Fuel Cell Power System Research Articles

Projecting the Impact of Aircraft Design Decisions on the Performance of a Fuel Cell Power and Energy System in Unmanned Aircraft Systems

Projecting the Impact of Aircraft Design Decisions on the Performance of a Fuel Cell Power and Energy System in Unmanned Aircraft Systems

Exergy, Economic, and Environmental Analysis of a PEM Fuel Cell Power System to Meet Electrical and Thermal Energy Needs of Residential Buildings

Abstract In this paper, a Polymer Electrolyte Membrane (PEM) fuel cell power system including burner, steam reformer, heat exchanger, and water heater has been considered. A PEM fuel cell system is designed to meet the electrical, domestic hot water, heating, and cooling loads of a residential building located in Tehran. Operating conditions of the system with consideration of the electricity cost has been studied. The cost includes social cost of the environmental pollutants (e.g. CO2, CO and NO). The results show that the maximum energy needs of the building can be met by 12 fuel cell stacks with nominal capacity of 8.5 kW. Annual average electricity cost of thissystem is equal to 0.39 US$/kWh and entropy generation of this system through a year is equal to 1004.54 GJ/K1. It is also concluded that increase in ambient temperature from 1 °C to 40 °C increases the entropy generation by 5.73%, carbon monoxide by 14.56%, and nitrogen monoxide by 8.9%, but decreases carbon dioxide by 0.47%.

Dynamic modelling and simulation of a polymer electrolyte membrane fuel cell used in vehicle considering heat transfer effects

Fuel cell technology is recently becoming one of the most interesting fields for the car companies to invest in. This interest is because of their high efficiency and zero environmental pollution. Polymer electrolyte membrane fuel cells are the most appropriate type of fuel cells for use in vehicles due to their low performance temperature and high power density. Air and fuel mass flow rate and partial pressure, fuel cell stack temperature, relative humidity of fuel cell membrane, and heat and water management are the effective parameters of fuel cell power systems. Good transient behavior is one of the important factors that affect the success of fuel cell vehicles. In order to avoid stack voltage drop during transient condition, the control system of fuel cell vehicle is required to preserve optimal temperature, membrane hydration, and partial pressure of reactants across the membrane. In this paper, we developed a dynamic model for fuel cell power system. The compressor dynamic, supply and return manifold filling dynamics (anode and cathode), cooling system dynamic, membrane hydration, and time-evolving reactant partial pressure are the most significant parameters in transient and steady state of system. The effects of membrane humidity, varying inlet air pressure, and compressor performance condition on the generated power are studied in this paper.

Generalized Predictive Control for Gas Supply System in a Proton Exchange Membrane Fuel Cell

Gas supply system in a proton exchange membrane fuel cell power system consists of hydrogen supply and oxygen supply. In order to improve the system output performance and maintain the pressure difference between the anode and cathode at the setting points under the variational load currents, a generalized predictive control strategy is applied to the gas supply system of a proton exchange membrane fuel cell in this paper. The fuel cell stack and gas supply system were modeled for the purpose of performance analysis and controller design. And then the designed generalized predictive controller was implemented to control the hydrogen flow rate and oxygen compressor voltage. The simulation results illustrated that the proposed controller can provide better response characteristics of the pressure difference, hydrogen and oxygen supply system as compared with PID controller.

Input ripple current compensation using DSP control in reliable fuel cell power systems

Fuel cell power systems have increasingly become popular because of their inherent advantages over conventional energy systems. A fuel cell system typically requires some kind of power conditioning that usually includes a DC–DC converter and a DC-AC inverter. In a single phase system, the operation of a single phase inverter introduces a second harmonic (120 Hz) current ripple into the system. This ripple has been found to be detrimental to the performance, life and efficiency of the fuel cell if it is not adequately controlled. This paper proposes an active filtering method to cancel the second harmonic current ripple drawn from the fuel cell source in a single phase fuel cell system. This approach provides an alternate path for the 120 Hz current preventing it from flowing through the fuel cell. The conventional and the proposed systems have been simulated using PSpice and the results have been presented. Experimental results from a laboratory prototype are also included to validate the proposed approach. A major feature of this implementation is the use of a DSP TMS 320F2808 for the overall control and monitoring of the system.

