Fuel Cell Power Source Research Articles

Assessment of Alane as a hydrogen storage media for portable fuel cell power sources

Aluminum hydride (AlH3), often referred to as Alane, is examined as a hydrogen storage media for fuel cell-based portable power applications. The hydrogen storage capacity and thermally activated dehydrogenation of Alane makes it a candidate as a hydrogen storage material for portable fuel cell systems. In this study, Alane is found to provide a high gravimetric and volumetric energy density for portable power applications; however, there are significant challenges that must be addressed. These challenges include proper thermal control of the Alane dehydrogenation, fuel utilization and storage/treatment of excess hydrogen, and most importantly safety measures to prevent failure from an over-pressurization caused by excess hydrogen.

Novel High Step-Up DC–DC Converter for Fuel Cell Energy Conversion System

A novel high step-up dc-dc converter for fuel cell energy conversion is presented in this paper. The proposed converter utilizes a multiwinding coupled inductor and a voltage doubler to achieve high step-up voltage gain. The voltage on the active switch is clamped, and the energy stored in the leakage inductor is recycled. Therefore, the voltage stress on the active switch is reduced, and the conversion efficiency is improved. Finally, a 750-W laboratory prototype converter supplied by a proton exchange membrane fuel cell power source and an output voltage of 400 V is implemented. The experimental results verify the performances, including high voltage gain, high conversion efficiency, and the effective suppression of the voltage stress on power devices. The proposed high step-up converter can feasibly be used for low-input-voltage fuel cell power conversion applications.

A proposed new energy source: The “mixing energy” of engine exhaust gas

One potential source of useful energy that seems to be unrecognized and overlooked is the “entropy of mixing” of engine exhaust gases with the atmosphere. In particular, exhaust gases from combustion engines typically contain carbon dioxide at concentrations 250 times greater than in the atmosphere and have an oxygen concentration that is typically less than one-tenth the oxygen concentration in the atmosphere. Fuel cell power sources can produce exhaust gases containing CO2 concentrations 1000 times greater than in the air. Currently, engine exhaust gases are simply ejected into the atmosphere where they spontaneously mix with the air, and the potential to do useful work is lost. Rather than discarding combustion gases into the atmosphere, it is possible—in principle—to exploit the entropy of mixing to produce useful work. However, the energy that could potentially be produced by mixing exhaust gases with air is at least an order of magnitude less than the energy released by combustion of the fuel. Exploiting this energy source is likely to prove difficult and expensive with current technology, but ultimately, this “mixing energy” could be an incremental energy source to be finessed from combustion engines, kilns, furnaces, and fuel cell power sources. This article proposes conceptual designs for “mixing engines” that could augment the power output of a diesel engine by as much as 3.0% or augment the power output of a fuel cell power plant by 3.5%.

Methanol decomposition fuel processor for portable power applications

A new fuel processor approach for portable fuel cell power sources significantly improves upon microreformers by overcoming the difficulties with heat deficiencies and contaminants in the product hydrogen. Instead of reforming, the processor uses methanol decomposition to enable the byproduct, carbon monoxide (CO), to be used as the heat source. A hydrogen permselective membrane segregates the CO for combustion in an integrated burner, maximizes the decomposition conversion, and provides pure hydrogen for a fuel cell. Discharging the CO-rich retentate through an ejector to draw combustion air into the burner greatly simplifies the system. High and stable hydrogen yields are attained with optimized catalysts and fuel compositions. The resultant simple, efficient, and self-heating processor produces 85% of the hydrogen content of the fuel. A 20 W autonomous power source based on this novel fuel processor demonstrates a fuel energy density >1.5 Wh g−1(electrical), nearly twice as high as microreformer power sources.

High-Energy Portable Fuel Cell Power Sources

The energy density requirement for portable power sources is ever on the increase. Technology companies are working to find ways to enhance the run time of mobile devices such as portable computers, MP3 players, and mobile phones.

Synthesis and high catalytic properties of mesoporous Pt nanowire array by novel conjunct template method

A novel conjunct template method for fabricating mesoporous Pt nanowire array through direct current (DC) electrodeposition of Pt into the pores of anodic aluminum oxide (AAO) template on Ti/Si substrate from hexagonal structured lyotropic liquid crystalline phase is demonstrated in this paper. The morphology and structure of as-prepared Pt nanowire array are characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic properties of Pt nanowire array for methanol are also investigated in detail. The results indicate that Pt nanowire array has the unique mesoporous structure of approximate 40–50 nm in diameter, which resulted in the high surface area and greatly improved electrocatalytic activity for methanol. The mesoporous Pt nanowire array synthesized by the new conjunct template method has a very promising application in portable fuel cell power sources.

