- Email: [email protected]
03428 Solving state estimation in power systems by an interior point method
06 Nectrical power supply and utihzation (scientific, technical)
recast ionic conductor added to the catalyst layer is a sensittve function of the nature of the catalyst. Other elements of membrane/electrode assembly (MEA) optimization efforts are also described, highlighting the ability to resolve, to a large degree, a well-documented problem of polymer electrolyte DMFCs, namely ‘methanol crossover’. This was achieved by appropriate cell design, enabling fuel utilization as high as 90% in highly performing DMFCs.
of the negative plate without creating unacceptable temperature increases. This has resulted in deep-discharge lifetimes of 800-1000 cycles, particularly when using a charging algorithm employing only partial recharges (97100% return) interspersed with full conditioning recharges every tenth cycle. With such minimal average overcharge levels, deep-cycle lifetimes approaching 1000 cycles have been achieved without experiencing failure due to massive grid corrosion.
00103419 Research update from European Advanced Lead-Acid Battery Consortium Cooper, A. Journal of Poner Sources, 2000, 88, (l), 53-70. In July 1997, the European members of the Advanced Lead-Acid Battery Consortium were awarded a second Brite-EuRam contract for research on lead-acid batteries for electric vehicles (EVs). This Project, entitled ‘Strategies for the further improvement of performance and life of leadacid batteries for electric vehicle applications’, commenced at the beginning of January 1998, is costing some US$4 million and is scheduled to run for 3 years. The project is divided into three principal tasks. The first is concentrating on separator design and compression in order to improve cycle-life. In the second task, attempts are being made to improve the specific energy of tubular-plate designs, which traditionally have good life characteristics in traction applications. In addition, work is being carried out to determine the effects of rapid-charging techniques on this type of battery design. The third task is attempting to improve the performance of negative plates by seeking improved expanders. The project has now reached its mid-point. This paper describes the work in progress and discusses some of the results achieved to date and their implication for the future of the research programme.
00103425 SOFC system with integrated catalytic fuel processing Finnerty, C. el al. Journal of POIW Sources, 2000. X6. (I-I), 459463. In recent years, there has been much interest in the development of solid oxide fuel cell technology operating directly on hydrocarbon fuels. The development of a catalytic fuel processing system, which is integrated with the solid oxide fuel cell (SOFC) power source IS outlined here. The catalytic device utilizes a novel three-way catalytic system consisting of an in situ prereformer catalyst, the fuel cell anode catalyst and a platinum-based combustion catalyst. The three individual catalytic stages have been tested in a model catalytic microreactor. Both temperature-programmed and isothermal reaction techniques have been applied. Results from these experiments were used to design the demonstration SOFC unit. The apparatus used for catalytic characterization can also perform in sim electrochemical measurements as described in previous papers. This enabled the performance of the SOFC to be determined at a range ofitemperatures and reaction conditions, with current output of 290 mA cm at 0.5 V, being recorded. Methane and butane have been evaluated as fuels. Thus, opttmization of the in sim partial oxidation pre-reforming catalyst was essential. with catalysts producing high Hz/CO ratios at reaction temperatures between 873 and II73 K being chosen, These included ruthemum and nickel/molybdenumbased catalysts. Hydrocarbon fuels were directly injected into the catalytic SOFC system. Microreactor measurements revealed the reactton mechanisms as the fuel was transported through the three-catalyst device. The demonstration system showed that the fuel processing could be successfully integrated with the SOFC stack.
