Fuel Cell Vehicle System Research Articles

Multi-objective reliability and cost optimization of fuel cell vehicle system with fuzzy feasibility

Fuel cell vehicles (FCVs) are among the so-called green vehicles. They offer high autonomy and fast refueling but are more expensive than other green vehicles. Several efforts are devoted to reducing costs to make FCV technology more accessible. Most research addressing the optimization of FCVs focuses on energy management, sizing of the subsystems, and cost. However, reducing cost conflicts with increasing reliability. This paper addresses the multi-objective reliability and cost optimization of FCVs. Due to inherent uncertainties, this work treats the feasibility of increasing the reliability of the subsystems as fuzzy values and introduces two defuzzification procedures to convert fuzzy values to crisp values, namely the ranking function and the graded mean integration value procedures. The non-dominated sorting genetic algorithm II (NSGA-II) is used with penalty functions to generate the Pareto fronts; then, a fuzzy decision method is adopted to find the best compromise solution. A numerical application of the proposed approach is illustrated. The results obtained show that the graded mean integration value procedure provides superior outcomes. The optimal reliability allocation of the subsystems in the FCV is determined.

From lab to practical: An ammonia-powered fuel cell electric golf cart system

Ammonia (NH3) is a carbon-free hydrogen (H2) carrier because it enables liquid-phase H2 storage and transport under mild conditions. Although the concept of NH3-to-H2 has been frequently proposed, the practical application of NH3 as the energy source for H2 power automotive systems is rarely reported. In this work, an NH3-powered fuel cell electric golf cart system was developed and demonstrated as a proof of concept for NH3-powered fuel cell vehicles. The integration of NH3 cracker (installed with catalyst), gas purifier, fuel cell, and energy management system formed a successful powertrain that thrusts a golf cart into motion. The catalytic performance of both nickel (Ni) and iron (Fe)-based catalysts were measured, and the optimal catalyst demonstrated a > 99.9 % NH3 conversion at 600 ℃. The gas purifier was confirmed to be capable of removing the residual NH3 for a proton exchange membrane fuel cell (PEMFC). The fuel cell, when powered by the cracked and purified gas mixture, revealed comparable performance and power output as compared with the pre-mixed fuel gas mixture (75 %H2/25 %N2), demonstrating the feasibility of the whole system. The integration can successfully power 300 and 600 W fuel cells and continuously charge the energy storage system, offering sufficient energy for a 3kW golf cart for>500 km at 25 km/h. This work is an innovative demonstration of an NH3-powered fuel cell vehicle system, giving rise to a future reference and inspiration for the practical developments of NH3-based H2 fuel applications.

Temperature and hydrogen flow rate controls of diesel autothermal reformer for 3.6 kW PEM fuel cell system with autoignition delay time analysis

In this paper catalyst temperature and hydrogen flow rate controls are an area of interest for autothermal reforming (ATR) of diesel fuel to provide continuous and necessary hydrogen flow to the on-board fuel cell vehicle system. ATR control system design is important to ensure proper and stable performance of fuel processor and fuel cell stack. Fast system response is required for varying load changes in the on-board fuel cell system. To cope with control objectives, a combination of PI and PID controllers are proposed to keep the controlled variables on their setpoints. ATR catalyst temperature is controlled with feedback PID controller through variable OCR (oxygen to carbon ratio) manipulation and kept to the setpoint value of 900 °C. Additionally diesel auto-ignition delay time is implemented through fuel flow rate delay to avoid complete oxidation of fuel. Hydrogen flow rate to the fuel cell stack is kept to setpoint of required hydrogen flow rate according to fuel cell load current using PI controller. An integrated dynamic model of fuel processor and fuel cell stack is also developed to check the fuel cell voltage. Product gas composition of 35, 18 and 4% is achieved for hydrogen, nitrogen, and carbon dioxide, respectively. The results show fast response capabilities of fuel processor following the fuel cell load change and successfully fulfills the control objectives.

Reliability reallocation for cost uncertainty of fuel cell vehicles via improved differential evolution algorithm

AbstractA fuel cell vehicle (FCV) is composed of many subsystems; it is necessary to reallocate subsystem reliability to improve FCV system reliability. A comprehensive evaluation method considering uncertainty is proposed to obtain the interval value of feasibility factor. The FCV cost uncertainty model is established on the basic of parameters such as feasibility factor, initial reliability, limit reliability, and subsystem cost. To solve the optimization problem for cost uncertainty, the cost interval model is transformed into a deterministic model by interval order relation. An improved differential evolution (DE) algorithm is proposed to reallocate subsystem reliability for minimum cost.

Ram air compensation analysis of fuel cell vehicle cooling system under driving modes

The cooling system is one of the major factors used to ensure the performance of the fuel cell vehicle system. In general, the cooling system is composed of a radiator, a reservoir, a water pump, a bypass valve, and a radiator fan. The ram air that enters the vehicle frontal area is also critically important while the vehicle is operating. In this study, cooling system responses considering ram air compensation were investigated to evaluate the control strategy, and control gain was addressed to optimize the control strategy. A dynamic vehicle model was integrated with the fuel cell system model.Three driving cycles were applied to investigate the responses of the cooling system under driving conditions. Three driving conditions considering ram air compensation were investigated to evaluate the cooling system operating trajectory. When the ram air compensation is considered, the cooling system operating trajectory and parasitic power can be accurately predicted. The control adjustment also needs to optimize the parasitic power. As a consequence, the trajectory of system pressure line 1 was found to be more effective for energy saving.