Operating Characteristics of a Direct Methanol Fuel Cell and Li-ion Battery Hybrid Power Sources

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A New Palladium-Based Catalyst for Methanol Steam Reforming in a Miniature Fuel Cell Power Source

A novel palladium-based catalyst has been developed for use in a miniature fuel cell power source for portable applications, incorporating a polymer electrolyte membrane (PEM) fuel cell. Hydrogen, which is the fuel for the cell, is produced in a ceramic microreactor via the catalytic reaction of methanol steam reforming: CH3OH + H2O → 3H2 + CO2. The need for a new catalyst in this application is driven by the limitations of traditional particulate catalysts based on copper oxide, zinc oxide and alumina (Cu-Zn-Al catalysts), which have low thermal stability and high sensitivity towards air and condensing steam. These features result in a declining activity and mechanical integrity of Cu-Zn-Al catalysts under the frequent start-stop conditions typical of the operational mode of the miniature power source. The new Pd-based catalyst has activity and selectivity similar to those of Cu-Zn-Al catalysts, but is more durable and stable under the duty cycle conditions of a portable power source. In the microreformer, the catalyst is washcoated directly on the walls of the steam reforming section, providing favourable conditions for efficient heat transfer between the heat-generating catalytic combustion section of the microreformer and its heat-consuming steam reforming section.

Nanowire‐Based High‐Performance “Micro Fuel Cells”: One Nanowire, One Fuel Cell

Numerous investigations have resulted in novel nanodevices and applications based on nanomaterials; examples include biosensors, resonators, transistors, in situ real-time biomedical monitoring and detection, and optoelectronics. Unfortunately, such devices currently cannot work without an external power supply. A nanometer-sized power source would overcome this problem; development of such a ‘‘nano’’ power source is therefore urgently needed. Among the increasing number of studies on nanodevices, several research groups have reported research into power sources at the nanoscale. Fuel cells have many advantages over conventional batteries, including more rapid recharging and much higher energy storage density. It is expected that fuel cells of sizes in the nanometer range will be accomplished eventually. In the current study, we present the first micrometer-sized fuel cell using Nafion/poly(vinyl pyrrolidone) (PVP) nanowires (NPNWs) as the electrolyte. A ‘‘micro fuel cell’’ was monolithically integrated on a silicon substrate and consisted of NPNWs, PtRu/C and Pt/C catalysts, two outleading electrodes, methanol as fuel, and air as oxidant (see Fig. 1). The performance of the micro fuel cell was orders of magnitude higher than that of a traditional fuel cell power source. The developed micro fuel cell may be integrated

Design of a Wide Input Range DC–DC Converter With a Robust Power Control Scheme Suitable for Fuel Cell Power Conversion

In this paper, an analysis and design of a wide input range dc-dc converter is proposed along with a robust power control scheme. The proposed converter and its control are designed to be compatible with a fuel cell power source, which exhibits 2 : 1 voltage variation as well as a slow transient response. The proposed approach consists of two stages: a three-level boost converter stage cascaded with a current-fed two-inductor boost converter topology, which has a higher voltage gain and provides galvanic isolation from the input source. The function of the front-end boost converter stage is to maintain a constant voltage at the input of the cascaded dc-dc converter to ensure optimal performance characteristics and high efficiency. At the output of the first boost converter, a battery or ultracapacitor energy storage is connected to handle slow transient response of the fuel cell (200 W/min). The robust features of the proposed control system ensure a constant output dc voltage for a variety of load fluctuations, thus limiting the power being delivered by the fuel cell during a load transient. Moreover, the proposed configuration simplifies power management and can interact with the fuel cell controller. Simulation and the experimental results confirm the feasibility of the proposed system.

