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00146 A flow-tracing method for transmission networks
06 Electrical power supply and utilization (economics, policy, supplies, forecasts) electrodes is around 44%. Catalysts obtained with mild nitric acidtreated CNTs give a better performance of 680 mV at 500 mA cm 2 and 600 mV at 800 mA cm 2 than catalysts prepared with ethylene glycol and Pt salt.
whereas at higher current density the influence is very significant. The porosity variation causes non-uniformity in the mass transport which in turn reduces the current density and a lower fuel cell performance is obtained.
06•00140 Preparation and characterization of PtSn/C anode electrocatalysts for direct ethanol fuel cell
06•00144 Thermoelectric-generator with linear phenomenological heat-transfer law
Jiang, L. el al. Cala[ysis Today, 2004, 93 95, (1), 665 670. Highly active PtSn/C catalyst was prepared by a polyol method. The catalyst was reduced in Hz/Ar atmosphere at 600°C for 2 h in order to obtain different metallic phase. TEM images show uniform dispersion of spherical metal nanoparticles with average diameters of 1.8 and 3.9 nm for the as-prepared and treated catalysts, respectively. UV-vis spectrophotometry is employed to monitor the preparation process and the results indicate that Pt-Sn complex formed once the precursors of Pt and Sn were mixed together. The structure properties of the samples were characterized using X-ray diffraction. The results show that after reduction, the catalyst tends to form PtSn alloy. TPR experiment results show that Sn exists in multivalent state in the as-prepared sample while only zero-valence Sn was detected in the treated sample, while it could not be excluded that the multivalent tin existed in the treated sample. Cyclic voltammetry (CV) technique and single direct ethanol fuel cell (DEFC) tests indicate that the as prepared catalyst possesses superior catalytic activity for ethanol oxidation to the treated sample. The results suggest that Pt and multivalent Sn are the active species for ethanol oxidation.
Chen, L. et al. Applied Energy, 2005, 81, (4), 358 364. The performance of multi-element thermoelectric-generators, assuming heat-transfer irreversibilities which obey the linear phenomenological heat-transfer law Q ~ (AT i), is studied in this paper by combining finite-time thermodynamics with non-equilibrium thermodynamics. The performance characteristics of the output power, efficiency and working electrical-current are described by numerical examples.
06•00141 Simplified processing of anode-supported thin film planar solid oxide fuel cells Basu, R. et al. Journal qf the European Ceramic Society, 2005, 25, (4), 463471. The concept of anode-supported planar solid oxide fuel cells (SOFCs) involves different fabrication procedures and several sintering steps. This contribution is an attempt towards minimizing the number of sintering steps. By adopting an improved technique a pre-flring step was eliminated. Cells obtained following this co-firing technique showed relatively higher power density (~1 A cm 2 at 0.7 V) at an operating temperature of 800°C compared to the cells prepared by the conventional technique. In the present investigation, cells as large as 10 cm × 10 cm were prepared and characterized following the new cofiring approach. Detailed microstructural, leak-rate testing (gastightness of the sintered electrolyte film) and electrochemical characterizations were carried out.
06•00142 Switch time bifurcation elimination analysis in SVC plants Rostami, M. el al. Eleclric Power Sjslems Research, 2005, 74, (2), 177 185. Studies show that switching angle of thyristor controlled reactor (TCR) in VAR compensator (SVC) plant, which is typically linked by a coupling transformer to the grid, misshapes current waveforms, which may lead to bifurcation and unsatisfactory operation of the station. A system model is developed by intelligent resistance method (IRM) method and used to access the impact of coupling transformer on occurrence of bifurcation phenomenon. Next, methods for eliminating the bifurcation problem by TCR control procedures are presented and compared. A modified switching method, capable of eliminating the switch time bifurcation phenomenon and allowing SVC to perform freely in all control zones is elaborated. By using this method, the fundamental component of SVC current will be improved and harmonics will be reduced to acceptable levels, which guarantees the proper operation of SVC plant.
