A precious-metal free micro fuel cell accumulator

In recent years, integrated fuel cell (FC) type primary and secondary batteries attracted a great deal of attention as integrated on-chip power sources due to their high theoretical power densities. Unfortunately, the costs of these devices have been rather high. This is partially due to the involved clean-room processes, but also due to the fact that these devices generally rely on expensive precious-metals such as Pd and Pt. Therefore we developed a novel integrated FC type accumulator that is based on non-precious-metals only. The key component of the presented accumulator is its alkaline polymer electrolyte membrane that allows not only the usage of a low-cost AB₅ type hydrogen storage electrode, but also the usage of La_0.6Ca_0.4CoO₃ as a precious-metal free bifunctional catalyst for the air-breathing electrode. Additionally the presented design requires only comparatively few cleanroom processes which further reduces the overall production costs. Although abdicating precious-metals, the presented accumulator shows an open circuit voltage of 0.81 V and a maximum power density of 0.66 mW cm⁻² which is comparable or even superior to former precious-metal based cells.     

Design of an integrated power system using a proton exchange membrane fuel cell

Integrated power systems could be a solution to provide energy to remote communities based on the use of renewable energies (such as wind or sun). This work proposed the design of one of those systems including alkaline water electrolysers, storage tanks and a proton exchange membrane fuel cell for generating of 53 kW (working at 60% of its maximum power). Electrode sizes and the quantity of unit cells proposed in this work were the same as those suggested in the research work by Yang et al., where a phosphoric acid fuel cell was built and studied. The results obtained in that research allowed comparing energy efficiency by scaling a laboratory prototype. The dimensions of the alkaline water electrolysers are the result of satisfying the necessity of fuel and oxidant. The energy consumption results from extrapolating laboratory devices. The integrated power system has a storage tank capacity of 16 h.     

燃料电池用氢气燃料的制备和存储技术的研究现状

质子交换膜燃料电池（PEMFC）进行反应的燃料是高纯度氢气,氢气的制备和存储是质子交换膜燃料电池能否应用和规模化应用的先决条件和关键技术。对燃料电池用氢气的制备、纯化、存储技术的研究现状进行了综合分析。     

Development of optimisation model for direct methanol fuel cells via cell integrated network

A cell network consists of a combination of fuel cells to achieve the targeted power consumption for a specific application. The main objective of this study is to design and optimise direct methanol fuel cell (DMFC) via cell integrated network model targeted for small portable application, such as cell phones and tablets. The target current and voltage was 1400 mA and 3.7 V, respectively, for a 5.18 W of cell network power. The optimisation was performed using 16 cells that were arranged in series with a voltage output of 3.781 V and a current of 1400 mA. The overall active area for the cell network was 128 cm², and the cost of 1 set of cell networks is USD 1400.     

Design and fabrication of a silicon-based direct methanol fuel cell with a new cathode spoke structure

In this paper, a self-breathing micro direct methanol fuel cell (μDMFC) featuring a new cathode current collector with a spoke configuration is presented to improve cell performance. Simulation results show that the new spoke structure can effectively increase the efficiency of oxygen mass transport and exhibit higher pressure than the conventional perforated structure. The water transfer to the proton exchange membrane (PEM) is promoted to reduce the PEM resistance with the increase in the membrane water content. Additionally, the effects of the spoke blades on performance were evaluated to determine the optimal cathode structure. The self-breathing μDMFCs with conventional and new cathode structures were fabricated using silicon-based micro-electromechanical system (MEMS) technologies and tested at room temperature with 1 M methanol solution. The experimental results revealed that the spoke cathode structure exhibits significantly higher performance than the conventional structure, showing a substantial 30% increase in peak power density.     

Design and evaluation of a passive self-breathing micro fuel cell for autonomous portable applications

A micro fuel cell system designed to power complex autonomous systems with dynamic pulse-shaped loads like wireless sensor nodes is presented in this work. The requirements posed by the corresponding pulse load profiles are considered for the design of the passive self-breathing micro fuel cell. The performance of the fuel cell is mainly affected by the oxygen and water management which is influenced by the openings in the cathodic current collector. Due to the comparatively low average cell current the performance can be strongly improved by retaining water within the cell using a reduced opening ratio and thus improving the ionic conductivity of the electrolyte.     

