The purpose of the fuel processing subsystem is the generation of a hydrogen- rich reformate gas, with a low CO-content (composition depends on the tolerance of the fuelcell type). Additionally other poisonous substances, such as H 2 S must be removed. To accomplish these tasks various processes must take place in appropriate components (e.g. reactors) in a series of several steps. A simplified configuration of a typical fuel processing subsystem arrangement is shown in Figure 7. The main components include heat exchangers, chemical reactors, a burner, pipelines and extraction equipment (Jahn & Schroer, 2005; Jannelli, Minutillo, & Galloni, 2007; Kolb, 2008; O’Hayre et al., 2009). A steam generator converts liquid water into superheated steam. Steam generation is necessary for the fulfillment of the chemical reactions (e.g. steam methane reforming) in the reactors. The compressed natural gas is also preheated to accelerate and facilitate the reforming reaction. Steam generation and fuel preheating requirements are usually easily accomplished by waste heat generated by either the fuelcell stack or fuel processing. Then the methane/steam mixture enters the reformer, where it reacts at a hightemperature (600-700 ), in the presence of a catalyst (to accelerate chemical kinetics), resulting in a hydrogen-rich reformate gas. The reformate gas then enters the water gas shift reactor, which increases the quantity of hydrogen in the stream and decreases the CO content.
Fuelcelltechnology, particularly for transport applications, would take a leap forward if a viable system were to be developed that could use a liquid fuel without the need for reformation. The prospects for anode catalysts being developed having the activity to operate on petroleum derived hydrocarbon fuels are poor. However, Shell and others in the 1960s established that Methanol, with anode catalysts such as Pt/Ru, had some potential. The early work utilized sulphuric acid as the electrolyte. With the introduction of proton conducting membranes, interest in DMFC systems in the 1990s has been renewed with projects in America, Japan and Europe. Of particular significance has been the work of Los Alamos National Laboratory. If the power density required for vehicle applications are to be achieved, further improvements to anode catalyst performance are necessary. In addition, existing membrane materials are subject to what is known as ‘methanol crossover’, which in turn contributes to poor cell performance. In this context, it is interesting to speculate on how hightemperature membranes such as that developed by Celanese would perform in a DMFC fuelcell (23) .
This study successfully used MEMS technology to develop new generation flexible microtemperature sensors applicable to hightemperature electrochemical environment, its carrier substrate is polyimide foil in thickness of 50μm, the protective layer material is PI with better temperature tolerance, and the overall production process is simple. This new generationmicro sensor has advantages of small size, acid corrosion resistance, good temperature tolerance, free placement, instant measurement and batch production.
include (1) the anode catalyst has poor CO poisoning resistance in low temperature (<80°C) environment; (2) the perfluorosulfonic acid membrane has good ionic conductivity only in high humidity environment; (3) high cathodic reduction overpotential; (4) liquid water and heat removal management , so that the bulk production schedule is delayed. Therefore, the latest international trend, such as U.S. DOE (Department of Energy), EU and Japan NEDO (New Energy Development Organization) develop towards hightemperaturefuelcelltechnology. However, the problems in the hightemperaturefuelcell stack, such as membrane material durability, catalyst corrosion, local flow, pressure and temperature nonuniformity inside the fuelcell stack, should be addressed to commercialize the fuelcell stack. The internal information of fuelcell stake can be discussed by using external measurement, invasive, theoretical modeling and single temperature, flow and pressure measurement. However, the aforesaid methods have some problems, such as too large volume of detector, measurement inaccuracy, influencing the fuelcell stack performance and unknown internal actual reactive state. Luke  used a self-made measuring plate to invade a hightemperaturefuelcell stack to measure the temperature, and compared it with simulation. Zhao  proposed the thermal management model and simulated the temperature, voltage and flow rate in the fuelcell. Kang  designed the numerical model of the rate in hightemperatureprotonexchangemembranefuelcell, and simulated the temperature distribution in the fuelcell. This paper applies the micro-electro-mechanical systems (MEMS) technology to develop flexible integrated (temperature, flow rate and pressure) micro sensor resistant to the high-temperature electrochemical environment. The real-time microscopic monitoring of local temperature, flow and pressure in the hightemperatureprotonexchangemembranefuelcell stack is the topic of this study.