00103420 Reuse of treated municipal wastewater for power plant water Zhang, J. Gongye Shuichuli, 1999. 19, (3), 5-7. (In Chinese) An analysis of the quantity and quality of water used in coal-fired power plant was made. It showed that it is feasible to reuse treated municipal wastewater in power plants, especially for circulating cooling water and ashrinsing water. 00/03421 Review of cast-on-strap joints and strap alloys for lead-acid batteries Lakshmi, C. S. Journal of Ponaer Sotrrces, 2000, 88, (I), 18-l 6. This review examines the influence of the various parameters involved in the cast-on-strap (COS) process on the quality of the resulting lug-strap joints. In addition, it provides the findings of an investigation on the macroscopic and microscopic features of COS joints in commercial leadacid batteries, Some examples of the most common defects that can affect the performance and life of batteries are presented. The nature of the fusion at the lug-strap interface for the various lugs and strap alloy compositions used in conventional, hybrid and valve-regulated lead-acid batteries are also discussed. OOiO3422 Safety studies of Li-ion battery materials by accelerated rate calorimetry Shi, J. er al. Proc. - Elecrrochem. Sot., 1999, 98-16, 493-499. The exothermic reactions of selected lithium-ion batteries were studied with accelerated rate calorimetry (ARC). Liquid electrolyte ECiDMC (l:l)LiPFe started exothermic reactions at 225”, which resulted in thermal runaway. The stability of gel polymer electrolytes consisting of P(VDFHFP) and EC/PC (l:l)-LiPF, is not significantly different from the liquid system. Solid polymer electrolytes made of high molecular weight PEO and LiClO,, or LiPF6 salts showed the highest thermal stability in the study. The onset temperatures of exothermic reactions of cathode materials in EC/ DMC-LiPF6 electrolyte are in the order of LiCoOz > LiMnz04 + LiNiO.aCoozOa. However, no significant difference was observed when testing these cathode materials without other battery components present. Fully lithiated graphite anodes proved to have very low thermal stability, and onset temperatures of exothermic reactions occurred at 75” followed by catastrophic self-heating rates in the 1000”imin. 00103423 Sealed Ni-Zn cells, 1996-1996 Jindra, J. Journal of POWU Source.s,2000, 88, (2) 202-205. Progress with sealed nickel-zinc cells in the period 1996-1998 is reviewed. No dramatic improvements stemming from R&D on cells were observed. Presently, the cells of Energy Research (ERC) seem to be the best and most widely used. Search for an optimized cyclic charging algorithm for 00/03424 valve-regulated lead-acid batteries Nelson, R. F. er (rl. Journal of Ponvr Sourcm, 2000, 88. (I). 44-52. Valve-regulated lead-acid (VRLA) batteries are characterized by relatively poor performance in cyclic applications of the order of two hundred to three hundred 100% depth-of-discharge (DOD) cycles. Failure is due to sulfation of the negative plate and softening of the positive active-material. It is felt that this failure mode arises from abnormally high levels of oxygen recombination that arise due to decreases in separator saturation levels as VRLA batteries age. Charging algorithms have been developed to address this changing condition throughout life. The key step is the finish of charge where, traditionally, low currents and low overcharge limits have been employed with poor results, It has been found that using high fimshing currents in an alternating charge-rest algorithm results in proper recharge
SOFC technology development at Rolls-Royce 00/03426 Gardner, F. J. Journal of Power Sources, 2000, 86. (I-2), 122-129 Fuel cells have the prospect for exploiting fossil fuels more benignly and more efficiently than alternatives. The various types represent quite different technologies, with no clear winner, yet. Nevertheless, the high temperature MCFC and solid oxide fuel cell (SOFC) types seem better suited to power generation in a hydrocarbon fuel economy. Presently, the costs of MCFCs and SOFCs are too high to compete directly with contemporary power generation plant. Seeking to overcome the drawbacks of first generation fuel cells, over the past 7 years an innovative second generation SOFC concept has been evolved in the Rolls-Royce Strategic Research Centre, with encouraging results. It is distinguished from other types by the name: integrated planar solid oxide fuel cell (IP-SOFC). It is a family of integrated system concepts supporting product flexibility with evolutionary stretch potential from a common SOFC module. Fabrication of the key component of the IP-SOFC, the ‘multi-cell membrane electrode crssembly (multi-cell MEA) module’ carrying many series connected cells wtth supported electrolyte membranes only IO-20 LLrn thick, has been proved. Development of the internal reforming subsystem, the next big hurdle, is now in hand. Following an outline of its salient features and test results, the methodology and results of recent IP-SOFC stack costing studies are presented, and the continuing research and development programme indicated. 00103427 Soft-combustion (wet-chemical) synthesis of a new 4V class cathode-active material, LiVMoO, for Li-ion batteries Michael, M. S. el rrl. Internafional Journal of Inor,qrrnicMarerds. 2000, 2, (2-3), 261-267. A new, 4-V class, lithiated transition metal oxide cathode, LiVMoOl,, has been synthesized by a novel soft-combustion (wet chemical) low temperature (LT) method that presents advantages compared to the clasical ceramic method, namely in terms of phase purity, Furface texture and size, preparation time, costs and electrochemical performances of the resulting products. The structural properties of the newly synthesized product have been examined by means of X-ray diffraction studies (XRD). The thermal reactions which occur during the soft-combustion of the precursor mixture have been examined by DTA/TG techniques. It has been found that the layered LiVMoOb can only be obtained upon calcining the precursor at 540°C beyond which the compound will thermally be reduced to LiVMoOs which exhibits inferior structural characteristics for the intercalation/ deintercalation reactions. The product (LiVMoO,,) thus prepared exhibits submicrometre spherical grains whose specific surface area is 5.01 m*/g. The intercalationideintercalation (redox) kinetics of the above product has been studied and its suitability as cathode matertal in actual electrochemical cells is discussed in the light of electrochemical properties. 00/03428 Solving state estimation in power systems by an interior point method Ramirez, J.M. and Barocio. E.E. Elec. Power ~rnd Emqv Svr., 2000. 22. (5). 355-365. A linear programming formulation is employed to solve the static state estimation problem in power systems usmg the primal-dual predictorcorrector algorithm. This has been selected because it has emerged as an efficient algorithm that makes the direction search toward the optimal point