A self-breathing metallic micro-direct methanol fuel cell with the improved cathode current collector

A self-breathing micro-direct methanol fuel cell (μDMFC) with active area of 0.64 cm² has been developed for powering portable applications. A cathode perforated current collector with parallel flow fields is presented in order to improve the cell performance. Compared with the conventional cathode self-breathing structure, the improved one can enhance oxygen transport and reduce water flooding utilizing multiphysics simulations. The stainless steel plates with the thickness of 0.3 mm as current collectors with parallel flow fields have been machined by thermally micro-stamping. For the cathode self-breathing openings, the perforated current collector has been realized using laser drilling. A 500 nm-thick titanium nitride (TiN) layer is deposited onto the surface of current collectors by magnetron sputtering ion plating (MSIP) technology to cover the cracks and prevent corrosion. Peak power density of the μDMFC reaches 27.1 mW/cm² at room temperature with 1.0 M methanol solutions of 1 ml/min. The results presented in this paper might be helpful for the development of micro power sources applied in future portable electronic devices.     

Regenerative energy control system for plug-in hydrogen fuel cell scooter

An intelligent control system was developed using simple control methodologies for an H₂-powered fuel cell scooter with the aid of a built-in microprocessor. This system increases the power input to drive a hydrogen fuel cell scooter, particularly during uphill conditions by running both the batteries and the fuel cell source in parallel. This system also improves the energy management of the scooter by recharging the battery using the fuel cell as well as automatic switching to the battery source when the hydrogen fuel cell is running low on hydrogen. This system was tested on a bench set simulating a 254 W hydrogen fuel cell stack equipped on a 200 W scooter. The test rig set-up depicts a practical scooter running on various load conditions. These results reflect the efficiencies of actual running conditions. The entire operation was embedded in a PICAXE-18 microcontroller for automatic switching between the batteries and the fuel cell source. An increase in the DC motor efficiency by 6 % has been shown. The uphill angle of the scooter has been increased by 19.3 %, which means the scooter would be able to travel on steeper hills. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermodynamic analysis and assessment of an integrated hydrogen fuel cell system for ships

In this thermodynamic investigation, an integrated energy system based on hydrogen fuel is developed and studied energetically and exergetically. The liquefied hydrogen fueled solid oxide fuel cell (SOFC) based system is then integrated with a steam producing cycle to supply electricity and potable water to ships. The first heat recovery system, after the fuel cells provide thrust for the ship, is by means of a turbine while the second heat recovery system drives the ship's refrigeration cycle. This study includes energy and exergy performance evaluations of SOFC, refrigeration cycle and ship thrust engine systems. Furthermore, the effectiveness of SOFCs and a hydrogen fueled engine in reducing greenhouse gas emissions are assessed parametrically through a case study. The main propulsion, power generation from the solid oxide fuel cells, absorption chiller, and steam bottoming cycle systems together have the overall energy and exergy efficiencies of 41.53% and 37.13%, respectively.     

Optimization of fuel cell system operating conditions for fuel cell vehicles

Proton exchange membrane fuel cell (PEMFC) technology for use in fuel cell vehicles and other applications has been intensively developed in recent decades. Besides the fuel cell stack, air and fuel control and thermal and water management are major challenges in the development of the fuel cell for vehicle applications. The air supply system can have a major impact on overall system efficiency. In this paper a fuel cell system model for optimizing system operating conditions was developed which includes the transient dynamics of the air system with varying back pressure. Compared to the conventional fixed back pressure operation, the optimal operation discussed in this paper can achieve higher system efficiency over the full load range. Finally, the model is applied as part of a dynamic forward-looking vehicle model of a load-following direct hydrogen fuel cell vehicle to explore the energy economy optimization potential of fuel cell vehicles.     

From waste to electricity through integrated plasma gasification/fuel cell (IPGFC) system

The waste management is become a very crucial issue in many countries, due to the ever- increasing amount of waste material, both domiciliary and industrial, generated.The main strategies for the waste management are the increase of material recovery (MR), which can reduce the landfill disposal, the improvement of energy recovery (ER) from waste and the minimization of the environmental impact.These two last objectives can be achieved by introducing a novel technology for waste treatment based on a plasma torch gasification system integrated with a high efficiency energy conversion system, such as combined cycle power plant or high-temperature fuel cells.This work aims to evaluate the performance of an Integrated Plasma Gasification/Fuel Cell system (IPGFC) in order to establish its energy suitability and environmental feature.The performance analysis of this system has been carried out by using a numerical model properly defined and implemented in Aspen Plus™ code environment. The model is based on the combination of a thermochemical model of the plasma gasification unit, previously developed by the authors (the so-called EquiPlasmaJet model), and an electrochemical model for the SOFC fuel cell stack simulation.The EPJ model has been employed to predict the syngas composition and the energy balance of an RDF (Refuse Derived Fuel) plasma arc gasifier (that uses air as plasma gas), whereas the SOFC electrochemical model, that is a system-level model, has allowed to forecast the stack performance in terms of electrical power and efficiency.Results point out that the IPGFC system is able to produce a net power of 4.2 MW per kg of RDF with an electric efficiency of about 33%. This efficiency is high in comparison with those reached by conventional technologies based on RDF incineration (20%).     

