Electrical power supply and utilization (economics, policy, supplies, forecasts)
procedure and in pulverized coal combustion are investigated based on relating sulfur retention to contents of these elements relative to sulfur in the parent coal. The role of calcium is predominant and the contributions of other alkaline elements are limited in laboratory-prepared ash and the percentage of sulfur retention increased with an exponential function as the Ca/S molar ratio of the parent coal increased. The behaviour of sulfur retention by laboratory-prepared ash can be applied to fluidized bed combustion (FBC) due to similar behaviours of calcium in laboratory and lime sorbent in FBC. In contrast, the contribution of calcium is reduced markedly owing to higher temperature and shorter resident time in pulverized coal combustion, while the contributions of other alkaline elements are obviously enhanced.
Seven years of operational experience with highdust DENOX units following slag-tap pulverized coal firing. Effects on subsequent plants
Schoenrock, M. and Hem, M. VGB Kraftwerkstech., 1998, 78, (7) 85-88. (In German) Reported are experiences and problems with two firing plants retrofitted with DENOX units. Initiallv several failures occurred, includine slag deposit on the catalyst layers; high residual carbon contents in the fi; ash; increasing pressure drop in the catalyst layers, high NH4 contents in the fly ash and occurrence of NH4 in the wastewater of the flue gas desulfurization plant. Briefly described are measures to eliminate the failures by changing the catalyst structure, by biological and physical-chemical wastewater treatment and by application of other coal mixtures.
Simulation of load shedding as a corrective action against voltage collapse
Parker, C. J. er al. Electric Power Systems Research, 1998, 46, (3) 235-241. Controlled load shedding associated with rearrangement of generator outputs can alleviate the evolution of a lot of voltage collapse scenarios on large power systems. To adequately determine the impact of load shedding actions and to design appropriate control systems dynamic simulation of power system mid-term voltage response is required. Load-voltage behaviour, transformer tap changer controls and limits, generator overexcitation limiters, automatic generation control and system protective devices must all be taken into account in the dynamic simulation. This paper demonstrates the impact of load shedding as a corrective action through simulation of the system dynamic response to a disturbance. Whilst load shedding can stabilise a system, rigorous techniques are required to identify the magnitude and location of shedding. This paper demonstrates the application of voltage modal analysis in combination with the determination of reactive power margins in resolving this problem.
Stability of LiAIOz as electrolyte matrix for molten 99101319 carbonate fuel cells Terada, S. et al. J. Power Sources, 1998, 75, (2) 223-229. If the life of molten carbonate fuel cells is to be prolonged, the amount of electrolyte in the matrix must be maintained at an appropriate level over long-term operation. Lithium aluminate, the state-of-the-art material for the matrix substrate, still presents some problems, such as crystal phase stability and particle growth. This paper investigates the mechanism of phase transformation and particle growth of lithium aluminate under various conditions (temperature, gas composition, carbonate composition). In addition, the effect of several additives for inhibiting particle growth are investigated. It is found that the allotropic phase transformation and particle growth occurs via a ‘dissolution-deposition’ mechanism. The results obtained suggest that lower temperature, higher partial pressure of COz or lower basicity of carbonates are preferable to control the particle growth of lithium aluminate and that lithium aluminate appears more stable under typical MCFC operating conditions.
Studies with porous zinc electrodes with additives 99101311 for secondary alkaline batteries Shivkumar, R. et al. J. Power Sources, 1998, 75, (1) 90-100. An evaluation has been made of small additions of HgO, SbzOs, Ti02 and Pbs04 to pasted zinc electrodes using cyclic voltammetry, potentiodynamic polarization (with temperature effect), a.c. impedance measurements, solution analysis and porosity measurements. Though the additives HgO and SbzOs are known for their high hydrogen overpotential, HgO additive has the beneficial effect of imparting minimum standby corrosion, enhanced ageing behaviour and minimum shape change. As regards the additive TiO, its behaviour is superior to that of HgO as far as the ageing and high temperature performance are concerned. The corrosion behaviour as well as ageing are fairly good for PbsO.+ However, this additive imparts a disadvantage of lead getting deposited on the counter electrode which would become a setback from the battery point of view.