Demonstration of a highly efficient solid oxide fuel cell power system using adiabatic steam reforming and anode gas recirculation

Solid oxide fuel cells (SOFCs) are being developed for a wide variety of applications because of their high efficiency over a wide range of power levels. Applications for SOFCs include 1–2kW residential combined heat and power applications, 100–250kW systems for distributed generation and grid extension, and megawatt-scale power plants utilizing coal. This paper reports on the development of a highly efficient, small-scale SOFC power system operating on methane. The system uses adiabatic steam reforming of methane and anode gas recirculation to achieve high net electrical efficiency. The heat and water required for the endothermic reforming reaction are provided by the recirculated anode gas emerging from the SOFC stack. Although the single-pass fuel utilization is only about 55%, because of the anode gas recirculation the overall fuel utilization is up to 93%. The demonstrated system achieved net power output of 1650–2150W with a maximum net LHV efficiency of 0.566 at 1720W. Overall system efficiency could be further improved to over 0.60 with use of properly sized blowers.

Optimization of Fuel Processing Unit of Fuel Cell System using Six-Sigma Technique

A reformer for a small fuel cell system is an apparatus which converts hydrocarbon fuel into hydrogen-rich gas. Among many indices of a reformer, the most crucial index of a reformer is CO concentration in the off-gas out of reformer which must be controled under 5ppm for the efficiency and performance of a system. This paper suggests the criteria of a reformer operation for the stability of a reformer in a fuel cell system by deducing crucial indices and improving processes. The six-sigma technique was applied to verify the optimum control and operation of a reformer of a fuel cell combined heat and power system. The result of temperature control of each parts of a reformer system is the concentration of CO which is the most important factor for the operation of a fuel cell system. The temperature of the parts of a reformer, MTS, LTS and Prox, were controled so that the concentration of CO.

Effects of Compression Distribution on PEMFC Stacks Using Reformate as Fuel

A PEM fuel cell stack is usually integrated with a reformer into a stationary fuel cell power system. Reformate may cause a phenomenon of voltage vibration in some cells of a stack, and these cells are usually close to end plates. In this work, we studied the instability phenomenon within a 10-cell stack. The instability was observed by monitoring the voltage variation of each cell at high currents. From the test of the assembly pressure distribution, it was found that the pressure distribution of cells close to the end plates was more uneven than others. The scanning electron microscopy (SEM) was used to observe the microstructure of gas diffusion layers within these cells. These scanning electron microscopy images showed that the gas diffusion layers close to end plates suffered more fibers damage, i.e. disabling the hydrophobic structure. The contact angle test results supported this concept as well. In this study, we interpreted that the instability was caused by flooding. If a stack clamping apparatus, providing uniform compression, was used to clamp the stack during testing, the performance of each cell remained stable even in harsh operational conditions. In this paper, it is considered that the pressure distribution of gas diffusion layers is intensely related with water removal ability as reformate is fuel for a proton exchange membrane fuel cell stack.

Power Management Unit With Its Control for a Three-Phase Fuel Cell Power System Without Large Electrolytic Capacitors

This paper investigates a three-phase four-wire fuel cell power system. The system is sensitive to the load characteristic in a stand-alone mode, because variation or unbalance of the three-phase load will affect the safety and lifespan of the fuel cell. A novel power management unit (PMU) with its control strategy is proposed. The PMU can compensate fuel cell slow dynamics. In addition, the PMU acts as dc bus capacitors to deal with the low-frequency current ripple. Therefore, the large dc bus electrolytic capacitors can be eliminated in the fuel cell power system. The control strategy of the PMU is derived and the whole system is verified by the experimental results.