Multi-objective optimal droop control of solid oxide fuel cell based integrated energy system

Solid oxide fuel cell (SOFC) based integrated energy system (IES) is promising in the future low-carbon power generation market, due to the high efficiency and flexibility. However, it is challenging for the dynamic control design in dealing with the conflicting objectives in terms of fast power tracking and overall efficiency during the transient process of load response. To this end, this paper develops a multi-objective optimal droop control strategy for the real-time power dispatch of the IES. Firstly, a nonlinear implicit dynamic model consisting of SOFC, lithium-ion battery, photovoltaic array and DC-DC converter is developed. Then, a multi-objective optimization is formulated to balance the power tracking performance and transient efficiency. Non-dominated sorting genetic algorithm-II (NSGA-II) is adopted to search the optimal parameters for droop controller. Simulation results demonstrates that the electricity loss of the proposed method can be reduced by 96.26% with a slight compromise in power tracking performance.     

Analysis of a solid oxide fuel cell and a molten carbonate fuel cell integrated system with different configurations

A solid oxide fuel cell with internal reforming operation is run at partial fuel utilization; thus, the remaining fuel can be further used for producing additional power. In addition, the exhaust gas of a solid oxide fuel cell still contains carbon dioxide, which is the primary greenhouse gas, and identifying a way to utilize this carbon dioxide is important. Integrating the solid oxide fuel cell with the molten carbonate fuel cell is a potential solution for carbon dioxide utilization. In this study, the performance of the integrated fuel cell system is analyzed. The solid oxide fuel cell is the main power generator, and the molten carbonate fuel cell is regarded as a carbon dioxide concentrator that produces electricity as a by-product. Modeling of the solid oxide fuel cell and the molten carbonate fuel cell is based on one-dimensional mass balance, considering all cell voltage losses. Primary operating conditions of the integrated fuel cell system that affect the system efficiencies in terms of power generation and carbon dioxide utilization are studied, and the optimal operating parameters are identified based on these criteria. Various configurations of the integrated fuel cell system are proposed and compared to determine the suitable design of the integrated fuel cell system.     

Portable direct hydrogen fed PEM fuel cell model and experimental verification

This paper focuses on the experimental verification of an electrochemical model of 100 W portable direct hydrogen fed proton exchange membrane (PEM) fuel cell (FC). The model is built based on the relationship between the FC terminal voltage and the partial pressures of hydrogen and oxygen. The model is then used to predict the output voltage and study the transient response of a PEMFC when subjected to rapid changes in the load. To validate the model, the measurements obtained from a commercially available 100 W FC are compared against the model results. Three different scenarios are considered for testing the model and the actual FC. In the first two scenarios, a step change in the load is used. In the third scenario, the load is replaced by a laptop computer. Results show a close agreement between the voltage and the power responses of the proposed model and the actual PEM FC. Copyright © 2009 John Wiley & Sons, Ltd.     

生物质气化高温燃料电池一体化发电技术研究

介绍了国内外生物质气化高温燃料电池一体化发电技术的研究现状，主要包括高温燃料电池的特点和研究现状；一体化发电技术的理论模拟；国外相关的试验研究和一体化示范工程。分析了生物质气化高温燃料电池一体化发电技术在我国应用的可行性，提出了目前需要解决的关键技术问题。     

Thermally integrated energy storage system for hybrid fuel cell electric bike: An experimental study

The hybrid fuel cell/battery technology is an attractive option for a sustainable mobility with zero emissions. In fact, this solution owns system scalability features and high efficiency and, compared to battery electric solutions, it offers advantages in terms of flexibility of use and fast charging times. However, the thermal management for the battery in this type of powertrain is a crucial issue, since operating temperatures can significantly affect safety and performance. In this study, an innovative system aimed at providing high storage energy density and improving the battery pack performance of hybrid fuel cell/battery vehicles is investigated for use on-board of a plug-in fuel cell electric bike. The proposed system, developed by the authors in previous studies, integrates the battery pack with a hydrogen storage based on metal hydrides. The idea behind this solution is to exploit the endothermic desorption processes of hydrogen in metal hydrides to cool down the battery pack during operation. An experimental analysis is conducted to assess the thermal management capabilities of this system: by considering a typical duty cycle designed on the base of road test measurements, battery pack temperature profiles are evaluated and compared against those from a control experiment where no battery thermal management is enabled (i.e. no hydrogen desorption from the metal hydride tank). The results show that, beside enhancing the on-board stored energy capacity, the proposed system represents an effective solution to provide an efficient thermal management for the battery pack, with significant advantages in terms of attainable riding range.     

