Portable Fuel Cell Systems Research Articles

Investigation of metal alloy catalyst for hydrogen release from sodium borohydride for polymer electrolyte membrane fuel cell application

Sodium borohydride ( NaBH 4 ) is a promising candidate for storing hydrogen in portable fuel cell systems. In order to reduce the volume and cost of the hydrogen generation systems, a high-performance catalyst containing a less precious metal is imperative. In this present investigation, a number of metal alloy compositions are compared in a high throughput screening (HTS) test. In the case of tertiary alloy suspension, the hydrogen release rate of Ru 60 Co 20 Fe 20 shows highest H 2 release ( 26.8 L min - 1 g - 1 ). In the case of the activated carbon fiber (ACF) supported ruthenium catalyst, the reduction process plays an important role in both the particle size of the formed catalyst and consequent enhancement of the hydrogen release rate. Ru 60 Co 20 Fe 20 / ACF showed its highest hydrogen release rate at 41.73 L min - 1 g Ru - 1 . The prepared catalysts were analyzed by XRD and XPS spectra. The suitability of the catalyst in the real proton exchange membrane fuel cell application has been examined and it shows the applicability for common use.

Fabrication and high-speed characterization of SU-8 shrouded two-dimensional microimpellers

In this study, the performance of shrouded two-dimensional microimpellers was measured for application to a micro centrifugal pump used in a portable fuel cell system. Two types of microimpellers were designed, and fabricated by a multi-layer photolithography process using an ultrathick photoresist (SU-8 3000). Microimpellers with a diameter of 10 mm were tested using an air spindle up to maximum rotation speeds determined by the destruction of the microimpellers, which are 350 000 rpm for a purely-radial-outlet blade impeller and 450 000 rpm for a backward blade impeller. The purely-radial-outlet blade impeller showed a higher pressure rise—2.8 kPa at 150 000 rpm, 5.1 kPa at 200 000 rpm and 12.5 kPa at 300 000 rpm. The measured performance satisfies the requirement of the micro centrifugal pump. However, the measured pressure rises are roughly half of the simulated values. The influence of the radial clearance and height difference between the impeller and the diffuser was investigated using an electromagnetic motor and impellers with a diameter of 16 mm. Against expectation, a better pumping performance was obtained with a larger tip clearance, and the height difference did not affect the pumping performance. These unexpected results suggest that the tip clearance and the clearance between the impeller shroud and the stationary housing act as a diffuser.

Self-assembled PEMs for Direct Formic Acid Fuel Cells

Direct liquid fuel cells have attracted intensive research because of the promised application in portable fuel cell systems. Liquid fuel such as formic acid crossover through the proton exchange membranes (PEMs, e.g. NafionTM membrane) is one of the major obstacles that currently prevent the widespread commercial applications of direct liquid fuel cell. In this paper, PEMs constructed by self-assembling metal nanoparticles on NafionTM membranes were prepared to probe the direct formic crossover behaviors. The results show that the fuel crossover has a remarkable decrease comparing with the original PEMs. This satisfactory performance gives the self- assembled PEMs a promised prospect in direct liquid fuel cells.

Microstructured Fuel Processors for Fuel-Cell Applications

Microstructured reactors are being developed at IMM for the processing of various fuels to provide hydrogen for mobile and portable fuel-cell systems. The key feature of the systems is the integrated-plate heat-exchanger technology, which allows for thermal integration of several functions in a single device. For example, steam reforming may be coupled with exothermic reactions in separate flow-paths of a heat exchanger. Catalyst coatings are also under development for numerous reactions, such as propane steam reforming, methanol steam reforming, catalytic combustion, water-gas shift, and preferential oxidation of carbon monoxide. These catalysts are being investigated in specially developed testing reactors. Reactors and complete fuel processors are being tested up to 5 kW power output of the corresponding fuel cell.

Hydrogen and fuel cells: emerging technologies and applications

A hydrogen economy, in which this one gas provides the source of all energy needs, is often touted as the long-term solution to the environmental and security problems associated with fossil fuels. However, before hydrogen can be used as fuel on a global scale we must establish cost effective means of producing, storing, and distributing the gas, develop cost efficient technologies for converting hydrogen to electricity (e.g. fuel cells), and creating the infrastructure to support all this. Sorensen is the only text available that provides up to date coverage of all these issues at a level appropriate for the technical reader. The book not only describes the 'how' and 'where' aspects of hydrogen fuels cells usage, but also the obstacles and benefits of its use, as well as the social implications (both economically and environmental). Written by a world-renowned researcher in energy systems, this thoroughly illustrated and cross-referenced book is an excellent reference for researchers, professionals and students in the field of renewable energy. It includes updated sections on PEM fuel cells, Molten carbonate cells, Solid Oxide cells and Biofuel cells. It includes updated material to reflect the growing commercial acceptance of stationary and portable fuel cell systems, while also recognizing the ongoing research in automotive fuel cell systems. This title includes a new example of a regional system based on renewable energy sources reflects the growing international attention to uses of renewable energy as part of the energy grid. This title includes examples of life cycle analysis of environmental and social impacts.