06•00143 The effects of porosity distribution variation on PEM fuel cell performance Roshandel, R. et al. Renewable Energy, 2005, 30, (10), 1557 1572. Gas diffusion layers (GDL) are one of the important parts of the PEM fuel cell as they serve to transport the reactant gases to the catalyst layer. Porosity of this layer has a large effect on the PEM fuel cell performance. The spatial variation in porosity arises due to two effects: (1) compression of the electrode on the solid landing areas and (2) water produced at the cathode side of gas diffusion layers. Both of these factors change the porosity of gas diffusion layers and affect the fuel cell performance. To implement this performance analysis, a mathematical model which considers oxygen and hydrogen mass fraction in gas diffusion layer and the electrical current density in the catalyst layer, and the fuel cell potentials are investigated. The porosity variation in the GDL is calculated by considering the applied pressure and the amount of the water generated in the cell. The validity of the model is approved by comparing the computed results with experimental data. The obtained results show that the decrease in the average porosity causes the reduction in oxygen consumption, so that a lower electrical current density is generated. It is also shown that when the electrical current density is low, the porosity variation in gas diffusion layer has no significant influence on the level of polarization
06/00145 Valveless piezoelectric micropump for fuel delivery in direct methanol fuel cell (DMFC) devices Zhang, T. and Wang, Q. Journal of Power Sources, 2005, 140, (1), 72 80. Fuel cells are being considered as an important technology that can be used for various power applications. For portable electronic devices such as laptops, digital cameras, cell phone, etc., the direct methanol fuel cell (DMFC) is a very promising candidate as a power source. Compared with conventional batteries, DMFC can provide a higher power density with a long-lasting life and recharging which is almost instant. However, many issues related to the design, fabrication and operation of miniaturized DMFC power systems still remain unsolved. Fuel delivery is one of the key issues that will determine the performance of the DMFC. To maintain a desired performance, an efficient fuel delivery system is required to provide an adequate amount of fuel for consumption and remove carbon dioxide generated from fuel cell devices at the same time. In this paper, a novel fuel delivery system combined with a miniaturized DMFC is presented. The core component of this system is a piezoelectric valveless naicropump that can convert the reciprocating movement of a diaphragm activated by a piezoelectric actuator into a pumping effect. Nozzle/diffuser elements are used to direct the flow from inlet to outlet. As for DMFC devices, the micropump system needs to meet some specific requirements: low energy consumption but a sufficient fuel flow rate. Based on theoretical analysis, the effect of piezoelectric materials properties, driving voltage, driving frequency, nozzle/diffuser dimension, and other factors on the performance of the whole fuel cell system will be discussed. As a result, a viable design of a micropump system for fuel delivery can be achieved and some simulation results will be presented as well.
Economics, policy, supplies, forecasts 06/00146
A flow-tracing method for transmission networks
Pantos, M. and Gubina, F. Energy, 2005, 30, (10), 1781 1792. This paper presents a new network flow-tracing method. This new method is designed to trace flow paths across a network from selected consumers to a specified producer. Flow tracing gives fundamental insight into the relations between consumers and producers. The new method is based on a matrix calculation that considers the transmission losses in a simple way. The authors tested the new flow-tracing method on an 18-bus electric-power test system. Since all the transmission systems have some common characteristics, knowledge from one technical field can be imposingly used in the other fields. The idea is to spread the knowledge and to find some basic principles of observed phenomena enabling to solve problems in a proper manner. In this way, a better insight into the system operation and control can be obtained, especially nowadays when deregulation and liberalization of transmission systems are introduced.
06/00147 A light diet for a giant appetite: An assessment of China's fluorescent lamp standard Lin, J. Energy, 2005, 30, (10), 1873 1887. Lighting has been one of the fastest growing electric end uses in China over the last 20 years, with an average annual growth rate of 14%. Fluorescent lighting provides a significant portion of China's lighting needs. In 1998, China produced 680 million fluorescent lamps, of which 420 million were linear fluorescent lamps of various diameters (T8T12). There are substantial variations both in energy efficiency and lighting performance among locally produced fluorescent lamps. Such variations present a perfect opportunity for policy intervention through energy efficiency standards to promote the adoption of more efficient fluorescent lamps in China. This paper analyses China's 2003 minimum
Fuel and Energy Abstracts
January 2006
21
whereas at higher current density the influence is very significant. The porosity variation causes non-uniformity in the mass transport which in turn reduces the current density and a lower fuel cell performance is obtained.
