Portable Proton Exchange Membrane Research Articles

Ruthenium nanoparticles supported on functionalized carbon nanotubes as high-efficiency catalysts for ammonia borane hydrolysis

Developing high-activity catalysts for the hydrolysis of ammonia borane (NH3BH3; AB) is a crucial and urgent task, which is presently considered an effective strategy for hydrogen generation in the applications of portable proton exchange membrane fuel cells (PEMFCs). In this study, carbon nanotubes (CNTs) were modified by self-growth of metal-organic frameworks (MOFs) on their surfaces. As self-sacrificial templates, the carbonization of cobalt and nitrogen containing MOFs led to the modification of CNT. Subsequently, cobalt was transformed into cobalt phosphide (Co2P) via phosphatization to form Co2P/N co-decorated CNTs (NCP-CNTs). Ru/NCP-CNT catalysts were obtained by loading ruthenium nanoparticles (NPs) using a chemical reduction method and their catalytic performance for H2 production via the hydrolysis of AB was systematically investigated. Ru/NCP-CNTs exhibited excellent catalytic activity, with an initial high turnover frequency (TOF) of 193.9 molH2·molRu−1·min−1 and a low activation energy of 32.4 kJ·mol−1. The incorporation of Ru NPs and their excellent synergistic effect with the NCP-CNT supports can explain the improved performance. This work provides an updated approach for fabricating low-cost and high-efficiency catalysts for the hydrolysis of AB.

Hydrogen generation from NaBH4 for portable proton exchange membrane fuel cell

Sodium borohydride (NaBH4) is considered as the most potential hydrogen storage material for portable proton exchange membrane fuel cells (PEMFC) because of its high theoretical hydrogen capacity. However, the slow and poor kinetic stability of hydrogen generation from NaBH4 hydrolysis limits its application. There are two main factors influencing the kinetics stability of hydrogen generation from NaBH4. One factor is that the alkaline by-products (NaBO2) of the hydrolysis reaction can increase the pH of the solution, thus inhibiting the reaction process. It mainly happens in the NaBH4 solution hydrolysis system. Another factor is that the monotonous increase in reaction temperature leads to uncontrollable and unpredictable hydrolysis rates in the solid NaBH4 hydrolysis system. This is due to the excess heat generated from this exothermic reaction in the initial reaction of NaBH4 hydrolysis. In this perspective, we summarize the latest research progress in hydrogen generation from NaBH4 and emphasize the design principles of catalysts for hydrogen generation from NaBH4 solution and solid state NaBH4. The importance of carbon as catalyst support material for NaBH4 hydrolysis is also highlighted.

Fabrication, Design, and Performance Investigation of Portable Proton Exchange Membrane Fuel Cell and Control System

Fabrication, Design, and Performance Investigation of Portable Proton Exchange Membrane Fuel Cell and Control System

Effects of fractal network channel on heat and mass transfer in methanol steam reforming

Hydrogen production by methanol steam reforming is one of the best choices for portable proton exchange membrane fuel cells (PEMFC). The channel is a dominant role in hydrogen production performance as the main reaction site. In this study, a fractal network channel architecture was designed and a three-dimensional (3D) numerical simulation was conducted in accordance with the Uniform Latin Hypercube design simulation scheme to explore the influence mechanism of branch grade (m), branch angle (θ), branch length ratio (α) and branch width ratio (β) on hydrogen production performance. Furthermore, four factors (m, θ, α, β) for the hydrogen production performance of fractal network channel were optimized by combining response surface method and non dominated sorting genetic algorithm II. The results showed that the hydrogen production performance is most sensitive to changes in β with the growth of the fractal network, followed by m, α, and θ. And the optimum parameter combination in terms of yield hydrogen is m of 3, θ of 134°, α of 0.88, and β of 0.85. The mechanism of the influence of fractal network structure parameters on the methanol reforming reaction as revealed in this study may provide a workable guideline for effective heat and mass transfer in new fractal reaction channel.

