushkova and P. Atanassov, Phys. Chem. Chem. Phys., 16, 8956 (2014). doi:10.1039/c4cp00566j

Zachary A. Stoll, Jan Dolfing, Zhiyong Jason Ren et al.

Energy Technology • 2016

Abstract The anode and cathode potentials determine the overall performance of a microbial fuel cell (MFC). Thus far, research has focused on understanding the performance of individual electrodes, but there has been no investigation of how the anode or cathode potential changes as a function of the other. This study demonstrates for the first time that interplay exists between the anode and cathode electrodes, a phenomenon whereby reduction of voltage losses at one electrode increases voltage losses at the other. With our experimental data and results from the literature, a model was developed to quantify the interplay at theoretical and applied levels for wastewater treatment. The cause of the interplay was attributed to the reactant/product concentration gradient that exists between the bulk‐catholyte–cathode and biofilm–anode electrode surfaces. These findings advance our fundamental understanding of MFCs and provide new insight into how to improve performance for wastewater treatment and energy production.