Recommended Practice for General Fuel Cell Vehicle Safety

<div class="htmlview paragraph">The purpose of this system study was to compare the performance and fuel consumption of a pure fuel cell vehicle (<i>i.e.</i> with no battery included) with an internal combustion engine (ICE) vehicle of similar weight in different drive cycles. Both light and heavy duty vehicles are studied.</div> <div class="htmlview paragraph">For light duty vehicles, the New European drive cycle, NEDC [70/220/EEC], the FTP75 [EPA] and a Swedish driving pattern from the city of Lund [<span class="xref">Ericsson, 2000</span>] are utilised. The fuel consumption for these drive cycles was compared with ICE vehicles of similar weight, an Ibiza Stella 1.4 (year 2000) from Seat and a Volvo 960 2.5 E sedan (year 1995). For heavy duty vehicles, urban buses in this study, two drive cycles were employed, the synthetic CBD14 and the real bus route 85 from Gothenburg, Sweden.</div> <div class="htmlview paragraph">It can be concluded that marked improvements in fuel economy can be achieved for hydrogen-fuelled light and heavy duty vehicles. The fuel consumption of a small fuel cell vehicle was 50% less than the corresponding ICE vehicle in both the NEDC and the FTP75. With proper dimensioning of the system components, e.g. the engine, further reductions in fuel consumption can be achieved. The range of more than 500 km with 5 kg of hydrogen in a 345 bar fuel tank was comparable to an ICE vehicle. If the pressure is raised to 690 bar, a driving range of 600 km could be achieved. As the auxiliary system counteracts the increase in fuel cell efficiency, raising the minimum operating voltage from 0.6 to 0.75 V in a 50 kW fuel cell system, provides only a 5% reduction in fuel consumption. A fuel cell bus operated in the CBD14 and the bus route 85, compared with diesel-fuelled urban bus of similar weight, demonstrates a reduction in fuel consumption of 33 and 37 % respectively.</div>

<div class="section abstract"><div class="htmlview paragraph">Fuel cell electric vehicles are expected to support the effort to overcome the economic and ecological challenges in the automotive sector. Just as battery electric vehicles, fuel cell electric vehicles also offer locally emission free mobility. The drive system of fuel cell electric vehicles consists of a fuel cell system, an electric motor, power electronics, a hydrogen storage system as well as a rechargeable energy storage system, typically a battery. The quantified power ratio between the fuel cell system and the rechargeable energy storage system is referred to as the degree of hybridization, although inconsistent definitions are used. As these existing definitions of the degree of hybridization of fuel cell electric vehicles don’t support a distinct differentiation and characterization of the vehicles, a new definition of the degree of hybridization is proposed considering the ratio of the energy contents of the hydrogen storage system and the rechargeable energy storage system, effectively adding a second dimension. The degree of hybridization is then evaluated for existing fuel cell electric vehicles using the proposed definition and enables the characterization and clustering of the different vehicles. While this two-dimensional degree of hybridization can be used as optimization criteria during the design and optimization of fuel cell drive systems, the aforementioned clusters can be assigned to already established qualitative degree of hybridization definitions used to describe types of hybrid electric vehicles. This supports customers to be able to more easily distinguish between different types of fuel cell electric vehicles while also increasing the suitability of the degree of hybridization as an optimization criterion in drive system development.</div></div>