Hydrogen production with integrated microchannel fuel processor using methanol for portable fuel cell systems

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/Al 2O 3 catalyst inside the microchannel reactor. Pt/Al 2O 3 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 60 mm × 40 mm × 30 mm, produced 450 ml/min dry reformate including 73.3% H 2, 24.5% CO 2 and 2.2% CO at 250 °C which can produce power output of 59 W.

Hydrogen production with integrated microchannel fuel processor for portable fuel cell systems

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/Al 2O 3 catalyst was coated inside the microchannel of the unit reactor for steam reforming. Pt/Al 2O 3 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 60 mm × 40 mm × 30 mm, and produced 450sccm reformed gas containing 73.3% H 2, 24.5% CO 2 and 2.2% CO at 230–260 °C which can produce power output of 59 Wt.

Statistic analysis of operational influences on the cold start behaviour of PEM fuel cells

For portable fuel cell systems a multitude of applications have been presented over the past few years. Most of these applications were developed for indoor use, and not optimised for outdoor conditions. The key problem concerning this case is the cold start ability of the polymer electrolyte membrane fuel cell (PEMFC). This topic was first investigated by the automotive industry, which has the same requirements for alternative traction systems as for conventional combustion engines. The technical challenge is the fact that produced water freezes to ice after shut-down of the PEMFC and during start-up when the temperature is below 0 °C. To investigate the basic cold start behaviour isothermal, potentiostatic single cell experiments were performed and the results are presented. The cold start behaviour is evaluated using the calculated cumulated charge transfer through the membrane which directly corresponds with the amount of produced water in the PEMFC. The charge transfer curves were mathematically fitted to obtain only three parameters describing the cold start-up with the cumulated charge transfer density and the results are analysed using the statistical software Cornerstone 4.0. The results of the statistic regression analyses are used to establish a statistic-based prediction model of the cold start behaviour which describes the behaviour of the current density during the experiment. The regression shows that the initial start current mainly depends on the membrane humidity and the operation voltage. After the membrane humidity has reached its maximum, the current density drops down to zero. The current decay also depends on the constant gas flows of the reactant gases. Ionic conductivity of the membrane and charge transfer resistance were investigated by a series of ac impedance spectra during potentiostatic operation of the single cell at freezing temperatures. Cyclic voltammetry and polarisation curves between cold start experiments show degradation effects by ice formation in the porous structures which lead to significant performance loss.

Structure and characterization of a planar normally closed bulk-micromachined piezoelectric valve for fuel cell applications

Microfuel cell systems require microvalves that are chemically tolerant of hydrogen, have thermally insensitive activation mechanisms, and tight geometric constraints. A planar bulk-micromachined piezoelectric valve for portable fuel cell system is proposed. The actuating diaphragm and the valve seat are etched on silicon wafers. A piezoelectric bimorph disc is glued to the actuating diaphragm to lift the diaphragm and open the valve. The pressure differential between the valve chamber and the outlet and the initial pressure caused by the deformed tethers are employed to increase the sealing force. The actuating device with four Z-tethers attached to the actuating diaphragm is thermally insensitive and can reduce thermally induced deflection at the center and avoid clamping effect at circumferential edge. The proposed actuating diaphragm with Z-tethers shows good thermal stability and excellent actuating performance through the finite element method (FEM) analyses. The prototype valve of 20 mm in diameter and 2 mm thick was fabricated and tested as a regulator. Using compressed air, the flow characteristics for the prototype valve were measured at different inlet pressure and elevated air temperature. The design, fabrication, simulation and characterization of the prototype valve are described.

Microvalve to Control Fuel for Portable Fuel Cells

This paper describes a microvalve which is actuated by electrostatic force for the flow control of fuel in portable direct methanol fuel cell systems. The microvalve is fabricated by using standard MEMS fabrication techniques including photolithography, wet etching, thin film deposition and anodic bonding. The microvalve is equipped with a novel pressure-balance mechanism for normally-closed operation against pressurized fuel. The pressure-balance mechanism is composed of a pressure-balance tank whose pressure is adjusted to the same pressure as inlet by a soft corrugated diaphragm. This balanced pressure pushes the boss, which is supported by a soft actuator diaphragm, to close the microvalve, enabling a low driving voltage operation. By applying 100 Vdc, the microvalve controlled the flow rate of methanol up to maximum flow rate of 100 μl/min at an inlet pressure of 40 kPa. The microvalve is expected to miniaturize the fuel delivery system, and eventually increase the practical energy density of portable fuel cell systems.

