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    Exergetic performance analysis of a PEM fuel cell
    (WILEY, 2006) Ay, M; Midilli, A; Dincer, I
    In this paper we investigate the effects of thermodynamic irreversibilities on the exergetic performance of proton exchange membrane (PEM) fuel cells as a function of cell operating temperature, pressures of anode and cathode, current density, and membrane thickness. The practical operating conditions are selected to be 3-5 atm for anode and cathode pressures, and 323-353 K for the cell temperatures, respectively. In addition, the membrane thicknesses are chosen as 0.016, 0.018 and 0.02cm, respectively. Moreover, the current density range of the PEM fuel cell is selected to be 0.01-2.0 A cm(-2). It is concluded that exergy efficiency of PEM fuel cell decreases with a rise in membrane thickness and current density, and increases with a rise of cell operating pressure and with a decrease of current density for the same membrane thickness. Thus, it can be said that, in order to increase the exergetic performance of PEM fuel cell, the lower membrane thickness, the lower current density and the higher cell operating pressure should be selected in case PEM fuel cell is operated at constant cell temperature. Copyright (c) 2005 John Wiley & Sons, Ltd.
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    On hydrogen and hydrogen energy strategies I: current status and needs
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Midilli, A; Ay, M; Dincer, I; Rosen, MA
    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. (C) 2004 Elsevier Ltd. All rights reserved.
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    On hydrogen and hydrogen energy strategies II: Future projections affecting global stability and unrest
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Midilli, A; Ay, M; Dincer, I; Rosen, MA
    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 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. (C) 2004 Elsevier Ltd. All rights reserved.