Micro Combined Heat and Power (microCHP) systems based on HighTemperature Polymer Electrolyte Membrane (HTPEM) fuel cells is a promising technology allowing to produce electricity and heat with very high efficiency and low emissions also for small power systems. Polybenzimidazole (PBI) based HTPEM fuel cells, thanks to their high CO tolerance, allow the use of fuels other than pure hydrogen by means of a simplified fuel processing unit. However, their relatively low performance and performance degradation rate are still issues to be overcome in order to allow commercialization. In this work, an energy simulation model developed by the authors in a previous research work, has been improved taking into account the degradation of the fuelcell stack in order to assess the performance of the system over long period of operation. The fuel cells performance degradation over time has been implemented on the basis of experimental data obtained by the authors and on data found in literature. The performance of the system has been studied in different configurations that include the introduction of a lithium battery storage in addition to the fuelcell stack.
Based on the operating temperature, PEMFCs can be classified into high-temperature PEMFCs (HT-PEMFCs) and low-temperature PEMFCs (LT-PEMFCs). The HT-PEMFCs are a kind of promising technology that may overcome many problems faced in LT-PEMFCs, such as carbon monoxide (CO) poison [7, 8], waste heat removal difficulty and comparatively complicated water management system [9, 10]. In addition, HT-PEMFC does not require a humidifier or CO removal process, so the system configuration of HT-PEMFC is simpler than that of LT-PEMFC [11, 12]. Moreover, HT-PEMFC has a higher operating temperature (120℃~200℃), which greatly simplifies the complexity of HT-PEMFC thermal management [13-15] and provides higher quality thermal energy than LT-PEMFC.
the performance of MFCs can significantly improve. Some other inorganic proton conductors such as zirconium phosphate (ZrP) are also a kind of multifunctional material that can be developed for membrane modification [8-9]. One dimensional chain of zirconium phosphate has the advantage of structural regularity, designability, higher thermal stability, good acid and alkali resistance; at the same time, it is also a good water retaining material with good electrical conductivity. In recent years, preparing protonexchange composite membranes by doping ZrP into Nafion membranes has been reported, and it is pointed out that ZrP can improve the water holding capacity of the membrane and thus improve the performance of the MFC [10-13]. The two-dimensional layered structure of α- zirconium phosphate (α-ZrP) make it not only keep the regularity and stability of inorganic zirconium phosphate, but also has the designability to introduce interlayer organic compounds . α-ZrP is a good alternative material for the preparation of composite membranes.
The use of compaction pressure during the assembly of fuel cells plays a crucial role particularly at the interface between the GDL and the reactant-flow plates. It reduces the interfacial contact resistance between those two parts as well as it serves as sealant to ensure proper delivery of reactants to the active flow channels. However, the increase in pressure must be controlled accurately since it may cause damage to some components of the cell. If the reactant-flow plate breaks, the reactants can escape from the reaction channels to the outer side of the cell; alternatively they can cross from channel to channel making less use of the active area of the catalyst. In addition, the bulk resistance of the reactant-flow plate becomes higher and the same applies to the GDL. Any hole or broken strip on the surface of the GDL allows the reactants to cross more easily from the anode to the cathode, or visa versa, increasing the amount of fuel crossover. The reactants can also flow directly from the channels into the catalyst layer without being uniformly distributed on the surface of the catalyst. Finally, the conducting area between the GDL and the catalysts will be reduced.
