- Email: [email protected]
01469 Hydrogen energy systems. Concepts and practical applications
03 Gaseous fuels (derived gaseous fuels) allows only the current to pass through and does not permit the ions to move from one compartment to the other. This permits one to apply chemical bias. With this set-up it has been demonstrated that water can be split into hydrogen and oxygen at as low a potential as ~1.0 volt. Based on these studies a patent has been applied.
05/01467 An overview of current and future sustainable gas turbine technologies Poullikkas, A. Renewable and Sustainable Energy Reviews, 2005, 9, (5), 409 443. In this work an overview of current and future sustainable gas turbine technologies is presented. In particular, the various gas turbine technologies are described and compared. Emphasis has been given to the various advance cycles involving heat recovery from the gas turbine exhaust, such as, the gas to gas recuperation cycle, the combined cycle, the chemical recuperation cycle, the Cheng cycle, the humid air turbine cycle, etc. The thermodynamic characteristics of the various cycles are considered in order to establish their relative importance to future power generation markets. The combined cycle technology is now well established and offers superior to any of the competing gas turbine based systems, which are likely to be available in the medium term for large-scale power generation applications. In small-scale generation, less than 50 MWe, it is more cost effective to install a less complex power plant, due to the adverse effect of the economics of scale. Combined cycle plants in this power output range normally have higher specific investment costs and lower electrical efficiencies but also offer robust and reliable performance. Mixed air steam turbines (MAST) technologies are among the possible ways to improve the performance of gas turbine based power plants at feasible costs (e.g. peak load gas turbine plants).
05/01468 Forecasting total natural-gas consumption in Spain by using the stochastic Gompertz innovation diffusion model Gutidrrez, R. et al. Applied Energy, 2005, 80, (2), 115-124. The principal objective of the present study is to examine the possibilities of using a Gompertz-type innovation diffusion process as a stochastic growth model of natural-gas consumption in Spain, and to compare these results with those obtained, on the one hand, by stochastic logistic innovation modelling and, on the other, by using a stochastic lognormal growth model based on a non-innovation diffusion process. Such a comparison is carried out taking into account the macroeconomic characteristics and natural-gas consumption patterns in Spain, both of which reflect the current expansive situation characterizing the Spanish economy. From the technical standpoint a contribution is also made to the theory of the stochastic Gompertz Innovation diffusion process (SGIDP), as applied to the case in question.
05/01469 Hydrogen energy systems. Concepts and practical applications Berndt, D. Refocus, 2004, 5, (6), 48 51. In an ideal world we might envisage a future where electricity, heat and motive power are derived from renewable energy sources. Hydrogen could be a key player in certain applications in this future world as an energy storage medium. This article provides an overview of some of the technologies and processes that might play a part in a future hydrogen economy.
05•01470 On hydrogen and hydrogen energy strategies h current status and needs Midilli, A. et al. Renewable and Sustainable Energy Reviews, 2005, 9, (3), 255-271. This article deals with hydrogen energy as a clean energy carrier, discusses the key role of hydrogen energy technologies and systems, and compares hydrogen with other energy forms. Energy strategies that incorporate hydrogen are considered, and the importance of hydrogen energy in achieving a sustainable energy system is discussed. Exergetic, environmental, sustainability and other perspectives are considered.
05101471 On hydrogen and hydrogen energy strategies I1: future projections affecting global stability and unrest Midilli, A. et al. Renewable and Sustainable Energy Reviews, 2005, 9, (3), 273-287. This article focuses on hydrogen energy strategies and discusses the key role of hydrogen as an energy carrier in this century and beyond. Two important empirical relations that describe the effects of fossil fuels on world peace and global unrest are developed. These relations incorporate predicted utilization ratios for hydrogen energy from non-fossil fuels, and are used to investigate whether hydrogen utilization can reduce the negative global effects related to fossil fuel use, eliminate or reduce the possibilities of global energy conflicts, and contribute to achieving world peace and stability. Consequently, the highest levels of global peace and global unrest can be estimated. If hydrogen use from non-fossil fuels increases, for a fixed usage of
222 Fuel and Energy Abstracts
July 2005
petroleum, coal and natural gas, the level of global unrest decreases. However, if the utilization ratio of hydrogen energy from non-fossil fuels is lower than 100%, the level of global peace decreases as the symptoms of global unrest increase. Thus, to reduce the causes of global unrest and increase the likelihood of global peace in the future, it is suggested that hydrogen energy be widely and efficiently used as part of sustainable technologies and systems. It is expected that the results of this study will be of use to decision makers and scholars who want to develop and promote the use of hydrogen-based technologies and solve future energy and environment related problems globally.
