Most recent issue published online for the International Journal of Alternative Propulsion.

Time and scale in Life Cycle Assessment: the case of fuel choice in the transport sector

Karl M. Hillman — 2008-07-21T23:20:50-05:00

Time and scale in Life Cycle Assessment: the case of fuel choice in the transport sector
Karl M. Hillman, Bjorn A. Sanden
International Journal of Alternative Propulsion, Vol. 2, No. 1 (2008) pp. 1 - 12
Life Cycle Assessments (LCA, including Well-to-Wheel studies) that are to support decisions that strive to change large technical systems need to consider time and scale related factors, which are given little attention in standard LCA procedures. Here, we address three issues and provide examples from the case of alternative fuels. First, shifting time frame gives room for technical development that should affect not only the choice of performance data, but perhaps also the functional unit and the selection of technologies under study. Secondly, background systems, such as heat and power production, change over time and increased production volumes of the alternative fuel change the transport system that is used to produce transport fuel. We show that such changes have consequences not only for Greenhouse Gas (GHG) emissions from each fuel-chain, but also for the ranking order of, e.g. Rapeseed Methyl Esther (RME) and ethanol in terms of GHG emissions. Finally, different types of feedstock are available in different quantities and different by-product markets vary in size. Key markets for RME by-products in EU correspond to an RME production that covers about 3% of transport fuel demand. Consequently, GHG emissions that are allocated to the fuel should change with the scale of adoption.

Production of synthetic gasoline and diesel fuels by alternative processes using natural gas, coal and biomass: process simulation and economic analysis

Maria Sudiro — 2008-07-21T23:20:50-05:00

Production of synthetic gasoline and diesel fuels by alternative processes using natural gas, coal and biomass: process simulation and economic analysis
Maria Sudiro, Alberto Bertucco
International Journal of Alternative Propulsion, Vol. 2, No. 1 (2008) pp. 13 - 25
The problem of producing synthetic liquid fuels by alternative routes is addressed. Industrial processes known as Gas To Liquid (GTL), Coal To Liquid (CTL) and Biomass To Liquid (BTL) are considered: they use natural gas, coal and biomass as feedstocks, respectively. By means of process simulation, it is shown that the fuel produced on a weight basis per unit of feedstock (natural gas, coal and wood) are 66.7, 32.5 and 16.8%, respectively; in addition, the CO2 emitted per unit mass of liquid fuel is 0.90 kg CO2/kg for GTL, 4.79 kg CO2/kg for CTL and 6.08 kg CO2/kg for BTL process. In this last case, carbon dioxide is not an issue because it derives from a renewable source. The evaluation of production costs of synthetic fuel for a GTL process is carried out under two different scenaries: a plant localised where natural gas is readily available, and another one built far from the country where the gas is produced. A comparison between the costs of synthetic fuels from a GTL process and conventional fuel from oil refining is carried out to show the competitiveness of this alternative fuel. A financial analysis permits to conclude that, if a GTL plant is localised where the natural gas is extracted, the return of investment is after 2.4 years, whereas it changes to 6.9 years if the plant is located in western industrialised countries.

Characterisation of two-phase flow and its impact on the performance of a Polymer Electrolyte Membrane fuel cell stack

G. Karimi — 2008-07-21T23:20:50-05:00

Characterisation of two-phase flow and its impact on the performance of a Polymer Electrolyte Membrane fuel cell stack
G. Karimi, F. Jafarpour, M. Binazadeh, X. Li
International Journal of Alternative Propulsion, Vol. 2, No. 1 (2008) pp. 26 - 38
Water management is one of the most critical issues for high-performance Polymer Electrolyte Membrane (PEM) fuel cells. A flow network model was developed to study the possibility of two-phase flow inception along the gas flow channels in the cathode side of a PEM fuel cell stack. The conventional Darcy-Weisbach equation and homogeneous flow model are used to estimate the pressure distributions in the network. The corresponding species concentrations as well as the thermodynamic quality distributions are also calculated. The simulation results have revealed that under certain operating conditions, the quality is lower than one for parts of the stack. However, the amount of the liquified water in the stack is not significant to cause a major pressure drop or an appreciable change in the O2 concentration. Effects of current density and channel diameter on the system quality are also investigated.