Portable fuel cell systems for America’s army: technology transition to the field

The US Army Communications, Electronics Research Development and Engineering Center (CERDEC) envisions three thrust areas for portable fuel cell systems for military applications. These areas include soldier power (<500 W), sensor power (0–100 W), and auxiliary power units or APUs (0.5–10 kW). Soldier and sensor fuel cell systems may be man-portable/backpackable while APUs could be employed as squad battery chargers or as ‘Silent Watch’ APUs where low signature (acoustic, thermal, etc.) operation is a requirement. The Army’s research and development efforts are focusing on methods of either storing or generating hydrogen on the battlefield. Hydrogen storage technology is considered critical to small military and/or commercial fuel cell systems, and is being pursued in a host of commercial and government programs. CERDEC, in a joint effort with the Army Research Office (ARO) and the Defense Advanced Research Projects Agency (DARPA), is developing several promising hydrogen generating technologies. The goal of this program is a safe, reliable hydrogen source that can provide rates up to 100 W with an energy density of greater than 1000 Wh/kg. For larger fuel cell units (>500 W), it is imperative that the fuel cell power units be able to operate on fuels within the military logistics chain [DOD 4140.25-M, DOD Directive 4140.25 (1993)]. CERDEC is currently conducting research on catalysts and microchannel fuel reformers that offer great promise for the reforming of diesel and JP-8 fuels into hydrogen. In addition to research work on PEM fuel cells and enabling technologies, the Army is also conducting research on direct methanol and solid oxide fuel cells, and combined heat and power applications utilizing new high temperature fuel cells.

System Control and Efficiency Measurements for a Portable High Temperature PEM Fuel Cell System with Onboard Fuel Processor

System Control and Efficiency Measurements for a Portable High Temperature PEM Fuel Cell System with Onboard Fuel Processor

QinetiQ, Voller team up for portable fuel cells

In the UK, QinetiQ has signed a licensing agreement with Voller Energy, a manufacturer of portable fuel cell systems, to manufacture QinetiQ’s 2 We tubular PEM fuel cell technology. Visit www.re-focus.net for the latest renewable energy news

A microfabricated suspended-tube chemical reactor for thermally efficient fuel processing

We present a suspended-tube chemical reactor/heat exchanger for high-temperature fuel processing in micro energy conversion systems, primarily for hydrogen production in portable fuel cell systems. This reactor, designed to thermally isolate a high-temperature reaction zone, consists of four free-standing silicon nitride tubes comprising two independent U-shaped fluidic channels. Portions of the tubes are encased in silicon to enable heat exchange between the fluids in these channels. A thin-film platinum resistor is embedded for localized heating and temperature sensing. This paper describes the design and fabrication process for the MEMS fuel processor. Fluidic testing, thermal characterization up to 825/spl deg/C, and preparation of catalyst washcoats in the reactor microchannels are discussed. In addition, results from catalytic autothermal butane combustion and ammonia cracking in the reactor are presented.

Palcan unveils fuel cell scooter, selected by Voller Energy

Vancouver-based Palcan Fuel Cells has successfully integrated its 2 kWe PEM fuel cell stack system into a fuel cell powered scooter, designed specifically to address the world’s need for a low-end mass transport vehicle. The company’s PC-150 fuel cell stack has also been selected by UK-based Voller Energy as the power source in the latter’s VE100 portable fuel cell system. This is a short news story only. Visit www.re-focus.net for the latest renewable energy industry news.

Fuel processing for transportation and portable fuel cell systems

Fuel processing for transportation and portable fuel cell systems

Portable fuel cell systems

Three types of portable fuel-cell systems were developed. These systems consist of a small fuel-cell stack, two hydrogen cylinders, and a power converter. Each system is complete in one cabinet. Each system supplies 200-250 W of power for more than 6 hours using the two 6.7-liter hydrogen cylinders. These systems generate power quietly and cleanly, and are thus suitable as indoor emergency power sources for various types of equipment.

Portable Solid Oxide Fuel Cell System Integration and Demonstration

Portable Solid Oxide Fuel Cell System Integration and Demonstration

Portable fuel cell systems

Portable fuel cell systems

Portable fuel cell systems

Portable fuel cell systems