Portable Fuel Cell Systems Research Articles

High Power Density Fuel Cell Systems for Portable Electric Generators

It is of utmost importance to develop light weight fuel cell stacks and find the ways to integrate these to light weight and low temperature fuel cell systems. In order to meet the future energy demands non-polluting, compact, transportation and portable applications are required. Current energy systems have lower power density (kW/kg) resulting in optimized power only at higher overall weight. Systems with higher power density demands higher initial setup costs. Low temperature PEMFC, on other hand offers various advantages but fails to provide the required output without exceeding the weight of the fuel cell stack and thereby fuel cell systems. A fuel cell system consists of a fuel cell stack, compressed gas in cylinder, pressure relief valves, regulators, water pump, sensors and cvm. A fuel cell stack is the main component consisting of one of the devices with maximum weight and cost contribution. In such case, developing a system with stack having higher power density reduces overall weight and increases power density (kW/kg). PowerUP Energy Technologies has developed light weight fuel cell stack to achieve higher power density. Experiments considering flow field designs, recirculation strategy, different anode configuration has been a subject of study. Dead-end anode, closed cathode configuration of fuel cell stack further improves fuel utilization. Recirculation line of hydrogen if further added can improve in overall fuel utilization. Counter flow arrangement for reactant distribution further removes the necessity of humidifying the gases. This result in removal of humidifiers and thereby reducing the weight of the fuel cell system in total. Portable fuel cell systems have flexibility for ease in transportation and stationery solutions. Furthermore, lighter fuel cell stacks add advantage for higher output power at lower overall weights. This stack developed is further optimized with improved flow field designs and design of manifold. These fuel cell stacks are used in PowerUP’s portable fuel cell electric generators that are more efficient and sustainable than the currently used fossil fuel based solutions.

Easy fabrication of a novel electro-spun PVDF-g-C3N4-Pd nanocomposite material as improved anode electrocatalyst for direct alcohol fuel cell

In this study, we account a simple, effortless one-step electrospinning process to prepare high-performance poly(vinylidene fluoride)-graphitic carbon nitride/palladium (PVDF-g-C3N4-Pd) nanocomposite fibers (NCFs) for methanol and ethanol electro-oxidation process. As-synthesized PVDF-g-C3N4-Pd NCFs were examined to ensure its physicochemical assets such as surface morphology, structural geometry, elemental structure, and thermal stability. The acquired long and continuous NCFs morphology with elemental and structural results authenticates the successful fabrication of PVDF-g-C3N4-Pd NCFs. Holding to the substantial synergistic effects of each component in the PVDF-g-C3N4-Pd NCFs electrocatalyst displays forward peak current densities as high as 0.53 mA/cm2 and 10.50 mA/cm2 for methanol and ethanol electro-oxidation reactions, respectively, far outperforming than PVDF-g-C3N4 NCFs electrocatalyst. Also, PVDF-g-C3N4-Pd NCFs exhibit reliable mechanical stability and as well as thermal stability and could possibly open up an excellent high-performance portable fuel cell system for DAFCs application.

Jet Fuel Desulfurization for Portable Solid Oxide Fuel Cell Applications

Solid oxide fuel cells (SOFCs) are capable of utilizing energy-dense hydrocarbon fuels such as jet fuels for highly efficient power generation. Currently, a major challenge for using the jet fuel (e.g. JP-8) in SOFC power systems is its sulfur content, which poisons the SOFC anode and fuel reforming catalysts. The reduction of sulfur to <1 ppmw is generally desired and required to ensure reliable SOFC operation. Our research aimed at developing a lightweight, compact desulfurization reactor for onboard application in portable fuel cell systems. After several versions of improvements, including the use of a selective laser sintering (SLS) 3D printing method, we have developed a miniature one-piece stainless-steel reactor which can remove >99.5% sulfur in the jet fuel with the final sulfur concentrations close to a sub-ppm level. The reactor could be adapted to the desulfurization of other liquid hydrocarbon fuels such as gasoline and diesel.

