bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Design of a High-Flux Microchannel Solar Receiver
Authors: Rymal Charles J. , Apte Sourabh V. , Narayanan Vinod , Drost Kevin
Published: December 2013

This computational study investigates design of microchannel based solar receiver for use in concentrated solar power. A design consisting of a planar array of channels with solar flux incident on one side and using supercritical carbon dioxide as the working fluid is sought. Use of microchannels is investigated as they offer enhanced heat transfer in solar receivers and have the potential to dramatically reduce the size and increase the performance. Designs are investigated for an incident heat flux of 1 MW/m2, up to 3.3 times that of current solar receivers [1], resulting in significant reduction of size and cost. The goal is to design a microchannel receiver with inlet and outlet temperatures of the working fluid of 500°C and 650°C, operating pressure of 100 bar, pressure drop less than 0.35 bar and surface efficiency greater than 90% defined by radiation and convection losses to the environment. Three micro-channel designs are considered: rectangular cross section with high and low aspect ratio (designs A and B) and rectangular cross section with an array of micro pin-fins of various shape spanning the height of the channel (design C). Numerical simulations are performed on individual channels and on a unit cell of the pin-fin design. Structural analysis is performed to ensure that the design can withstand the operating pressure and thermal stresses. The effects of flow maldistribution and header system in an array of channels are also investigated. Preliminary results show that all three designs are capable of meeting the requirements, with the pin-fin design having the lowest pressure drop and highest efficiency.
Improving a Valve Packing Model to Increase Packing Lifetime in Molten Salt
Authors: Gill David , Farley Bryan J.
Published: December 2013

Valves used in molten salt thermal energy storage systems often utilize conventional packing methodology and materials. These packing materials often exhibit relatively short lifetimes because of the reactive interaction of the salt and packing. Past research has indicated that valve packing lifetime is affected by both stress and temperature in the packing. Because of this interaction, it is important to understand the stress in the packing and to find ways to reduce the packing stress. A finite element model of a valve stem/packing system was created and material properties of the packing were determined and validated against previous work. The model was then used to evaluate the stress induced in the packing system through linear axial motion and then extended to include rotational stem motion as well. The analysis confirmed previous results that axial translation created a significant amount of stress in the valve packing. The newly included rotational motion of the valve stem was found to affect the packing stress only minimally. This result suggests that development of better rotary valves would be very useful for utilization in molten salt service, especially as the temperature of the salts are increased in an effort to achieve higher power cycle efficiencies.
Advanced Gel Polymer Electrolyte for Lithium-Ion Polymer Batteries
Authors: Zhang Ruisi , Hashemi Niloofar , Ashuri Maziar , Montazami Reza
Published: December 2013

We report improved performance of Li-ion polymer batteries through advanced gel polymer electrolytes (GPEs). Compared to solid and liquid electrolytes, GPEs are advantageous as they can be fabricated in different shapes and geometries; also ionic properties are significantly superior to that of solid and liquid electrolytes. We have synthetized GPE in form of membranes by trapping ethylene carbonate and propylene carbonate in a composite of polyvinylidene fluoride and N-methylpyrrolidinore. By applying phase-transfer method, we synthetized membranes with micro-pores, which led to higher ionic conductivity. The proposed membrane is to be modified further to have higher capacity, stronger mechanical properties, and lower internal resistance. In order to meet those requirements, we have doped the samples with gold nanoparticles (AuNPs) to form nanoparticle-polymer composites with tunable porosity and conductivity. Membranes doped with nanoparticles are expected to have higher porosity, which leads to higher ion mobility; and improved electrical conductivity. Four-point-probe measurement technique was used to measure the sheet resistance of the membranes. Morphology of the membranes was studied using electron and optical microscopies. Cyclic voltammetry and potentiostatic impedance spectroscopy were performed to characterize electrochemical behavior of the samples as a function of weight percentage of embedded AuNPs.
Understanding Flow of Energy in Buildings Using Modal Analysis Methodology
Authors: Gardner John , Heglund Kevin , Van Den Wymelenberg Kevin , Rieger Craig
Published: December 2013

It is widely understood that energy storage is the key to integrating variable generators into the grid. It has been proposed that the thermal mass of buildings could be used as a distributed energy storage solution and several researchers are making headway in this problem. However, the inability to easily determine the magnitude of the building’s effective thermal mass, and how the heating ventilation and air conditioning (HVAC) system exchanges thermal energy with it, is a significant challenge to designing systems which utilize this storage mechanism. In this paper we adapt modal analysis methods used in mechanical structures to identify the primary modes of energy transfer among thermal masses in a building. The paper describes the technique using data from an idealized building model. The approach is successfully applied to actual temperature data from a commercial building in downtown Boise, Idaho.
Metallic Composites Phase-Change Materials for High-Temperature Thermal Energy Storage
Authors: Li Xiaobo , Wang Hengzhi , Wang Hui , Kim Sohae , Esfarjani Keivan , Ren Zhifeng , Chen Gang
Published: December 2013