Thermodynamic analysis of high temperature fuel cells: methane reforming
Call, F. W. AES (Am. Sot. Mech. Eng.), 1996,36, 305-311. Exergy, the ability to produce electricity, is wasted by the endothermic or exothermic processing of methane to a suitable fuel for fuel cell applications. The paper proposes a fuel cell process that converts (waste) heat (251 kW) into power (214 kW) while the methane (752 kW) is being reformed. Much more heat is processed than might be anticipated from the small values of enthalpy increase (37 kW) or the availability loss (36 kW) of the (endo-) thermochemical reaction. The resulting water gas (789 kW) can
Fuel and Energy Abstracts
be used in an ordinary fuel cell, in co-generation, or as a chemical feed stock. A practical compromise is suggested and comparison is made to standardize reforming methods.
Thermodynamic considerations potential for the nickel electrode
of the reversible
Jam, M. E. et al. Elecfrochim. Acta, 1998, 43, (18), 2649-2660. The thermodynamics of ideal and non-ideal solutions were applied to nickel hydroxide, the electrochemical active material in the positive electrode of a nickel battery, to provide a theoretical insight into reversible potential as a function of the state-of-discharge. The models were fit to experimentally discharge curves to obtain the activity-coefficient parameters and the standard potential over a temperature range from 5 to 55°C. The twoparameter activity coefficient models perform significantly better than the protons into the lattice occurs in an ordered, non-random fashion. The standard potential decreases linearly with temperature by 0.84 mV/K. The thermodynamic expressions and parameters given here enable the prediction of the reversible potential of nickel hydroxide as a function of temperature and state-of-discharge.
Tin-based oxide anode for lithium-ion batteries with low irreversible capacity
Wan, K. et al. J. Power Sources, 1998, 75, (l), 9-12. The synthesis has taken place of several kinds of tin-oxide composites that can replace the carbon-based lithium intercalation materials as the anode of lithium-ion batteries. The electrochemical behaviour of these materials is investigated in ethylene carbonate and dimethyl carbonate (EC-DMC) based solutions containing lithium salts, LiClO+ The lithium intercalation capacities in the tin-oxide materials were prepared from the same raw materials and by the same method depend on the heat-treatment temperature. A higher charge capacity and lower irreversible capacity material based on Sn2P2P7 is obtained by preparation at high temperature (700°C). The element manganese is added to these materials to obtain a material with lower irreversible capacity. This material, prepared by the same method, exhibits a lower irreversible capacity.
The use of thermoelectric production of electricity from biomass
M. and Schmidt,
Proc. Inf. Conf
In the last few years the use of renewable sources of energy to replace fossil fuels has been discussed in great detail. Their role in reducing carbon dioxide emissions and conserving natural resources was widely realized. Out of all the renewable sources of energy, bioenergy appears to have at the present the greatest potential. The use of biofuels for heating purposes in rural areas was developed extensively in the past years especially in the Nordic countries and Austria. In these countries the contribution of biofuels to the total energy demand has reached 12-15%. Efforts to produce electricity from biomass were less successful although this would be of great interest for small scale decentralized power production in remote rural areas. Three technologies were suggested: steam engines, gasification of biomass combined with gas motors and Stirling engines. During the past 25 years thermoelectric converters were developed mainly for space applications. This technology is now also being applied to supply electricity in remote places such as light houses or on mountains but appear also possible in bioenergy applications. These installations are normally supplying hot water for space heating. 99101316 VaOs xerogel lithium-polymer electrolyte batteries Prosini, P. P. et al. J. Power Sources, 1998, 75, (l), 73-83. In this report the fabrication and the characterization of a lithium-metal, polymer electrolyte battery using a VaOs xerogel cathode is described. The system operates at moderate temperatures (SO-1OOC). The electrochemical characterization of separate components as well as of small scale devices is also reported. The work is focused on the determination of important ‘application’ properties of the polymer electrolyte, i.e. the properties of the polymer electrolyte in real systems and true operating conditions. The work was developed within the ALPE (advanced lithium polymer electrolyte) project, an Italian project devoted to the realization of lithium polymer batteries for electric vehicle applications.
99101317 Advanced pulverized coal plant technology more efficient coal-fired power generation Torrens,
I. M. and Stenzel, W. C.
PWR (Am. Sot. Mech. Eng.),
The results of a study of two key issues for the Coal Industry Advisory Board’s Global Climate Committee are presented in this paper. (1) What is holding back the selection of commercially available state-of-the-art technologies by independent power plant developers for new pulverized coal fired plants. (2) What are the technical questions, performance and economics of conventional pulverized coal fired plants compared to supercritical pressure and commercially available state-of-the-art ultra supercritical pressure plants.