In the prepared of catalyst layer was used weight ratio 65/35 between catalyst and dry Nafion, following the pattern that has been used at IPEN . The suitable catalyst were mixed with Nafion D520 solution by ultrasonic and then applied to GDL by hand painting. In membrane electrode assemblies (MEAs) preparation was used Nafion 115 membrane and gas diffusion layer (GDL) called MF15 (IPEN Patent PI 1106530-3). Additionally electrodes and MEAs with the same structure described were prepared using Pt/C BASF catalyst to compare results. Thus MEAs were prepared with anode and cathode of palladium (Pd/Pd), anode and cathode of platinum (Pt/Pt), and both combinations anode of palladium and cathode of platinum (Pd/Pt) and the opposite (Pt/Pd). Such MEAs were evaluated in single cells with H 2 and O 2 analytical and atmospheric pressure and
[4-5]. In many applications, keeping a fuelcell in a state of constant power output is necessary. So, maintaining a fuelcellsystem in correct operating conditions is necessary and it requires good control system. Model predictive control (MPC) is an optimization strategy for the control of constrained dynamic systems [6-7]. MPC uses multi-step prediction, rolling optimization and feedback correction control strategies , so it can not only give a good control effect and strong robustness, but also have an advantage of less demand on the accuracy of the model. It is an effective method to solve complex industrial process control [9-10]. However, some problems still need to be solved when using MPC in a real system. It is well know that the traditional approach of expanding the future control signal uses the forward shift operator to obtain the linear-in-the-parameters relation for predicted output in designing a MPC. In the case of rapid sampling, complicated process dynamics or high demands on closed-loop performance, satisfactory approximation of the control signal requires a very large number of forward shift operators, and leads to poorly numerically conditioned solutions and heavy computational load when implemented on-line. So, improved strategies are needed to solve these problems.
This study investigates the influence of microporous layer (MPL) on the performance of a high- temperatureprotonexchangemembranefuelcell utilizing a phosphoric-acid-doped polybenzimidazole (PBI) electrolyte. The effects of MPL compositions including polytetrafluorethylene (PTFE) and carbon black are considered. Under the same catalyst loading, phosphoric acid doping level, and operation conditions, the fuelcell performance is measured to evaluate the importance of MPL and determine the optimal PTFE content and carbon loading. The method of electrochemical impedance spectroscopy is employed to characterize the variations in the ohmic resistance and polarization losses within the cell. The results show that both the PTFE content and carbon loading in the MPL may affect the cell performance significantly. The MPL with a PTFE content of 40 wt% and carbon loading of 1.0 mg cm -2 is found to give the optimal cell performance.
Pressure is one of effective basic operating parameter similar to the temperature. The operating pressure has an effect on many transport parameters that are important for the fuelcell operation. The saturation pressure of water vapor depends only on the temperature and it remains constant for a variation of the inlet pressure. The open circuit volt is function on input temperature and input pressure. From equation described in previous section, it was found that the change in pressure effects in open circuit volt ,but the variation would be have small effect because the pressure factor multiple in very small number. The pressure has major effect on amount of water vapor water product from cathode and amount of vapor water enter with hydrogen at anode side. Pressure would be increasing leads to mass flow rate increasing in due to increasing in output heat. Fig.6 shows I-V curve for different pressure values 2, 3, 5 bar variation at cell polarization curve. It was noted that the activation losses decreases when pressure increasing, due to increasing the cell voltage with pressure increasing. On another hand, unlimited pressure increasing could not achieve higher voltage. Because, with increasing pressure the cell voltage increasing very small value. Furthermore, the cost used for increasing pressure doesn’t produce higher voltage as expected. And, the cell could be damaged in case pressure more than 12 bars.
Structural, physicochemical, and electrical analyses of the obtained products were carried out in this work. The membraneproton conductivities and the fuelcell performances over 200°C were characterised, and these results indicate that the mesoporous structure tetravalent metal ion Brunauer– Emmett–Teller (BET) specific surface areas were measured through nitrogen adsorption using a conventional flow-type adsorption apparatus. The particle size were characterized at 25°C for 1 min by ETA potential meter (Nano-ZS90, Malvern)The catalyst ink (40 wt% Pt/C in a water–ethanol mixture) was directly deposited on the membranes for both the anode and cathode, and the MEAs were held at a temperature of 150 °C . The Pt loading was 0.1 mg cm -2
as shown in Figure 3. It consists of a photovol- taic (PV) cell array, an electrolyzer, a hydrogen (H 2 ) storage, a fuelcell, a catalytic burner, a lead-acid battery, DC/DC converters, DC/AC inverters, diodes, a solar collector, and a water storage tank. The results showed that the size of the solar-hydrogen system can be significantly reduced .