Configuration of solar-hydrogen mild hybrid fuel cell power systems for electric vehicles

This paper considers the evaluation of a configuration of solar-hydrogen mild hybrid fuel cell power systems for electric vehicles. The primary objectives are to relieve the prerequisite need on the infrastructure for hydrogen supply and reduce the cost of fuel cell module compared to the conventional fuel cell electric vehicles. The advantage of the proposed vehicle power system configuration is addressed in terms of the criteria of availability and affordability. Availability considers issues of energy resource and engineering technology. Affordability considers issues of operational cost and environmental cost. With regard to issues of implementation, a cost-benefit ratio is defined and used to evaluate the feasibility of the proposed mild hybrid power systems. A demonstration is conducted based on four exemplary vehicles. The value of the computed cost-benefit ratio can be used to determine the suitability of implementation of the proposed configuration of a hybrid power system for electric vehicles. The presented costs are based on per/unit prices as cited by manufacturers on the Internet and are useable guidelines for further development. In actual practice, substantial further efforts would be needed to facilitate safe, reliable cost-efficient operation of the proposed system.

Design and implementation of interleaved boost converter for fuel cell systems

Fuel cell is one of the promising renewable and sustainable power sources because of its high power density and very low emission. It can be utilized as a clean power source for various applications such as portable electronic appliances, transportation and residential building. In order to design a highly efficient fuel cell power system, a suitable DC–DC converter is required. Among the various topologies of DC–DC converters, interleaved boost converter (IBC) has been proposed as a suitable interface for fuel cells to convert low voltage high current input into a high voltage low current output. The advantages of interleaved boost converter compared to the classical boost converter are low input current ripple, high efficiency, faster transient response, reduced electromagnetic emission and improved reliability. In the proposed interleaved converter, the front end inductors are magnetically coupled to improve the electrical performance and reduce the weight and size. This paper focuses on a three-phase directly coupled IBC using CoolMOS transistor and Silicon carbide (SiC) diode instead of the classical two-phase reported in the literature based on the tradeoff between the ripple content, cost and complexity. Mathematical analysis of overall current ripple, design equations and switching loss studies for IBC have been presented. Simulation of IBC interfaced with fuel cells have been performed using MATLAB/SIMULINK. Hardware prototypes have been built to validate the results.

Integration of Hybrid Energy System in Vehicle

The main purpose of this paper is to integrate and apply hydrogen-oxygen fuel cells as the major power system, which is combined with the auxiliary power system of a lead-acid battery in the hybrid fuel cell vehicles, and design and modify vehicle structure and a transmission system in order to improve stability and controllability. Furthermore, this study designs an appropriate power control system to increase vehicle travel time, reduce power consumption, and finally, integrate the hydrogen storage system into the power source of hybrid fuel cell vehicles for the development of energy-saving carbon-free transport vehicles. In general road surface driving tests, a low-pressure metallic hydrogen storage tank under the pressure of 0.5bar is used to provide 10g of hydrogen gas fuel to a 200W hydrogen-oxygen fuel cell stack as the major power source, and the auxiliary power source of two serially connected 12V 1.5Ah lead-acid batteries is used. The total weight of the hybrid hydrogen-oxygen fuel cell power system is 1.3 kg. In the general road surface test of a hybrid hydrogen-oxygen fuel cell vehicle, the average driving speed is 11km/hr, the motor consumption power is 45W, and the travel time is 90 minutes. The hydrogen-oxygen fuel cell vehicle is equipped with a three-stage gear box, and is able to automatically shift to the desired gear. The maximum driving speed can be up to 20km/hr, with motor power consumption of 90W.