<div class="htmlview paragraph">Alternative powertrain configurations such as hybrid electric vehicles and fuel cell vehicles seem to be the best response to the need of reduced pollutant emissions, especially in urban areas, and to meet future emission limits, that appear to be very severe targets for traditional technologies.</div> <div class="htmlview paragraph">In hybrid electric vehicles (HEVs) an internal combustion engine is combined with one or more electric machines, with the aim of extending the range of the electric and making the entire vehicle more energy–efficient. The architecture of a hybrid drive train is complex, comprising at least two different energy conversion devices (i.e. internal combustion engine and electric machine) drawing energy from at least two different energy storage devices (i.e. fuel tank and battery). Moreover, complex control strategies must be defined in order to properly control the division of load between the thermal engine and the electric machines.</div> <div class="htmlview paragraph">To meet increasing global competition, which means reducing lead-time and costs for hybrid vehicles design, it is necessary to develop methods that wouldquickly evaluate various design concepts. Even if many computational models are available to simulate the performances of HEVs, there’s still a lack of generalized mathematical analyses.</div> <div class="htmlview paragraph">An analytical model has been developed in order to study power flows in hybrid vehicle drive trains. The mathematical formulation allows a quick analysis of the complete energy cascade from fuel energy to tractive power, comprising electricity generation and consumption and energy recovery from braking. As a result a general formulation of the total tractive energy and of the global efficiency of hybrid electric vehicles in function of the main characteristics of its components is provided.</div> <div class="htmlview paragraph">The goal of the analytical model is to enable a quick exploration of design possibilities of hybrid powertrains. Some results are presented in order to show how the present model allows a quick insight into the effects of the main system characteristics on the power flows and the corresponding component losses of the drive train.</div>

<div class="htmlview paragraph">Because of their high efficiency and low emission potential, fuel cell vehicles are undergoing extensive research and development. However, several major barriers have to be overcome to enable a hydrogen economy. Because fuel cell vehicles remain expensive, very few fueling stations are being built. To try to accelerate the development of a hydrogen economy, the automotive manufacturers developed a hydrogen-fueled Internal Combustion Engine (ICE) as an intermediate step. Despite being cheaper, the hydrogen-fueled ICE offers a lower driving range because of its lower efficiency. The current study evaluates the impact of combining a hydrogen-fueled ICE with a fuel cell to maximize fuel economy while minimizing the cost and amount of onboard fuel needed to maintain an acceptable driving range.</div>

<div class="htmlview paragraph">While the ZEV program's electric vehicles did not become successful market-driven products, many of the technical advantages of electric vehicles were validated by enthusiastic California consumers. Yet, battery technology has been and continues to be the limiting factor in terms of cost, functionality (range) and durability of EV systems.</div> <div class="htmlview paragraph">The automotive industry has largely moved on to research and development of other approaches to extremely low emissions and reduced fossil fuel consumption. PZEV gasoline vehicles, Hybrid electric vehicles, clean (EPA Tier 2) diesel vehicles and Proton Exchange Membrane (PEM) fuel cell electric vehicles (FCEVs) are the focus of attention.</div> <div class="htmlview paragraph">The purpose of this paper is to explore another possible solution: a battery electric vehicle with a relatively small fuel cell auxiliary power unit (APU) to recharge the battery pack during driving. The attraction of this configuration is the use of a relatively small battery pack (to allow 65 - 110 km of ZEV range) while increasing vehicle range and functionality to be equivalent to conventional vehicles (400 - 650 km). Another key attraction is that a majority of km could be efficiently refueled from the grid allowing low or zero CO<sub>2</sub> power generating technology to be deployed in private transportation without the enormous cost and inefficiency of the H<sub>2</sub> infrastructure.</div> <div class="htmlview paragraph">The combination of Solid Oxide Fuel Cell (SOFC) APU and advanced Lithium Ion battery systems appears to make the fuel cell range extender EV an attractive system in terms of efficiency, weight and (in the midterm) cost. This paper will discuss the product attributes and advantages that such a system would bring to the customer and society and compare SOFC to Proton Exchange Membrane (PEM) fuel cell and other competing APU technologies. This paper will present system level assessment and analysis of the SOFC/Lithium Ion range extender EV applied to a GM EV1 platform.</div>