Window gasketing for self humidified H2|O2 and H2 |air polymer electrolyte membrane fuel cells fed dry gases

Abstract Polymer electrolyte fuel cells (PEFCs) are often formed with the cation exchange polymer Nafion® sandwiched between two electrodes and run on humidified H2 and O2 gases fed to electrodes held in tight gaskets. The tight gasket opening is only slightly wider than the electrodes. When run on dry H2 and O2, tight gasketed cells fail as water becomes imbalanced across the membrane. Here, the cathode is framed by a narrow perimeter washer so the cathode is centered in a generous Nafion window and surrounded by a thin (≈ 0.05 cm) reservoir volume. Unlike tight gasketed cells, water generated at the cathode crosses the large Nafion window to sustain self humidification at 0.522 V on dry H2 and O2 at 70, 37, and 25 oC and dry H2 and air at 37 oC for 1 atm pressure and moderate flow rates. Built from commercial components, window gasketed PEFCs provided stable, steady state current and power at 0.5 V for >170 h on dry H2 and oxidant. Tight gaskets always fail to yield self humidification whereas window gaskets enable effective self humidification on dry gases. A sketch is provided of how the Nafion window enhances water flux from the cathode. Because humidification hardware can be eliminated, window gasketed PEFCs may be especially useful in portable fuel cell systems. Submitted In Honor of Andrej Wieckowski.

Portable Fuel Cell System Emulator as a Hardware-in-Loop Setup

PEM (Proton exchange membrane) fuel cell is an electrochemical device that generates electricity along with heat and water as by-products. Hence, it is a clean source of energy for stationary as well as automotive applications. The fuel cell is being researched and experimented for its applications, durability, and efficiency. An experimental setup needs expensive fuel cell or stack, measuring instruments, programmable load, reactant gas cylinders, humidifier, and heater. The use of hydrogen in the laboratory needs safety compliance. Hence, it adds difficulty in making experimental setups. Moreover, conducting experiments with various membrane sizes, reactant pressure, stack sizes, power densities, fault conditions simulation is difficult with real fuel cell setup. This paper proposes a portable fuel cell system emulator for experimentation and fault testing. The emulator is designed using a Renesas microcontroller RL78. The fuel cell is emulated by a model developed using MATLAB®/Simulink®. The emulator enables configuring stack size, reactant pressures, membrane sizes, gas humidification levels. It helps to conduct various experiments without having expensive fuel cell and associated system components.

Palladium Nanoparticles Supported on Nitrogen and Sulfur Dual-Doped Graphene as Highly Active Electrocatalysts for Formic Acid and Methanol Oxidation.

Optimized designing of highly active electrocatalysts has been regarded as a critical point to the development of portable fuel cell systems with high power density. Here we report a facile and cost-effective strategy to synthesis of ultrafine Pd nanoparticles (NPs) supported on N and S dual-doped graphene (NS-G) nanosheets as multifunctional electrocatalysts for both direct formic acid fuel cell and direct methanol fuel cell. The incorporation of N and S atoms into graphene frameworks is achieved by a thermal treatment process, followed by the controlled growth of Pd NPs via a solvothermal approach. Owning to the unique structural features as well as the strong synergistic effects, the resulting Pd/NS-G hybrid exhibits outstanding electrocatalytic performance toward both formic acid and methanol electro-oxidation, such as higher anodic peak current densities and more exceptional catalytic stability than those of Pd/Vulcan XC-72R and Pd/undoped graphene catalysts. These findings open up new possibility in the construction of advanced Pd-based catalysts, which is conducive to solving the current bottlenecks of fuel cell technologies.

Design and synthesis of palladium/graphitic carbon nitride/carbon black hybrids as high-performance catalysts for formic acid and methanol electrooxidation

Here we report a facile two-step method to synthesize high-performance palladium/graphitic carbon nitride/carbon black (Pd/g-C3N4/carbon black) hybrids for electrooxidizing formic acid and methanol. The coating of g-C3N4 on carbon black surface is realized by a low-temperature heating treatment, followed by the uniform deposition of palladium nanoparticles (Pd NPs) via a wet chemistry route. Owning to the significant synergistic effects of the individual components, the preferred Pd/g-C3N4/carbon black electrocatalyst exhibits exceptional forward peak current densities as high as 2155 and 1720 mA mg−1Pd for formic acid oxidation in acid media and methanol oxidation in alkaline media, respectively, far outperforming the commercial Pd-C catalyst. The catalyst also shows reliable stability, demonstrating that the newly-designed hybrids have great promise in constructing high-performance portable fuel cell systems.