Portable proton exchange membrane fuel cell using polyoxometalates as multi-functional hydrogen carrier

Proton exchange membrane fuel cell (PEMFC) is an ideal energy-conversion technology for portable, motile as well as stationary applications. However, the use as a portable power source is still hindered by the stringent requirements for hydrogen storage. Herein, we propose a PEMFC system using hydrogenable polyoxometalate (POM) solution as hydrogen carrier that enables the whole system to work under atmospheric temperature and pressure. A proof-of-concept air-breathing PEMFC is constructed and three typical POMs are tested, the corresponding results demonstrate good cell performance and stability. Another impressive result shows that the hydrogen carrier, POMs, can be hydrogenated by multiple hydrogen sources such as H2, H2O and NaBH4 through both electrochemical and chemical ways. The newly designed system obtained a peak power density of 51 mW cm−2, making the real-world application of portable PEMFC possible.

Thermal management of edge-cooled 1 kW portable proton exchange membrane fuel cell stack

Comprehensive numerical analyses are conducted to study the influence of thermal management on performance of 1 kW edge-cooled proton exchange membrane fuel cell stack without external humidification. The experimental stack and numerical three-dimensional computational fluid dynamics model are characterized by several novelty aspects. Two numerical approaches are considered and compared for a prescribed load profile: (i) lumped model and novel (ii) real-time transient computational fluid dynamics model incorporating realistic modeling of forced air convection on the edge-cooling of the stack. The novelty of the developed computational fluid dynamics model is the capability to give insight in the transient results in only a fraction of time vs. experimental testing (40 min vs. 4 h) and other computational fluid dynamics models of fuel cells which are only capable of steady-state analysis. The developed computational fluid dynamics model is used to study the influence of (i) bipolar plate materials (ii) operating delta pressure along the flow field and (iii) different cooling fin configurations on the water and heat balance inside the stack. The results indicate that (i) maximal and average temperatures of the stack are almost linearly correlated to the thermal conductivity of bipolar plate materials and maximal temperatures can be significantly higher (ii) the operating delta pressure can be manipulated to increase the performance of the stack and (iii) the cooling fin redesign has major influence on the overall temperature uniformity across the stack. Additionally, the heat transfer between the stack and metal hydride tank is studied.

Preparation, characterization, and properties of Pt/Al2O3/cordierite monolith catalyst for hydrogen generation from hydrolysis of sodium borohydride in a flow reactor

High-purity hydrogen can be generated by hydrolysis of sodium borohydride and used for operating portable proton exchange membrane fuel cells. The monolith supported catalyst is suitable for practical NaBH4-based hydrogen generation system due to its simple reactor structure miniaturizing for small size applications and easy separation from the spent solution. In the present study, a structured catalyst was prepared by wash-coating the Al2O3 sol over the wall of cordierite monolith followed by depositing Pt using incipient wet impregnation method; then the monolithic catalysts were characterized by XRF, XRD, SEM, HRTEM and XPS. The catalytic activity of the Pt-based monolithic catalyst towards hydrolysis of NaBH4 was tested using a flow reactor under ambient conditions in an autothermal manner. The characterization results show that Pt nanoparticles are highly dispersed on the surface of the Al2O3-coated layer. A continuous and stable hydrogen generation can be obtained by feeding the reactant (10 wt% NaBH4–5 wt % NaOH) into the tube reactor loaded with the monolithic catalyst at feed rates of 0.5–2.0 mL min−1.

Hydrogen generation from solid state NaBH4 by using FeCl3 catalyst for portable proton exchange membrane fuel cell applications

Being a boron-based compound, sodium borohydride, NaBH4, is a convenient hydrogen storage material for applications like unmanned air vehicles. There are several concerns behind commercialization of hydrogen gas generator by NaBH4 hydrolysis systems. This study aims to contribute to the solution of the problems of NaBH4 hydrolysis system in three main ways. First, the usage of solid state NaBH4 enables to increase the durability and the gravimetric H2 storage capacity of the system in order to meet US DOE targets. Second, solid NaBH4 usage decreases the system's weight since it does not require a separate fuel storage tank, which is very important for portable, on demand applications. Finally, the system's cost is decreased by using an accessible and effective non-precious catalyst such as ferric chloride, FeCl3. The maximum hydrogen generation rate obtained was 2.6 L/min and the yield was 2 L H2/g NaBH4 with an efficiency of 76% at its most promising condition. Moreover, the novel solid NaBH4 hydrogen gas generator developed in the present work was integrated into a proton exchange membrane fuel cell and tested at the optimum operating conditions.