<div class="section abstract"><div class="htmlview paragraph">One of the most critical elements in engineering a hydrogen fuel cell vehicle is the design of the on-board hydrogen storage system. Because the current compressed-gas hydrogen storage technology has several key challenges, including cost, volume and capacity, materials-based storage technologies are being evaluated as an alternative approach. These materials-based hydrogen storage technologies include metal hydrides, chemical hydrides, and adsorbent materials, all of which have drawbacks of their own. To optimize the engineering of storage systems based on these materials, it is critical to understand the impacts these systems will have on the overall vehicle system performance and what trade-offs between the hydrogen storage systems and the vehicle systems might exist that allow these alternative storage approaches to be viable.</div><div class="htmlview paragraph">To gain a better understanding of the interactions that exist between various materials-based hydrogen storage systems and the vehicle system as well as the engineering challenges that exist when integrating one of these systems with a vehicle, the National Renewable Energy Laboratory (NREL) developed a vehicle-level model designed to be sensitive to these issues. The Hydrogen Storage Simulation Model (HSSIM) was developed under the Hydrogen Storage Engineering Center of Excellence (HSECoE) as a specialized tool that could be used to assist in the design and engineering of materials-based hydrogen storage systems being considered by the HSECoE. This tool is designed to not only allow for understanding key trade-offs, but also to have a seamless integration with the HSECoE fuel cell and detailed hydrogen storage system models and to evaluate progress towards the U.S. Department of Energy's hydrogen storage technical targets. This model has been integrated with a fuel cell model developed by Ford Motor Company in a HSECoE common modeling framework developed by United Technologies Research Center and other HSECoE partners.</div><div class="htmlview paragraph">This paper focuses on the development, structure, and validation of the vehicle model HSSIM and summarizes its integration within the framework. HSSIM and the framework are then used to obtain trade-offs for various specific materials-based storage system designs. This includes hydrogen storage sizing analyses, mass compounding analyses, range versus volume studies, and vehicle and component performance analyses, such as acceleration rates and fuel cell and energy storage interactions.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Fuel cell electric vehicles offer an attractive option for decarbonizing long-haul on-road transport. However, there are still several barriers to widespread adoption of hydrogen-fueled fuel cells for this application including system durability and total cost of ownership compared to traditional diesel engines. A primary contributor to fuel cell system costs and maintenance requirements is the air management system. It is common for heavy duty fuel cell electric vehicles to use light-duty automotive air management components which are ill-suited for the requirements of larger, long-haul vehicles. This study focuses on the development of a durable and efficient air management system for heavy duty vehicle applications as part of a cooperative research project funded by the Department of Energy’s Hydrogen and Fuel Cell Technologies Office.1</div><div class="htmlview paragraph">The proposed air management design incorporates a novel two stage filtration system, an innovative water-lubricated bearing and electrically-assisted variable turbine geometry turbocharger, charge air cooler, and humidifier. To achieve the ambitious Department of Energy project goals for efficiency and durability, a system-level optimization approach has been employed using a semi-empirical 1D model. Design optimization of the compressor and turbine wheel geometries yielded a large compressor wheel diameter and small trim to reduce mass flow capacity, resulting in a broad efficiency map and a relatively small turbine wheel diameter with non-radial inlet blade angle suitable for the low temperature exhaust. 1D simulations of the optimized system compared to a baseline e-compressor showed a >40% reduction in required e-motor power at steady-state conditions and a >30% reduction in e-motor energy consumption in a transient cycle.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Zero emission vehicles are essential for achieving sustainable and clean transportation. Hybrid vehicles such as Fuel Cell Electric Vehicles (FCEVs) use multiple energy sources like batteries and fuel cell stacks to offer extended driving range without emitting greenhouse gases. Optimal performance and extended life of the important components like the high voltage battery and fuel-cell stack go a long way in achieving cost benefits as well as environmental safety. For this, energy management in FCEVs, particularly thermal management, is crucial for maintaining the temperature of these components within their specified range. The fuel cell stack generates a significant amount of waste heat, which needs to be dissipated to maintain optimal performance and prevent degradation, whereas the battery system needs to be operated within an optimal temperature range for its better performance and longevity. Overheating of batteries can lead to reduced efficiency and potential safety hazards, while low temperatures can decrease battery performance and range. The multiple temperature control loops in the thermal system design of the current FCEVs require significant energy for continuous heating and cooling. This is due to the fact that each of them exchanges energy directly with an external source or sink without redistributing energy among themselves. This can lead to energy losses during the heat exchange process. Our goal is to optimize thermal energy usage while maintaining the same performance and efficiency of both battery electric system and the fuel cell stack in a vehicle. In this paper, an analysis of thermal energy utilization of a single system is compared to the exchange of thermal energy across multiple systems, considering various heating and cooling scenarios. We compare our proposed strategy (with redistribution) with the existing strategy (without redistribution) quantitatively with respect to controller effort/ energy spent in achieving thermal target.</div></div>

