Validation and Sensitivity Studies for SAE J2601, the Light Duty Vehicle Hydrogen Fueling Standard

<div class="htmlview paragraph">The analysis reported on in this paper examines environmental, energy and economic benefits for specific, though different, proposed state wide high speed rail (HSR) systems combined with a regional maglev proposal under review in Florida. One of the HSR proposals and the maglev system are projected to be fully permitted within the next eighteen months and operational by the 1994-96 period.</div> <div class="htmlview paragraph">The specifics of each applicants proposals are integrated into a complex computer model which reflect different; 1) technologies and speeds, 2) energy demands and other resource needs, 3) system service level characteristics, 4) ridership levels, 5) modal splits combined with 6) other system differences.</div> <div class="htmlview paragraph">This computer model then integrates the unique a) fuel consumption and b) emission levels of the actual electrical generation grid supplying the HSR and maglev systems in central and south Florida.</div> <div class="htmlview paragraph">Finally, the model quantitatively combines this data with equivalent emissions, energy and other system information on auto and airplane transportation modes. This data and pertinent user characteristics enable the model to estimate precise environmental, energy and economic benefits (expressed in 1990 dollars) for each unique HSR and maglev transportation system for the year 1999 alone.</div> <div class="htmlview paragraph">The results of this Florida specific analysis conclude that implementation of a HSR proposal and the maglev system will annually result in:</div> <section id="s_1" class="section"> <h2 class="title">Economic and Energy Benefits</h2> <div class="htmlview paragraph">- Time savings valued to $85 million.</div> <div class="htmlview paragraph">Automobile wear and maintenance savings valued to $37.4 million.</div> <div class="htmlview paragraph">Property and injury loss savings valued to $8 million.</div> <div class="htmlview paragraph">Reduction in annual transportation energy consumption of between 1.13 to 1.69 trillion Btus.</div> <div class="htmlview paragraph">Reduced dependence of $28.4 million on fossil fuel to power our transportation systems.</div> <div class="htmlview paragraph">Reduction of $23.5 million in imported oil thereby strengthening this nation's domestic economy by A) reducing negative balance of payments, B) increasing reliance on domestic sources of energy, and C) increasing domestic security.</div> <div class="htmlview paragraph">Reduce the annual economic damages (externalities) from transportation air pollution emissions.</div> <div class="htmlview paragraph">Additionally HSR/maglev systems will result in</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"> <div class="htmlview paragraph">Savings in new highway construction costs exceeding $1 billion.</div> </li> <li class="list-item"> <div class="htmlview paragraph">Up to 217,979 man year direct and indirect construction employment.</div> <div class="htmlview paragraph">Up to $20 billion in indirect construction income.</div> </li> <li class="list-item"> <div class="htmlview paragraph">As much as 9,908 annual permanent operations jobs created both direct and indirect.</div> <div class="htmlview paragraph">Over $300 million annually in direct and indirect operation employment income.</div> </li> <li class="list-item"> <div class="htmlview paragraph">- Enhanced transportation productivity by a factor of three over current modes.</div> </li> </ul> </div> </section> <section id="s_2" class="section"> <h2 class="title">Environmental Emissions Benefits and Costs</h2> <div class="htmlview paragraph">- Annual reductions of between 555 to 633 tons/year of Volatile Organic Carbons (VOC) emissions.</div> <div class="htmlview paragraph">Annual reductions of between 3,035 to 4,746 tons (2753 to 4305 mtons) year of Carbon Monoxide (CO).</div> <div class="htmlview paragraph">Annual reductions of between 53,890 to 54,467 tons (48878 to 49402 mtons) year of Carbon Dioxide (CO<sub>2</sub>).</div> <div class="htmlview paragraph">Annual reductions of between 877 to 1,184 tons (795 to 1074 mtons) year of Nitrogen Oxides (NOx).</div> <div class="htmlview paragraph">Annual reductions of between 57 to 84 tons (52 to 76 mtons) year of Total Suspended Particulate (TSP) matter.</div> <div class="htmlview paragraph">Annual reductions of between 49 to 78 tons (44 to 71 mtons) year of tire wear particulate matter.</div> <div class="htmlview paragraph">Annual increases of between 132 to 173 tons (120 to 157 mtons) year of Sulfur Oxides (SOx).</div> <div class="htmlview paragraph">Total non-CO<sub>2</sub> auto and airplane emissions exceed HSR and maglev emissions by a factor of 14.</div> <div class="htmlview paragraph">Total automobile and airplane emissions (including CO<sub>2</sub>) exceed HSR and maglev emissions by 200%.</div> <div class="htmlview paragraph">With proper mitigation measures, environmentally related noise impacts can be resolved.</div> </section> <section id="s_3" class="section"> <h2 class="title">Growth in all Benefits/Costs</h2> <div class="htmlview paragraph">All of these HSR/maglev social benefits will rise by a factor of 1.75 of any percentage improvements in trip times while ridership revenues to system owners could rise by a factor of 2.7.</div> </section>