Fuel and Energy
Abstracts
November 2000
385
06 Electrical power supply and utilization (scientific, technical)
easy. The technique was applied successfully into several power systems when simultaneous gross errors were considered. Results are presented showing that this algorithm exhibits a good performance under critical measurement errors. 00/03429 Stainless steel as a bipolar plate material for solid polymer fuel cells Davies, D. P. et al. Journal of Power Sources, 2000, 86, (l-2), 237-242. Stainless steel bipolar plates for the solid polymer fuel cell (SPFC) offer many advantages over conventional graphitic materials. These include relative low cost, high strength, ease of manufacture and as they can be shaped into thin sheets, significant improvement in the power/volume ratio. However, interfacial ohmic losses across the metallic bipolar plate and the Membrane Electrode Assembly (MEA), reduce the overall power output from a SPFC. Despite a large range of commercially available alloys, 316 stainless steel has traditionally been the alloy of choice for bipolar plates. A number of alternative grades of stainless steel have been evaluated in terms of the electrical resistance of their surface oxide film. This showed that ohmic losses exhibited in fuel cell performance varied depending on the elemental composition of the stainless steel alloy. Three stainless steel alloys, 310, 316 and 904L, were chosen as candidate bipolar plate materials. Increased polarization was observed in the order 904L c 310 < 316. This was maintained throughout an ongoing endurance test, where these cells have been run for over 3000 h without significant performance degradation. This difference in polarization behaviour was attributed to variation in thickness of the oxide film. Analysis has shown no deleterious effect on the surface of the bipolar plate and no evidence of corrosion. 00103430 Start-up, testing and operation of 1000 kW class MCFC power plant Ishikawa, T. and Yasue, H. Journal of Power Sources, 2000, 86, (l-2), l45150. The MCFC Research Association has been conducting R&D of the 1000 kW class MCFC power plant under contracting research with New Energy and Industrial Technology Development Organization (NEDO) as a part of the New Sunshine Programme, promoted by the Agency of Industrial Science and Technology (AIST) and the Ministry of International Trade and Industry (MITI). The plant consists of four 250-kW stacks, a reformer, two cathode gas recycle blowers, a turbine compressor, a heat recovery steam generator (HRSG). The power plant is the first Japanese practical external reforming pressurized type MCFC power generation plant intended for large-scale commercial plant in the near future. The construction of the 1000 kW MCFC power plant started in autumn of 1995 on Kawagoe test station in Kawagoe Thermal Power Station of Chubu Electric Power, which is located in the prefecture of Mie, Japan. The construction and installation of the plant progressed very well, and process and control (PAC) testing of the power plant (not including fuel cell stacks and inverters) was carried out through March-November of 1998. After the PAC test, the cell stacks and inverters were installed in the test site; currently, the power generation test has just started. This paper describes the outline of the plant, the status of the test and the future schedule. Status of tubular SOFC field unit demonstrations 00103431 George, R. A. Journal of Power Sources, 2000, 86, (l-2), 134-139. Siemens Westinghouse is in the final stage of its tubular solid oxide fuel cell (SOFC) development programme, and the emphasis has shifted from basic technology development to cost reduction, scale-up and demonstration of pre-commercial power systems at customer sites. This paper describes the field unit demonstration programme including the EDB/ELSAM lOO-kW e combined heat and power (CHP) system, the Southern California Edison (SCE) 220-kW e pressurized SOFC/gas turbine (PSOFC/GT) power system, and the planned demonstrations of commercial prototype power systems. In the Spring of 1999, the EDB/ELSAM lOO-kWe SOFC-CHP system produced 109 kWe net AC to the utility grid at 46% electrical efficiency and 65 kWt to the hot water district heating system, verifying the analytical predictions. The SCE 220-kWe PSOFCIGT power system will undergo factory startup in the autumn of 1999. 00103432 Studies on .methanol fuel cell Verma, L. K. Journal of Power Sources, 2000, 86, (l-2), 464-468. A fuel cell using methanol dissolved in 6 N KOH solution with (Fe(II1) and AI(II1) and without treated graphite cathode at ambient temperature (25°C) was studied for the following parameters: (a) current-voltage behaviour at ambient temperature; (b) voltage drop with time; (c) methanol ‘concentration as a function of time’; (d) carbon dioxide generation as a function of time; (e) effect of catalyst on the performance of the cell. The OCV of the cell was 0.273, 0.850 and 1.4 V, while current density was 0.5, 4.52 and 17.2 Am-* with untreated and treated (Fe(II1) and AI(III)) graphite electrode, respectively. The highest current density was 180 Am SUP>-2 at 0.3 V and 540 Am-* at 1.04 V for Fe(II1) and AI(III), respectively. polarization was found to be higher in AI(III) than Fe(III)treated graplute electrod? due to the low heat of adsorption of AI(III) [406 kJ mol- vs 518 kJ mol. for Fe(III)]. The catalytic oxidation of methanol in terms of electrical energy output shows efficiency of about 78% for AI(III) and 80% for Fe(III)-treated graphite electrode, 00103433 Study of passivation at the positive active material/ grid interface in lead-acid batteries Chen, H. Y. et al. Journal of Power Sources, 2000, 88, (l), 78-82.