<div class="htmlview paragraph">In 1981, one of us authored an SAE Paper - Hydrogen as an Alternative Automotive Fuel [<span class="xref">1</span>] and concluded that although the hydrogen fuel/vehicle system was technically feasible, it was not competitive with other alternative fuel/vehicle systems and predicted that hydrogen would not be used as an automotive fuel in this century. The current paper revisits the subject 12 years later. In 1981, energy concerns were dominant, and coal-based synthetic fuels were viewed as viable alternatives to petroleum and natural gas, which were predicted to become scarce and very expensive. Today, environmental issues are crucial and global warming concerns will probably limit the future use of coal, and petroleum and natural gas are cheaper than they were in 1981. The paper examines advances in hydrogen production, distribution, on-board storage and use as an automotive fuel in internal combustion engines (ICE) and fuel cell electric vehicles. It also considers tailpipe and overall CO<sub>2</sub> emissions. Hydrogen ICE vehicles are less attractive than competing battery electric vehicles and natural gas ICE vehicles. Fuel cell vehicles are theoretically more attractive, but face technical challenges which will bar them as a prospect for automotive applications before 2010 at the earliest. Setting up a large-scale hydrogen fuel infrastructure will be extremely expensive and will take decades. Therefore, it is concluded that hydrogen will not be used as an automotive fuel before the year 2020.</div>

<div class="htmlview paragraph">After about a decade of considerable investments in polymer electrolyte fuel cell (PEMFC) and in solid oxide fuel cell (SOFC) technology, both are being actively considered for vehicle applications. The two vehicle applications being most actively considered for fuel cells are propulsion (mainly for PEMFC) and auxiliary power (for both PEMFC and SOFC). For all transportation applications, fuel cells promise the benefits of clean and quiet operation, potentially low maintenance and high efficiency, and ultimately greater utility to drivers and passengers.</div> <div class="htmlview paragraph">Initial system and vehicle prototypes have started to demonstrate some of these benefits, but much technology development is still needed before commercialization can occur. Not surprisingly then, there are serious hurdles to be overcome if fuel cells are to become true competitors for internal combustion engines (ICEs) in automotive applications. The most serious hurdle appears to be manufactured cost, which would appear to be several times too high for propulsion applications to be competitive, based on today's technology. Another considerable hurdle is power density, which is critical to be able to develop compelling fuel cell vehicles (FCVs) without sacrificing vehicle utility or performance. Finally, proving and improving system life should receive far more attention than has been the case so far.</div> <div class="htmlview paragraph">While the barriers may seem daunting, the automotive industry and other stakeholders are bringing many of the critical scientific and engineering resources to bear on solving the problem.</div>