Inorganic materials and organic salts are usually used as phase change materials (PCMs) for thermal energy storage. Some of these materials have high latent heat of fusion; however one major drawback of these materials is the low thermal conductivity, which limits the rate of charging and discharging process. In this paper, we studied metallic alloys (eutectic alloys or alloys with a narrow melting temperature range) as phase-change materials, which have both high thermal conductivity and high latent heat of fusion. A formula was presented from entropy change to predict the latent heat of fusion of metallic alloys. We found that the latent heat of fusion of alloys can be expressed from three different contributions: the latent heat from each element, the sensible heat, and the mixing entropy. From the theory we also showed that latent heat of fusion could be greatly increased by maximizing the entropy of mixing, which can be realized by introduce more elements in the alloys, i.e., form ternary alloys by adding elements to binary alloys. This idea is demonstrated by the synthesis and measurement of the binary alloy 87.8Al-12.2Si (at%) and ternary alloy 45Al-40Si-15Fe (at%). The metallic alloy is synthesized by hot pressing method. The latent heat of fusion of 45Al-40Si-15Fe (at%) is about 865 kJ/kg with melting temperature from 830 °C to 890 °C from the differential scanning calorimetry (DSC) measurement, comparing with 554.9 kJ/kg and 578.3 °C for the binary alloy 87.8Al-12.2Si (at%). From the binary to the ternary alloy, the contribution to the latent heat from mixing entropy increases by 17%.
Supercritical CO2 Rankine Cycle Using Low and Medium Temperature Heat Sources
Authors: Guo Cong , Du Xiaoze , Zhou Yingyan , Yang Lijun , Yang Yongping
Published: December 2013

Recovery of industrial waste heat is significant to both energy saving and emission reduction. In the present paper, two types of supercritical CO2 Rankine cycles with and without internal heat exchanger (IHX) are integrated for analyzing the performance of low and medium temperature industrial heat recovery. Cycles were simulated with Aspen software, by which the influences of the initial temperature, initial pressure and temperature of cooling water were observed. The results indicate that cycle efficiency and net output work increase with growth of initial temperature, yet they fell as temperature of cooling water ramps down for the two types of cycle. For a given initial temperature, the cycle efficiency and net output work have maximum values under various initial pressures. This can be attributed to the power consumption of CO2 pump, which goes up significantly with increase of initial pressure. The performances of supercritical CO2 Rankine cycles with and without IHX utilizing four typical industrial heat sources at low and medium temperature were analyzed, which were the heat of non-concentrating solar collector, the exhaust gas heat of a 600MW coal fired plant, the exhaust gas heat of a CFB boiler and the exhaust gas heat of industrial furnace of a cement plant. The optimal cycle efficiencies range from 7% to 12% without IHX and 9% to 15% with IHX, respectively, under the temperature of heat source varying from 130°C to 200°C.
An Innovative Heating Energy System Planning and Design: Case of Yinchuan City
Authors: Zheng Zhonghai , Fu Lin , Wu Zi , Zhao Xiling , Wu Yanting
Published: December 2013

The current heating system in Yinchuan city, the capital of the Ningxia Autonomous Region in northwest China, is investigated and analyzed. Lacking an integrated planning, the heating systems have developed with low energy efficiency, high environment emission and economic cost. The choice of heating energy structure vary between coal and gas, the heating modes including gas-fired CHP, coal-fired CHP, gas-fired boiler and coal-fired boiler are facing challenges. In this paper, several innovative planning scenarios are proposed to achieve high energy efficiency, low environment emission and reasonable economic cost. In the heating schemes, three innovative technologies are designed. The first technology is waste heat recovery based on the Co-generation-based absorption heat-exchange (Co-ah) cycle. The waste heat can be both from circulating water or flue gas in CHP heating system and the industrial waste heat recovery. The second technology is the heating network with large temperature difference. The third technology is the gas distributed peak-shaving, gas-driven absorption heat-exchange in the substation.
Investigation of Thermochemical Hydrogen Production via the Novel Thermo-Mechanical Stabilized Iron Oxide-Zirconia Porous Structure
Authors: Mehdizadeh Ayyoub M. , Randhir Kelvin , Klausner James F. , AuYeung Nicholas , Al-Raqom Fotouh , Mei Renwei , Hahn David
Published: December 2013

In this study we have developed a unique method for synthesizing very reactive water splitting materials that will remain stable at temperatures as high as 1450 °C to efficiently produce clean hydrogen from concentrated solar energy. The hydrogen production for a laboratory scale reactor using a “Thermo-mechanical Stabilized Porous Structure” (TSPS) is experimentally investigated for oxidation and thermal reduction temperatures of 1200 and 1450 °C, respectively. The stability and reactivity of a 10 g TSPS over many consecutive oxidation and thermal reduction cycles for different particle size ranges has been investigated. The novel thermo-mechanical stabilization exploits sintering and controls the geometry of the matrix of particles inside the structure in a favorable manner so that the chemical reactivity of the structure remains intact. The experimental results demonstrate that this structure yields peak hydrogen production rates of 1–2 cm3/(min.gFe3O4) during the oxidation step at 1200 °C and the 30 minute thermal reduction step at 1450 ° C without noticeable degradation over many consecutive cycles. The hydrogen production rate is one of the highest yet reported in the open literature for thermochemical looping processes using thermal reduction. This novel process has strong potential for developing an enabling technology for efficient and commercially viable solar fuel production.
Compound Parabolic Concentrators in Solar Thermal Applications: A Review
Authors: Xu Donghao , Qu Ming
Published: December 2013

