Fuel Cell Vehicle Simulation – Part 1: Benchmarking Available Fuel Cell Vehicle Simulation Tools

Fuel cell vehicle simulation is one method for systematic and fast investigation of the different vehicle options (fuel choice, hybridization, reformer technologies). However, a sufficient modeling program, capable of modeling the different design options, is not available today. Modern simulation programs should be capable of serving as tools for analysis as well as development. Shortfalls of the existing programs, initially developed for internal combustion engine hybrid vehicles, are: (i)Insufficient modeling of transient characteristics; (ii) Insufficient modeling of the fuel cells system; (iii) Insufficient modeling of advanced hybrid systems; (iv) Employment of a non‐causal (backwards looking) structure; (v) Significant shortcomings in the area of controls. In the area of analysis, a modeling tool for fuel cell vehicles needs to address the transient dynamic interaction between the electric drive train and the fuel cell system. Especially for vehicles with slow responding on‐board fuel processor, this interaction is very different from the interaction between a battery (as power source) and an electric drive train in an electric vehicle design. Non‐transient modeling leads to inaccurate predictions of vehicle performance and fuel consumption. When applied in the area of development, the existing programs do not support the employment of newer techniques, such as rapid prototyping. This is because the program structure merges control algorithms and component models, or different control algorithms (from different components) are lumped together in one single control block and not assigned to individual components as they are in real vehicles. In both cases, the transfer of control algorithms from the model into existing hardware is not possible. This paper is the first part of a three part series and benchmarks the “state of the art” of existing programs. The second paper introduces a new simulation program, which tries to overcome existing barriers. Specifically it explicitly recognizes the dynamic interaction between fuel cell system, drive train and optional additional energy storage.     

Strategies for Dimensioning Two‐Wheeled Fuel Cell Hybrid Electric Vehicles Using Numerical Analysis Software

Owing to the limitation of fossil fuels and high consumption and pollution for transportation, the vehicle industry is looking for other sources of energy. A fuel cell hybrid electric vehicle (FCHEV) could be a suitable solution considering the state of the art of main components. This paper presents the simulation of powertrains for FCHEVs in order to dimension the fuel cell (FC) as primary source of energy and to investigate the power flows during both motoring and recuperative braking. For this purpose a Matlab/Simulink^® model has been built up which can be used for a wide range of applications. The results of simulation show which is the best powertrain configuration for two‐wheeled vehicles in three different cases: a bike in which the traction force is provided by both electric motor and the pedaling of the cyclist, a bike in which the traction force is provided only by an electric motor without pedaling and a motorcycle for 2 passengers. Specifically, the consumption, the state of charge (SOC) of battery and the amount of energy generated by each source of energy have been monitored. The model validation was done by comparison between the obtained results and scientific articles in the literature.     

Hydrogen Automobile Heads Toward Series Production HydroGen3 Puts Fuel Cells on the Road

General Motor's concept vehicle HydroGen3, based on the Opel Zafira production model, represents the third generation of fuel cell concept vehicles. Groundbreaking new technical and engineering improvements have been reached, e.g. the integration of the latest generation of fuel cell stacks. The fleet demonstrations will start this year. Given the current stage of development at GM/Opel, hydrogen‐powered automobiles could be mass‐produced in about eight years. An efficient fuel cell technology suitable for everyday use is the essential pre‐condition for the development of an alternative propulsion system, which would replace the classic crude oil‐based fuels for the vehicles of the future. However, this technology alone is not sufficient to establish fuel cell automobiles as viable substitutes for conventional vehicles with gasoline and diesel engines. Factors such as purchase price, safety, engine performance and driving dynamics also play a decisive role for the customer. General Motors (GM) has therefore invested more than one billion dollars to develop an automobile incorporating state‐of‐the‐art fuel cell technology with vehicle characteristics suited to the marketplace. The hydrogen concept vehicle HydroGen3 (Figure 1) marks the newest and most comprehensive advance made by GM/Opel on the road to fuel cell vehicle market readiness. Test drives conducted by an international group of expert journalists at the Grand‐Prix course in Monte Carlo in December 2002 confirmed that the HydroGen3 has brought mass production of hydrogen‐fuelled automobiles within reach.     