Development and evaluation of portable and wearable fuel cells for soldier use

A number of fuel cell systems have been recently developed to meet the U.S. Army's soldier power requirements. The operation and performance of these systems are discussed based on laboratory results and limited soldier evaluation. The systems reviewed are primarily intended for soldier use in an austere environment with minimum access to resupply and vehicular transportation. These applications require high power and energy density sources that are portable (300 W) and wearable (20 W) to minimize the soldier's load burden. Based on soldier field evaluations of portable fuel cell systems, improvements in power density and compatibility with logistical fuels are required to be successfully deployed. For soldier worn applications, a novel chemical hydride system has shown significant advances in power and energy density while maintaining a small form factor. The use of a high energy dense fuel cartridge (800 Wh kg−1) based on AlH3 (Alane) thermolysis, allows a power density of (28 W kg−1) which offers promising weight savings compared to the standard military batteries.

Hybrid Bi-Cell for Water Independent Direct Methanol Fuel Cells: I. The Passive Fuel Cell

The bi-cell, or pseudo-bipolar electrode, configuration provides a compact cell design that is well suited for small and portable fuel cell systems. This format places two membrane electrode assemblies (MEAs) within a unit. The MEAs’ anodes are mirrored around a common fuel reservoir, or channel, with the anode of the first MEA electrically connected to the cathode of the second. A hybrid bi-cell format using a first acidic proton exchange membrane (PEM) based MEA and a second alkaline anion exchange membrane (AEM) based MEA is put forth. In this scenario, the respective anodes balance faradaic water requirements. A computational approach is used to explore transport in passive direct methanol bi-cell units, which are fueled from a fixed internal reservoir. The merit of the hybrid bi-cell approach is examined by comparing to a passive standard bi-cell unit configuration using two PEM based MEAs. Relative to the standard bi-cell, our model shows that the balanced water stoichiometry of the acidic and alkaline methanol oxidations reactions in the hybrid bi-cell reduces the overall rate/volume of water loss from the fuel reservoir during discharge. This benefit is exploited in our complementary manuscript [K. N. Grew and D. Chu, J. Electrochem. Soc., Accepted for publication].

200 W급 휴대용 연료전지 시스템의 빠른 기동 특성을 위한 수성 가스 반응기 설계

휴대용 연료전지 시스템에 사용되는 연료 개질 시스템은 수소 발생기, 산화기, 일산화탄소 제거기로 구성되어 있다. 휴대용 연료전지 시스템 설계에서 시스템의 기동 시간은 매우 중요한 설계 인자이다. 특히, WGS 반응기의 기동 시간은 리포메이트의 질을 결정하기 때문에 전체 시스템의 기동 시간에 중요한 부분을 차지한다. 본 논문에서는 과량의 일산화탄소가 포함되어 있는 리포메이트 가스를 WGS 반응기에서 산화시킴으로써 WGS 반응기를 가열하는 방법을 사용하였다. 이때 공급되는 공기는 WGS 반응기 입구에 공급되어 기동 초기에 발생되는 과량의 일산화탄소가 함유된 리포메이트 가스를 제거하므로써, 운전 중에 일산화탄소의 과잉 공급없이 안정적으로 리포메이트를 공급함으로써 기동 시간을 단축할 수 있었다. The fuel processor for the portable fuel cell includes multi-step processes consisting of hydrogen generator, heat generator and several CO clean-up stages. One of requirements of the fuel processor for portable fuel cell system is a rapid start-up time. Especially, the warm-up time for WGS reactor is crucial factors for total start-up time. In this paper, active heating protocol, which is the heating protocol of WGS reactor supplied by the oxidation of CO rich reformate in the initial stage, is used for a rapid start-up. The air stream fed to the inlet of WGS reactor rapidly oxidize the CO rich reformate in the WGS reactor. Therefore, CO concentration in reformate quickly stabilized at the desired concentration without CO surges.