366
Fuel and Energy Abstracts
November 2000
A valuable additive-boric acid - to eliminate passivation of the active material/grid interface in positive plates of lead-acid batteries - has been selected through comparison of single-cell discharge tests. This overcomes the problem of rapid decline in initial performance when using lowantimony (1.7 wt%) grid alloys. The performance of the oxide film on positive grids, as well as its composition and amount, is determined through cathodic reduction of the film with a linear sweep voltammetric (LSV) method. The results confirm that passivation of the positive grid and rapid decline in the initial discharge voltage are due to a resistive layer of PbS04, and not PbO,, (1 5 n 2 2). The PbO,, layer has little effect on passivation. The findings of this study are useful for the production of lead-acid batteries. 00/03434 Sustainable energy conversion: fuel cells - the competitive option? Hart, D. Journal of Power Sources, 2000, 86, (l-2), 23-27. The definition of sustainability is still under discussion, but it is becoming increasingly clear that present practices of energy supply and distribution are causing severe environmental pressures, and that they cannot be continued indefinitely. The fuel cell has been undergoing rapid development and is now at a stage immediately prior to commercialisation for a number of markets. It is expected to be economically competitive with many other energy conversion technologies within the next 5 years. However, introduction of the fuel cell may also speed the economic introduction of emissions-free energy carriers such as hydrogen, linking directly to renewably generated electricity. Hydrogen could be used as a form of energy storage in cases where electricity demand and supply were not matched. The fuel cell would then be complementary to, rather than competitive with, renewable generation technologies. Ultimately the fuel cell, in both its high and low-temperature derivatives, could become one of the pillars of a future sustainable energy system. 00/03435 Synthesis and characterization of spine1 LiMnp04 for lithium secondary battery Jang, S.-W. Journal of Power Sources, 2000, 88, (2), 274-271. The preparation and characterization of spine1 LiMn20r have been studied. Spine1 lithium manganese oxides are prepared by a sol-gel method using LiN03 and Mn(CH$00)2 4H20 as starting materials in which the obtained gel is heated at various temperatures after pre-treatment at 350°C or without pre-treatment in air. The LiMnsOd samples prepared with pretreatment have uniform micro-sized particles while those obtained without pre-treatment have agglomerated particles of irregular shapes. The thermal pre-treatment at 350°C improves the electrochemical behaviour in terms of discharge capacity and rate capability. The results can be correlated with an increase in lithium surface reaction sites in these materials, as inferred by this small grain size and large surface area. 00103436 Synthesis of LiMn204 by modified Pechini method and characterization as a cathode for rechargeable LilLiMna04 cells Han, Y.-S. and Kim, H.-G. Journal qfPower Sources, 2000, 88, (2), 161-168. The Pechini process to produce LIMnZ04 powder is modified such that precursors are pre-ignited in open air followed by calcining in the range of 600-800°C for 4 h. The molar ratio (R) of ethylene glycol (EG) to citric acid (CA) is 0, 1, 2 or 4. The effect of EG content on powder characteristics and electrochemical performance is evaluated. With increasing R, the homogeneity and the specific surface area of the powder are increased. Lithium is evaporated during ignition (and/or the charring reaction) and calcination because of the inhomogeneous mixing and exothermic heat of decomposition of polymer. Samples calcined at 800°C for 4 h yield maximum specific capacity for both charge and discharge (130.7 and 126.7 mA h gg’). The cycleability of the powder increases with increasing R. The effect of the EG content on the homogeneity is discussed. 00/03437 Synthesis of power system load profiles by class load study Chen, C.S. et al. Elec. Power md Energy Syst., 2000, 22, (5), 325-330. This paper proposes a methodology for the synthesis of power system load profiles by class load study. There are more than 900 customers over various customer classes, they are selected by the sampling design for the installation of intelligent meters over six districts in the Taipower system. The load data of all the test customers have been collected and the typical load patterns of customer classes have been derived for each service district. The billing data of all the customers in the Taipower customer information system are retrieved and the typical load patterns derived are applied to solve the hourly load composition of all customer classes. The actual power consumption in each study district, which has been recorded by the Taipower distribution dispatch control system, is used to verify the accuracy of the power profiles derived. By the same way, the power profiles of Taipower system are then synthesized too. It is concluded that the system power profile can be estimated by the aggregation of class load patterns in a precise manner. 00103436 Synthesis, characterization, and cell performance LiNiV04 cathode materials prepared by a new solution precipitation method Fey, G. T.-K. Chen, K.-S. J. Power Sources, 1999, 81-82, 467471.