Among all types of concentrators, compound parabolic concentrators (CPCs) have been designed as stationary solar collectors for relative high temperature operations with high cost effectiveness. The CPCs are potentially the favorable option for solar power systems and high temperature solar thermal system. This paper provided a review on studies of CPCs in solar thermal applications. It covered basic concepts, principles, and design of CPCs. It also reviewed optical models and thermal models of CPCs, as well as the thermal applications of CPCs. The challenges were also summarized.
3D Modeling of an Anode Supported SOFC Using FEM and LBM
Authors: Andersson Martin , Paradis Hedvig , Yuan Jinliang , Sundén Bengt
Published: December 2013

Solid oxide fuel cells (SOFCs) are promising as energy producing device, which at this stage of its development will require extensive analysis and benefit from numerical modeling at different time- and length scales. In this study, two models based on finite element method (FEM) and Lattice Boltzmann model (LBM), respectively, are evaluated and compared for an anode-supported SOFC. First, a 3D model is developed based on the FEM, using COMSOL, of a single SOFC operating at an intermediate temperature range. Heat, gas-phase species, momentum, ion and electron transport are implemented and coupled to the kinetics of the electrochemical reactions. Secondly, a 3D model of the porous anode of a SOFC is developed using LBM to investigate the effects of electrochemical reactions on the transport processes at microscale for 3 components (H2, H2O and O2−). Parallel computing in Python is employed through the program Palabos to capture the active microscopic catalytic reaction effects on the heat and mass transport.

It is found that LBM can be effectively used at a mesoscale ranging down to a microscale and proven to effectively take care of the interaction between the fluid particles and the walls of the porous media. The 3D LBM model takes into account the transport of oxygen ions within the solid particles of the SOFC anode. Both the oxygen ions and the hydrogen are mainly consumed by the reaction layer. One of the improvements in this study compared to our previous (FEM) models is the captured 3D effects which was not possible in 2D. High current density spots are identified, where the electron transport distance is short and the oxygen concentration is high. The relatively thin cathode results in a significant oxygen mole fraction gradient in the direction normal to the main flow direction.
Optimization of PEM Fuel Cell Flow Channels: Modeling Analysis and Experimental Tests
Authors: Liu Hong , Li Peiwen
Published: December 2013

The dimensions of gas flow channels and walls/ribs of PEM fuel cells are optimized using a convenient mathematical model. Experimental work for several PEM fuel cells with modeling-optimized gas flow channels was conducted, and the tested results validate the modeling work and the optimization.

The model considered average mass transfer and species’ concentrations in flow channels, which allows the determination of an average concentration polarization, the humidity in anode and cathode gas channels, and thus the proton conductivity of membranes, as well as the activation polarization. An electrical circuit for the current and ion conduction is applied to analyze the ohmic losses from anode current collector to cathode current collector. The modeling computation required relatively less computational time and thus can be applied to compute a large number of cases with various flow channel designs and operating parameters for optimization analysis. Optimum ratio of the width of flow channels against the walls/ribs was found from the modeling analysis.

In the experimental work, PEM fuel cells were fabricated based on the flow channel dimensions optimized from the modeling analysis. Experimental results agreed with the modeling analysis satisfactorily in respect to the comparison of V-I performance between fuel cells with several optimized designs. The model is recommended as a tool for optimization design of gas flow channels for PEM fuel cells. The optimization results are of significance to the improvement of PEM fuel cell designs and performance.
Lattice Boltzmann Modeling of Advection-Diffusion Transport With Electrochemical Reactions in a Porous SOFC Anode Structure
Authors: Paradis Hedvig , Andersson Martin , Sundén Bengt
Published: December 2013

Lattice Boltzmann method (LBM) is a method that can be used to capture the detailed activities of the transport processes at microscale. Here LBM is used to model the porous anode for an anode-supported Solid Oxide Fuel Cell (SOFC). The purpose of this study is to investigate the effects of electrochemical reactions on the transport processes by a 3D model at microscale. A porous 3D modeling domain is created with randomly placed spheres to resemble the part of the anode structure close to the electrolyte. The 3D model is simulated with parallel computing in Python using Palabos and also MATLAB to capture the active microscopic catalytic effects on the heat and mass transport. A multicomponent reaction-advection-diffusion transport for three components (H2, H2O and O2−) is analyzed with electrochemical reactions and particle collisions. This combined with the heat, momentum and charge transport in the 3D model.