내부 가습형 연료전지 스택의 출력전압 왜곡 보상기법

In this paper, the characteristics of portable fuel cell system are introduced and the dynamic response of output voltage of fuel cell stack with internal humidifier is analyzed. When the output of the fuel cell (FC) stack is short-circuited for humidification, the output voltage of the FC stack rapidly drops. In order to maintain the load voltage in the required range, dynamic compensation methods are proposed: 1) installing a capacitor behind the output of the FC stack; 2) utilizing the bi-directional converter. Especially, bi-directional converter is used when short of the FC output is detected or predicted by algorithm using data which is measured during previous three cycles. These methods are simulated by PSIM 9.0, then experimental results from the fuel cell system prototype verify the validity of the proposed methods.

Design and synthesis of Pd–MnO2 nanolamella–graphene composite as a high-performance multifunctional electrocatalyst towards formic acid and methanol oxidation

One great challenge in the development of portable fuel cell systems is to explore novel electrocatalysts with better performance and lower costs. Here we report a facile strategy to fabricate a ternary nanocomposite based on Pd/MnO2 nanolamella-graphene sheets (Pd/MNL/GS) and demonstrate its application as a multifunctional catalyst for both the direct formic acid fuel cell (DFAFC) and direct methanol fuel cell (DMFC). The developed route rationally utilizes graphene as both a green reducing agent in the synthesis of MnO2 nanolamella and a superior supporting material for growing and supporting Pd nanoparticles (NPs). Whether for formic acid oxidation or methanol oxidation, the as-prepared Pd/MNL/GS hybrid has extremely large electrochemically active surface area (ECSA) values and exhibits significantly high forward peak current densities, both of which are nearly 3 times greater than those of the Pd/GS catalyst and 6 times the Pd/Vulcan XC-72 catalyst, revealing that metal Pd can be effectively utilized in the presence of promoter components (MNL and GS). Therefore, such a ternary composite with a sophisticated 2D configuration may bring new design opportunities of high-performance energy conversion devices in the future.

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.

A Portable Fuel Cell System Using Activated Aluminum

A Portable Fuel Cell System Using Activated Aluminum

Modeling, Control, and Integration of a Portable Solid Oxide Fuel Cell System

A novel method for the control and integration of a portable hybrid solid oxide fuel cell (SOFC) system, based on hydrocarbon fuel, is presented in this paper. The balance of plant (BOP) and power electronics systems are treated as separate local units, and local controllers are designed for each unit using established linear techniques. For the control of the integration of these two systems, a higher level supervisory controller is developed. The supervisory controller is an intelligent controller that decides how each of the local controllers should perform based on the status of the respective local units. Two energy buffer units (battery and super-capacitor) have been used for the mitigation of load transients. The supervisory controller is developed using state-flow and fuzzy logic toolbox of Matlab. All the modeling and control is implemented in a Matlab/Simulink environment.

Deactivation characteristics of Ni/CeO2-Al2O3 catalyst for cyclic regeneration in a portable steam reformer

The requirements of process parameters, e.g. air pump flow rate and operational pressure are restricted by confined space and limit the performance of portable steam propane reformer. This makes it difficult to operate a catalyst in the portable reformer under mild operation conditions. Hence, the catalyst can be rapidly deactivated. The deactivation behavior of Ni/CeO2-Al2O3 catalyst was investigated for coke deposition and active metal sintering. Coke formation by the propane pyrolysis was predominantly responsible for deactivation at low reaction temperature. Coke formation can be thermodynamically reduced by elevating the temperature and hence the steam reformer was operated at high temperature to inhibit coke formation. Although the Ni/CeO2-Al2O3 catalyst made small amounts of coke at high temperature, it was deactivated by the encapsulated carbon on active metal during long term operation. Because a compact air pump for catalyst regeneration was available during the shut-down procedure of our portable fuel cell system, the catalysts could be regenerated by coke oxidation. The cyclic oxidation was useful for long term operation. The properties of the used catalyst and the coke were investigated by XRD, NEXAFS, XANES-TPO, TGA and TEM. The Ni/CeO2-Al2O3 catalyst in our portable reformer showed stable activity for steam propane reforming in cyclic oxidation operation for 500h.

