Performance Of Fuel Cell System Research Articles

The influence of psychrophilic and mesophilic start-up temperature on microbial fuel cell system performance

The successful scale-up of microbial fuel cells (MFC) for wastewater treatment in temperate regions requires the development of reactor systems that are robust to seasonal fluctuations and are energy efficient. Therefore, as part of this study, a MFC was acclimated for operation over a 8–35 °C temperature range. Employing single chamber air cathode MFCs, system performance was initially examined at three different operating temperatures (10 °C, 20 °C and 35 °C). At each temperature a maximum steady-state voltage of 0.49 ± 0.02 V was achieved after an operational period of 47 weeks, with the time to reach steady-state voltage being dependent on acclimation temperature. The highest COD removal rates of 2.98 g COD L−1 d−1 were produced in the 35 °C reactor but coulombic efficiencies (CEs) were found to be significantly higher at psychrophilic temperatures. Acclimation at different temperatures was found to a have a significant effect on the dynamic selection of psychrophilic, psychrotolerant and mesophilic anode respiring bacteria (ARB). This was demonstrated by subsequent static temperature studies which showed that only the 20 °C acclimated reactor was capable of optimal operation over a 10–35 °C temperature range and this was facilitated by the activity of psychrotolerant microorganisms. These results show that MFC systems may be successfully adapted for use in temperate climates to provide a stable method of bioenergy recovery and organic contaminant removal as part of wastewater treatment processes.

Effects of PEMFC operating parameters on the performance of an integrated ethanol processor

In this paper the performance of a complete fuel cell system processing ethanol fuel has been analyzed as a function of the main fuel cell operating parameters. The fuel processor is based on the steam reforming process, followed by high- and low-temperature shift reactors, and carbon monoxide preferential oxidation reactor, which are coupled to a polymeric fuel cell (PEMFC). The goal was to analyze and improve the fuel cell system performance by simulation techniques. PEMFC operation has been analyzed using an available parametric model, which was implemented within HYSYS environment software. Pinch Analysis concepts were used to investigate the process energy integration and determine the maximum efficiency minimizing ethanol consumption. The system performance was analyzed for the SR-12 Modular PEM Generator, the Ballard Mark V fuel cell and the BCS 500 W stack. The net system efficiency is dependent on the required power demand. Efficiency values higher than 50% at low loads and less than 30% at high power demands are computed. In addition, the effect of fuel cell temperature, pressure and hydrogen utilization was analyzed. The trade-off between the reformer yield and the fuel cell performance defines the optimal operation pressure. The cell temperature determines operating zones where the water, involved in the reforming reactions, can be produced or demanded.

A practical model for evaluating the performance of proton exchange membrane fuel cells

Several models have been proposed in the literature to predict the performance of proton exchange membrane fuel cells (PEMFC). These models have different levels of complexity and can be divided basically into two groups: ( i) mechanistic (theoretical); and ( ii) semi-empirical models. The mechanistic models are obtained from electrochemical, thermodynamic, and fluid dynamic equations, and describes, with a high level of details, the processes in the operation of the fuel cell. The main drawback of the mechanistic approach is that, in general, the models are very complex, requiring the knowledge of parameters that are difficult to be obtained. Semi-empirical models, on the other hand, are easier to be obtained and can also be used to accurately predict the fuel cell system performance for engineering applications. In this paper, a new semi-empirical model, that is simpler than others presented in the literature, is proposed. It is derived by using semi-empirical equations and the resulting empirical coefficients are calculated through linear least squares. The model can be used in the evaluation of performance of small-distributed electrical generation systems, and also for the design of fuel cell systems for vehicles and portable electronics.

Performance Assessment of Bioethanol-Fed Solid Oxide Fuel Cell System Integrated with Distillation Column

This paper investigated the performance of a bioethanol-fed Solid Oxide Fuel Cell (SOFC) system integrated with a distillation column (SOFC-D). Excess heat from the SOFC system was directly utilized in the distillation column where bioethanol (5 mol%) was purified to a desired concentration before feeding to the SOFC system consisting of an air heater, an ethanol/water heater, a reformer, an SOFC preheater, an SOFC stack and an afterburner. The SOFC-D system was simulated using Aspen PlusTM for the distillation portion and MatlabTM for the SOFC portion. The effects of operating parameters; i.e., ethanol concentration, ethanol recovery, fuel utilization and operating voltage on the performance and energy involved in the SOFC-D system (e.g. distillation energy: QD and the net exothermic heat of the SOFC system: QSOFC,Net) were examined. In addition, the performance of the SOFC-D system at the energy sufficient point where QD = QSOFC,Net was considered. The integration of the distillation column with the SOFC system was found to offer superior SOFC performance. The ethanol recovery and fuel utilization significantly influenced the overall electrical efficiency and power density. Quite low performances are obtained when one operated the SOFC-D without an external heat source. The maximum overall efficiency and power density (~35% and 0.22 W cm-2) occured at an ethanol recovery of 80% and Uf of 90%.

Parameters Affecting the Performance of a Residential-Scale Stationary Fuel Cell System

Researchers at the National Institute of Standards and Technology have measured the performance of a residential fuel cell system when subjected to various environmental and load conditions. The system, which uses natural gas as its source fuel, is capable of generating electrical power at three nominal power levels (2.5, 4.0, and 5.0kW) while providing thermal energy for user-supplied loads. Testing was conducted to determine the influence of ambient temperature, relative humidity, electrical load, and thermal load on system performance. Steady-state and transient tests were conducted. The steady-state tests were performed in accordance with the American Society of Mechanical Engineering Fuel Cell Power Systems Performance Test Code (PTC-50) for fuel cell power systems. The results of the investigation are being used to develop a proposed rating procedure for residential fuel cell units.