It is here been shown that LBM can be used to evaluate the microscale effect of electrochemical reactions on the transport processes and some potential risk of hot spots to reduce harming interaction sites. The electrochemical potential is gradually increased along the flow direction as the species come in contact with each other. There is a potential risk for a hot spot when the active interacting species reach a catalytic layer and the smooth flow pattern is disturbed. Improving the flow structure by the catalytic interface can increase interaction of the reforming reactions and the electrochemical reactions, which in turn can improve the cell performance.
Desulfurization of Liquid Phase Jet-A Fuel by Selective Adsorption at Room Temperature
Authors: Xu Xinhai , Zhang Shuyang , Li Peiwen
Published: December 2013

To produce syngas from reforming of jet fuels for fuel-cell-based auxiliary power units, it is necessary to keep the fuel ultra-clean of sulfur. Several Ni-Ce based adsorbents for sulfur cleaning from jet-A fuel under room temperature were developed and tested in fixed bed reactors in this work. The adsorbent preparation procedure and calcination atmosphere were optimized for the highest adsorbent desulfurization capacity. Desulfurization performance due to the ratio of fixed bed column diameter (Dc) and adsorbent particle size (Dp) and liquid hourly space velocity (LHSV) were also investigated in a factorial experiment. The adsorbents can effectively remove sulfur in Jet-A fuel from over 1000 ppmw level to below 30 ppmw. The highest sulfur adsorption capacity achieved is 2.44 mg S/g adsorbent at the breakthrough point of 30 ppmw. To effectively scale up the fixed bed reactor, the LHSV should be kept lower than 0.65 and the Dc/Dp needs to be larger than 124.
Dynamic Modeling of a Reformed Methanol Fuel Cell System Using Empirical Data and Adaptive Neuro-Fuzzy Inference System Models
Authors: Justesen Kristian K. , Andreasen Søren J. , Shaker Hamid R.
Published: December 2013

In this work, a dynamic MATLAB Simulink model of a H3-350 Reformed Methanol Fuel Cell (RMFC) stand-alone battery charger produced by Serenergy® is developed on the basis of theoretical and empirical methods. The advantage of RMFC systems is that they use liquid methanol as a fuel instead of gaseous hydrogen, which is difficult and energy consuming to store and transport. The models include thermal equilibrium models of the individual components of the system. Models of the heating and cooling of the gas flows between components are also modeled and Adaptive Neuro-Fuzzy Inference System models of the reforming process are implemented. Models of the cooling flow of the blowers for the fuel cell and the burner which supplies process heat for the reformer are made. The two blowers have a common exhaust, which means that the two blowers influence each other’s output. The models take this into account using an empirical approach. Fin efficiency models for the cooling effect of the air are also developed using empirical methods. A fuel cell model is also implemented based on a standard model which is adapted to fit the measured performance of the H3-350 module. All the individual parts of the model are verified and fine-tuned through a series of experiments and are found to have mean absolute errors between 0.4% and 6.4% but typically below 3%. After a comparison between the performance of the combined model and the experimental setup, the model is deemed to be valid for control design and optimization purposes.
The Analysis of Mass Transport Phenomena in Micro Porous Layer for High Current Density Operation in PEMFC for Automobile Application
Authors: Kotaka Toshikazu , Aotani Koichiro , Tabuchi Yuichiro , Mukherjee Partha
Published: December 2013

Cost reduction is the most important issue for commercialization of Fuel Cell Electric Vehicle (FCEV). High current density operation is one of the solutions for it. In order to realize high current density operation, it is necessary to reduce both of electron and oxygen transport resistance in the porous materials such as gas diffusion layer (GDL) and micro porous layer (MPL). However, the impacts of MPL microstructure on their properties are not fully understood yet compared with GDL because of the necessity of higher spatial resolution. In previous study, the transport analysis on the micro-structure which were visualized by Nano X-ray CT and FIB-SEM were conducted for it. However, it was not enough to understand both of the electron and oxygen transport phenomena and find the dominant factors, because there is no study which focused on the comparison of the numerical and experimental results on both of the electron and oxygen transport. In this study, the comprehensive analysis on both of electron and oxygen transport phenomena in GDL and MPL was conducted with experimental and numerical study based on the three-dimensional (3D) micro structure data. As a result, it was found that pore structure, such as a local porosity and/or tortuosity significantly affected the oxygen transport phenomena. On the other hands, especially in the case of electron transport phenomena in MPL, our results suggested that the dominant factor is not the solid structure such as local solid fraction and/or tortuosity but the contact resistance between carbon particles. This fact revealed that it is effective way to reduce the contact resistance between carbon particles and/or the number of contact points in unit length of a transport path in order to improve electrical transport of MPL.
Development and Validation of a Dynamic Thermal Model for a Polymer Electrolyte Membrane Fuel Cell
Authors: Headley Alexander , Hadisujoto Budi , Chen Dongmei , Moon Tess J.
Published: December 2013

The development and validation of a control-oriented dynamic thermal model for a polymer electrolyte membrane (PEM) fuel cell stack is presented. This model is based on the first law of thermodynamics within four defined control volumes in the fuel cell; the cathode channel, anode channel, coolant channel, and fuel cell stack body. Energy and mass conservation equations are developed for each control volume. Transient dynamics captured by this model include the electrochemical reaction, heat transfer and mass transport. Activation, ohmic, and concentration voltage losses are also modeled to improve the accuracy of the voltage model response. This allows the stack voltage and cell temperature to be modeled based on the inlet temperature, pressure, and species flow rate and the relative humidity level setting.