Energy Management Fuzzy Logic Supervisory for Electric Vehicle Power Supplies System

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper introduces an energy management strategy based on fuzzy logic supervisory for road electric vehicle, combining a fuel cell power source and two energy storage devices, i.e., batteries and ultracapacitors. The control strategy is designed to achieve the high-efficiency operation region of the individual power source and to regulate current and voltage at peak and average power demand, without compromising the performance and efficiency of the overall system. A multiple-input power electronic converter makes the interface among generator, energy storage devices, and the voltage dc-link bus. Classical regulators implement the control loops of each input of the converter. The supervisory system coordinates the power flows among the power sources and the load. The paper is mainly focused on the fuzzy logic supervisory for energy management of a specific power electronic converter control algorithm. Nevertheless, the proposed system can be easily adapted to other converters arrangements or to distributed generation applications. Simulation and experimental results on a 3-kW prototype prove that the fuzzy logic is a suitable energy management control strategy. </para>

An integrated MEMS infrastructure for fuel processing: hydrogen generation and separation for portable power generation

Portable fuel cells are an enabling technology for high efficiency and ultra-high density distributed power generation, which is essential for many terrestrial and aerospace applications. A key element of fuel cell power sources is the fuel processor, which should have the capability to efficiently reform liquid fuels and produce high purity hydrogen that is consumed by the fuel cells. To this end, we are reporting on the development of two novel MEMS hydrogen generators with improved functionality achieved through an innovative process organization and system integration approach that exploits the advantages of transport and catalysis on the micro/nano scale. One fuel processor design utilizes transient, reverse-flow operation of an autothermal MEMS microreactor with an intimately integrated, micromachined ultrasonic fuel atomizer and a Pd/Ag membrane for in situ hydrogen separation from the product stream. The other design features a simpler, more compact planar structure with the atomized fuel ejected directly onto the catalyst layer, which is coupled to an integrated hydrogen selective membrane.

A MEMS-based reformed methanol fuel cell for portable power

A reformed methanol fuel cell system is described. The use of a microfluidic fuel processor enables component scaling and integration sufficient to achieve power sources in the 2–10 W regime that are competitive in size and energy density in comparison to alternative power sources. While carbon monoxide tolerance of proton conducting membranes has typically limited the performance of reformed methanol fuel cells, phosphoric-acid-doped polybenzimidazole (PBI) membranes have been tested that exhibit no degradation for carbon monoxide >2% mole fraction. Further benefits of the PBI membrane include operating temperature of 150–200 °C, and no need for water to assist protonic conduction. As a result, a chemically and thermally robust fuel cell power source is realized. Results of methanol steam reforming and catalytic combustor heating elements formed in a silicon MEMS platform, and PBI membrane performance with reformate fuel feed will be discussed.

Life-cycle assessment of diesel, natural gas and hydrogen fuel cell bus transportation systems

The Sustainable Transport Energy Programme (STEP) is an initiative of the Government of Western Australia, to explore hydrogen fuel cell technology as an alternative to the existing diesel and natural gas public transit infrastructure in Perth. This project includes three buses manufactured by DaimlerChrysler with Ballard fuel cell power sources operating in regular service alongside the existing natural gas and diesel bus fleets. The life-cycle assessment (LCA) of the fuel cell bus trial in Perth determines the overall environmental footprint and energy demand by studying all phases of the complete transportation system, including the hydrogen infrastructure, bus manufacturing, operation, and end-of-life disposal. The LCAs of the existing diesel and natural gas transportation systems are developed in parallel. The findings show that the trial is competitive with the diesel and natural gas bus systems in terms of global warming potential and eutrophication. Emissions that contribute to acidification and photochemical ozone are greater for the fuel cell buses. Scenario analysis quantifies the improvements that can be expected in future generations of fuel cell vehicles and shows that a reduction of greater than 50% is achievable in the greenhouse gas, photochemical ozone creation and primary energy demand impact categories.

High-Efficiency DC-DC Converter With High Voltage Gain and Reduced Switch Stress

In this paper, a high-efficiency dc-dc converter with high voltage gain and reduced switch stress is proposed. Generally speaking, the utilization of a coupled inductor is useful for raising the step-up ratio of the conventional boost converter. However, the switch surge voltage may be caused by the leakage inductor so that it will result in the requirement of high-voltage-rated devices. In the proposed topology, a three-winding coupled inductor is used for providing a high voltage gain without extreme switch duty-cycle and enhancing the utility rate of magnetic core. Moreover, the energy in the leakage inductor is released directly to the output terminal for avoiding the phenomenon of circulating current and the production of switch surge voltage. In addition, the delay time formed with the cross of primary and secondary currents of the coupled inductor is manipulated to alleviate the reverse-recovery current of the output diode. It can achieve the aim of high-efficiency power conversion. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage drift problem of the power source under the variation of loads. Some experimental results via an example of a proton exchange membrane fuel cell power source with 250-W nominal rating are given to demonstrate the effectiveness of the proposed power conversion strategy

Performance of battery-powered airships

The performance of airships using battery and fuel cell power sources for propulsion is investigated. A parametric analysis is used to determine the mass breakdown of several, helium-filled, pressurized, non-rigid design concepts, in order to estimate maximum power source mass. It is concluded that the use of existing lithium-ion batteries permits airships with volumes &gt; 7000 m to attain airspeeds in excess of 86 km/h, or endurances in excess of 24 h. Further refinement of the parametric analysis and improved drag estimation methods are recommended.