고농도 NaBH4수용액에서 비담지 촉매의 가수분해 반응 특성

휴대용 고분자전해질 연료전지의 수소발생용으로써 <TEX>$NaBH_4$</TEX>는 많은 장점을 갖고 있다. 본 연구에서는 고농도 <TEX>$NaBH_4$</TEX> 용액에서 비담지 Co-P-B, Co-B 촉매의 <TEX>$NaBH_4$</TEX> 가수분해 특성에 대해 연구하였다. 고농도에서 수소 발생 수율을 높이기 위해 <TEX>$NaBH_4$</TEX> 가수분해 반응의 수소 발생 수율에 미치는 촉매 형태, <TEX>$NaBH_4$</TEX> 농도, 응축수 회수 등의 영향에 대해 실험하였다. Co-P-B 제조과정에서 붕소의 비가 높아질수록 수소 발생 수율이 증가하였다. Co-P:B = 1:5 촉매를 사용해 <TEX>$NaBH_4$</TEX> 수용액 농도를 20 wt%에서 25 wt%로 증가시켰을 때 수소 발생 수율이 감소하였다. Co-P-B와 Co-B 촉매를 같이 사용한 반응기에서 촉매 팩의 두께를 감소시키고 응축수를 회수하여, <TEX>$NaBH_4$</TEX> 25 wt% 수용액으로 최고 수소 발생수율 96.4%를 얻었다. Sodium borohydride, <TEX>$NaBH_4$</TEX>, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). Properties of <TEX>$NaBH_4$</TEX> hydrolysis reaction using unsupported Co-P-B Co-B, catalyst at high concentration <TEX>$NaBH_4$</TEX> solution were studied. In order to enhance the hydrogen generation yield at high concentration of <TEX>$NaBH_4$</TEX>, the effect of catalyst type, <TEX>$NaBH_4$</TEX> concentration and recovery of condensing water on the hydrogen yield were measured. The yield of hydrogen evolution increased as the boron ratio increased in preparation process of Co-P-B catalyst. The hydrogen yield decreased as the concentration increased from 20 wt% to 25 wt% in <TEX>$NaBH_4$</TEX> solution during hydrolysis reaction using 1:5 Co-P-B catalyst. Maximum hydrogen yield of 96.4% obtained by recovery of condensing water and thinning of catalyst pack thickness in reactor using Co-P-B with Co-B catalyst and 25 wt% <TEX>$NaBH_4$</TEX> solution.

A Study of Heating Mechanism Applied to Hydrogen Storage Alloy Tank of Portable Proton Exchange Membrane Fuel Cell

This study developed a heating mechanism applicable to hydrogen storage tank, in order to enhance the stability and durability of proton exchange membrane fuel cell (PEMFC). This study discussed two heating modes. The first mode was using heating wire to wind the hydrogen storage tank body. Heating wires were used to wind the upper, middle and lower parts of the hydrogen storage tank and the whole tank respectively for discussion. The second heating mode was to use the PEMFC cathode waste heat to heat the hydrogen storage tank body. This study discussed the variations of hydrogen release rate and tank body temperature with the hydrogen release time in different heating mechanisms. The research results can serve as reference for system design in various applications.