연료전지 자동차용 질소/응축수 통합배출시스템 및 기술 개발

Abstract >> Proper discharge of nitrogen gas and water condensate is required in a conventional fuel cell systemfor performance, stability and durability of fuel cell stacks. Present study covers the development of integratedunit and its functioning logic for simultaneous nitrogen gas purge and water condensate drainage in a fuel cellvehicle system. Configuration of condensate drainage pipe, purge valve and level sensor is considered and optimizedin physical integration. As a key factor, discharge time is considered and optimized based on the test result ofconstant-current operation with various operating temperature in logic development. Consequently, derived optimalvalues are applied and verified in actual vehicle drive mode test.Increase of system design flexibility, weight reduction and cost reduction are anticipated with this study. Additional study for physical and logical improvement is currently being implemented. Key words : Nitrogen purge(질소 배출), Condensate drainage(응축수 배출), Electrochemical reaction(전기화학반응), Fuel cell(연료전지), Constant-current driving test(정전류 운전 시험)

Testing of Lightweight Fuel Cell Vehicles System at Low Speeds with Energy Efficiency Analysis

A fuel cell vehicle power train mini test bench was developed which consists of a 1 kW open cathode hydrogen fuel cell, electric motor, wheel, gearing system, DC/DC converter and vehicle control system (VCS). Energy efficiency identification and energy flow evaluation is a useful tool in identifying a detail performance of each component and sub-systems in a fuel cell vehicle system configuration. Three artificial traction loads was simulated at 30 kg, 40 kg and 50 kg force on a single wheel drive configuration. The wheel speed range reported here covers from idle to 16 km/h (low speed range) as a preliminary input in the research work frame. The test result shows that the system efficiency is 84.5 percent when the energy flow is considered from the fuel cell to the wheel and 279 watts of electrical power was produced by the fuel cell during that time. Dynamic system responses was also identified as the load increases beyond the motor traction capabilities where the losses at the converter and motor controller increased significantly as it tries to meet the motor traction power demands. This work is currently being further expanded within the work frame of developing a road-worthy fuel cell vehicle.

Study of Bidirectional DC-DC Converter Interfacing Energy Storage for Vehicle Power Management Using Real Time Digital Simulator (RTDS)

The bidirectional dc-dc converter, being the interface between Energy Storage Element (ESE) and DC bus, is an essential component of the power management system for vehicle applications including electric vehicle (EV), hybrid electric vehicle (HEV), and fuel cell vehicle (FCV). In this paper, a novel multiphase bidirectional dc-dc converter interfacing with battery to supply and absorb the electric energy in the FCV system was studied with the help of real time digital simulator (RTDS). The mathematical models of fuel cell, battery and dc-dc converter were derived. A power management strategy was developed and first simulated in RTDS. A Power Hardware-In-the-Loop (PHIL) simulation using RTDS is then presented. The main challenge of this PHIL is the requirement for a highly dynamic bidirectional Simulation-Stimulation (Sim-Stim) interface. This paper describes three different interface algorithms. The closed-loop stability of the resulting PHIL system is analyzed in terms of time delay and sampling rate. A prototype bidirectional Sim-Stim interface is designed to implement the PHIL simulation.

Design and implementation of renewable hydrogen fuel cell vehicles

In this paper, a systematic approach for investigating a hydrogen fuel cell hybrid vehicle system is considered. This approach involves developing a mathematical model incorporating renewable hydrogen production, storage and refuelling of the fuel cell vehicle system. The University of Glamorgan’s (UOG) Sustainable Environment Research Centre (SERC) have developed the UK’s first alternative energy refuelling facility at the University’s Hydrogen Centre in Baglan. Hydrogen produced from renewable energy on-site will be use to refuel the UOG, Faculty of Advanced Technology, Hydrogen Bus (UOGHB). The simulation model is used to analyse the effect of operating conditions and energy demand of the UOGHB. Comparisons are made between the simulation results from the mathematical model and UOGHB experimental data. A general agreement exists but where disagreements and anomalies occur, reasoned arguments are presented in explanation. The model represents a reasonable overall representation of the UOGHB. This model can be used for controller development, to improve operational quality and performances.

Study on a Regenerative Fuel Reformer for a Zero-Emission Vehicle System.

A zero-emission fuel cell vehicle system using a thermally regenerative fuel reformer, which had a performance of carbon dioxide fixation from a reformed gas, was proposed. A packed-bed regenerative reforming reactor containing a reforming catalyst and calcium oxide was examined for methane steam reforming under atmospheric pressure. It was demonstrated that carbon dioxide was well fixed by chemical absorption of calcium oxide in a preliminary experiment. The methane reforming, carbon monoxide shifting and calcium oxide carbonation proceeded simultaneously in the regenerative reactor. The carbonation of calcium oxide fixed the carbon dioxide generated through the reforming, and the hydrogen purity of effluent gas was raised beyond the equilibrium amount of a conventional fuel reformer. The vehicle system was expected to improve the efficient utilization of surplus thermal energy and surplus electricity by utilizing them for the regeneration of the reformer.