An experiment was conducted to give a baseline with which to tune the model. Tuning of the model parameters was performed and validation of these adjustments was then conducted through comparison to another experiment. The model predicts the dynamic thermal and electrical response of the fuel cell system with a good degree of accuracy in both cases.
Numerical Simulation of Liquid Water Behavior in Microchannel With a 90° Bend
Authors: Alrahmani Mosab , Chen Rui , Ibrahim Salah
Published: December 2013

Water management is an effective way of improving Proton Exchange Membrane (PEM) fuel cell performance and durability. Changing the wettability of gas channel walls and gas diffusion layer (GDL) is one way of controlling the water management in a fuel cell for its influence on the liquid water dynamic behavior. The objective of this study is to investigate liquid water dynamic behavior in a microchannel with a 90° bend and different surface wettability combinations through 3D numerical simulation. Volume-of-fluid (VOF) method was employed to track the fluid-fluid interface in the multiphase flow.

The simulated microchannel has a square cross-section with a dimension of 0.25 mm and a total length of 1.5 mm. Water is introduced to the channel via two pores in the bottom surface representing a GDL while air flows from one end to another. The air and water velocities used are in the order of magnitude of a high current density fuel cell. Nine different combinations of wall/GDL wettability are investigated.

The results show that liquid water takes less time to leave the channel in a hydrophilic GDL compared to moderate and hydrophobic GDL regardless of wall wettability. Furthermore, the GDL wettability shows more significant impact on liquid water behavior compared to the wall wettability; however, wall wettability has a slight but considerable impact.
Review of Microbial Fuel Cells for Wastewater Treatment: Large-Scale Applications, Future Needs and Current Research Gaps
Authors: Waller Michael G. , Trabold Thomas A.
Published: December 2013

There is growing interest in innovative waste water treatment technologies that can utilize the inherent energy-producing potential of organic waste. A microbial fuel cell (MFC) is a type of bioreactor that produces electricity by converting energy in the chemical bonds of organic material, through a catalytic reaction of microorganisms under anaerobic conditions. MFCs provide a promising low cost, highly efficient, and renewable energy-producing alternative to conventional wastewater treatments. MFC technology at the laboratory scale has advanced to the point where chemical oxygen demand (COD) removal efficiencies (RE) over 90% are commonly achieved; however, low coulombic efficiencies (CE) and power densities often result when treating actual industrial and domestic wastewaters. In spite of their low energy recovery and power production, MFCs have been shown to be economically viable when factoring in costs savings from the sale of produced chemical byproducts and reduction of solid waste removal costs. However, further research of large-scale MFC wastewater treatment applications must be performed to determine the extent of their feasibility. This paper reviews several pilot-test MFC systems, addresses promising future industrial applications, and discusses current research gaps in MFC technology for wastewater treatment. Of particular interest in our research program is the use of MFCs to treat liquid-phase organic waste generated at food processing plants. Because of the general scalability of fuel cell systems, there is reason to believe that an MFC treatment system would be better suited to relatively small waste flow rates, unlike other treatment methods (e.g., anaerobic digestion) which typically require large volume to achieve economic viability.
Effect of Membrane Properties on Dynamic Behavior of Polymer Electrolyte Membrane Fuel Cells
Authors: Verma Atul , Pitchumani Ranga
Published: December 2013

Understanding the performance of proton exchange membrane (PEM) fuel cells is critical to the water management in the fuel cell system. Low-humidity operating conditions present a complex interaction between dynamic behavior and water transport owing to different time scales of water transport mechanisms in the transient process. Toward understanding the effects of membrane properties on the dynamic behavior, this paper presents numerical simulations for a single channel PEM fuel cell undergoing changes in load, by subjecting the unit cell to step change in current. The objective is to elucidate the complex interaction between cell voltage response and water transport dynamics for various membrane properties, where the performance is critically related water content of the membrane. Detailed computational fluid dynamics (CFD) simulations are carried out to show that step increase in current density leads to anode dryout due to electro-osmotic drag, and investigate its dependence on variations in membrane properties.
Clean Energy Generation by a Nanostructured Biophotofuel Cell
Authors: Liu Xiaolu , Liu Yang , Ren Kai , Lawson Paul , Moening Andrew , Haubert Matthew , Gan Yong X. , Mohammed Omar , Zhang Lihua , De Santos Omar , Diazvaldez Jose R. , Hom Kaitlin E.
Published: December 2013