06•00140 Preparation and characterization of PtSn/C anode electrocatalysts for direct ethanol fuel cell
06•00144 Thermoelectric-generator with linear phenomenological heat-transfer law
Jiang, L. el al. Cala[ysis Today, 2004, 93 95, (1), 665 670. Highly active PtSn/C catalyst was prepared by a polyol method. The catalyst was reduced in Hz/Ar atmosphere at 600°C for 2 h in order to obtain different metallic phase. TEM images show uniform dispersion of spherical metal nanoparticles with average diameters of 1.8 and 3.9 nm for the as-prepared and treated catalysts, respectively. UV-vis spectrophotometry is employed to monitor the preparation process and the results indicate that Pt-Sn complex formed once the precursors of Pt and Sn were mixed together. The structure properties of the samples were characterized using X-ray diffraction. The results show that after reduction, the catalyst tends to form PtSn alloy. TPR experiment results show that Sn exists in multivalent state in the as-prepared sample while only zero-valence Sn was detected in the treated sample, while it could not be excluded that the multivalent tin existed in the treated sample. Cyclic voltammetry (CV) technique and single direct ethanol fuel cell (DEFC) tests indicate that the as prepared catalyst possesses superior catalytic activity for ethanol oxidation to the treated sample. The results suggest that Pt and multivalent Sn are the active species for ethanol oxidation.
Chen, L. et al. Applied Energy, 2005, 81, (4), 358 364. The performance of multi-element thermoelectric-generators, assuming heat-transfer irreversibilities which obey the linear phenomenological heat-transfer law Q ~ (AT i), is studied in this paper by combining finite-time thermodynamics with non-equilibrium thermodynamics. The performance characteristics of the output power, efficiency and working electrical-current are described by numerical examples.
06•00141 Simplified processing of anode-supported thin film planar solid oxide fuel cells Basu, R. et al. Journal qf the European Ceramic Society, 2005, 25, (4), 463471. The concept of anode-supported planar solid oxide fuel cells (SOFCs) involves different fabrication procedures and several sintering steps. This contribution is an attempt towards minimizing the number of sintering steps. By adopting an improved technique a pre-flring step was eliminated. Cells obtained following this co-firing technique showed relatively higher power density (~1 A cm 2 at 0.7 V) at an operating temperature of 800°C compared to the cells prepared by the conventional technique. In the present investigation, cells as large as 10 cm × 10 cm were prepared and characterized following the new cofiring approach. Detailed microstructural, leak-rate testing (gastightness of the sintered electrolyte film) and electrochemical characterizations were carried out.
06•00142 Switch time bifurcation elimination analysis in SVC plants Rostami, M. el al. Eleclric Power Sjslems Research, 2005, 74, (2), 177 185. Studies show that switching angle of thyristor controlled reactor (TCR) in VAR compensator (SVC) plant, which is typically linked by a coupling transformer to the grid, misshapes current waveforms, which may lead to bifurcation and unsatisfactory operation of the station. A system model is developed by intelligent resistance method (IRM) method and used to access the impact of coupling transformer on occurrence of bifurcation phenomenon. Next, methods for eliminating the bifurcation problem by TCR control procedures are presented and compared. A modified switching method, capable of eliminating the switch time bifurcation phenomenon and allowing SVC to perform freely in all control zones is elaborated. By using this method, the fundamental component of SVC current will be improved and harmonics will be reduced to acceptable levels, which guarantees the proper operation of SVC plant.