Strategies for stationary and portable fuel cell markets

In the future, hydrogen-based stationary and portable fuel cell systems can help supply some or all of the power demanded with additional advantages of higher reliability, lower emissions, independence from the general grid, and cogeneration capability. In order to understand how to prepare the future for this technology, this paper describes a thorough investigation of past alternative stationary and portable power projects in order for an assessment of the opportunities for stationary and portable fuel cell markets, as well as interactions with transportation hydrogen systems. The lessons learned from the programs are used to establish best practices and recommendations for a hydrogen strategy that addresses opportunities for hydrogen in power generation systems, as well as to make recommendations for market transformation within the hydrogen fuel cell industry.

Start-up characteristics of commercial propane steam reformer for 200 W e portable fuel cell system

Fuel processors in portable fuel cell systems require high efficiency, stable operation and rapid start-up time. External heating stabilizes operation of the conventional steam reforming system and allows higher hydrogen concentration in the reformate stream. In this study, we utilized a modified fuel processor that introduced a slip stream of air into the process line right before the water gas shift reactor. The air stream rapidly heated the water gas shift reactor to the desired temperature, eliminating initial CO concentration surges in the downstream. CO concentration quickly stabilized at the minimum concentration without surges by rapid preheating of the water gas shift reactor. The modified system reached a steady state within 10 min.

Study on the dynamic behavior of Zn-based hydrogen generating cells as fuel storage for a PEM micro fuel cell system

Portable fuel cell systems consist of three essential parts: the fuel cell stack, the fuel storage and the balance of plant (BOP) which contains all required peripheral components. Scaling down fuel cell systems to smaller dimensions in the power range of 1 mW to 1 W currently leads to an increased volume fraction of the peripheral components. Consequently it is necessary to forego peripheral components in small systems and develop passive systems. Furthermore fuel storage is a challenging issue for portable micro fuel cell systems. Common approaches for hydrogen storage, e.g. pressure cartridges or reversible metal hydrides yield a low energy density for the entire system. In our approach a gas evolving cell (GEC) is used to generate hydrogen “on demand”. This allows to develop small micro fuel cell systems with a high energy density. The GEC is electrically connected in series to the fuel cell. Hydrogen is generated through the electro catalytic Zn-H 2O reaction and proportional to the cell current according to Faraday's law, which leads to a simple and passive system. The dynamic and long-term behavior of the GEC is studied experimentally in this work. The electrical and chemical behavior of the GEC plays an important role in the design and operation of the micro fuel cell system. Portable applications generally imply dynamic load profiles. Therefore the study focuses on the dynamic response of the GEC. The electric response of the GEC is examined for load pulses in the range of milliseconds with an amplitude of up to 150 mA for the lifecycle of a cell. The results are compared to the behavior of the GECs under an equivalent static load in order to draw conclusions on the effect of the dynamic load. Furthermore the electrical and chemical capacity of the GECs is examined for different loads. The obtained results provide an insight into the dynamic behavior of the GEC and provide the basis for the design and operation of the micro fuel cell system.

Increase of the fuel cell system efficiency — Modular testing, analysis and development environment

The main issue in preparing fuel cell systems for the future market is system reliability and efficiency. Apart from successful field test trials, any type of stationary, in general automotive or portable fuel cell systems are at the development stage. One task to deal with is to increase the component and system efficiencies by facilitating the system construction or eliminating parasitic components.With newly established effective standardised system and component tests, linked with a flexible modelling and simulation environment, the development process and the determination of the system efficiencies as well as the inaccessible system values can be accelerated.In this work a modular model-aided system analysis and development environment is presented which has been evaluated and validated at the IWE. The tool, a combination of standardised testing, modelling and simulation, has been applied to different types of fuel cell systems showing the tool flexibility, modularity and accuracy. In the presented case the tool was used for system analysis and studies on efficiency increase of a complex prototype stationary PEMFC system.