Derived gaseous fuels 05•01472 Coal conversion submodels for design applications at elevated pressures. Part I1. Char gasification Liu, G.-S. and Niksa, S. Progress in Energy and Combustion Science, 2004, 30, (6), 679-717. This paper surveys the database on char gasification at elevated pressures, first, to identify the tendencies that are essential to rational design of coal utilization technology, and second, to validate a gasification mechanism for quantitative design calculations. Four hundred and fifty-three independent tests with 28 different coals characterized pressures from 0.02 to 3.0 MPa, COz and steam mole percentages from 0 to 100%, CO and Hz levels to 50%, gas temperatures from 800 to 1500°C, and most of coal rank spectrum. Only a handful of cases characterized inhibition by CO and H2, and only a single dataset represented the complex mixtures of H20, COz, CO, and H2 that arise in practical applications. With uniform gas composition, gasification rates increase for progressively higher pressures, especially at lower pressures. Whereas the pressure effect saturates at the higher pressures with bituminous chars, no saturation is evident with low-rank chars. With fixed partial pressures of the gasification agents, the pressure effect is much weaker. Gasification rates increase for progressively higher gas temperatures. In general, gasification rates diminish for coals of progressively higher rank, but the data exhibit this tendency only for ranks of hv bituminous and higher. These tendencies are interpreted with CBK/G, a comprehensive gasification mechanism based on the Carbon Burnout Kinetics Model. CBK/G incorporates three surface reactions for char oxidation plus four reactions for gasification by COs, H20, CO and H2. Based on a one-point calibration of rate parameters for each coal in the database, CBK/G predicted extents of char conversion within --11.4 daf wt% and gasification rates within +22.7%. The predicted pressure, temperature, and concentration dependencies and the predicted inhibiting effects of CO and H2 were generally confirmed in the data evaluations. The combination of the annealing mechanism and the random pore model imparts the correct form to the predicted rate reductions with conversion. CBK/G in conjunction with equilibrated gas compositions accurately described the lone dataset on complex mixtures with all the most important gasification agents, but many more such datasets are needed for stringent model evaluations. Practical implications are illustrated with single-particle simulations of various coals, and a 1D gasifier simulation for realistic Oz and steam stoichiometries. The rank dependence of gasification rates is the determining factor for predicted extents of char conversion at the gasifier outlet. But soot gasification kinetics will determine the unburned carbon emissions for all but the highest rank fuels. Only gasification kinetics for gas mixtures with widely variable levels of H20, Hz, and CO are directly relevant to gasifier performance evaluations.
05•01473 Effect of the Mg/AI ratio of the hydrotalcite-type precursor on the dispersion and activity of Rh and Ru catalysts for the partial oxidation of methane Basile, F. et al. Catalysis' Today, 2004, 91-92, (15), 293-297. Active and stable catalysts for the partial oxidation of methane based on Rh and Ru nanoparticles strongly interacting with a MgO or spinel matrix have been prepared by calcination and reduction of hydrotalcite-type precursors. A Rh catalyst containing an high metal loading was used to calculate, by Rietveld analysis, the distribution of the Rh in the MgO-type and spinet-type phases obtained after calcination. The Rh particle size distribution analysed after reduction by HRTEM, has evidenced that the size of Rh particles supported on MgO is smaller than that of Rh particles supported on spinel matrix. The differences in the catalytic activity of the two type of matrix have been studied changing the Mg/A1 ratio of the precursor. High Mg/A1 ratio depressed the formation of the spinel and led to a narrow distribution of the particle size. The sample with the highest percentage of the MgO phase showed the highest activity. Similar tests have been carried out with Ru containing samples and in this case the increase of the MgO phase decreases the formation of RuO~.