In this paper, clean energy generation from hazardous materials by a nanostructured biophotofuel cell was studied. Specifically, electrodeposition of polyaniline on TiO2 nanotube as photoelectrochemical anode for a sodium sulfide fuel cell was performed. The photoelectrochemical response of the TiO2 nanotube capped by polyaniline nanoparticles was studied in UV and visible light illumination using sodium sulfide as the electrolyte. The polyaniline was added onto the top end of the nanotube via electrochemical deposition from 0.1 M aniline (C6H7N) in 1 M HCl solution. Polyaniline nanoparticle/TiO2 nanotube was made into an anode and put into 0.5 M sodium sulfide solution for photoelectrochemical response tests under both visible and ultraviolet light irradiation. The photoelectrochemical anode shows good photo-catalytic property, as evidenced by the open circuit potential changes when the illumination conditions were changed. Its response to ultraviolet light is much stronger than to visible light. It is also found that the higher the temperature of the sodium sulfide solution, the weaker the photo-catalytic response of the anode.
Unitized Regenerative Fuel Cell Performance Using Polymer Wicks for Passive Water Management
Authors: Lele Sandeep S. , Sizemore Michael A. , Zalawadia Sutyen S. , Zabalegui Aitor P. , Tabrizi Abdie H. , Fabris Drazen
Published: December 2013

Proton Exchange Membrane (PEM) fuel cells rely on effective internal water transport to provide stable performance. Many water management schemes require high heat, high pressure, or high flow rates — effectively introducing parasitic losses and reducing round-trip efficiency. In this work, a radial, non-recirculating, unitized regenerative fuel cell prototype with passive water transport is designed and tested. The cell features a 5 cm2 active area with 1.2 mm wide by 0.6 mm high gas flow channels. Porous polymer wicks are fabricated in the cathode side flow channels and coupled with a bulk water storage structure. The resulting wicks are 0.3 mm wide and 0.6 mm high. Discharge operating voltage measured during current control testing resulted in 1 V at open circuit, 0.8 V at 0.3 A·cm−2, and 0.2 V at 1 A·cm−2. Charge operating current density measured during voltage control testing resulted in 0.1 A·cm−2 at 1.5 V, 0.3 A·cm−2 at 1.6 V, and 0.8 A·cm−2 at 2 V. During the membrane electrode assembly (MEA) conditioning procedure, degradation in operating current density is seen over a 30–100 minute time span.
A Compact Versatile Microbial Fuel Cell From Paper
Authors: Wagner Luke T. , Hashemi Niloofar , Hashemi Nastaran
Published: December 2013

Microbial fuel cells (MFCs) have been a potential green energy source for a long time but one of the problems is that either the technology must be used on a large scale or special equipment have been necessary to keep the fuel cells running such as syringe pumps. Paper-based microbial fuel cells do not need to have a syringe pump to run and can run entirely by themselves when placed in contact with the fluids that are necessary for it to run. Paper-based microbial fuel cells are also more compact than traditional MFCs since the device doesn’t need any external equipment to run.

The goal of this paper is to develop a microbial fuel cell that does not require a syringe pump to function. This is done by layering chromatography paper with wax design printed onto it. This restricts the fluids to a specific flow path allowing it to act like the tubes in a typical microbial fuel cell device by delivering the fluids to the chamber. The fluids are picked up by tabs that sit in the fluid and use capillary attraction to flow up the tab and into the device. The fluids are directed to the chambers where the chemical and biological processes take place. These flows are then directed out of the device so that they are taken to a waste container and out of the system.

Our microliter scale paper-based microbial fuel cell creates a significant current that is sustained for a period of time and can be repeated. A paper-based microbial fuel cell also has a fast response time. These results mean that it could be possible for a set of paper-based microbial fuel cells to create a power density capable of powering small, low power circuits when used in series or parallel.

In this paper, we discuss the fabrication and experimental results of our paper-based microbial fuel cell. Also there will be a discussion of how paper-based microbial fuels cells compare to the traditional microbial fuel cells and how they could be used in the future.
Impact of Gas Diffusion Layer Properties on Liquid Water Breakthrough Pressure in Polymer Electrolyte Fuel Cell
Authors: Mortazavi Mehdi , Tajiri Kazuya
Published: December 2013

Liquid water transport through gas diffusion layers (GDLs) with different thicknesses and different amounts of polytetrafluoroethylene (PTFE) is studied by taking an ex-situ approach. Droplet static contact angles on GDLs were also measured. Using a constant flow syringe pump, liquid water was introduced to the surface of GDL sample and the breakthrough pressure at which liquid water passes through the GDL and forms droplet on the other side of the GDL was measured by a differential pressure transducer. Liquid water can pass through the pores when its pressure exceeds the capillary pressure. It was observed that the breakthrough pressure increases with GDL thickness. Also, applying some amount of PTFE to an untreated GDL was observed to significantly increase the breakthrough pressure while more amount of PTFE within the GDL had negligible effect on liquid water breakthrough pressure. Using measured breakthrough pressures and contact angles, maximum pore diameter of GDLs were calculated based on the GDL’s single layer model.
Effects of Compression on GDL Microstructure by High-Resolution X-Ray Computed Tomography
Authors: Khajeh Hosseini D. Navvab , Sasabe Takashi , Tokumasu Takashi , Pasaogullari Ugur
Published: December 2013

