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Maximum Power Density (maximum + power_density)
Selected AbstractsVertically Aligned Nanocomposite Thin Films as a Cathode/Electrolyte Interface Layer for Thin-Film Solid Oxide Fuel CellsADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Jongsik Yoon Abstract A thin layer of a vertically aligned nanocomposite (VAN) structure is deposited between the electrolyte, Ce0.9Gd0.1O1.95 (CGO), and the thin-film cathode layer, La0.5Sr0.5CoO3 (LSCO), of a thin-film solid-oxide fuel cell (TFSOFC). The self-assembled VAN nanostructure contains highly ordered alternating vertical columns of CGO and LSCO formed through a one-step thin-film deposition process that uses pulsed laser deposition. The VAN structure significantly improves the overall performance of the TFSOFC by increasing the interfacial area between the electrolyte and cathode. Low cathode polarization resistances of 9,×,10,4 and 2.39,, were measured for the cells with the VAN interlayer at 600 and 400,°C, respectively. Furthermore, anode-supported single cells with LSCO/CGO VAN interlayer demonstrate maximum power densities of 329, 546, 718, and 812,mW cm,2 at 550, 600, 650, and 700,°C, respectively, with an open-circuit voltage (OCV) of 1.13,V at 550,°C. The cells with the interlayer triple the overall power output at 650,°C compared to that achieved with the cells without an interlayer. The binary VAN interlayer could also act as a transition layer that improves adhesion and relieves both thermal stress and lattice strain between the cathode and the electrolyte. [source] Samarium-Doped Ceria Nanowires: Novel Synthesis and Application in Low-Temperature Solid Oxide Fuel CellsADVANCED MATERIALS, Issue 14 2010Ying Ma Samarium-doped ceria (SDC) nanowires are synthesized by a novel, template-, surfactant-free and cost-effective method, using citric acid as precipitating/complexing agent for formation of citrate precursor nanowires. The single SOFC based on SDC nanowires/Na2CO3 nanocomposites as electrolyte is fabricated and the maximum power densities of 417 and 522,mW,cm,2 at 550 and 600,°C are achieved, showing great potential for low-temperature SOFCs. [source] Evaluating Enzyme Cascades for Methanol/Air Biofuel Cells Based on NAD+ -Dependent EnzymesELECTROANALYSIS, Issue 7-8 2010Abstract Previous work by the group has entailed encapsulating enzymes in polymeric micelles at bioelectrode surfaces by utilizing hydrophobically modified Nafion membranes, which are modified in order to eliminate the harsh acidity of Nafion while tailoring the size of the polymer micelles to optimize for the encapsulation of an individual enzyme. This polymer encapsulation has been shown to provide high catalytic activity and enzyme stability. In this study, we employed this encapsulation technique in developing a methanol/air biofuel cell through the combined immobilization of NAD+ -dependent alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AldDH) and formate dehydrogenase (FDH) within a tetrabutylammonium bromide (TBAB) modified Nafion to oxidize methanol to carbon dioxide with poly(methylene green) acting as the NADH electrocatalyst electropolymerized on the surface of the electrode. The methanol biofuel/air cell resulted in a maximum power density of 261±7.6,,W/cm2 and current density of 845±35.5,,A/cm2. This system was characterized for the effects of degree of oxidation, temperature, pH, and concentration of fuel and NAD. [source] Study on Glucose Biofuel Cells Using an Electrochemical Noise DeviceELECTROANALYSIS, Issue 14 2008Yueming Tan Abstract An electrochemical noise (ECN) device was utilized for the first time to study and characterize a glucose/O2 membraneless biofuel cell (BFC) and a monopolar glucose BFC. In the glucose/O2 membraneless BFC, ferrocene (Fc) and glucose oxidase (GOD) were immobilized on a multiwalled carbon nanotubes (MWCNTs)/Au electrode with a gelatin film at the anode; and laccase (Lac) and an electron mediator, 2,2,-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS), were immobilized on a MWCNTs/Au electrode with polypyrrole at the cathode. This BFC was performed in a stirred acetate buffer solution (pH,5.0) containing 40,mmol/L glucose in air, with a maximum power density of 8,,W/cm2, an open-circuit cell voltage of 0.29,V, and a short-circuit current density of 85,,A/cm2, respectively. The cell current at the load of 100,k, retained 78.9% of the initial value after continuous discharging for 15,h in a stirred acetate buffer solution (pH,5.0) containing 40,mmol/L glucose in air. The performance decrease of the BFC resulted mainly from