01990 Fuel economy of hydrogen fuel cell vehicles

01990 Fuel economy of hydrogen fuel cell vehicles

03 Gaseous fuels (economics, business, marketing, policy) and carbon dioxide. High purity, (99.72%) hydrogen can be achieved from a low ~urity (30%) f...

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03 Gaseous fuels (economics, business, marketing, policy) and carbon dioxide. High purity, (99.72%) hydrogen can be achieved from a low ~urity (30%) feed via a two-stage separation process at 700 mA cm -.

05•01986 Numerical study of fuel temperature influence on single gas jet combustion in highly preheated and oxygen deficient air Yang, W. and Blasiak, W. Energy, 2005, 30, (2 4), 385 398. Combustion of a single jet of propane in a cross-flowing stream of preheated and oxygen deficient air is numerically analysed with emphasis on influences of fuel temperature. Both Eddy-Break-Up and PDF/mixture fraction combustion models coupled with RNG k turbulent model were applied and the predicted results were compared. Thermal and prompt NO models were employed to calculate NO emissions. Results show that the Eddy-Break-Up model is more suitable for predicting temperature field and flame shape. It was showed that flame during high temperature air combustion condition is spread over a much larger volume. Flame volume increases with a reduction of oxygen concentration, and this trend is clearer if oxygen concentration in the preheated air is below 10%. Additionally, it is almost constant at fixed oxygen concentration and fuel inlet temperature for the temperature of the preheated and oxygen deficient air equal to 1041 1273 K. Increase of the fuel inlet temperature results in smaller flame, shorter mean residence time, smaller temperature peaks, and lower emission of NO.

Transport, storage 05•01987 Effect of particle size on the electrode performance of MgNi hydrogen storage alloy Rongeat, C. and Rou6, L. Journal of Power Sources, 2004, 131, (1 2), 302 308. Amorphous MgNi material has been synthesized by mechanical alloying and sieved into three particle size fractions: >75, 20 75, and <20 ~am. The influence of the MgNi particle size on its electrochemical behaviour as negative electrode for Ni metal hydride (MH) batteries has been investigated. The initial discharge capacity is higher as the MgNi particle size increases, i.e. the initial discharge capacity of particles larger than 75 m is 439 mAh/g compared to 396 and 328 mAh/ g for 20 75 and <20 ~am particles, respectively. In addition, the cycle life of the MgNi electrode is improved by increasing the particle size. That is, the >75 ~am particles electrode retains 41% of its initial capacity after 15 cycles compared to 35 and 23% for 20 75 ~am and <20 ~am particles electrodes, respectively. The rate dischargeability is also improved by increasing the MgNi particle size. For example, at 400 mA/g, the >75 ~am particles electrode delivers 33% of its capacity measured at 20 ~amA/g compared to 25 and 19% for 20 75 ~am and <20 ~am powders, respectively. These results can be explained by the lower specific surface area of the electrode constituted of large particles which limits the formation of Mg(OH)2 resulting from the MgNi oxidation by the electrolyte. Moreover, on the basis of the evolution of the cycling discharge capacities with increasing charge input for the different powder fractions, it appears that the electrode resistance to pulverization is improved by increasing the MgNi particle size.

05•01988 Influence of moist combustion gas on performance of a sub-critical turbine Yang, W. and Su, M. Energy Conversion and 3lanagement, 2005, 46, (5), 821 832. In the HAT cycle, as the absolute humidity of the moist combustion gas increases, the performance of the turbine will also change. In this paper, one model to calculate the thermodynamic properties of the moist combustion gas is introduced, and another model to calculate the performance of the turbine is formulated based on the equations of one-dimensional flow. Using these models with the geometric parameters of the turbine fixed, at the design working condition, the performance of the turbine is calculated and analysed for different absolute humidities. Finally, some conclusions about the turbine performance are presented.