<div class="htmlview paragraph">Controlled Auto-Ignition (CAI) combustion, also known as HCCI or PCCI, has recently emerged as a viable alternative combustion process to the conventional spark ignition (SI) or compression ignition (CI) process for internal combustion (IC) engines, owing to its potential for high efficiency and extremely low emissions. One of the most effective and practical means of achieving CAI combustion in an engine is to retain or recycle the burnt gases. In order to understand better the effects of recycled burnt gases on CAI combustion, detailed analytical and experimental studies have been carried out. The analytical studies were performed using an engine simulation model with detailed chemical kinetics.</div> <div class="htmlview paragraph">The five effects of the recycled burned gases studied include:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(1.)</span><div class="htmlview paragraph">Charge heating effect: higher intake charge temperature due to hot burned gases;</div></li> <li class="list-item"><span class="li-label">(2.)</span><div class="htmlview paragraph">Dilution effect: the reduction of oxygen due to the presence of the burned gases;</div></li> <li class="list-item"><span class="li-label">(3.)</span><div class="htmlview paragraph">Heat capacity effect: due to higher specific heat capacity of burned gases;</div></li> <li class="list-item"><span class="li-label">(4.)</span><div class="htmlview paragraph">Chemical effect: chemical reactions involving CO<sub>2</sub> and H<sub>2</sub>O in the burned gases</div></li> <li class="list-item"><span class="li-label">(5.)</span><div class="htmlview paragraph">Stratification effect: recycled burned gases are stratified from the fuel/air mixture.</div></li> </ol> </div> <div class="htmlview paragraph">And the main conclusions are:</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"><span class="li-label">(1.)</span><div class="htmlview paragraph">The charge heating effect is mainly responsible for the advanced AI timing due to hot burned gases. It increases the heat release rate and shortens the combustion duration.</div></li> <li class="list-item"><span class="li-label">(2.)</span><div class="htmlview paragraph">The dilution effect does not affect AI timing, but it extends combustion duration. Its slows down the heat release rate only when large amount of burned gases is present.</div></li> <li class="list-item"><span class="li-label">(3.)</span><div class="htmlview paragraph">The heat capacity effect is mainly responsible for the reduction in the heat release rate, and it has a similar effect to extend the combustion duration as the dilution effect.</div></li> <li class="list-item"><span class="li-label">(4.)</span><div class="htmlview paragraph">The chemical effect does not affect AI timing and heat release rate. It reduces the combustion duration slightly at high concentrations of burned gases.</div></li> <li class="list-item"><span class="li-label">(5.)</span><div class="htmlview paragraph">The stratified burned gases facilitate the CAI combustion due to the presence of higher temperature region at the boundary between of the hot burned gases and combustible charge.</div></li> </ol> </div>

<div class="section abstract"><div class="htmlview paragraph">This paper describes research focused upon improved the quality of automobile engine quality. Methods and models were developed for estimating and predicting the technical condition of internal combustion engine (ICE), which provides usage of the decision support making in the search for minimum fuel consumption regimes. We developed models of multi-criterion, multiparametric optimization of energy and material-material characteristics of ICE according to the system approach.</div><div class="htmlview paragraph">The developed methods and models for estimating and predicting the technical state of the functionally interconnected and interacting ICE components are performed taking into account their hierarchy and topologies, energy resource used and the fuel. The cognitive methodology has been used to make engine models researches and analysis. The paper focuses on the fuzzy logic approach applying, considering the indeterminacy, incompleteness and unclear information in the engines operation processes. Cognitive, imitation and fuzzy models for estimating and predicting the technical state of ICE have been developed by the authors of this paper, which allowed to identify ICE’s most vulnerable components, set weight values, influence on fuel consumption according to the quantitative and qualitative energy interchange between ICE components.</div><div class="htmlview paragraph">The received results provide quality enlargement of the ICE operation and their functional components, based on the developed estimation and prediction methods of their technical condition.</div><div class="htmlview paragraph">The paper describes results the cross-platform software application which was implemented using the high-level Java programming language and XML markup language. Developed software allows us to provide user’s flexible interaction process with the module of the decision support system, which is based on implementation of the developed methods and models for the ICE technical condition estimating and predicting.</div><div class="htmlview paragraph">Usage of the developed software helped to obtain optimization results of the energy and material characteristics of the explored ICE, which allows us to find several Pareto-optimal solutions for quality criteria that affect fuel consumption for each single model. This has led to a reduction of components wear, which leads to reducing fuel consumption during ICE operation.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Powertrain architecture is being reshaped by the electrification of heavy-duty military vehicles using hydrogen fuel cell technology, particularly in transmission systems. Unlike conventional internal combustion engines, hydrogen fuel cell electric vehicles (FCEVs) typically use single-speed or direct-drive configurations due to the high torque of electric motors. This paper examines the impact of hydrogen electrification on military vehicle transmissions, focusing on armored multi-role models such as the VBMT-LSR, Guarani, and Leopard 1A5 of the Brazilian Army. The study compares traditional gearboxes with alternative solutions optimized for fuel cells, analyzing the trade-offs in efficiency, durability, and operational adaptability. Additionally, it explores adaptations required for hydrogen internal combustion engines (H2-ICEs), considering their distinct characteristics and demands. The study employs a three-step validation methodology combining computational simulations, technical data analysis, and case studies of military vehicles. MATLAB and similar tools are used to assess efficiency, durability, and torque response under field conditions. Next, specifications from existing military vehicles in the Brazilian Army are analyzed to evaluate the feasibility of hydrogen powertrains compared to diesel-based solutions. Finally, the study examines international military projects that have already integrated hydrogen or electrification, such as GM SURUS and Rheinmetall Mission Master, drawing insights into the applicability of these concepts in the Brazilian military context. This research enhances the understanding of hydrogen-powered transmissions, contributing to the future development of more sustainable powertrain solutions and thus supporting the adaptation of military fleets to alternative energy sources and accelerating the adoption of hydrogen-based mobility in defense applications.</div></div>