Sulfonation of cPTFE Film grafted Styrene for ProtonExchangeMembraneFuelCell. Sulfonation of γ-ray iradiated and styrene-grafted crosslinked polytetrafluoroethylene film (cPTFE-g-S film) have been done. The aim of the research is to make hydropyl membrane as protonexchangemembranefuelcell. Sulfonation was prepared with chlorosulfonic acid in chloroethane under various conditions. The impact of the percent of grafting, the concentration of chlorosulfonic acid, the reaction time,and the reaction temperature on the properties of sulfonated film is examinated. The results show that sulfonation of surface-grafted films is incomplete at room temperature. The increasing of concentration of chlorosulfonic acid and reaction temperature accelerates the reaction but they also add favor side reactions. These will lead to decreasing of the ion-exchange capacity, water uptake, and proton conductivity but increasing the resistance to oxidation in a perhidrol solution. The cPTFE-g-SS membrane which is resulted has stability in a H 2 O 2 30% solution for 20 hours.
Hitherto, the coupled stress-strain and CFD model and simulation is seldom seen in public publication. The effect of compression on transportation phenomena and the performance of PEMFCs are investigated in this paper. A geometrical model of a PEMFC after compression was obtained and subjected to further simulation using FLUENT to estimate performance. The compression effect of different assembly pressures are then computed and compared and an optimum assembly pressure is subsequently determined for the actual fuelcell assembly.
Carbon Trust's report titled MicroCHP Accelerator demonstrates the benets of micro-CHP eld trials . The programme included the installation of 87 micro- CHP units based on internal combustion and Stirling engines in domestic and com- mercial applications in the UK. The report presents the energy and cost savings in the eld trials and concludes that the economics of micro-CHP systems can be im- proved further by increasing the electrical eciency of the systems. According to the report the micro-CHP - household system would perform better if the electrical e- ciency of the prime mover was higher and the electricity production similar to heat production. In addition, the report claims that with optimised controls, the car- bon savings by domestic micro-CHP systems could potentially be higher. The trials did not include any fuelcellmicro-CHPs as the commercially available products at the period the project started were limited. However, based on the heat-to-power characteristics and higher electrical eciency, fuelcellbasedmicro-CHPs may be more eective over other micro-CHP technologies which are based on thermal en- gines in terms of the potential to reduce energy consumption in buildings. Despite the benecial technical characteristics of fuel cells, there has been small interest by manufacturers in developing fuelcellmicro-CHPs compared to engine based tech- nologies. The Energy Saving Trust places the fuelcellmicro-CHP as an emerging technology in the energy market and suggests that this is due to the reason that the cost per kW of fuelcell is still much greater compared to established technologies such as the Stirling or internal combustion engines .
In this study the influence of polymeric ionomer concentration on the performance of gas diffusion electrode containing Pd/C as a substitute for usual Pt/C electrodes in PEMFC was verified. Values between 56 and 59 % of ionomer related to the mass of the catalyst layer resulted in the highest current densities. It was found that the optimum value was strongly dependent on the work potential and temperature. Current density values of 214 mA.cm -2 were obtained at 500 mV, 85 °C and 1 atm for MEAs with Pd/C on both electrodes of PEMFC. With commercial Pt/C only on the cathode side, a value of 745 mA.cm -2 was reached. For comparison, platinum anodes running under the same conditions showed only 13.9 % higher performance than palladium, indicating that improvements in the synthesis method can enhance the performance for palladium getting to be similar to platinum on the hydrogen oxidation reaction. Indeed, these results proved that, from an economic point of view, it is feasible to apply palladium on anodes to replace platinum, although an adequate assessment of durability is still to be investigated.