A Dynamic Simulation Tool for the Battery‐Hybrid Hydrogen Fuel Cell Vehicle

This paper describes a dynamic fuel cell vehicle simulation tool for the battery‐hybrid direct‐hydrogen fuel cell vehicle. The emphasis is on simulation of the hybridized hydrogen fuel cell system within an existing fuel cell vehicle simulation tool. The discussion is focused on the simulation of the sub‐systems that are unique to the hybridized direct‐hydrogen vehicle, and builds on a previous paper that described a simulation tool for the load‐following direct‐hydrogen vehicle. The configuration of the general fuel cell vehicle simulation tool has been previously presented in detail, and is only briefly reviewed in the introduction to this paper. Strictly speaking, the results provided in this paper only serve as an example that is valid for the specific fuel cell vehicle design configuration analyzed. Different design choices may lead to different results, depending strongly on the parameters used and choices taken during the detailed design process required for this highly non‐linear and n‐dimensional system. The primary purpose of this paper is not to provide a dynamic simulation tool that is the “final word” for the “optimal” hybrid fuel cell vehicle design. The primary purpose is to provide an explanation of a simulation method for analyzing the energetic aspects of a hybrid fuel cell vehicle.     

The Performance of SOFC Model Under Different Three‐phase Load Conditions

In this paper, the dynamic performance of a modified thermal based dynamic model of a solid oxide fuel cell (SOFC) is presented under different three‐phase load conditions. The modified thermal based fuel cell model contains ohmic, activation and concentration voltage losses, thermal dynamics, methanol reformer and fuel utilization factor limiting stage. SOFC model and the power conditioning unit (PCU), which consists of a DC‐DC boost converter, a DC‐AC inverter, their controller, transformer and filter, are developed on Matlab/Simulink environment. The simulation results show that the real and reactive power management of the inverter is performed successfully in an AC power system with the proposed thermal based SOFC model under three‐phase load conditions such as ohmic loads, switched ohmic−inductive loads and a three‐phase induction motor. Finally, the three‐phase induction motor is performed both no load and load conditions. The simulation results show that the modified thermal based fuel cell model provides an accurate representation of the dynamic and steady state behavior of the fuel cell under different three‐phase load conditions.     

Modelling and Performance Evaluation of Solid Oxide Fuel Cell for Building Integrated Co‐ and Polygeneration

Models of fuel cell based combined heat and power systems, used in building energy performance simulation codes, are often based on simple black or grey box models. To model a specific device, input data from experiments are often required for calibration. This paper presents an approach for the theoretical derivation of such data. A generic solid oxide fuel cell (SOFC) system model is described that is specifically developed for the evaluation of building integrated co‐ or polygeneration. First, a detailed computational cell model is developed for a planar SOFC and validated with available numerical and experimental data for intermediate and high temperature SOFCs with internal reforming (IT‐DIR and HT‐DIR). Results of sensitivity analyses on fuel utilisation and air excess ratio are given. Second, the cell model is extended to the stack model, considering stack pressure losses and the radiative heat transfer effect from the stack to the air flow. Third, two system designs based on the IT‐DIR and HT‐DIR SOFCs are modelled. Electric and CHP efficiencies are given for the two systems, as well as performance characteristics, to be used in simulations of building integrated co‐ and polygeneration systems.     

The Operation of HT‐PEM Fuel Cells Coupled to Lithium Ion Batteries in a Fleet of Light Passenger Vehicles

High temperature polymer electrolyte membrane (HT‐PEM) fuel cells offer some advantages over their low temperature equivalent, but there have been relatively few reports into their use in vehicles. This paper describes the power train design and operation of a fleet of Microcab H2EV vehicles. The power train consisted of a HT‐PEM fuel cell coupled via a DC/DC convertor to a lithium iron phosphate traction battery, which was then connected to two Lynch motors. The integration and operation of all the major power train components is described. Also described here is the vehicle control unit that uses digital and analog communications to provide overall management of the vehicle. Details are given of all the safety systems designed into the vehicle. Some data describing the performance of the H2EV power‐train during typical drive cycles is presented, which shows that the system was functional. It is concluded that HT‐PEM fuel cell light vehicles are viable, but the heating and cooling time of the fuel cell needs to be significantly reduced.     

A comprehensive comparison of fuel options for fuel cell vehicles in China

Fuel cell vehicles (FCVs) offer the potential of ultra-low emissions combined with high efficiency. Proton exchange membrane (PEM) fuel cells being developed for vehicles require hydrogen as a fuel. Due to the various pathways of hydrogen generation, both onboard and off-board, the question about which fuel option is the most competitive for fuel cell vehicles is of great current interest. In this paper, a life-cycle assessment (LCA) model was made to conduct a comprehensive study of the energy, environmental, and economic (3E) impacts of FCVs from well to wheel (WTW). In view of the special energy structure of China and the timeframe, 10 vehicle/fuel systems are chosen as the study projects. The results show that methanol is the most suitable fuel to serve as the ideal hydrogen source for fuel cell vehicles in the timeframe and geographic regions of this study. On the other hand, gasoline and pure hydrogen can also play a role in short-term and regional applications, especially for local demonstrations of FCV fleets.     