of
recast ionic conductor added to the catalyst layer is a sensittve function of the nature of the catalyst. Other elements of membrane/electrode assembly (MEA) optimization efforts are also described, highlighting the ability to resolve, to a large degree, a well-documented problem of polymer electrolyte DMFCs, namely ‘methanol crossover’. This was achieved by appropriate cell design, enabling fuel utilization as high as 90% in highly performing DMFCs.
of the negative plate without creating unacceptable temperature increases. This has resulted in deep-discharge lifetimes of 800-1000 cycles, particularly when using a charging algorithm employing only partial recharges (97100% return) interspersed with full conditioning recharges every tenth cycle. With such minimal average overcharge levels, deep-cycle lifetimes approaching 1000 cycles have been achieved without experiencing failure due to massive grid corrosion.
00103419 Research update from European Advanced Lead-Acid Battery Consortium Cooper, A. Journal of Poner Sources, 2000, 88, (l), 53-70. In July 1997, the European members of the Advanced Lead-Acid Battery Consortium were awarded a second Brite-EuRam contract for research on lead-acid batteries for electric vehicles (EVs). This Project, entitled ‘Strategies for the further improvement of performance and life of leadacid batteries for electric vehicle applications’, commenced at the beginning of January 1998, is costing some US$4 million and is scheduled to run for 3 years. The project is divided into three principal tasks. The first is concentrating on separator design and compression in order to improve cycle-life. In the second task, attempts are being made to improve the specific energy of tubular-plate designs, which traditionally have good life characteristics in traction applications. In addition, work is being carried out to determine the effects of rapid-charging techniques on this type of battery design. The third task is attempting to improve the performance of negative plates by seeking improved expanders. The project has now reached its mid-point. This paper describes the work in progress and discusses some of the results achieved to date and their implication for the future of the research programme.
00103425 SOFC system with integrated catalytic fuel processing Finnerty, C. el al. Journal of POIW Sources, 2000. X6. (I-I), 459463. In recent years, there has been much interest in the development of solid oxide fuel cell technology operating directly on hydrocarbon fuels. The development of a catalytic fuel processing system, which is integrated with the solid oxide fuel cell (SOFC) power source IS outlined here. The catalytic device utilizes a novel three-way catalytic system consisting of an in situ prereformer catalyst, the fuel cell anode catalyst and a platinum-based combustion catalyst. The three individual catalytic stages have been tested in a model catalytic microreactor. Both temperature-programmed and isothermal reaction techniques have been applied. Results from these experiments were used to design the demonstration SOFC unit. The apparatus used for catalytic characterization can also perform in sim electrochemical measurements as described in previous papers. This enabled the performance of the SOFC to be determined at a range ofitemperatures and reaction conditions, with current output of 290 mA cm at 0.5 V, being recorded. Methane and butane have been evaluated as fuels. Thus, opttmization of the in sim partial oxidation pre-reforming catalyst was essential. with catalysts producing high Hz/CO ratios at reaction temperatures between 873 and II73 K being chosen, These included ruthemum and nickel/molybdenumbased catalysts. Hydrocarbon fuels were directly injected into the catalytic SOFC system. Microreactor measurements revealed the reactton mechanisms as the fuel was transported through the three-catalyst device. The demonstration system showed that the fuel processing could be successfully integrated with the SOFC stack.
00103420 Reuse of treated municipal wastewater for power plant water Zhang, J. Gongye Shuichuli, 1999. 19, (3), 5-7. (In Chinese) An analysis of the quantity and quality of water used in coal-fired power plant was made. It showed that it is feasible to reuse treated municipal wastewater in power plants, especially for circulating cooling water and ashrinsing water. 00/03421 Review of cast-on-strap joints and strap alloys for lead-acid batteries Lakshmi, C. S. Journal of Ponaer Sotrrces, 2000, 88, (I), 18-l 6. This review examines the influence of the various parameters involved in the cast-on-strap (COS) process on the quality of the resulting lug-strap joints. In addition, it provides the findings of an investigation on the macroscopic and microscopic features of COS joints in commercial leadacid batteries, Some examples of the most common defects that can affect the performance and life of batteries are presented. The nature of the fusion at the lug-strap interface for the various lugs and strap alloy compositions used in conventional, hybrid and valve-regulated lead-acid batteries are also discussed. OOiO3422 Safety studies of Li-ion battery materials by accelerated rate calorimetry Shi, J. er al. Proc. - Elecrrochem. Sot., 1999, 98-16, 493-499. The exothermic reactions of selected lithium-ion batteries were studied with accelerated rate calorimetry (ARC). Liquid electrolyte ECiDMC (l:l)LiPFe started exothermic reactions at 225”, which resulted in thermal runaway. The stability of gel polymer electrolytes consisting of P(VDFHFP) and EC/PC (l:l)-LiPF, is not significantly different from the liquid system. Solid polymer electrolytes made of high molecular weight PEO and LiClO,, or LiPF6 salts showed the highest thermal stability in the study. The onset temperatures of exothermic reactions of cathode materials in EC/ DMC-LiPF6 electrolyte are in the order of LiCoOz > LiMnz04 + LiNiO.aCoozOa. However, no significant difference was observed when testing these cathode materials without other battery components present. Fully lithiated graphite anodes proved to have very low thermal stability, and onset temperatures of exothermic reactions occurred at 75” followed by catastrophic self-heating rates in the 1000”imin. 00103423 Sealed Ni-Zn cells, 1996-1996 Jindra, J. Journal of POWU Source.s,2000, 88, (2) 202-205. Progress with sealed nickel-zinc cells in the period 1996-1998 is reviewed. No dramatic improvements stemming from R&D on cells were observed. Presently, the cells of Energy Research (ERC) seem to be the best and most widely used. Search for an optimized cyclic charging algorithm for 00/03424 valve-regulated lead-acid batteries Nelson, R. F. er (rl. Journal of Ponvr Sourcm, 2000, 88. (I). 44-52. Valve-regulated lead-acid (VRLA) batteries are characterized by relatively poor performance in cyclic applications of the order of two hundred to three hundred 100% depth-of-discharge (DOD) cycles. Failure is due to sulfation of the negative plate and softening of the positive active-material. It is felt that this failure mode arises from abnormally high levels of oxygen recombination that arise due to decreases in separator saturation levels as VRLA batteries age. Charging algorithms have been developed to address this changing condition throughout life. The key step is the finish of charge where, traditionally, low currents and low overcharge limits have been employed with poor results, It has been found that using high fimshing currents in an alternating charge-rest algorithm results in proper recharge
SOFC technology development at Rolls-Royce 00/03426 Gardner, F. J. Journal of Power Sources, 2000, 86. (I-2), 122-129 Fuel cells have the prospect for exploiting fossil fuels more benignly and more efficiently than alternatives. The various types represent quite different technologies, with no clear winner, yet. Nevertheless, the high temperature MCFC and solid oxide fuel cell (SOFC) types seem better suited to power generation in a hydrocarbon fuel economy. Presently, the costs of MCFCs and SOFCs are too high to compete directly with contemporary power generation plant. Seeking to overcome the drawbacks of first generation fuel cells, over the past 7 years an innovative second generation SOFC concept has been evolved in the Rolls-Royce Strategic Research Centre, with encouraging results. It is distinguished from other types by the name: integrated planar solid oxide fuel cell (IP-SOFC). It is a family of integrated system concepts supporting product flexibility with evolutionary stretch potential from a common SOFC module. Fabrication of the key component of the IP-SOFC, the ‘multi-cell membrane electrode crssembly (multi-cell MEA) module’ carrying many series connected cells wtth supported electrolyte membranes only IO-20 LLrn thick, has been proved. Development of the internal reforming subsystem, the next big hurdle, is now in hand. Following an outline of its salient features and test results, the methodology and results of recent IP-SOFC stack costing studies are presented, and the continuing research and development programme indicated. 00103427 Soft-combustion (wet-chemical) synthesis of a new 4V class cathode-active material, LiVMoO, for Li-ion batteries Michael, M. S. el rrl. Internafional Journal of Inor,qrrnicMarerds. 2000, 2, (2-3), 261-267. A new, 4-V class, lithiated transition metal oxide cathode, LiVMoOl,, has been synthesized by a novel soft-combustion (wet chemical) low temperature (LT) method that presents advantages compared to the clasical ceramic method, namely in terms of phase purity, Furface texture and size, preparation time, costs and electrochemical performances of the resulting products. The structural properties of the newly synthesized product have been examined by means of X-ray diffraction studies (XRD). The thermal reactions which occur during the soft-combustion of the precursor mixture have been examined by DTA/TG techniques. It has been found that the layered LiVMoOb can only be obtained upon calcining the precursor at 540°C beyond which the compound will thermally be reduced to LiVMoOs which exhibits inferior structural characteristics for the intercalation/ deintercalation reactions. The product (LiVMoO,,) thus prepared exhibits submicrometre spherical grains whose specific surface area is 5.01 m*/g. The intercalationideintercalation (redox) kinetics of the above product has been studied and its suitability as cathode matertal in actual electrochemical cells is discussed in the light of electrochemical properties. 00/03428 Solving state estimation in power systems by an interior point method Ramirez, J.M. and Barocio. E.E. Elec. Power ~rnd Emqv Svr., 2000. 22. (5). 355-365. A linear programming formulation is employed to solve the static state estimation problem in power systems usmg the primal-dual predictorcorrector algorithm. This has been selected because it has emerged as an efficient algorithm that makes the direction search toward the optimal point
Fuel and Energy
Abstracts
November 2000
385
06 Electrical power supply and utilization (scientific, technical)
