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The size of a functioning "system" rather than the individual components determines the success of many miniaturization efforts. While most of the existing micro fuel-cell research has been focusing on the fuel-cell stack, our approach has been to systematically eliminate all the ancillary components with the goal of miniaturizing the full system. In this paper, we present a miniature fuel-cell system that combines the self-pumping of fuel and self-generation of oxidant altogether in a box-shape device of a few centimeters. Since the fuel is pumped on demand inside the system without requiring any external assistance, the device is self-sufficient and portable. Furthermore, the oxygen is generated on demand inside the system without requiring the ambient air, so that the device can be stacked in multiple. Constructed simply as liquids in a solid container, this active fuel-cell system resembles a battery to the user.

The size of a functioning "system" rather than the individual components determines the success of many miniaturization efforts. While most of the existing micro fuel-cell research has been focusing on the fuel-cell stack, our approach has been to systematically eliminate all the ancillary components with the goal of miniaturizing the full system. In this paper, we present a miniature fuel-cell system that combines the self-pumping of fuel and self-generation of oxidant altogether in a box-shape device of a few centimeters. Since the fuel is pumped on demand inside the system without requiring any external assistance, the device is self-sufficient and portable. Furthermore, the oxygen is generated on demand inside the system without requiring the ambient air, so that the device can be stacked in multiple. Constructed simply as liquids in a solid container, this active fuel-cell system resembles a battery to the user.

The size of a functioning “system” rather than the individual components determines the success of many miniaturization efforts. While most of the existing micro fuel-cell research has been focusing on the fuel-cell stack, our approach has been to systematically eliminate all the ancillary components with the goal of miniaturizing the full system. In this paper, we present a miniature fuel-cell system that combines the self-pumping of fuel and self-generation of oxidant altogether in a box-shape device of a few centimeters. Since the fuel is pumped on demand inside the system without requiring any external assistance, the device is self-sufficient and portable. Furthermore, the oxygen is generated on demand inside the system without requiring the ambient air, so that the device can be stacked in multiple. Constructed simply as liquids in a solid container, this active fuel-cell system resembles a battery to the user. [ABSTRACT FROM AUTHOR]

Abstract: Fuel cell technology is becoming a significant option as an energy technology. Attracting significant research funding, industry research and development (R&D), and commercial anticipation different fuel cell technologies are indicating potential as viable products. One of the anticipated applications of the technology is portable fuel cells. Ranging from small back-up power systems to small micro watt solutions portable fuel cells have been widely demonstrated but lacking widespread commercial exploitation. This paper presents the prospects of portable fuel cells which resulted from a Delphi study. [Copyright &y& Elsevier]

Abstract: The small PEMFC stack to be integrated with miniaturized fuel reformer is usually operated under very poor operating conditions such as low relative humidity and reformed gas conditions including trace amounts of CO. Hence, for the stable operation of the stack under such real conditions, the effect of reactants feeding method and stack operating conditions such as stack temperature and gas humidity were experimentally investigated and the optimal operating strategy was suggested. The external-manifolds configuration was not efficient compared to the internal-manifolds due to their poor water management. The fuel introduction to the stack by opposite directions between air and hydrogen enhanced the stack stability, particularly under low humidified conditions, by enhancing water exchange between the two fuel streams. Even 10ppm of CO in the reformed gas deteriorated the stack performance seriously under low stack temperature or low relative humidity conditions. Hence, for the stable operation of the small PEMFC stack, particularly under practical operating conditions, air-bleeding method seems to be a promising strategy. [Copyright &y& Elsevier]

Abstract: The start up behaviour of PEM fuel cells below 0°C is one of the most challenging tasks to be solved before commercialisation. The automotive industry started to develop solutions to reduce the start up time of fuel cell systems in the middle of the nineties. The strategies varied from catalytic combustion of hydrogen on the electrode catalyst to fuel starvation or external stack heating via cooling loops to increase the stack temperature. Beside the automotive sector the cold start ability is as well important for portable PEMFC applications for outdoor use. But here the cold start issue is even more complicated, as the fuel cell system should be operated as passive as possible. Below 0°C freezing of water inside the PEMFC could form ice layers in the electrode and in the gas diffusion layer. Therefore the cell reaction is limited or even inhibited. Product water during the start up builds additional barriers and leads to a strong decay of the output power at isothermal operating conditions. In order to find out which operational and hardware parameters affect this decay, potentiostatic experiments on single cells were performed at isothermal conditions. These experiments comprise investigations of the influence of membrane thickness and different GDL types as well as the effect of gas flow rates and humidification levels of the membrane. As pre stage to physical based models, empirical based prediction models are used to gain a better understanding of the main influence parameters during cold start. The results are analysed using the statistical software Cornerstone 4.0. The experience of single cell investigations are compared to start up behaviour of portable fuel cell stacks which are operated in a climate chamber at different ambient temperatures below 0°C. Additional flow sharing problems in the fuel cell stack could be seen during cold start up experiments. [Copyright &y& Elsevier]

Abstract: Microchannel methanol steam reformer was developed as compact hydrogen supplier for small fuel cells. Two types of reactors comprising fuel vaporizer, heat exchanger, catalytic combustor and steam reformer were integrated and their hydrogen production performance was evaluated. Each basic unit reactor consists of microchannel patterned stainless sheets. Methanol steam reformer was fabricated by coating a commercially available Cu/ZnO/Al2O3 catalyst inside the microchannel reactor. Pt/Al2O3 pellets prepared by incipient wetness method were filled in the cavities of the catalytic combustor. The prepared unit reactors were integrated to have independent two flow paths including catalytic combustor and methanol steam reformer for the supply of reaction heat and for the production of hydrogen, respectively. The comparison of two types of integrated reactors revealed that the fabrication process of reactor such as microchannel patterning, catalyst coating and microchannel bonding can significantly affect the reactor performance. In this work, the superior fuel processor, which has the dimensions of 60mm×40mm×30mm, produced 450ml/min dry reformate including 73.3% H2, 24.5% CO2 and 2.2% CO at 250°C which can produce power output of 59W. [Copyright &y& Elsevier]

Abstract: An integrated microchannel methanol processor was developed by assembling unit reactors, which were fabricated by stacking and bonding microchannel patterned stainless steel plates, including fuel vaporizer, heat exchanger, catalytic combustor and steam reformer. Commercially available Cu/ZnO/Al2O3 catalyst was coated inside the microchannel of the unit reactor for steam reforming. Pt/Al2O3 pellets prepared by ‘incipient wetness’ were filled in the cavity reactor for catalytic combustion. Those unit reactors were integrated to develop the fuel processor and operated at different reaction conditions to optimize the reactor performance, including methanol steam reformer and methanol catalytic combustor. The optimized fuel processor has the dimensions of 60mm×40mm×30mm, and produced 450sccm reformed gas containing 73.3% H2, 24.5% CO2 and 2.2% CO at 230–260°C which can produce power output of 59Wt. [Copyright &y& Elsevier]