煤基燃料油品特性与煤制油产业发展分析

基于最新汽油、柴油和航煤质量标准,结合我国市场对成品油需求走向,本文探讨了煤直接液化油、煤间接液化油、加氢煤焦油、煤油共炼产品、甲醇制汽油（MTG汽油）和聚甲氧基二甲醚（DMM_n）等煤基油品的馏分结构与性质,分析了它们对煤制油产业发展的影响。文章指出国家绿色可持续发展需要低硫、低烯烃、低芳烃和高抗爆性能的交通运输燃料,需要降低柴汽比,增产航空煤油。煤基油品的硫氮等有害物质含量低、清洁性很好。除了MTG汽油外,煤基油品的柴汽比过高,需要与石油产品协同发展以满足我国未来的成品油市场需求。费托合成工艺能够直接生产优质柴油和航空喷气燃料油组分,是煤制油产业发展的主要技术路线;煤直接液化工艺所产汽煤柴油馏分性质均不理想,需要持续改进提高;煤油共炼工艺在成品油质量方面弥补了煤直接液化工艺的不足,可作为一条新的煤制油途径。煤焦油加氢可以生产出质量指标达到或接近国Ⅵ标准的车用柴油调和组分,是一条高效利用煤炭加工过程副产品的煤制油技术路线。MTG汽油和DMM_n是优质汽油和柴油组分,能改善炼油企业成品油的柴汽比结构和交通运输燃料产品质量,应加大低成本工艺技术研发、扩大产能。     

燃料电池电动轿车样车的改进设计和仿真分析

主要介绍针对LN2000燃料电池电动轿车的改进设计方案及基于有关试验数据的仿真分析结果,原有开发的燃料电池电动轿车,在电机电控系统、燃料电池发动机系统和整车控制策略以及安全考虑方面还都有一定的欠缺。本文介绍的燃料电池电动轿车样车方案在上述提及的有关方面都进行了较大的完善,其中包括电池及能量管理系统的匹配设计、电池及控制器的选择、动力总成系统的设计(设计了一种电动轿车用两档行星变速装置,并选用交流电机电控系统,大大改善了燃料电池电动轿车的动力性能和使用经济性)、燃料电池发动机及辅助系统的设计(采用空气压缩机和高集成FCE系统)和整车控制策略分析,这使得完善后的燃料电池电动轿车在系统性能、控制优化和安全控制等方面都有了一定程度的改进。本文详细介绍了上述方案及基于试验数据的详细的设计计算和仿真分析结果。     

Modelling Approach for Planar Self‐Breathing PEMFC and Comparison with Experimental Results

This paper presents a model‐based analysis of a proton exchange membrane fuel cell (PEMFC) with a planar design as the power supply for portable applications. The cell is operated with hydrogen and consists of an open cathode side allowing for passive, self‐breathing, operation. This planar fuel cell is fabricated using printed circuit board (PCB) technology. Long‐term stability of this type of fuel cell has been demonstrated. A stationary, two‐dimensional, isothermal, mathematical model of the planar fuel cell is developed. Fickian diffusion of the gaseous components (O₂, H₂, H₂O) in the gas diffusion layers and the catalyst layers is accounted for. The transport of water is considered in the gaseous phase only. The electrochemical reactions are described by the Tafel equation. The potential and current balance equations are solved separately for protons and electrons. The resulting system of partial differential equations is solved by a finite element method using FEMLAB (COMSOL Inc.) software. Three different cathode opening ratios are realized and the corresponding polarization curves are measured. The measurements are compared to numerical simulation results. The model reproduces the shape of the measured polarization curves and comparable limiting current density values, due to mass transport limitation, are obtained. The simulated distribution of gaseous water shows that an increase of the water concentration under the rib occurs. It is concluded that liquid water may condense under the rib leading to a reduction of the open pore space accessible for gas transport. Thus, a broad rib not only hinders the oxygen supply itself, but may also cause additional mass transport problems due to the condensation of water.     