easy. The technique was applied successfully into several power systems when simultaneous gross errors were considered. Results are presented showing that this algorithm exhibits a good performance under critical measurement errors. 00/03429 Stainless steel as a bipolar plate material for solid polymer fuel cells Davies, D. P. et al. Journal of Power Sources, 2000, 86, (l-2), 237-242. Stainless steel bipolar plates for the solid polymer fuel cell (SPFC) offer many advantages over conventional graphitic materials. These include relative low cost, high strength, ease of manufacture and as they can be shaped into thin sheets, significant improvement in the power/volume ratio. However, interfacial ohmic losses across the metallic bipolar plate and the Membrane Electrode Assembly (MEA), reduce the overall power output from a SPFC. Despite a large range of commercially available alloys, 316 stainless steel has traditionally been the alloy of choice for bipolar plates. A number of alternative grades of stainless steel have been evaluated in terms of the electrical resistance of their surface oxide film. This showed that ohmic losses exhibited in fuel cell performance varied depending on the elemental composition of the stainless steel alloy. Three stainless steel alloys, 310, 316 and 904L, were chosen as candidate bipolar plate materials. Increased polarization was observed in the order 904L c 310 < 316. This was maintained throughout an ongoing endurance test, where these cells have been run for over 3000 h without significant performance degradation. This difference in polarization behaviour was attributed to variation in thickness of the oxide film. Analysis has shown no deleterious effect on the surface of the bipolar plate and no evidence of corrosion. 00103430 Start-up, testing and operation of 1000 kW class MCFC power plant Ishikawa, T. and Yasue, H. Journal of Power Sources, 2000, 86, (l-2), l45150. The MCFC Research Association has been conducting R&D of the 1000 kW class MCFC power plant under contracting research with New Energy and Industrial Technology Development Organization (NEDO) as a part of the New Sunshine Programme, promoted by the Agency of Industrial Science and Technology (AIST) and the Ministry of International Trade and Industry (MITI). The plant consists of four 250-kW stacks, a reformer, two cathode gas recycle blowers, a turbine compressor, a heat recovery steam generator (HRSG). The power plant is the first Japanese practical external reforming pressurized type MCFC power generation plant intended for large-scale commercial plant in the near future. The construction of the 1000 kW MCFC power plant started in autumn of 1995 on Kawagoe test station in Kawagoe Thermal Power Station of Chubu Electric Power, which is located in the prefecture of Mie, Japan. The construction and installation of the plant progressed very well, and process and control (PAC) testing of the power plant (not including fuel cell stacks and inverters) was carried out through March-November of 1998. After the PAC test, the cell stacks and inverters were installed in the test site; currently, the power generation test has just started. This paper describes the outline of the plant, the status of the test and the future schedule. Status of tubular SOFC field unit demonstrations 00103431 George, R. A. Journal of Power Sources, 2000, 86, (l-2), 134-139. Siemens Westinghouse is in the final stage of its tubular solid oxide fuel cell (SOFC) development programme, and the emphasis has shifted from basic technology development to cost reduction, scale-up and demonstration of pre-commercial power systems at customer sites. This paper describes the field unit demonstration programme including the EDB/ELSAM lOO-kW e combined heat and power (CHP) system, the Southern California Edison (SCE) 220-kW e pressurized SOFC/gas turbine (PSOFC/GT) power system, and the planned demonstrations of commercial prototype power systems. In the Spring of 1999, the EDB/ELSAM lOO-kWe SOFC-CHP system produced 109 kWe net AC to the utility grid at 46% electrical efficiency and 65 kWt to the hot water district heating system, verifying the analytical predictions. The SCE 220-kWe PSOFCIGT power system will undergo factory startup in the autumn of 1999. 00103432 Studies on .methanol fuel cell Verma, L. K. Journal of Power Sources, 2000, 86, (l-2), 464-468. A fuel cell using methanol dissolved in 6 N KOH solution with (Fe(II1) and AI(II1) and without treated graphite cathode at ambient temperature (25°C) was studied for the following parameters: (a) current-voltage behaviour at ambient temperature; (b) voltage drop with time; (c) methanol ‘concentration as a function of time’; (d) carbon dioxide generation as a function of time; (e) effect of catalyst on the performance of the cell. The OCV of the cell was 0.273, 0.850 and 1.4 V, while current density was 0.5, 4.52 and 17.2 Am-* with untreated and treated (Fe(II1) and AI(III)) graphite electrode, respectively. The highest current density was 180 Am SUP>-2 at 0.3 V and 540 Am-* at 1.04 V for Fe(II1) and AI(III), respectively. polarization was found to be higher in AI(III) than Fe(III)treated graplute electrod? due to the low heat of adsorption of AI(III) [406 kJ mol- vs 518 kJ mol. for Fe(III)]. The catalytic oxidation of methanol in terms of electrical energy output shows efficiency of about 78% for AI(III) and 80% for Fe(III)-treated graphite electrode, 00103433 Study of passivation at the positive active material/ grid interface in lead-acid batteries Chen, H. Y. et al. Journal of Power Sources, 2000, 88, (l), 78-82.