Transport phenomena within gas diffusion layers (GDLs) of of proton exchange membrane fuel cells (PEMFCs) are crucially important for an optimum PEM fuel cell performance. The microstructure properties of the GDLs, such as porosity, tortuosity and pore size distribution govern the transport of fluid, heat and charge. Additionally, PEM fuel cells are assembled under high compression pressure to minimize the contact resistance between components. The compression significantly alters the microstructure of the GDLs, and affects the cell performance substantially by blocking the pathways of liquid and gas species to and from the catalyst layer reaction sites. This study gives detailed understanding on the effect of compression on a GDL microstructure using high resolution X-ray Computed Tomography. Porosity distributions were shown when the GDL is compressed. A significant GDL penetration into the gas channel was observed at high compression pressures.
Degradation of Extracytoplasmic Catalysts for Protein Folding in Bacillus subtilis
Authors: Krishnappa Laxmi , Monteferrante Carmine G. , Neef Jolanda , Dreisbach Annette , van Dijl Jan Maarten
Published: December 2013

The general protein secretion pathway of
Bacillus subtilis
has a high capacity for protein export from the cytoplasm, which is exploited in the biotechnological production of a wide range of enzymes. These exported proteins pass the membrane in an unfolded state, and accordingly, they have to fold into their active and protease-resistant conformations once membrane passage is completed. The lipoprotein PrsA and the membrane proteins HtrA and HtrB facilitate the extracytoplasmic folding and quality control of exported proteins. Among the native exported proteins of
B. subtilis
are at least 10 proteases that have previously been implicated in the degradation of heterologous secreted proteins. Recently, we have shown that these proteases also degrade many native membrane proteins, lipoproteins, and secreted proteins. The present studies were therefore aimed at assessing to what extent these proteases also degrade extracytoplasmic catalysts for protein folding. To this end, we employed a collection of markerless protease mutant strains that lack up to 10 different extracytoplasmic proteases. The results show that PrsA, HtrA, and HtrB are indeed substrates of multiple extracytoplasmic proteases. Thus, improved protein secretion by multiple-protease-mutant strains may be related to both reduced proteolysis and improved posttranslocational protein folding and quality control.
Characterization of a Multiresistant Mosaic Plasmid from a Fish Farm Sediment Exiguobacterium sp. Isolate Reveals Aggregation of Functional Clinic-Associated Antibiotic Resistance Genes
Authors: Yang Jing , Wang Chao , Wu Jinyu , Liu Li , Zhang Gang , Feng Jie
Published: December 2013

The genus
Exiguobacterium
can adapt readily to, and survive in, diverse environments. Our study demonstrated that
Exiguobacterium
sp. strain S3-2, isolated from marine sediment, is resistant to five antibiotics. The plasmid pMC1 in this strain carries seven putative resistance genes. We functionally characterized these resistance genes in
Escherichia coli
, and genes encoding dihydrofolate reductase and macrolide phosphotransferase were considered novel resistance genes based on their low similarities to known resistance genes. The plasmid G+C content distribution was highly heterogeneous. Only the G+C content of one block, which shared significant similarity with a plasmid from
Exiguobacterium arabatum
, fit well with the mean G+C content of the host. The remainder of the plasmid was composed of mobile elements with a markedly lower G+C ratio than the host. Interestingly, five mobile elements located on pMC1 showed significant similarities to sequences found in pathogens. Our data provided an example of the link between resistance genes in strains from the environment and the clinic and revealed the aggregation of antibiotic resistance genes in bacteria isolated from fish farms.
Listeria monocytogenes Associated with New Zealand Seafood Production and Clinical Cases: Unique Sequence Types, Truncated InlA, and Attenuated Invasiveness
Authors: Cruz Cristina D. , Pitman Andrew R. , Harrow Sally A. , Fletcher Graham C.
Published: December 2013

Listeriosis is caused by the food-borne pathogen
Listeria monocytogenes
, which can be found in seafood and processing plants. To evaluate the risk to human health associated with seafood production in New Zealand, multi-virulence-locus sequence typing (MVLST) was used to define the sequence types (STs) of 31
L. monocytogenes
isolates collected from seafood-processing plants, 15 from processed foods, and 6 from human listeriosis cases. The STs of these isolates were then compared with those from a collection of seafood isolates and epidemic strains from overseas. A total of 17 STs from New Zealand clustered into two lineages: seafood-related isolates in lineages I and II and all human isolates in lineage II. None of the New Zealand STs matched previously described STs from other countries. Isolates (belonging to ST01-N and ST03-N) from mussels and their processing environments, however, were identical to those of sporadic listeriosis cases in New Zealand. ST03-N isolates (16 from mussel-processing environments, 2 from humans, and 1 from a mussel) contained an
inlA
premature stop codon (PMSC) mutation. Therefore, the levels of invasiveness of 22 isolates from ST03-N and the three other common STs were compared using human intestinal epithelial Caco-2 cell lines. STs carrying
inlA
PMSCs, including ST03-N isolates associated with clinical cases, had a low invasion phenotype. The close relatedness of some clinical and environmental strains, as revealed by identical MVLST profiles, suggests that local and persistent environmental strains in seafood-processing environments pose a potential health risk. Furthermore, a PMSC in
inlA
does not appear to give
L. monocytogenes
a noninvasive profile.
Disruption of Putrescine Biosynthesis in Shewanella oneidensis Enhances Biofilm Cohesiveness and Performance in Cr(VI) Immobilization
Authors: Ding Yuanzhao , Peng Ni , Du Yonghua , Ji Lianghui , Cao Bin
Published: December 2013