Efficiency analysis of hydrogen production methods from biomass

Krzysztof J. Ptasinski — 2008-07-21T23:20:50-05:00

Efficiency analysis of hydrogen production methods from biomass
Krzysztof J. Ptasinski
International Journal of Alternative Propulsion, Vol. 2, No. 1 (2008) pp. 39 - 49
Hydrogen is considered as a universal energy carrier for the future, and biomass has the potential to become a sustainable source of hydrogen. This article presents an efficiency analysis of hydrogen production processes from a variety of biomass feedstocks by a thermochemical method – gasification as well as biochemical methods – fermentation and anaerobic digestion. The exergetic efficiency of H2 production by gasification of more dry biomass is comparable to that of the commonly used Steam Methane Reforming. The detailed exergy analysis of H2 production by biomass gasification shows that the largest exergy losses occur in the gasifier.

Sensitivity analysis in a simulated auto thermal Natural Gas reforming process

H. Baloglu — 2008-07-21T23:20:50-05:00

Sensitivity analysis in a simulated auto thermal Natural Gas reforming process
H. Baloglu, G. Nasin-Saygili
International Journal of Alternative Propulsion, Vol. 2, No. 1 (2008) pp. 50 - 71
Auto Thermal natural gas Reforming (ATR) is one of the mostly used conventional hydrogen generation technologies by the highly developed countries. ATR reactors do not need any direct or indirect heat exchanger, and that is why they are more compact and so preferable than the other reformers. In this study, a process including reformers, carbon dioxide sequestration and a cryogenic separation sub-process is simulated for a defined standardised base case feed streams. Operating conditions of the main equipments, the inlet and the outlet stream properties and compositions, general mass balances and also the possible solid carbon dioxide formation conditions of the process streams are estimated to show the consistency of the process for the base case. In the sensitivity study, the effects of O2/C and H2O/C feed stream mass ratios and the capacity of the process on flow rates of the process stream compositions, e.g. hydrogen, carbon monoxide, carbon dioxide, residual water and methane, etc. are investigated. In addition, the effects of reforming and the shift reactor temperatures on the total hydrogen generation are determined. Consequently, the possible steam generation conditions and hydrogen, carbon dioxide separation units' operating conditions are examined for the simulated process, considering the base case defined.

Corrosion and contact resistance measurements of different bipolar plate material for Polymer Electrolyte Membrane Fuel Cells

Yue Hung — 2008-07-21T23:20:50-05:00

Corrosion and contact resistance measurements of different bipolar plate material for Polymer Electrolyte Membrane Fuel Cells
Yue Hung, Hazem Tawfik, K.M. El-Khatib, Hammam El-Abd
International Journal of Alternative Propulsion, Vol. 2, No. 1 (2008) pp. 72 - 85
Different types of commercial stainless steels (SS316, SS310 and incoloy 800), poco graphite, composite graphite, titanium carbide, zirconium carbide and carbide base coating on aluminum substrate using thermal spray technique were evaluated as metallic bipolar plate in terms of Interfacial Contact Resistance (ICR) and corrosion resistance in a solution simulating the environment of a bipolar plate in a Polymer Electrolyte Membrane Fuel Cell (PEMFC), 0.5 M H2SO4 and 200 ppm HF at room temperature. In addition, a comparison between graphite composites and carbide-based amorphous metallic coating alloy bipolar plate cost analysis. Results show that stainless steels have a high ICR and undergo corrosion in both anode and cathode due to the passive film formation. Moreover, although carbide-based alloy showed an ICR much less than composite graphite, their behaviour was not satisfactory in corrosive acidic medium.