<div class="section abstract"><div class="htmlview paragraph">Electric Vehicles (EVs) are rapidly transforming the automotive landscape, offering a cleaner and more sustainable alternative to internal combustion engine vehicles. As EV adoption grows, optimizing energy consumption becomes critical to enhancing vehicle efficiency and extending driving range. One of the most significant auxiliary loads in EVs is the climate control system, commonly referred to as HVAC (Heating, Ventilation, and Air Conditioning). HVAC systems can consume a substantial portion of the battery's energy—especially under extreme weather conditions—leading to a noticeable reduction in vehicle range.</div><div class="htmlview paragraph">This energy demand poses a challenge for EV manufacturers and users alike, as range anxiety remains a key barrier to widespread EV acceptance. Consequently, developing intelligent climate control strategies is essential to minimize HVAC power consumption without compromising passenger comfort. These strategies may include predictive thermal management, cabin pre-conditioning, zonal climate control, and integration with renewable energy sources. By implementing such energy-efficient solutions, EVs can achieve better range performance, improved user satisfaction, and greater environmental benefits.</div><div class="htmlview paragraph">Modern EV climate control systems increasingly rely on intelligent features such as Auto mode, which dynamically adjusts fan speed, airflow direction, and temperature settings based on real-time cabin and ambient conditions. By leveraging sensor data and adaptive control algorithms, Auto mode optimizes thermal comfort while minimizing unnecessary energy expenditure. This automated regulation plays a crucial role in reducing HVAC-related power consumption, thereby contributing to overall range improvement and enhancing system efficiency without compromising passenger comfort.</div><div class="htmlview paragraph">This study focuses on the development of three distinct Auto mode calibration levels for each set condition, designed to achieve the same cabin temperature with varying dynamic responses and energy consumption profiles. In Auto mode, the cabin temperature is regulated through intelligent control of compressor speed, blower speed, and evaporator temperature. While all Auto levels can maintain the desired setpoint, the time required to reach this temperature and the system’s responsiveness to sudden thermal loads can vary significantly. This study introduces three distinct calibration profiles, each engineered to achieve the same cabin temperature under different dynamic conditions and energy consumption levels. These profiles allow users to choose between faster thermal response or reduced power usage, effectively enabling a trade-off between immediate comfort and extended driving range</div></div>

<div class="section abstract"><div class="htmlview paragraph">The transition towards sustainable transportation necessitates the development of advanced thermal management systems (TMS) for electric vehicles (EVs), hybrid electric vehicles (HEVs), hydrogen fuel cell vehicles (FCVs), and hydrogen internal combustion engine vehicles (HICEVs). Effective thermal control is crucial for passenger comfort and the performance, longevity, and safety of critical vehicle components. This paper presents a rigorous and comparative analysis of TMS strategies across these diverse powertrain technologies. It systematically examines the unique thermal challenges associated with each subsystem, including cabin HVAC, battery packs, fuel cell stacks, traction motors, and power electronics. For cabin HVAC, the paper explores methods for minimizing energy consumption while maintaining thermal comfort, considering factors such as ambient temperature, humidity, and occupant load. The critical importance of battery thermal management is emphasized, with a focus on preventing thermal runaway and maximizing battery lifespan through precise temperature regulation. The complexities of fuel cell stack thermal management are addressed, considering the electrochemical reactions and the need for uniform temperature distribution for optimal performance and durability. Furthermore, the paper investigates the thermal behavior of high-power traction motors and power electronics, analyzing different cooling techniques and their impact on efficiency and reliability. A comparative assessment of various cooling technologies, including forced air convection, liquid cooling, and emerging two-phase cooling methods, is provided. The paper also delves into integrating these individual TMS components, exploring opportunities for waste heat recovery and holistic system optimization. Finally, the paper identifies critical research gaps and outlines future directions in the development of intelligent and adaptive thermal management systems for next-generation electrified vehicles, emphasizing the need for robust control algorithms, advanced materials, and innovative cooling architectures.</div></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">This SAE Recommended Practice identifies and defines requirements relating to the safe integration of the fuel cell system, the hydrogen fuel storage and handling systems (as defined and specified in SAE J2579) and high voltage electrical systems into the overall Fuel Cell Vehicle. The document may also be applied to hydrogen vehicles with internal combustion engines.</div> <div class="htmlview paragraph">This document relates to the overall design, construction, operation and maintenance of fuel cell vehicles.</div> </div>