Start‐Up of HT‐PEFC Systems Operating with Diesel and Kerosene for APU Applications

Fuel‐cell‐based auxiliary power units offer power generation with reduced fuel consumption and low emissions. A very promising system is the combination of an autothermal reformer with a high‐temperature polymer electrolyte fuel cell. A fast start‐up procedure is a crucial requirement for the use of this system as an auxiliary power unit. This paper reports on the development of a suitable start‐up strategy for a 10 kW_el auxiliary power unit with a start‐up burner. A commercially available diesel burner was tested as a start‐up device. A dynamic MATLAB/Simulink model was developed to analyze different start‐up strategies. With the currently available apparatus and start‐up burner it takes 2,260 s before power generation can begin according to simulation results. The fuel processor alone would be ready for operation after 1,000 s. An optimization of the fuel cell stack with regard to its thermal mass would lead to a start‐up time of 720 s. A reduction to 600 s is possible with a slight customization of the start‐up burner.     

Acceleration tests using gasolines formulated with di-TAE, TAEE and MTBE ethers

This study evaluates the acceleration and performance of car engines fueled by gasoline formulated with di-tert-amyl ether (di-TAE), tert-amyl ethyl ether (TAEE), and methyl tert-butyl ether (MTBE), whose compositions contain an oxygen concentration of 2.7 wt.%. The performance tests were carried out in a roll dynamometer using a Fiat-Strada commercial vehicle equipped with open-loop electronic fuel injection. The use of ethers from partially renewable sources, such as di-TAE and TAEE in gasoline formulations, is an attractive alternative to reduce fossil fuel consumption. These ethers, both pure and in formulations, require a lower air/fuel ratio, since part of the oxygen needed to oxidize the fuel is already present in the molecule. The results obtained in acceleration tests using gasoline formulated with the di-TAE, TAEE and MTBE ethers indicated that the best acceleration response was obtained with the gasoline/TAEE mixture and the lowest specific consumption was with the gasoline/di-TAE mixture. TAEE is an adequate alternative to replace MTBE in Otto cycle internal combustion engines, since this compound is partially biorenewable and provides a comparable thermal efficiency and lower specific fuel consumption.     

大功率PEMFC空气供给系统建模与实验验证

近年来,质子交换膜燃料电池(PEMFC)作为车载燃料电池的主要动力源受到广泛关注。空气压缩机为电堆提供系统所需的氧气和阴极压力,是质子交换膜燃料电池系统中必不可少的一部分,其工作性能对燃料电池稳态和动态工作性能有很大的影响。基于实验室已有150 kW质子交换膜燃料电池系统,对离心式空压机的工作特性进行了研究,建立了包含离心式空气压缩机的空气供给系统应用模型。通过实验验证,仿真模型能够准确地反映离心式空压机与空气系统的特性,同时能真实反映包含离心式空压机的大功率质子交换膜燃料电池空气系统的稳态控制效果,以及不同控制策略下的动态响应效果。该模型对研究大功率质子交换膜燃料电池空气供给系统以及相应的控制策略提供理论支持,仿真模型与实验结果为下一步控制策略优化提供基础与参考。     

Design of a New Multilevel Inverter Standalone Hybrid PV/FC Power System

This paper analyzes different topologies of hybrid photovoltaic (PV)/fuel cell (FC) power system in standalone applications. Proposed topology with a compact conversion system using less number of power semiconductor, switches will improve hybrid system power quality. The MATLAB SIMULINK tool is utilized to design and develop the proposed system by which voltage regulators common coupling point voltage is controlled and regulated. Simulated results are compared with IEEE 1547 standard to authenticate the effectiveness of the proposed model. The proposed system will be implemented in real time prototype model. The real time prototype model results are compared with simulation results.     

Simulation and Experiment of a Cogeneration System Based on Proton Exchange Membrane Fuel Cell

This project designs and simulates a cogeneration system of proton exchange membrane fuel cell using Matlab/Simulink software and Thermolib heat module components. The system not only satisfies the need for electric power, but also provides heat recovery for future uses, thus increasing energy transfer efficiency. PEM fuel cell‐based cogeneration system is introduced, including the hydrogen supply subsystem, air supply subsystem, load control subsystem, real‐time monitoring block, and heat recovery subsystem. The complete fuel cell‐based cogeneration system is constructed by assembling the fuel cell stack, fuel, coolant flow rate control system, and all the subsystems. In addition to the fuel cell experiment, influencing factors on the fuel cell‐based system, such as the fuel inhale rate, coolant flow rate, system temperature, fuel humidification, thermal efficiency, electrical efficiency, and combined heat and power (CHP) system efficiency, are analyzed and charted regarding different loads. In this system, with the power at 3 kW, the CHP efficiency reaches 64%. The CHP efficiency is 76.6% with the load power at 4 kW. When the power is at 5 kW, the thermal efficiency reaches 36.9% and the CHP efficiency reaches 82.9%.     