Cost Benefit Analysis of Using Clean Energy Supplies to Reduce Greenhouse Gas Emissions of Global Automotive Manufacturing

Automotive manufacturing is energy-intensive. The consumed energy contributes to the generation of significant amounts of greenhouse gas (GHG) emissions by the automotive manufacturing industry. In this paper, a study is conducted on assessing the application potential of such clean energy power systems as solar PV, wind and fuel cells in reducing the GHG emissions of the global auto manufacturing industry. The study is conducted on the representative solar PV, wind and fuel cell clean energy systems available on the commercial market in six representative locations of GM’s global facilities, including the United States, Mexico, Brazil, China, Egypt and Germany. The results demonstrate that wind power is superior to other two clean energy technologies in the economic performance of the GHG mitigation effect. Among these six selected countries, the highest GHG emission mitigation potential is in China, through wind power supply. The maximum GHG reduction could be up to 60 tons per $1,000 economic investment on wind energy supply in China. The application of wind power systems in the United States and Germany could also obtain relatively high GHG reductions of between 40–50 tons per $1,000 economic input. When compared with wind energy, the use of solar and fuel cell power systems have much less potential for GHG mitigation in the six countries selected. The range of median GHG mitigation values resulting from solar and wind power supply are almost at the same level.

ZVS Resonant Converter With Series-Connected Transformers

This paper presents a new series-resonant converter with series-connected transformers in order to realize zero voltage switching (ZVS) for power switches, zero current switching (ZCS) for rectifier diodes at full load, less transformer secondary winding with a full-wave rectifier, and load current sharing. Two series-resonant converters using the same switches are operated with interleaved half switching cycle. The secondary windings of transformers are connected in series in order to ensure that the primary side currents are balanced to share load current. Thus, the sizes of the transformer core and bobbin are reduced. The full-wave diode rectifier is adopted on the output side such that the voltage stress of the rectifier diodes is equal to the output voltage, rather than being two times the output voltage as in a conventional center-tapped rectifier topology. Based on the resonant behavior, all switches are turned on at ZVS, and rectifier diodes are turned off at ZCS if the switching frequency is less than the series resonant frequency. The proposed converter can be applied for the power supply unit of all-in-one PCs, liquid crystal display (LCD) TVs and servers, and dc-dc converters for fuel-cell power system. Laboratory experiments with a 1000-W prototype, verifying the effectiveness of the proposed converter, are described.

선박동력용 SOFC/ST 하이브리드시스템의 성능 평가

연료전지시스템의 고효율화를 목적으로 수소가 가진 화학적 에너지를 최대한 전력화하기 위하여 연료전지에서 발생하는 폐열을 적극 활용할 필요가 있다. 이런 목적에 폐열을 이용하는 증기터빈과 연료 전지를 결합시킨 SOFC/ST 하이브리드시스템이 적합하다. 본 논문은 SOFC/ST 하이브리드시스템에 대한 셀의 작동온도와 전류밀도, 연소기 출구 온도, 보일러 출구 가스온도가 시스템의 성능에 미치는 영향 등을 시뮬레이션을 통하여 검토한 것으로 증기터빈의 일정 조건에서는 연료전지 스택에서 다량의 폐열이 발생하는 경우가, 연료전지의 일정 조건에서는 연소기에 추가적 연료 공급을 억제하는 경우에서 하이브리드시스템의 효율이 증가됨을 확인하였다.

An integrated simulation model for PEM fuel cell power systems with a buck DC–DC converter

Fuel cell powered systems generally have a high current and a low voltage. Therefore, the output voltage of the fuel cell must be stepped-down using a DC–DC buck converter. However, since the fuel cell and converter have different dynamics, they must be suitably coordinated in order to satisfy the demanded load. Accordingly, this study commences by constructing a MATLAB/Simulink model of a proton exchange membrane fuel cell (PEMFC) system comprising a PEMFC stack, an air/fuel supply system, and a temperature control system. The validity of the PEMFC model is demonstrated by comparing the simulation results obtained for the polarzation curves of a single fuel cell with the corresponding experimental curves. A model is then constructed of the DC–DC buck converter used to step-down the PEMFC output voltage. In addition, a sliding mode control (SMC) scheme is proposed for the DC–DC buck converter which guarantees a low and stable output voltage given transient variations in the output voltage of the PEMFC. Finally, a model is constructed of a DC–AC inverter with a pulse width modulated (PWM) control scheme which enables the PEMFC stack to supply the grid or power AC applications directly. Overall, the combined PEMFC/DC–DC buck converter/DC–AC inverter model provides a powerful and versatile tool for the design and development of a wide range of PEMFC power systems.