05/01467 An overview of current and future sustainable gas turbine technologies Poullikkas, A. Renewable and Sustainable Energy Reviews, 2005, 9, (5), 409 443. In this work an overview of current and future sustainable gas turbine technologies is presented. In particular, the various gas turbine technologies are described and compared. Emphasis has been given to the various advance cycles involving heat recovery from the gas turbine exhaust, such as, the gas to gas recuperation cycle, the combined cycle, the chemical recuperation cycle, the Cheng cycle, the humid air turbine cycle, etc. The thermodynamic characteristics of the various cycles are considered in order to establish their relative importance to future power generation markets. The combined cycle technology is now well established and offers superior to any of the competing gas turbine based systems, which are likely to be available in the medium term for large-scale power generation applications. In small-scale generation, less than 50 MWe, it is more cost effective to install a less complex power plant, due to the adverse effect of the economics of scale. Combined cycle plants in this power output range normally have higher specific investment costs and lower electrical efficiencies but also offer robust and reliable performance. Mixed air steam turbines (MAST) technologies are among the possible ways to improve the performance of gas turbine based power plants at feasible costs (e.g. peak load gas turbine plants).
05/01468 Forecasting total natural-gas consumption in Spain by using the stochastic Gompertz innovation diffusion model Gutidrrez, R. et al. Applied Energy, 2005, 80, (2), 115-124. The principal objective of the present study is to examine the possibilities of using a Gompertz-type innovation diffusion process as a stochastic growth model of natural-gas consumption in Spain, and to compare these results with those obtained, on the one hand, by stochastic logistic innovation modelling and, on the other, by using a stochastic lognormal growth model based on a non-innovation diffusion process. Such a comparison is carried out taking into account the macroeconomic characteristics and natural-gas consumption patterns in Spain, both of which reflect the current expansive situation characterizing the Spanish economy. From the technical standpoint a contribution is also made to the theory of the stochastic Gompertz Innovation diffusion process (SGIDP), as applied to the case in question.
05/01469 Hydrogen energy systems. Concepts and practical applications Berndt, D. Refocus, 2004, 5, (6), 48 51. In an ideal world we might envisage a future where electricity, heat and motive power are derived from renewable energy sources. Hydrogen could be a key player in certain applications in this future world as an energy storage medium. This article provides an overview of some of the technologies and processes that might play a part in a future hydrogen economy.
05•01470 On hydrogen and hydrogen energy strategies h current status and needs Midilli, A. et al. Renewable and Sustainable Energy Reviews, 2005, 9, (3), 255-271. This article deals with hydrogen energy as a clean energy carrier, discusses the key role of hydrogen energy technologies and systems, and compares hydrogen with other energy forms. Energy strategies that incorporate hydrogen are considered, and the importance of hydrogen energy in achieving a sustainable energy system is discussed. Exergetic, environmental, sustainability and other perspectives are considered.
05101471 On hydrogen and hydrogen energy strategies I1: future projections affecting global stability and unrest Midilli, A. et al. Renewable and Sustainable Energy Reviews, 2005, 9, (3), 273-287. This article focuses on hydrogen energy strategies and discusses the key role of hydrogen as an energy carrier in this century and beyond. Two important empirical relations that describe the effects of fossil fuels on world peace and global unrest are developed. These relations incorporate predicted utilization ratios for hydrogen energy from non-fossil fuels, and are used to investigate whether hydrogen utilization can reduce the negative global effects related to fossil fuel use, eliminate or reduce the possibilities of global energy conflicts, and contribute to achieving world peace and stability. Consequently, the highest levels of global peace and global unrest can be estimated. If hydrogen use from non-fossil fuels increases, for a fixed usage of
222 Fuel and Energy Abstracts
July 2005
petroleum, coal and natural gas, the level of global unrest decreases. However, if the utilization ratio of hydrogen energy from non-fossil fuels is lower than 100%, the level of global peace decreases as the symptoms of global unrest increase. Thus, to reduce the causes of global unrest and increase the likelihood of global peace in the future, it is suggested that hydrogen energy be widely and efficiently used as part of sustainable technologies and systems. It is expected that the results of this study will be of use to decision makers and scholars who want to develop and promote the use of hydrogen-based technologies and solve future energy and environment related problems globally.