车用乙醇汽油挥发性研究

分析了车用乙醇汽油中影响挥发性的组分,介绍了变性燃料乙醇对汽油挥发性及车用乙醇汽油挥发性对汽车运行和环境的影响。通过对车用乙醇汽油族组成、蒸汽压和蒸馏特性的解析,明确了催化裂化汽油、催化重整汽油、烷基化汽油、异构化汽油、直馏汽油及含氧化合物等的调合作用。车用乙醇汽油挥发性的增大使汽车的启动性能增强、驱动性能变差、发生光化学污染的可能性变大。针对环保方面提出了车用乙醇汽油调合组分偏重一些,少加或不加其他含氧化合物,增加高辛烷值调合组分调合量的建议。     

Hydrogen for the Mobility of the Future Results of GM/Opel's Well‐to‐Wheel Studies in North America and Europe

General Motors conducted two well‐to‐wheel studies for fundamental clarification on the question of which is the cleanest and most environmentally sustainable source of energy for the mobility of the future. In both studies the complete energy chains were analyzed from fuel production using primary energy to the actual consumption of the fuel in the car, i.e. from the well up to the wheels of the vehicle (well to wheel). The aim of the studies was to evaluate total energy consumption on the one hand and, on the other, the total greenhouse gas emissions arising between the production of a fuel and its final use to power an automobile. The results of the studies clearly show that fuel cell vehicles can greatly reduce greenhouse gas emissions from passenger cars or, if they run on hydrogen from renewable energy sources, they can eliminate them entirely. Regenerative fuels, however, will be more expensive than current products. With the fuel cell, because of its superior efficiency (35 – 45% less energy consumption well to wheel), it will be possible to keep individual mobility affordable in the future.     

PEM Fuel Cell Stack Cold Start Thermal Model

For passenger fuel cell vehicles (FCVs), customers will expect to start the vehicle and drive almost immediately, implying a very short system warmup to full power. While hybridization strategies may fulfill this expectation, the extent of hybridization will be dictated by the time required for the fuel cell system to reach normal operating temperatures. Quick‐starting fuel cell systems are impeded by two problems: (i) the freezing of residual water or water generated by starting the stack at below freezing temperatures and (ii) temperature‐dependent fuel cell performance, improving as the temperature reaches the normal range. Cold start models exist in the literature; however, there does not appear to be a model that fully captures the thermal characteristics of the stack during sub‐freezing startup conditions. Existing models lack the following features: (i) modeling of stack internal heating methods (other than stack reactions) and their impact on the stack temperature distribution and (ii) modeling of endplate thermal mass effect on end cells and its impact on the stack temperature distribution. Unlike a lumped model, which may use a single temperature as an indicator of the stack's thermal condition, a model considering individual cell layers can reveal the effect of the endplate thermal mass on the end cells, and accommodate the evaluation of internal heating methods that may mitigate this effect. This paper presents and discusses results from simulations performed with a new, layered model.     

Model‐based optimization of hydrogen generation by methane steam reforming in autothermal packed‐bed membrane reformer

An autothermal membrane reformer comprising two separated compartments, a methane oxidation catalytic bed and a methane steam reforming bed, which hosts hydrogen separation membranes, is optimized for hydrogen production by steam reforming of methane to power a polymer electrolyte membrane fuel cell (PEMFC) stack. Capitalizing on recent experimental demonstrations of hydrogen production in such a reactor, we develop here an appropriate model, validate it with experimental data and then use it for the hydrogen generation optimization in terms of the reformer efficiency and power output. The optimized reformer, with adequate hydrogen separation area, optimized exothermic‐to‐endothermic feed ratio and reduced heat losses, is shown to be capable to fuel kW‐range PEMFC stacks, with a methane‐to‐hydrogen conversion efficiency of up to 0.8. This is expected to provide an overall methane‐to‐electric power efficiency of a combined reformer‐fuel cell unit of ～0.5. Recycling of steam reforming effluent to the oxidation bed for combustion of unreacted and unseparated compounds is expected to provide an additional efficiency gain. © 2010 American Institute of Chemical Engineers AIChE J, 2011