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Fuel and Energy Abstracts
November 2000
A valuable additive-boric acid - to eliminate passivation of the active material/grid interface in positive plates of lead-acid batteries - has been selected through comparison of single-cell discharge tests. This overcomes the problem of rapid decline in initial performance when using lowantimony (1.7 wt%) grid alloys. The performance of the oxide film on positive grids, as well as its composition and amount, is determined through cathodic reduction of the film with a linear sweep voltammetric (LSV) method. The results confirm that passivation of the positive grid and rapid decline in the initial discharge voltage are due to a resistive layer of PbS04, and not PbO,, (1 5 n 2 2). The PbO,, layer has little effect on passivation. The findings of this study are useful for the production of lead-acid batteries. 00/03434 Sustainable energy conversion: fuel cells - the competitive option? Hart, D. Journal of Power Sources, 2000, 86, (l-2), 23-27. The definition of sustainability is still under discussion, but it is becoming increasingly clear that present practices of energy supply and distribution are causing severe environmental pressures, and that they cannot be continued indefinitely. The fuel cell has been undergoing rapid development and is now at a stage immediately prior to commercialisation for a number of markets. It is expected to be economically competitive with many other energy conversion technologies within the next 5 years. However, introduction of the fuel cell may also speed the economic introduction of emissions-free energy carriers such as hydrogen, linking directly to renewably generated electricity. Hydrogen could be used as a form of energy storage in cases where electricity demand and supply were not matched. The fuel cell would then be complementary to, rather than competitive with, renewable generation technologies. Ultimately the fuel cell, in both its high and low-temperature derivatives, could become one of the pillars of a future sustainable energy system. 00/03435 Synthesis and characterization of spine1 LiMnp04 for lithium secondary battery Jang, S.-W. Journal of Power Sources, 2000, 88, (2), 274-271. The preparation and characterization of spine1 LiMn20r have been studied. Spine1 lithium manganese oxides are prepared by a sol-gel method using LiN03 and Mn(CH$00)2 4H20 as starting materials in which the obtained gel is heated at various temperatures after pre-treatment at 350°C or without pre-treatment in air. The LiMnsOd samples prepared with pretreatment have uniform micro-sized particles while those obtained without pre-treatment have agglomerated particles of irregular shapes. The thermal pre-treatment at 350°C improves the electrochemical behaviour in terms of discharge capacity and rate capability. The results can be correlated with an increase in lithium surface reaction sites in these materials, as inferred by this small grain size and large surface area. 00103436 Synthesis of LiMn204 by modified Pechini method and characterization as a cathode for rechargeable LilLiMna04 cells Han, Y.-S. and Kim, H.-G. Journal qfPower Sources, 2000, 88, (2), 161-168. The Pechini process to produce LIMnZ04 powder is modified such that precursors are pre-ignited in open air followed by calcining in the range of 600-800°C for 4 h. The molar ratio (R) of ethylene glycol (EG) to citric acid (CA) is 0, 1, 2 or 4. The effect of EG content on powder characteristics and electrochemical performance is evaluated. With increasing R, the homogeneity and the specific surface area of the powder are increased. Lithium is evaporated during ignition (and/or the charring reaction) and calcination because of the inhomogeneous mixing and exothermic heat of decomposition of polymer. Samples calcined at 800°C for 4 h yield maximum specific capacity for both charge and discharge (130.7 and 126.7 mA h gg’). The cycleability of the powder increases with increasing R. The effect of the EG content on the homogeneity is discussed. 00/03437 Synthesis of power system load profiles by class load study Chen, C.S. et al. Elec. Power md Energy Syst., 2000, 22, (5), 325-330. This paper proposes a methodology for the synthesis of power system load profiles by class load study. There are more than 900 customers over various customer classes, they are selected by the sampling design for the installation of intelligent meters over six districts in the Taipower system. The load data of all the test customers have been collected and the typical load patterns of customer classes have been derived for each service district. The billing data of all the customers in the Taipower customer information system are retrieved and the typical load patterns derived are applied to solve the hourly load composition of all customer classes. The actual power consumption in each study district, which has been recorded by the Taipower distribution dispatch control system, is used to verify the accuracy of the power profiles derived. By the same way, the power profiles of Taipower system are then synthesized too. It is concluded that the system power profile can be estimated by the aggregation of class load patterns in a precise manner. 00103436 Synthesis, characterization, and cell performance LiNiV04 cathode materials prepared by a new solution precipitation method Fey, G. T.-K. Chen, K.-S. J. Power Sources, 1999, 81-82, 467471.
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