<div class="section abstract"><div class="htmlview paragraph">In today’s world, due to fast depletion of fossil fuel and the increasing CO2 emission, the need to switch to alternate energy sources are higher. Stringent norms on exhaust emissions in IC Engine vehicles implies, very complex after treatment systems. Already many OEMs have refined their development strategies towards phasing out of IC Engines and bringing in Fuel Cell vehicles, Battery Electric Vehicles and Hydrogen IC Engine vehicles. Focus is on Hydrogen for Long Haul vehicles. In this paper cooling system design is demonstrated for Fuel Cell, Battery and Power Electronics system in a Heavy Duty Fuel Cell Electric Truck. Radiator and Fans are selected based on the overall heat rejection and Coolant inlet temperature requirements of components. Cooling system circuit and pump is decided to meet the coolant flow rate targets. High temperature cooling system and Low temperature cooling system are explained in detail. Thermal simulation is done using simulation software KULI. Test results signifies good correlation.</div></div>

<div class="section abstract"><div class="htmlview paragraph">An Air intake system (AIS) is a duct system which leads the airflow going into the internal combustion engine. Combustion requires oxygen, and the more oxygen is provided into the combustion process the more power it will produce. The lower the air temperature, the higher its density, and hence there is more oxygen in a unit volume. The quality of air entering engine can be measured with the air temperature.</div><div class="htmlview paragraph">AIS design and routing influence the air charge temperature (ACT) at intake manifold runners and ACT is normally measured at AIS throttle body in reality. Higher ACT lead to inefficient combustion and can lead to spark retard. Optimization of AIS designs and reduction of ACT can improve engine performance and vehicle fuel economy.</div><div class="htmlview paragraph">High ACT can be a result of two different phenomena: <ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Recirculation - Hot air from the underhood environment ingested into the dirty side of the air intake system. This is the result of the AIS snorkel not being isolated or sealed from the engine compartment hot air.</div></li><li class="list-item"><div class="htmlview paragraph">Underhood temperature rise - Air inside AIS is heated by the ducts walls because it is routed through a hot underhood environment. The longer the length and larger the diameter of the air induction system, and the higher duct skin temperatures, the worse the temperature rise.</div></li></ul></div><div class="htmlview paragraph">In this paper, it is planned to simulate and study the effects of following factors on ACT with CFD using a FCA production vehicle: <ul class="list disc"><li class="list-item"><div class="htmlview paragraph">Snorkel location: snorkel sucking fresh air at side air guide or snorkel sucking underhood hot recirculation air.</div></li><li class="list-item"><div class="htmlview paragraph">Exhaust hot end at front of an east-west engine or at the rear of the engine; these two arrangements will result in different underhood air temperatures and radiation to AIS surfaces.</div></li><li class="list-item"><div class="htmlview paragraph">Heat shield effects on ACT: heat shield blocks radiation from exhaust system to AIS surfaces, and hence reduces charge air heat pick from AIS duct walls.</div></li><li class="list-item"><div class="htmlview paragraph">The effects of other measures such as cutting holes on hood or fenders to lower engine compartment air temperatures.</div></li></ul></div><div class="htmlview paragraph">Although the airflow in vehicle AIS duct is transient in nature, steady CFD simulations will be performed to study the above cases for simplification, and CFD approach will be discussed in details. Vehicle test data will be used to validate the CFD models.</div><div class="htmlview paragraph">Finally, general practices of AIS development will be discussed, and future work on this topic will be outlined.</div></div>