Fuel cell hybrid taxi life cycle analysis

A small fleet of classic London Taxis (Black cabs) equipped with hydrogen fuel cell power systems is being prepared for demonstration during the 2012 London Olympics.This paper presents a Life Cycle Analysis for these vehicles in terms of energy consumption and CO2 emissions, focusing on the impacts of alternative vehicle technologies for the Taxi, combining the fuel life cycle (Tank-to-Wheel and Well-to-Tank) and vehicle materials Cradle-to-Grave.An internal combustion engine diesel taxi was used as the reference vehicle for the currently available technology. This is compared to battery and fuel cell vehicle configurations. Accordingly, the following energy pathways are compared: diesel, electricity and hydrogen (derived from natural gas steam reforming).Full Life Cycle Analysis, using the PCO-CENEX drive cycle, (derived from actual London Taxi drive cycles) shows that the fuel cell powered vehicle configurations have lower energy consumption (4.34MJ/km) and CO2 emissions (235g/km) than both the ICE Diesel (9.54MJ/km and 738g/km) and the battery electric vehicle (5.81MJ/km and 269g/km).

Direct methanol fuel cells: A database-driven design procedure

To test the feasibility of DMFC systems in preliminary stages of the design process the design engineer can make use of heuristic models identifying the opportunity of DMFC systems in a specific application. In general these models are to generic and have a low accuracy. To improve the accuracy a second-order model is proposed in this paper. The second-order model consists of an evolutionary algorithm written in Mathematica, which selects a component-set satisfying the fuel-cell systems’ performance requirements, places the components in 3D space and optimizes for volume. The results are presented as a 3D draft proposal together with a feasibility metric. To test the algorithm the design of DMFC system applied in the MP3 player is evaluated. The results show that volume and costs are an issue for the feasibility of the fuel-cell power-system applied in the MP3 player. The generated designs and the algorithm are evaluated and recommendations are given.

Efficiency analyses of ethanol-fueled solid oxide fuel cell power system

In this study, the balance of plant (BOP) of an ethanol-fueled SOFC is analyzed using the GCTool software package developed by Argonne National Laboratory (ANL). The effects of the excess air ratio and fuel utilization on the electric and heat efficiencies of the SOFC are systematically examined for two reforming methods (steam reforming and auto-thermal reforming) and two flow sheets (BOP A and BOP B). In BOP A, the cathode off-gas is passed directly to the afterburner together with the unreacted fuel, and the hot flue gas exiting the burner is then used to provide the thermal energy required for the ethanol reforming process. In BOP B, the cathode off-gas is passed through a heat exchanger in order to heat the ethanol fuel prior to the reforming process, and is then flowed into the burner with the unreacted fuel. The results show that given an SOFC inlet temperature of 650 °C, a fuel utilization of 70.2% and excess air ratios of 4, 6 and 7, respectively, the overall system efficiency is equal to 74.9%, 72.3% and 71.0%. In general, the results presented in this study provide a useful starting point for the design and development of practical ethanol-fueled SOFC test systems.

Development and dynamic characteristics of hybrid fuel cell-powered mini-train system

This paper describes the development of a hybrid Proton Exchange Membrane Fuel Cell and its integration into a mini-train (that can carry 9–12 people). The fuel cell power system is composed of a 200 W PEMFC, four metal hydrogen-storage tanks with a low pressure, lead-acid battery group, and an effectively designed electronic energy control system. The parallel connection of fuel cells and lead-acid batteries can supply power. The mini-train runs on a track that is 18.4 cm wide and 212 m long in the open air at the National Science and Technology Museum. After two years of running, the mini train has been operating over for 2000 h and transported more than 70,000 passengers. The dynamic response of the fuel cell group can be tested. The result demonstrates that the parallel connection of lead-acid batteries and fuel cells can withstand the high temperatures and high humidity of Taiwan and supply power stably. This fuel cell power supply system can provide the same power to the mini-train as do the lead–acid batteries.