Boosting cell performance and fuel utilization efficiency in a solar assisted methanol microfluidic fuel cell

Solar generated hydrogen from an optimized P25 thin film of 3.2 mg/cm² with 0.25% of platinum as co-catalyst improves the peak power output of a methanol microfluidic fuel cell operated with a methanol to water ratio of 1:1 almost ninefold, from 22 mW/cm² to 213 mW/cm². Different methanol to water ratios in the fuel tank generate similar amounts of hydrogen, but the cell performance has large variations due to the different oxidation kinetics of hydrogen and methanol in the fuel breathing anode, resulting in a mixed-potential anodic performance. The trade-off between power output and fuel utilization diminishes in this system. The methanol utilization efficiency at peak power operation increases from 50% (for 0.2 V) to 78% (for 0.5 V) for methanol to water ratio of 1:1. The result indicates that in-situ generation of hydrogen by solar light can be applied to both portable and large-scale stationary fuel cells.     

Dynamic analyses of regenerative fuel cell power for potential use in renewable residential applications

A model of a solar-hydrogen powered residence, in both stand-alone and grid parallel configurations, was developed using Matlab/Simulink^®$\mathrm{Matlab}/{\mathrm{Simulink}}^{\circledR }$. The model assesses the viability of employing a regenerative fuel cell (RFC) as an energy storage device to be used with photovoltaic (PV) electrical generation. Other modes of energy storage such as batteries and hybrid storage were also evaluated. Analyses of various operating conditions, system configurations, and control strategies were performed. Design requirements investigated included RFC sizing, battery sizing, charge/discharge rates, and state of charge limitations. Dynamic load demand was found to be challenging to meet, requiring RFC and or battery sizes significantly larger than those required to meet average power demand. Employing a RFC with batteries in a hybrid configuration increased PV utilization and both battery efficiency and power density. Grid parallel configurations were found to alleviate many of the difficulties associated with energy storage costs and meeting peak demand.     

Analysis of the current methods used to size a wind/hydrogen/fuel cell‐integrated system: A new perspective

As an alternative to the production and storage of intermittent renewable energy sources, it has been suggested that one can combine several renewable energy technologies in one system, known as integrated or hybrid system, that integrate wind technology with hydrogen production unit and fuel cells. This work assesses the various methods used in sizing such systems. Most of the published papers relate the use of simulation tools such as HOMER, HYBRID2 and TRNSYS, to simulate the operation of different configurations for a given application in order to select the best economic option. But, with these methods one may not accurately determine certain characteristics of the energy resources available on a particular site, the profiles of estimated consumption and the demand for hydrogen, among other factors, which will be the optimal parameters of each subsystem. For example, velocity design, power required for the wind turbine, power required for the fuel cell and electrolyzer and the storage capacity needed for the system. Moreover, usually one makes excessive use of bi‐parametric Weibull distribution function to approximate the histogram of the observed wind to the theoretical, which is not appropriate when there are bimodal frequency distributions of wind, as is the case in several places in the world. A new perspective is addressed in this paper, based on general system theory, modeling and simulation with a systematic approach and the use of exergoeconomic analysis. There are some general ideas on the advantages offered in this method, which is meant for the implementation of wind/hydrogen/fuel cell‐integrated systems and in‐situ clean hydrogen production. Copyright © 2009 John Wiley & Sons, Ltd.     

Metal hydride hydrogen storage tank for light fuel cell vehicle

We describe a metal hydride (MH) hydrogen storage tank for light fuel cell vehicle application developed at HySA Systems. A multi-component AB₂-type hydrogen storage alloy was produced by vacuum induction melting (10 kg per a load) at our industrial-scale facility. The MH alloy has acceptable H sorption performance, including reversible H storage capacity up to ∼170 NL/kg (1.5 wt% H). The cassette-type MH tank was made up of 2 cylindrical aluminium canisters with transversal internal copper fins and external aluminium fins for improving the heat exchange between the heating medium and the MH tank. Heat supply and removal was provided from the outside using air at T = 15–25 °C. The MH tank was tested at the conditions of natural or forced (velocity ∼2 m/s) air convection. The tests included H₂ charge of the tank at P = 15–40 bar and its discharge at P = 1 bar. The tank in the H₂ discharge mode was also tested together with open cathode low-temperature proton exchange membrane fuel cell (LT PEMFC).