the leakage of the ABTS mediator immobilized at the cathode, as revealed by the two-channel quartz crystal microbalance technique. In addition, a monopolar glucose BFC was performed with the same anode as that in the glucose/O2 membraneless BFC in a stirred phosphate buffer solution (pH,7.0) containing 40,mmol/L glucose, and a carbon cathode in Nafion-membrane-isolated acidic KMnO4, with a maximum power density of 115,,W/cm2, an open-circuit cell voltage of 1.24,V, and a short-circuit current density of 202,,A/cm2, respectively, which are superior to those of the glucose/O2 membraneless BFC. A modification of the anode with MWCNTs for the monopolar glucose BFC increased the maximum power density by a factor of 1.8. The ECN device is highly recommended as a convenient, real-time and sensitive technique for BFC studies. [source] Development of a Direct Alcohol Alkaline Fuel Cell StackFUEL CELLS, Issue 4 2010D. Gaurava Abstract Direct alcohol alkaline fuel cells (DAAFC) are one of the potential fuel cell types in the category of low temperature fuel cells, which could become an energy source for portable electronic equipment in future. In the present study, a simple DAAFC stack has been developed and studied to evaluate the maximum performance for a given fuel (methanol or ethanol) and electrolyte (KOH) at various concentrations and temperatures. The open circuit voltage of the stack of four cells was nearly 4.0,V. A particular combination, 2,M fuel (methanol or ethanol) and 3,M KOH, results in maximum power density of the stack. The maximum power density obtained from the DAAFC stack (25,°C) was 50,mW,cm,2 at 20,mA,cm,2 for methanol and 17,mA,cm,2 for ethanol. The stack power density corroborated with that obtained from a single cell, indicating there was no further loss in the stack. [source] Optimisation and Evaluation of La0.6Sr0.4CoO3,,,, Cathode for Intermediate Temperature Solid Oxide Fuel CellsFUEL CELLS, Issue 5 2009Youkun Tao Abstract In this work, La0.6Sr0.4CoO3,,,,/Ce1,,xGdxO2,,,, (LSC/GDC) composite cathodes are investigated for SOFC application at intermediate temperatures, especially below 700,°C. The symmetrical cells are prepared by spraying LSC/GDC composite cathodes on a GDC tape, and the lowest polarisation resistance (Rp) of 0.11,,,cm2 at 700,°C is obtained for the cathode containing 30,wt.-% GDC. For the application on YSZ electrolyte, symmetrical LSC cathodes are fabricated on a YSZ tape coated on a GDC interlayer. The impact of the sintering temperature on the microstructure and electrochemical properties is investigated. The optimum temperature is determined to be 950,°C; the corresponding Rp of 0.24,,,cm2 at 600,°C and 0.06,,,cm2 at 700,°C are achieved, respectively. An YSZ-based anode-supported solid oxide fuel cell is fabricated by employing LSC/GDC composite cathode sintered at 950,°C. The cell with an active electrode area of 4,×,4,cm2 exhibits the maximum power density of 0.42,W,cm,2 at 650,°C and 0.54,W,cm,2 at 700,°C. More than 300,h operating at 650,°C is carried out for an estimate of performance and degradation of a single cell. Despite a decline at the beginning, the stable performance during the later term suggests a potential application. [source] Theoretical analysis on thermoelectric power generation with rectangular-fin elements and its applicability in micro systemsHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2006Yutaka Oda Abstract A thermoelectric module, which consists of rectangular-fin elements and has a simple structure suitable for micro fabrication, was newly proposed for a micro- to milli-scale thermoelectric power generator. A unit model was introduced to examine the basic characteristics of thermoelectric power generation with rectangular-fin elements. Theoretical descriptions of the power density and conversion efficiency were given by solving one-dimensional heat and current flows inside the elements. Then, it was found that there exist optimum aspect ratios of the elements to achieve maximum power density and conversion efficiency. Power density becomes larger if the module is downsized with a similarity in shape, while conversion efficiency remains constant, i.e., smaller devices show better performance. Finally, comparative analysis with a standard pi-type module was conducted to emphasize the superiority of the proposed module in micro systems, when convective heat transfer resistance is taken into account. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 224,244, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20108 [source] Efficient power analysis for an irreversible Carnot heat engineINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2008Tamer Yilmaz Abstract In this paper, the finite-time thermodynamic optimization is carried out based on the efficient power criterion for an irreversible Carnot heat engine. The obtained results are compared with those obtained by using the maximum power (MP) and maximum power density (MPD) criteria. The optimal design parameters have been derived analytically, and the effect of the irreversibilities on the general and optimal performances is investigated. Maximizing the efficient power gives a compromise between power and efficiency. The results showed that the design parameter at the maximum efficient power (MEP) condition leads to more efficient engines than at the MP conditions and that the MEP criterion may have a significant power advantage with respect to the MPD criterion. Copyright © 2007 John Wiley & Sons, Ltd. [source] Evaluation of applied cathode potential to enhance biocathode in microbial fuel cellsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2009Peng Liang Abstract BACKGROUND: The biocathode is proving to be a promising feature for development of the microbial fuel cell (MFC), although much work remains to be done to increase its power generation. This study aimed to enhance the performance of a biocathode by applying selected cathode potential. RESULTS: When five two-chambered MFCs were operated at selected cathode potentials of 142, 242, 342, 442, or 542 mV (vs standard hydrogen electrode), those MFCs with selected potentials lower than 342 mV could start up, and the highest power density of 0.11 W m,3 was obtained at a selected potential of 242 mV. An inner-biocathode MFC was then constructed and operated at a start-up cathode potential of 242 mV for 30 days. The open circuit cathode potential increased from 477 ± 9 mV to 572 ± 8 mV compared with the potential of the initially abiotic cathode, resulting in an increase in the maximum power density (4.25 ± 0.16 W m,3) of 106%. In addition, tests of continuous operation showed that a loading rate of 135 mg COD L,1 d,1 was optimal for obtaining maximum power generation in the system developed for this study. CONCLUSION: The results indicated that an optimal cathode potential of 242 mV enhanced the performance of a biocathode using oxygen as the electron acceptor. Copyright © 2009 Society of Chemical Industry [source] Glass Strengthening Via High-Intensity Plasma-Arc HeatingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2010Andrew A. Wereszczak A high-intensity plasma-arc lamp was used to irradiate the surface of soda,lime silicate glass tiles to determine whether an increase in strength could be achieved. The lamp has a maximum power density of 3500 W/cm2, a processing area of 2 cm × 10 cm, a broad-spectrum energy distribution between 0.2 and 1.4 ,m, and was controlled to unidirectionally sweep across 50 mm2 tiles at a constant speed of 8 mm/s. Ring-on-ring (RoR) equibiaxial flexure and four-point unidirectional flexure testings of entire tiles were used to measure and compare uncensored and unimodal Weibull failure stress distributions of treated and untreated glass. Even under nonoptimized processing conditions, the RoR Weibull characteristic failure stress increased by approximately 25% and the four-point-bend Weibull characteristic failure stress increased by approximately 65%. Additionally, the failure stresses of the weakest samples of the heat-treated glass were significantly higher than those of the untreated glass. Strengthening was due to a fire-polishing-like mechanism. The arc-lamp heat treatment caused the location of the strength-limiting flaws in the four-point-bend tiles to change; namely, failure initiation occurred on the gauge section surface for the treated glass, whereas it occurred at a gauge section edge for the untreated glass. Arc-lamp heat treatment is attractive not only because it provides strengthening, but because it can (noncontact) process large amounts of glass quickly and inexpensively, and is a process that either a glass manufacturer or an end-user can readily use. [source] Combustion synthesis of ceramic nanoparticles for solid oxide fuel cellsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010Dehua Dong Abstract Two combustion synthesis methods involving the use of polyacrylamide hydrogel and humic acids (HAs) as fuels were developed to synthesize ceramic nanoparticles for fabrication of solid oxide fuel cells (SOFCs). Using polyacrylamide hydrogel as fuel, highly crystalline NiO/Ce0.8Sm0.2O1.9 (SDC) and SDC nanoparticles were synthesized to make a modified layer and subsequent dense electrolyte film on the anode support. HA was used as complexible fuel to synthesize Sm0.5Sr0.5CoO3 nanoparticles for preparing the SOFC porous cathode. The single SOFCs made from these nanoparticles exhibited a maximum power density of 740 mW cm,2 at 650 °C operated with H2/air as fuel/oxidant, suggesting the synthesized nanoparticles are of high quality as SOFC materials. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Influence of a pore-former and PTFE in the performance of the direct ethanol fuel cellASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009S. K. Biswas Abstract The direct ethanol fuel cell (DEFC) is a promising fuel cell device, which could provide power to portable and microelectronic equipment in the future. In the present investigation, the influence of a pore-former, polytetrafluoroethylene (PTFE) and catalyst loadings in the electrocatalyst of the anode on DEFC performance is studied. The decal transfer method is used to prepare the membrane electrode assembly (MEA) using PtRu/C (40:20% by wt) as the anode catalyst, and Pt/C (40% by wt) as the cathode catalyst, a pore-former, PTFE dispersion and Nafion ionomer. The pore-former used is 10% (by wt) NaHCO3 in the catalyst ink during the preparation of MEA. The voltage-current characteristics of DEFC were monitored at different loadings of the catalyst, PTFE and a pore-former in MEA. The DEFC performance improved with the use of a pore-former and higher loading of PTFE in MEA. Higher DEFC performance is obtained because PTFE, along with the network of pores in the anode side allowed easy removal of reaction species, thereby rendering the catalyst site available for ethanol oxidation. Further, the use of a pore-former and PTFE at the anode allowed higher loading of electrocatalyst resulting in an increase in the performance of DEFC. The DEFC, with 1 mg cm,2 of catalyst loading at the anode and cathode, 10% (by wt) NaHCO3 of a pore-former, 20% (by wt) PTFE loading in catalyst ink gives maximum power density of 8.5 mW cm,2 at a current density of 31.3 mA cm,2. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Energy scavenging for energy efficiency in networks and applicationsBELL LABS TECHNICAL JOURNAL, Issue 2 2010Kyoung Joon Kim Telecommunication networks will play a huge part in enabling eco-sustainability of human activity; one of the first steps towards this is to dramatically increase network energy efficiency. In this paper we present two novel approaches for energy scavenging in networks. One involves thermal energy scavenging for improving wireless base station energy efficiency, and the other involves mechanical energy scavenging for powering sensors in sensor networks, for machine-to-machine (M2M) communications, and for smart grid applications. Power amplifier (PA) transistors in base stations waste 30 percent of the total energy used in a wireless access network (WAN) as heat to the environment. We propose a thermoelectric energy recovery module (TERM) to recover electricity from the waste heat of PA transistors. A fully coupled thermoelectric (TE) model, combining thermoelectricity and heat transfer physics, is developed to explore the power generation performance and efficiency as well as the thermal performance of the TERM. The TE model is comprehensively used to determine optimized pellet geometries for power generation and efficiency as a function of PA transistor heat dissipation, heat sink performance, and load resistance. Maximum power generation and efficiency for various parametric conditions are also explored. Untapped kinetic energy is almost everywhere in the form of vibrations. This energy can be converted into electrical energy by means of transducers to power wireless sensors and mobile electronics in the range of microwatts to a few milliwatts. However, many problems limit the efficiency of current harvesting generators: narrow bandwidth, low power density, micro-electro-mechanical system (MEMS) scaling, and inconsistency of vibrating sources. We explore energy scavenger designs based on multiple-mass systems to increase harvesting efficiency. A theoretical and experimental study of two degrees-of-freedom (2-DOF) vibration-powered generators is presented. Both electromagnetic and piezoelectric conversion methods are modeled by using a general approach. Experimental results for the multi-resonant system are in agreement with the analytical predictions and demonstrate significantly better performance in terms of maximum power density per total mass and a wider bandwidth compared to single DOF (1-DOF) generators. © 2010 Alcatel-Lucent. [source] | ||||||||||||||||