Although biofilm-based bioprocesses have been increasingly used in various applications, the long-term robust and efficient biofilm performance remains one of the main bottlenecks. In this study, we demonstrated that biofilm cohesiveness and performance of
Shewanella oneidensis
can be enhanced through disrupting putrescine biosynthesis. Through random transposon mutagenesis library screening, one hyperadherent mutant strain, CP2-1-S1, exhibiting an enhanced capability in biofilm formation, was obtained. Comparative analysis of the performance of biofilms formed by
S. oneidensis
MR-1 wild type (WT) and CP2-1-S1 in removing dichromate (Cr
2
O
7
2−
), i.e., Cr(VI), from the aqueous phase showed that, compared with the WT biofilms, CP2-1-S1 biofilms displayed a substantially lower rate of cell detachment upon exposure to Cr(VI), suggesting a higher cohesiveness of the mutant biofilms. In addition, the amount of Cr(III) immobilized by CP2-1-S1 biofilms was much larger, indicating an enhanced performance in Cr(VI) bioremediation. We further showed that
speF
, a putrescine biosynthesis gene, was disrupted in CP2-1-S1 and that the biofilm phenotypes could be restored by both genetic and chemical complementations. Our results also demonstrated an important role of putrescine in mediating matrix disassembly in
S. oneidensis
biofilms.
Effects of Growth Medium on Matrix-Assisted Laser Desorption–Ionization Time of Flight Mass Spectra: a Case Study of Acetic Acid Bacteria
Authors: Wieme Anneleen D. , Spitaels Freek , Aerts Maarten , De Bruyne Katrien , Van Landschoot Anita , Vandamme Peter
Published: December 2013

The effect of the growth medium used on the matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectra generated and its consequences for species and strain level differentiation of acetic acid bacteria (AAB) were determined by using a set of 25 strains. The strains were grown on five different culture media that yielded a total of more than 600 mass spectra, including technical and biological replicates. The results demonstrate that the culture medium can have a profound effect on the mass spectra of AAB as observed in the presence and varying signal intensities of peak classes, in particular when culture media do not sustain optimal growth. The observed growth medium effects do not disturb species level differentiation but strongly affect the potential for strain level differentiation. The data prove that a well-constructed and robust MALDI-TOF mass spectrometry identification database should comprise mass spectra of multiple reference strains per species grown on different culture media to facilitate species and strain level differentiation.
PVv3, a New Shuttle Vector for Gene Expression in Vibrio vulnificus
Authors: Klevanskaa Karina , Bier Nadja , Stingl Kerstin , Strauch Eckhard , Hertwig Stefan
Published: December 2013

An efficient electroporation procedure for
Vibrio vulnificus
was designed using the new cloning vector pVv3 (3,107 bp). Transformation efficiencies up to 2 × 10
6
transformants per μg DNA were achieved. The vector stably replicated in both
V. vulnificus
and
Escherichia coli
and was also successfully introduced into
Vibrio parahaemolyticus
and
Vibrio cholerae
. To demonstrate the suitability of the vector for molecular cloning, the green fluorescent protein (GFP) gene and the
vvhBA
hemolysin operon were inserted into the vector and functionally expressed in
Vibrio
and
E. coli
.
The Gastrointestinal Tract of the White-Throated Woodrat (Neotoma albigula) Harbors Distinct Consortia of Oxalate-Degrading Bacteria
Authors: Miller Aaron W. , Kohl Kevin D. , Dearing M. Denise
Published: December 2013

The microbiota inhabiting the mammalian gut is a functional organ that provides a number of services for the host. One factor that may regulate the composition and function of gut microbial communities is dietary toxins. Oxalate is a toxic plant secondary compound (PSC) produced in all major taxa of vascular plants and is consumed by a variety of animals. The mammalian herbivore
Neotoma albigula
is capable of consuming and degrading large quantities of dietary oxalate. We isolated and characterized oxalate-degrading bacteria from the gut contents of wild-caught animals and used high-throughput sequencing to determine the distribution of potential oxalate-degrading taxa along the gastrointestinal tract. Isolates spanned three genera:
Lactobacillus
,
Clostridium
, and
Enterococcus
. Over half of the isolates exhibited significant oxalate degradation
in vitro
, and all
Lactobacillus
isolates contained the
oxc
gene, one of the genes responsible for oxalate degradation. Although diverse potential oxalate-degrading genera were distributed throughout the gastrointestinal tract, they were most concentrated in the foregut, where dietary oxalate first enters the gastrointestinal tract. We hypothesize that unique environmental conditions present in each gut region provide diverse niches that select for particular functional taxa and communities.