<div class="section abstract"><div class="htmlview paragraph">Honda’s purpose is to realize the joy and freedom of mobility and a sustainable society in which people can enjoy life. As such, three series of environmental vehicles-FCVs, BEVs, and PHEVs-have been developed so that users in communities around the world can select the ones best suited to their local energy circumstances and individual lifestyles.</div><div class="htmlview paragraph">This paper discusses a structure that enhances both the motive power performance and quietness of a newly developed FCV/BEV traction motor.</div><div class="htmlview paragraph">To enhance motive power performance, the research focused on the stator lamination technique. As for methods of affixing the stator’s layers, the practice with previous models has been adhesion lamination, using electric steel sheets that come pre-made with adhesive layers. Having adhesive layers, however, lowers the ratio (space factor) of steel sheet layers. The new motor uses electric steel sheets without an adhesive layer in order to enhance motive power performance.</div><div class="htmlview paragraph">To enhance the quietness of the auto interior, it is important to lower the magnetism excitation force. To do this, a new magnetic circuit was developed and magnet positioning was optimized. For the rotor structure, level skewing was used to shift the rotor yoke in the direction of the perimeter.</div><div class="htmlview paragraph">A new motor to go on new FCVs/BEVs was developed and a traction motor that offers quietness, power, and a smooth driving feeling was achieved. Compared to the previous motor, the new motor raises maximum output from 100 kW to 130 kW, and maximum torque from 256 Nm to 300 Nm, all while maintaining the same volume. It also lowers motor noise heard in the interior of the vehicle by 5-10 dB(A), when compared to the previous motor.</div></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="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">Adoption of fuel cell electric vehicles (FCEV) or battery electric vehicles (BEV) in heavy-duty (HD) commercial freight transportation is hampered by difficult technoeconomic obstacles. To enable widespread deployment of electrified powertrains, fleet and operational logistics need high uptime and parity with diesel system productivity/total cost of ownership (TCO), while meeting safety compliance. Due to a mix of comparatively high powerplant and energy storage costs, high energy costs (more so for FCEV), greater weight (more so for BEV), slow refueling / recharging durations, and limited supporting infrastructure, FCEV and BEV powertrains have not seen significant uptake in the HD freight transport market. The use of dynamic wireless power transfer (DWPT) systems, consisting of inductive electrical coils on the vehicle and power source transmitting coils embedded in the roadways, may address several of these challenges. An appropriately designed BEV, will absorb energy at highway speeds from these transmitting coils in the road, providing electrical energy to sustain its mission. This has the potential to reduce the onboard energy storage requirements for BEV while enabling significantly longer missions. While still contingent on considerable infrastructure development, this technology has the potential to disrupt the zero emission HD freight transport system by not only lowering the overall total cost of ownership and increasing asset uptime, but also reducing the use of rare earth minerals required to support the deployment of these vehicle systems. This paper presents a study of four use cases (Drayage, Short Haul, Regional Haul, and Long Haul) of HD vehicles comparing the diesel incumbent powertrain against FCEV, BEV with depot charging, and BEV with DWPT charging. By considering the interplay of several technoeconomic factors associated with each of these powertrain options and further considering real world vehicle weight and road variations, a systematic study is conducted to show critical signposts for both single and multi-parameter technology viability. This study also assesses the sensitivity of each factor to the overall TCO changes thus identifying critical areas of further research and development. Finally, by considering the four use cases together a preliminary strategy to introduce DWPT in freight roadway networks is stipulated. Future works will address the specific characteristics and develop this strategy more holistically based on freight volume, road conditions, and other key development factors.</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="section abstract"><div class="htmlview paragraph">The US trucking industry heavily relies on the diesel powertrain, and the transition towards zero-emission vehicles, such as battery electric vehicles (BEV) and fuel cell electric vehicles (FCEV), is happening at a slow pace. This makes it difficult for truck manufacturers to meet the Phase 3 Greenhouse Gas standards, which mandate substantial emissions reductions across commercial vehicle classes beginning of 2027. This challenging situation compels manufacturers to further optimize the powertrain to meet stringent emissions requirements, which might not account for customer application specifics may not translate to a better total cost of ownership (TCO) for the customer.</div><div class="htmlview paragraph">This study uses a simulation-based approach to connect customer applications and regulatory categories across various sectors. The goal is to develop a methodology that helps identify the overlap between optimizing for customer applications vs optimizing to meet regulations.</div><div class="htmlview paragraph">To use a data-driven approach, a real-world customer usage pattern analysis was conducted to identify key performance metrics required to optimize driveline components. Additionally, the impact of certification requirements on vehicle performance is examined to ensure compliance while maximizing the benefits of the proposed optimization strategies. The findings of this research will provide valuable insights for manufacturers, enabling the development of trucks that are not only efficient and high-performing but also compliant with environmental standards, ultimately leading to a more sustainable future in the trucking industry.</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="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">The trend towards renewable energy sources will continue under the pre-amble of greenhouse gas (GHG) emission reduction targets. The main question is how to harvest and store renewable energy properly.</div><div class="htmlview paragraph">The challenge of intermittency of the renewable energy resources make the supply less predictable compared to the traditional energy sources. Chemical energy carriers like hydrogen and synthetic fuels (e-Fuels) seem to be at least a part of the solution for storing renewable energy.</div><div class="htmlview paragraph">The usage of e-Fuels in the existing ICE-powered vehicle fleet has a big lever arm to reduce the GHG emissions of the transport sector in the short- and medium term.</div><div class="htmlview paragraph">The paper covers the whole well-to-wheel (WtW) pathway by discussing the e-Fuel production from renewable sources, the storage and the usage in the vehicle. It will be summarized by scenarios on the impact of e-Fuel to the WtW CO2 fleet emissions.</div><div class="htmlview paragraph">The pathway of renewable chemical energy carriers shows a positive impact to the well-to-wheel CO<sub>2</sub> fleet average in the long-term.</div></div>

<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>