06•00143 The effects of porosity distribution variation on PEM fuel cell performance Roshandel, R. et al. Renewable Energy, 2005, 30, (10), 1557 1572. Gas diffusion layers (GDL) are one of the important parts of the PEM fuel cell as they serve to transport the reactant gases to the catalyst layer. Porosity of this layer has a large effect on the PEM fuel cell performance. The spatial variation in porosity arises due to two effects: (1) compression of the electrode on the solid landing areas and (2) water produced at the cathode side of gas diffusion layers. Both of these factors change the porosity of gas diffusion layers and affect the fuel cell performance. To implement this performance analysis, a mathematical model which considers oxygen and hydrogen mass fraction in gas diffusion layer and the electrical current density in the catalyst layer, and the fuel cell potentials are investigated. The porosity variation in the GDL is calculated by considering the applied pressure and the amount of the water generated in the cell. The validity of the model is approved by comparing the computed results with experimental data. The obtained results show that the decrease in the average porosity causes the reduction in oxygen consumption, so that a lower electrical current density is generated. It is also shown that when the electrical current density is low, the porosity variation in gas diffusion layer has no significant influence on the level of polarization
06/00145 Valveless piezoelectric micropump for fuel delivery in direct methanol fuel cell (DMFC) devices Zhang, T. and Wang, Q. Journal of Power Sources, 2005, 140, (1), 72 80. Fuel cells are being considered as an important technology that can be used for various power applications. For portable electronic devices such as laptops, digital cameras, cell phone, etc., the direct methanol fuel cell (DMFC) is a very promising candidate as a power source. Compared with conventional batteries, DMFC can provide a higher power density with a long-lasting life and recharging which is almost instant. However, many issues related to the design, fabrication and operation of miniaturized DMFC power systems still remain unsolved. Fuel delivery is one of the key issues that will determine the performance of the DMFC. To maintain a desired performance, an efficient fuel delivery system is required to provide an adequate amount of fuel for consumption and remove carbon dioxide generated from fuel cell devices at the same time. In this paper, a novel fuel delivery system combined with a miniaturized DMFC is presented. The core component of this system is a piezoelectric valveless naicropump that can convert the reciprocating movement of a diaphragm activated by a piezoelectric actuator into a pumping effect. Nozzle/diffuser elements are used to direct the flow from inlet to outlet. As for DMFC devices, the micropump system needs to meet some specific requirements: low energy consumption but a sufficient fuel flow rate. Based on theoretical analysis, the effect of piezoelectric materials properties, driving voltage, driving frequency, nozzle/diffuser dimension, and other factors on the performance of the whole fuel cell system will be discussed. As a result, a viable design of a micropump system for fuel delivery can be achieved and some simulation results will be presented as well.
Economics, policy, supplies, forecasts 06/00146
A flow-tracing method for transmission networks
Pantos, M. and Gubina, F. Energy, 2005, 30, (10), 1781 1792. This paper presents a new network flow-tracing method. This new method is designed to trace flow paths across a network from selected consumers to a specified producer. Flow tracing gives fundamental insight into the relations between consumers and producers. The new method is based on a matrix calculation that considers the transmission losses in a simple way. The authors tested the new flow-tracing method on an 18-bus electric-power test system. Since all the transmission systems have some common characteristics, knowledge from one technical field can be imposingly used in the other fields. The idea is to spread the knowledge and to find some basic principles of observed phenomena enabling to solve problems in a proper manner. In this way, a better insight into the system operation and control can be obtained, especially nowadays when deregulation and liberalization of transmission systems are introduced.
06/00147 A light diet for a giant appetite: An assessment of China's fluorescent lamp standard Lin, J. Energy, 2005, 30, (10), 1873 1887. Lighting has been one of the fastest growing electric end uses in China over the last 20 years, with an average annual growth rate of 14%. Fluorescent lighting provides a significant portion of China's lighting needs. In 1998, China produced 680 million fluorescent lamps, of which 420 million were linear fluorescent lamps of various diameters (T8T12). There are substantial variations both in energy efficiency and lighting performance among locally produced fluorescent lamps. Such variations present a perfect opportunity for policy intervention through energy efficiency standards to promote the adoption of more efficient fluorescent lamps in China. This paper analyses China's 2003 minimum
Fuel and Energy Abstracts
January 2006
21