Derived gaseous fuels 05•01472 Coal conversion submodels for design applications at elevated pressures. Part I1. Char gasification Liu, G.-S. and Niksa, S. Progress in Energy and Combustion Science, 2004, 30, (6), 679-717. This paper surveys the database on char gasification at elevated pressures, first, to identify the tendencies that are essential to rational design of coal utilization technology, and second, to validate a gasification mechanism for quantitative design calculations. Four hundred and fifty-three independent tests with 28 different coals characterized pressures from 0.02 to 3.0 MPa, COz and steam mole percentages from 0 to 100%, CO and Hz levels to 50%, gas temperatures from 800 to 1500°C, and most of coal rank spectrum. Only a handful of cases characterized inhibition by CO and H2, and only a single dataset represented the complex mixtures of H20, COz, CO, and H2 that arise in practical applications. With uniform gas composition, gasification rates increase for progressively higher pressures, especially at lower pressures. Whereas the pressure effect saturates at the higher pressures with bituminous chars, no saturation is evident with low-rank chars. With fixed partial pressures of the gasification agents, the pressure effect is much weaker. Gasification rates increase for progressively higher gas temperatures. In general, gasification rates diminish for coals of progressively higher rank, but the data exhibit this tendency only for ranks of hv bituminous and higher. These tendencies are interpreted with CBK/G, a comprehensive gasification mechanism based on the Carbon Burnout Kinetics Model. CBK/G incorporates three surface reactions for char oxidation plus four reactions for gasification by COs, H20, CO and H2. Based on a one-point calibration of rate parameters for each coal in the database, CBK/G predicted extents of char conversion within --11.4 daf wt% and gasification rates within +22.7%. The predicted pressure, temperature, and concentration dependencies and the predicted inhibiting effects of CO and H2 were generally confirmed in the data evaluations. The combination of the annealing mechanism and the random pore model imparts the correct form to the predicted rate reductions with conversion. CBK/G in conjunction with equilibrated gas compositions accurately described the lone dataset on complex mixtures with all the most important gasification agents, but many more such datasets are needed for stringent model evaluations. Practical implications are illustrated with single-particle simulations of various coals, and a 1D gasifier simulation for realistic Oz and steam stoichiometries. The rank dependence of gasification rates is the determining factor for predicted extents of char conversion at the gasifier outlet. But soot gasification kinetics will determine the unburned carbon emissions for all but the highest rank fuels. Only gasification kinetics for gas mixtures with widely variable levels of H20, Hz, and CO are directly relevant to gasifier performance evaluations.
05•01473 Effect of the Mg/AI ratio of the hydrotalcite-type precursor on the dispersion and activity of Rh and Ru catalysts for the partial oxidation of methane Basile, F. et al. Catalysis' Today, 2004, 91-92, (15), 293-297. Active and stable catalysts for the partial oxidation of methane based on Rh and Ru nanoparticles strongly interacting with a MgO or spinel matrix have been prepared by calcination and reduction of hydrotalcite-type precursors. A Rh catalyst containing an high metal loading was used to calculate, by Rietveld analysis, the distribution of the Rh in the MgO-type and spinet-type phases obtained after calcination. The Rh particle size distribution analysed after reduction by HRTEM, has evidenced that the size of Rh particles supported on MgO is smaller than that of Rh particles supported on spinel matrix. The differences in the catalytic activity of the two type of matrix have been studied changing the Mg/A1 ratio of the precursor. High Mg/A1 ratio depressed the formation of the spinel and led to a narrow distribution of the particle size. The sample with the highest percentage of the MgO phase showed the highest activity. Similar tests have been carried out with Ru containing samples and in this case the increase of the MgO phase decreases the formation of RuO~.