05•01989 NaOH activation of anthracites: effect of temperature on pore textures and methane storage ability Perrin, P. et al. Carbon, 2004, 42, (14), 2855 2866. The main purpose of this work was to prepare various active carbons from the same precursor at various activation temperatures, and investigate both porosity development and corresponding methane storage capacities. An anthracite was thus chemically activated with sodium hydroxide under nitrogen flow at temperatures ranging from 600 to 830c'C, with a constant mass ratio: hydroxide/anthracite = 3. The pore textures of the corresponding activated carbons were investigated

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Fuel and Energy Abstracts

September 2005

using the adsorption isotherms of four probe molecules characterized by their increasing molecular diameters, namely CO2, N2, C6H6 and CC14. The changes occurring in each kind of pores were discussed and put in relation with the activation temperature. The specific volumes of different micro- and mesopore families were measured and discussed. Depending on the temperature range, two different activation mechanisms were evidenced. Methane storage isotherms at 20c'C and up to 3.5 MPa were measured for the investigated materials. Linear correlations between various textural parameters and methane storage capacities were given. Additionally, a number of results previously reported in the literature were confirmed by the present work.

Economics, business, marketing, policy 05•01990

Fuel economy of hydrogen fuel cell vehicles

Ahluwalia, R. K. et al. Journal of Power Sources, 2004, 130, (1 2), 192 201. On the basis of on-road energy consumption, fuel economy (FE) of hydrogen fuel cell light-duty vehicles is projected to be 2.5 2.7 times the fuel economy of the conventional gasoline internal combustion engine vehicles (ICEV) on the same platforms. Even with a less efficient but higher power density 0.6 V per cell than the base case 0.7 V per cell at the rated power point, the hydrogen fuel cell vehicles are projected to offer essentially the same fuel economy multiplier. The key to obtaining high fuel economy as measured on standardized urban and highway drive schedules lies in maintaining high efficiency of the fuel cell (FC) system at low loads. To achieve this, besides a high performance fuel cell stack, low parasitic losses in the air management system (i.e., turndown and part load efficiencies of the compressor expander module) are critical.

05•01991 Natural gas as an alternative to crude oil in automotive fuel chains well-to-wheel analysis and transition strategy development Hekkert, M. P. et al. Energy Policy, 2005, 33, (5), 579 594. Road transport produces significant amounts of CO2 by using crude oil as primary energy source. A reduction of CO2 emissions can be achieved by implementing alternative fuel chains. This article studies CO2 emissions and energy efficiencies by means of a well to wheel analysis of alternative automotive fuel chains, using natural gas (NG) as an alternative primary energy source to replace crude oil. The results indicate that NG-based hydrogen applied in fuel cell vehicles (FCVs) lead to largest CO2 emission reductions (up to 40% compared to current practice). However, large implementation barriers for this option are foreseen, both technically and in terms of network change. Two different transition strategies are discussed to gradually make the transition to these preferred fuel chains. Important transition technologies that are the backbone of these routes are traditional engine technology fuelled by compressed NG and a FCV fuelled by gasoline. The first is preferred in terms of carbon emissions. The results furthermore indicate that an innovation in the conventional chain, the diesel hybrid vehicle, is more efficient than many NG-based chains. This option scores well in terms of carbon emissions and implementation barriers and is a very strong option for the future.

05•01992 Optimum hydrogen generation capacity and current density of the PEM-type water electrolyzer operated only during the off-peak period of electricity demand Oi, T. and Sakaki, Y. Journal of Power Sources, 2004, 129, (2), 229 237. A requirement for widespread adoption of fuel cell vehicles in the transportation sector will be ready availability of pure hydrogen at prices that result in operating costs comparable to, or less than, that of gasoline internal combustion engine vehicles. The existing electrical power grid could be used as the backbone of the hydrogen infrastructure system in combination with water electrolysers. A water electrolyser can contribute to the load levelling by changing operational current density in accordance with the change of electricity demand. The optimum hydrogen generation capacity and current density of the polymer electrolyte membrane (PEM)-type water electrolyser operated only during the off-peak period of electricity demand in respect of both the shortest time required for start and the higher efficiency of water electrolysis are obtained as 500 N m3 h-1 and 30 kA m-2, respectively. This PEM-type water electrolyser could be used in the hydrogen refuelling stations and energy storage systems constructed around hydrogen.

05•01993 The political economy of trans-Pakistan gas pipeline project: assessing the political and economic risks for India Pandian, S. Energy Policy, 2005, 33, (5), 659 670.