High-efficiency single-stage bidirectional converter with multi-input power sources

A multiple-input, single-stage bidirectional converter is proposed. It takes a three-winding coupled inductor as the main component of energy transmission, and utilises only two switches to accomplish the multi-input mechanism. Depending on the switching conditions, the circuit can be operated at discharge, charge and alone states. The winding voltage in the high-voltage side of the coupled inductor is manipulated to further increase the corresponding voltage gain, a strategy that is superior to one in the conventional coupled-inductor. This topology is useful for low-power applications. In addition, all switches and diodes have favourable voltage-clamping effects so that the voltage spikes caused by the leakage-inductor energy can be alleviated effectively, and reverse-recovery currents within diodes can be reduced, because the leakage inductor has limited capability to handle quick current changes. There is also a low-voltage-type charge circuit with no increase in additional circuit elements. This helps -to avoid power losses that arise from multistage conversions in traditional auxiliary power systems. This strategy also utilises the synchronous rectification technique to further decrease conduction losses. Numerical simulations and experimental results via examples of a proton exchange membrane fuel cell power source and a traditional battery module are given to demonstrate the effectiveness of the proposed power conversion strategy.

Hardware-in-the-Loop testing platform for distributed generation systems

The rapid validation of the expected performance of distributed generation installations is a critical step in the design process. However, the plethora of distributed generator types and the uniqueness of the load characteristics make the testing quite challenging. This paper introduces an original approach to Hardware-in-the-Loop simulation aimed to evaluate the performance and suitability of distributed generation installations. The approach is based on the Virtual Test Bed real-time simulator and enables rapid evaluation of the capability of a power source to match the power demand and dynamic properties of the local load by testing the actual power source in a synthetic load environment. The same platform can also be used to validate a simulation model of the fuel cell power source. The procedure is illustrated by a specific example of a fuel cell power source.

Template preparation of Pt–Ru and Pt nanowire array electrodes on a Ti/Si substrate for methanol electro-oxidation

Pt and Pt–Ru nanowire array electrodes were obtained by dc (direct current) electrodeposition of Pt and Ru into the pores of an anodic aluminum oxide (AAO) template on a Ti/Si substrate. Transmission electron microscope (TEM) examination showed all the nanowires had a uniform diameter of about 30 nm. The brush shaped Pt and Pt–Ru nanowire array electrodes could be seen clearly by scanning electron microscope. Pt and Pt–Ru nanowire array electrodes gave the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure. The electro-oxidation of methanol on these electrodes was investigated at room temperature using cyclic voltammetry. The results demonstrated that the alloy nanowire array electrode was catalytically more active than a pure platinum nanowire array electrode and the Pt–Ru nanowire array electrode may have good potential for applications in portable fuel cell power sources.

High-efficiency DC∕DC converter with high voltage gain

A high-efficiency converter with high voltage gain applied to a step-up power conversion is presented. In the proposed strategy, a high magnetising current charges the primary winding of the coupled inductor, and the clamped capacitor is discharged to the auxiliary capacitor when the switch is turned on. In contrast, the magnetising current flows continuously to boost the voltage in the secondary winding of the coupled inductor, and the voltages across the secondary winding of the coupled inductor, the clamped capacitor and the auxiliary capacitor are connected in series to charge the output circuit. Thus, the related voltage gain is higher than in conventional converter circuits. Moreover, this scheme has soft-switching and voltage-clamped properties, i.e. the switch is turned on under zero-current switching and its sustainable voltage is comparatively lower than the output voltage, so that it can select low-voltage low-conduction-loss devices and there are no reverse-recovery currents within the diodes in this circuit. In addition, closed-loop control methodology is utilised in the proposed scheme to overcome the voltage drift problem of the power source under the load variations. As a result, the proposed converter topology can promote the voltage gain for a conventional boost converter with a single inductor, and deal with the problem of the leakage inductor and demagnetisation of the transformer for a coupled-inductor-based converter. Some experimental results via examples of a proton exchange membrane fuel cell power source and a traditional battery are given to demonstrate the effectiveness of the proposed power conversion strategy.