Direct Methanol Fuel Cell System Performance: From Materials, Components, to System and Fuel Efficiency

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Evaluation of fuel cell system efficiency and degradation at development and during commercialization

Two primary parameters stand out for characterizing fuel cell system performance. The first and most important parameter is system efficiency. This parameter is relatively easy to define, and protocols for its assessment are already available. Another important parameter yet to be fully considered is system degradation. Degradation is important because customers desire to know how long their purchased fuel cell unit will last. The measure of degradation describes this performance factor by quantifying, for example, how the efficiency of the unit degrades over time. While both efficiency and degradation concepts are readily understood, the coupling between these two parameters must also be understood so that proper testing and evaluation of fuel cell systems is achieved. Tests not properly performed, and results not properly understood, may result in improper use of the evaluation data, producing improper R&D planning decisions and financial investments. This paper presents an analysis of system degradation, recommends an approach to its measurement, and shows how these two parameters are related and how one can be “traded-off” for the other.

Development of a model for thermoeconomic design and operation optimization of a PEM fuel cell system

A thorough analysis of a polymer electrolyte membrane (PEM) fuel cell system is presented. A generalized performance model of a single PEM fuel cell is developed and applied in a semi-empirical form for a Ballard Mark V 35-cell, 5 kW PEM fuel cell. A thermodynamic and economic analysis of the components and of the whole system is performed. The purpose of this study is to explore the intrinsic relations among various fuel cell system performance and cost indicators in order to provide insights for new cost effective and high performance designs. Optimization techniques have been applied in order to determine the optimal design and operation mode of the system. An application of the system onboard merchant ships has been considered as an example.

Effects of ambient conditions on fuel cell vehicle performance

Ambient conditions have considerable impact on the performance of fuel cell hybrid vehicles. Here, the vehicle fuel consumption, the air compressor power demand, the water management system and the heat loads of a fuel cell hybrid sport utility vehicle (SUV) were studied. The simulation results show that the vehicle fuel consumption increases with 10% when the altitude increases from 0 m up to 3000 m to 4.1 L gasoline equivalents/100 km over the New European Drive Cycle (NEDC). The increase is 19% on the more power demanding highway US06 cycle. The air compressor is the major contributor to this fuel consumption increase. Its load-following strategy makes its power demand increase with increasing altitude. Almost 40% of the net power output of the fuel cell system is consumed by the air compressor at the altitude of 3000 m with this load-following strategy and is thus more apparent in the high-power US06 cycle. Changes in ambient air temperature and relative humidity effect on the fuel cell system performance in terms of the water management rather in vehicle fuel consumption. Ambient air temperature and relative humidity have some impact on the vehicle performance mostly seen in the heat and water management of the fuel cell system. While the heat loads of the fuel cell system components vary significantly with increasing ambient temperature, the relative humidity did not have a great impact on the water balance. Overall, dimensioning the compressor and other system components to meet the fuel cell system requirements at the minimum and maximum expected ambient temperatures, in this case 5 and 40 °C, and high altitude, while simultaneously choosing a correct control strategy are important parameters for efficient vehicle power train management.

Artificial Neural Network Modeling of PEM Fuel Cells

Artificial neural network (ANN) approaches for modeling of proton exchange membrane (PEM) fuel cells have been investigated in this study. This type of data-driven approach is capable of inferring functional relationships among process variables (i.e., cell voltage, current density, feed concentration, airflow rate, etc.) in fuel cell systems. In our simulations, ANN models have shown to be accurate for modeling of fuel cell systems. Specifically, different approaches for ANN, including back-propagation feed-forward networks, and radial basis function networks, were considered. The back-propagation approach with the momentum term gave the best results. A study on the effect of Pt loading on the performance of a PEM fuel cell was conducted, and the simulated results show good agreement with the experimental data. Using the ANN model, an optimization model for determining optimal operating points of a PEM fuel cell has been developed. Results show the ability of the optimizer to capture the optimal operating point. The overall goal is to improve fuel cell system performance through numerical simulations and minimize the trial and error associated with laboratory experiments.

GTI’s DMFC membrane in cooperative tests

The Gas Technology Institute (GTI) in Illinois, in a cooperative program with the US Army Research Laboratory (ARL), reports that a new membrane it has developed for PEM fuel cells offers substantially improved direct methanol fuel cell system performance. Visit www.re-focus.net for the latest renewable energy news

Optimal fuel cell system design considering functional performance and production costs

In this work the optimization-based, integrated concurrent design method is applied to the modelling, analysis, and design of a transportation fuel cell system. A general optimal design model considering both functional performance and production costs is first introduced. Using the Ballard Mark V Transit Bus fuel cell system as an example, the study explores the intrinsic relations among various fuel cell system performance and cost aspects to provide insights for new cost-effective designs. A joint performance and cost optimization is carried out to demonstrate this new approach. This approach breaks the traditional barrier between design (concerning functional performance) and manufacturing (concerning production costs), allowing both functional performance and production costs to be fed into design phase and to be jointly optimized.