NaBH4가수분해용 Co-P-B/Cu 촉매의 내구성

휴대용 고분자전해질 연료전지의 수소발생용으로써 <TEX>$NaBH_4$</TEX>는 많은 장점을 갖고 있다. 본 연구에서는 <TEX>$NaBH_4$</TEX> 가수분해 반응용 Co-P-B/Cu 촉매의 내구성에 대해 연구하였다. Co-P-B/Cu 촉매의 내구성 미치는 반응 온도, <TEX>$NaBH_4$</TEX> 농도, NaOH 농도, 촉매 소성온도 등의 영향에 대해 실험하였다. 촉매의 내구성은 가수분해 반응 중에 발생하는 gel 형성에 영향을 받았다. 즉 gel 형성에 의해 촉매 손실률이 증가하였다. <TEX>$NaBH_4$</TEX> 농도가 고농도일 때는 <TEX>$60^{\circ}C$</TEX> 이상에서는 gel 형성이 안 되어 촉매 손실률이 낮았다. 그러나 <TEX>$40^{\circ}C$</TEX> 이하에서는 gel이 형성되어 촉매 손실률이 증가했다. <TEX>$NaBH_4$</TEX> 20 wt%, <TEX>$40^{\circ}C$</TEX>에서 NaOH 농도증가에 따라 겔이 형성되어 촉매 손실률이 증가함을 보였다. Co-P-B/Cu 촉매의 높은 온도에서 소성은 내구성을 향상시켰지만 촉매 활성을 감소시켰다. Sodium borohydride, <TEX>$NaBH_4$</TEX>, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). The durability of Co-P-B/Cu catalyst for sodium borohydride hydrolysis reaction was studied. The effect of reaction temperature, <TEX>$NaBH_4$</TEX> concentration, NaOH concentration and calcination temperature of catalyst on the durability of Co-P-B/Cu catalyst were measured. The gel formed during hydrolysis reaction affected the durability of catalyst (loss of catalyst). Formation of gel increased the loss of the catalyst. When <TEX>$NaBH_4$</TEX> concentration was high and reaction temperature was higher than <TEX>$60^{\circ}C$</TEX>, loss of catalyst was low because gel was not formed. But under the temperature of <TEX>$40^{\circ}C$</TEX>, loss of catalyst increased due to gel formation When <TEX>$NaBH_4$</TEX> concentration was 40 weight % and the reaction temperature was <TEX>$40^{\circ}C$</TEX>, the loss of catalyst increased as the NaOH concentration increased. As the calcination temperature of catalyst decreased, the loss of catalyst decreased and the activity of catalyst decreased. Calcination of the catalyst at high temperature enhanced the durability of catalyst but diminished the activity of catalyst.

A flexible portable proton exchange membrane fuel cell

A flexible portable proton exchange membrane fuel cell (PEMFC) is developed with non-directional flexibility acquired through new carbon-fibre-made current collectors and a new cell structure. The performance of a pilot cell suffers no significant loss when bent to curvatures with various radii in multiple directions. It also compares well with a nonflexible cylindrical portable PEMFC composed of similar components.The new cell is made with a single cup-like flexible main body with the membrane glued to the inside rim. The current collector is composed of several bunches of carbon fibre, each with metal wires embedded in them. The soft and flexible fibres not only allow for close and evenly-distributed contact with the bent electrode, but also change the character of the contact so that a large compressional force is no longer required to acquire low contact resistance which is, above all, the key to the success of this flexible cell design. The metal wire provides the needed flexibility to cover large curved electrode areas. A wire spring is used to pressure the collector against the electrode while the main body bends.

NaBH4가수분해반응에서 수소 수율에 관한 연구

휴대용 고분자전해질 연료전지의 수소발생용으로써 <TEX>$NaBH_4$</TEX>는 많은 장점을 갖고 있다. 본 연구에서는 <TEX>$NaBH_4$</TEX> 가수분해 반응의 수소 수율에 대해 연구하였다. <TEX>$NaBH_4$</TEX> 가수분해 반응의 수소 수율에 미치는 촉매 형태, 온도, <TEX>$NaBH_4$</TEX> 농도, NaOH 농도 등의 영향에 대해 실험하였다. 촉매는 Co-P/Cu, Co-B/Cu와 Co-P-B/Cu를 사용하였는데 이들 촉매 종류에 따라 <TEX>$NaBH_4$</TEX> 가수분해 반응의 수소 수율에 미치는 영향은 거의 없었다. <TEX>$60^{\circ}C$</TEX> 이하의 온도에서 <TEX>$NaBH_4$</TEX> 농도가 증가하면 부산물과 <TEX>$NaBH_4$</TEX>에 의해 겔이 형성되면서 가수분해 반응의 수소 수율이 감소였다. 겔 형성에 의해서 <TEX>$NaBH_4$</TEX> 가수분해 반응 속도와 수소 총 발생량이 감소하였다. 안정화제인 NaOH를 첨가하면 겔 형성을 촉진해 수소 수율을 감소시켰다. Sodium borohydride, <TEX>$NaBH_4$</TEX>, shows a number of advantages as hydrogen source for portable proton exchange membrane fuel cells (PEMFCs). The hydrogen yield of sodium borohydride hydrolysis reaction was studied. The effect of temperature, <TEX>$NaBH_4$</TEX> concentration, NaOH concentration and catalyst type on the hydrogen yield from <TEX>$NaBH_4$</TEX> hydrolysis reaction were measured. The catalysts of Co-P/Cu, Co-B/Cu and Co-P-B/Cu were used in this study and there was no different effect of these catalysts on the hydrogen yield from <TEX>$NaBH_4$</TEX>. Under the temperature of <TEX>$60^{\circ}C$</TEX>, the hydrogen yield decreased as <TEX>$NaBH_4$</TEX> concentration increased due to formation of gel with by-products and reactants. The gel formed during <TEX>$NaBH_4$</TEX> hydrolysis reaction diminished the hydrogen evolution rate and total volume of hydrogen. Addition of NaOH stabilizer enhanced the formation of gel and then decreased the hydrogen yield.

Modeling and control of a portable proton exchange membrane fuel cell–battery power system

A portable proton exchange membrane (PEM) fuel cell–battery power system that uses hydrogen as fuel has a higher power density than conventional batteries, and it is one of the most promising environmentally friendly small-scale alternative energy sources. A general methodology of modeling, control and building of a proton exchange membrane fuel cell–battery system is introduced in this study. A set of fuel cell–battery power system models have been developed and implemented in the Simulink environment. This model is able to address the dynamic behaviors of a PEM fuel cell stack, a boost DC/DC converter and a lithium-ion battery. To control the power system and thus achieve proper performance, a set of system controllers, including a PEM fuel cell reactant supply controller and a power management controller, were developed based on the system model. A physical 100W PEM fuel cell–battery power system with an embedded micro controller was built to validate the simulation results and to demonstrate this new environmentally friendly power source. Experimental results demonstrated that the 100W PEM fuel cell–battery power system operated automatically with the varying load conditions as a stable power supply. The experimental results followed the basic trend of the simulation results.

Ni–Co–B catalyst-promoted hydrogen generation by hydrolyzing NaBH 4 solution for in situ hydrogen supply of portable fuel cells

A series of Ni–Co–B catalysts were synthesized by a two-step technique, namely, chemical reduction was used to prepare the precursors, and heat-treatment was used to adjust the crystal structures. The structures of the as-prepared Ni–Co–B catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption test. The catalytic activities of the Ni–Co–B catalysts for NaBH 4 hydrolysis were evaluated in a successive hydrogen generation mode, where a 5%NaBH 4 + 1%NaOH solution was pumped into the hydrogen generation reactor with a feeding rate of 5 ml per minute. It is found that the heat-treatment affects the crystal structure, the apparent morphology, the oxidation state, the surface structure, as well as the hydrogen generation performances of the Ni–Co–B catalysts. The sample treated at 673 K achieves an average hydrogen generation rate of 708 ml min −1 g −1 catalyst, which can give successive hydrogen supply for an 115 W portable proton-exchange membrane fuel cell (PEMFC).

Orientation-Dependent Performance of Portable Proton Exchange Membrane Fuel Cells

The effects of gravitational force on the orientation-dependent performance of portable proton exchange membrane (PEM) fuel cell using serpentine flow channels were investigated by the measurement and analysis of polarization curves. Whether the removal of produced water in the cathode flow channel is resisted or assisted by the gravity depends on the orientation variation, flow direction, and flow channel distribution of a fuel cell. This gravity will then affect the fuel cell performance, especially for fuel cells operating at a high current density. The results show that a fuel cell with perpendicular flow channel distribution and cathode gas flow in vertical direction requires a longer distance of pushing liquid droplets against gravity to remove the produced water, which is difficult to expel the produced water from the flow channels, and the performance reduction is obviously in high current density. A fuel cell operating in a normal position achieves higher performance than one operating in a horizontal position, except the cathode gas flow in vertical direction and feed from lower inlet. Furthermore, for a fuel cell operating in a horizontal position with anode below the membrane, gravitational force transports the water to the anode and blocks the fuel channel in the gas diffusion layer. This leads a fuel cell operating in high current densities with the cathode below the membrane performs better than one with the cathode above the membrane. Therefore, to reduce the effects of gravity on the orientation-dependent performance, a fuel cell with parallel flow channel distribution and feeding the cathode gas from the upper inlet port is recommended in this study.

A Fuel-Cell-Battery Hybrid Platform for Portable Embedded Systems

A portable proton exchange membrane (PEM) fuel cell operates at room temperature, has an energy density which is 4 to 6 times larger than that of a Li-ion battery, and thus is a promising next generation power source for power-hungry portable devices. However, in spite of the high energy density, fuel cells have limited power capacity and cannot respond to sudden changes in the load. Thus, a system powered solely by the fuel cell should be over-designed and not economical. Thus, fuel cells are commonly used with a battery to utilize both the high energy density of the fuel cell and the high power capacity of the battery.Since power consumption of embedded systems dynamically changes over time, the control of a fuel cell and the charge management in the battery is sophisticated. Ultimate fuel-optimal configuration is achievable only when the control of the fuel cell, charge management of the battery, and the power management of the embedded system are jointly optimized. Since this is certainly a new problem, we first need an evaluation platform for the measurement and characterization. Nevertheless, there has been no existing platform to tackle such a problem. In this paper, we demonstrate the design and implementation of a 20W average, 80W peak power fuel cell and dual Li-ion battery hybrid power source platform. This platform is designed to characterize the performance of hybrid power source, and also to explore new energy management strategies for embedded systems powered by a hybrid source. We devise a new hybrid power supply scheme named DTC (Dynamic duTy cycle Control) so that we may fully control the proportion of the fuel cell current and the battery current.

System identification and robust control of a portable proton exchange membrane full-cell system

This paper will discuss the application of system identification techniques and robust control strategies to a proton exchange membrane fuel-cell system. The fuel-cell system's dynamic behaviour is influenced by many factors, such as the reaction mechanism, pressure, flow-rate, composition and temperature change, and is inherently non-linear and time varying. From a system point of view, however, the system can be modelled as a two-input, two-output linear time-invariant system whose inputs are hydrogen and air flow rates, and whose outputs are cell voltage and current. On the other hand, the system's non-linearities and time-varying characteristics can be regarded as system uncertainties and disturbances that are treated by the designed robust controllers. This paper is comprised of three parts. First, system identification techniques were adopted to model the system's transfer functions. Second, the H ∞ robust control strategies were applied to stabilise the system. Finally, the system's stability and performance were compromised by introducing weighting functions to the controller's design. From the experimental results, the designed H ∞ robust controllers were deemed effective.

Micromachined methanol steam reforming system as a hydrogen supplier for portable proton exchange membrane fuel cells

In this paper, a novel hydrogen-supplying device for fuel cells has been designed, fabricated, and demonstrated. The proposed hydrogen supplier is a micromachined one-chip fuel processing system including vaporizer, catalytic combustor and methanol steam reformer. This fuel processing system utilizes the thermal energy generated from the catalytic hydrogen combustion to heat up the entire system. For the catalytic combustion, we have introduced carbon nanotubes as a supporting structure of Pt catalyst for the first time. We have also developed a new coating method of reforming catalyst (Cu/ZnO/Al 2O 3) and observed that adequate amount of hydrogen can be generated for PEM fuel cells. We have successfully reported the feasibility of the proposed fuel processing system.

Portable proton exchange membrane fuel-cell systems for outdoor applications

A hydrogen fuelled, 30 W proton exchange membrane fuel-cell (PEMFC) system is presented that is able to operate at an ambient temperature between −20 and 40 °C. The system, which comprises the fuel-cell stack, pumps, humidifier, valves and blowers is fully characterized in a climatic chamber under various ambient temperatures. Successful cold start-up and stable operation at −20 °C are reported as well as the system behaviour during long-term at 40 °C. A simple thermal model of the stack is developed and validated, and accounts for heat losses by radiation and convection. Condensation of steam is addressed as well as reaction gas depletion. The stack is regarded as a uniform heat source. The electrochemical reaction is not resolved. General design rules for the cold start-up of a portable fuel-cell stack are deduced by the thermal model and are taken into consideration for the design. The model is used for a comparison between active-assisted cold start-up procedures with a passive cold start-up from temperatures below 0 °C. It is found that a passive cold start-up may not be the most efficient strategy. Additionally, the influence of different stack concepts on the start-up behaviour is analysed by the thermal model. Three power classes of PEMFC stacks are compared: a Ballard Mk902 module for automotive applications with 85 kW, the forerunner stack Ballard Mk5 (5 kW) for medium power applications, and the developed OutdoorFC stack (30 W), for portable applications.