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Liquid pump-enabled hydrogen refueling system for heavy duty fuel cell vehicles: Pump performance and J2601-compliant fills with precooling
Abstract
We have developed a hydrogen (H2) refueling solution capable of delivering precooled, compressed gaseous hydrogen for heavy duty vehicle (HDV) refueling applications. The system uses a submerged pump to deliver pressurized liquid H2 from a cryogenic storage tank to a dispensing control loop that vaporizes the liquid and adjusts the pressure and temperature of the resulting gas to enable refueling at 35 MPa and temperatures as low as −40 °C. A full-scale mobile refueler was fabricated and tested over a 6-month campaign to validate its performance. We report results from tests involving a total of 9000 kg of liquid H2 pumped and 1350 filling cycles over a range of conditions. Notably, the system was able to repeatably complete multiple, back-to-back 30 kg filling cycles in under 6 min each, in full compliance with the SAE J2601-2 standard, demonstrating its potential for rapid-throughput HDV refueling applications.
... Liquid pumping approaches offer potential benefits in process flowsheet simplicity, lower energy requirements, less frequent delivery, sustained operation, and scalability, but have up to this point been limited by the capability and cost of high-pressure cryopump technology [4,5]. Recent development of a submerged LH2 cryopump and accompanying refueling system design with high pressure, high flow rate capabilities has the potential to enable commercial refueling station designs with significantly improved performance at a lower cost; the operational benefits are expected to be especially valuable for MDV and HDV applications which involve larger quantities of fuel per vehicle fill and higher daily use profiles by commercial fleet size [6,7]. While performance benefits of a recently developed submerged cryopump technology have been demonstrated in pilot studies, the economic potential of station designs based on this technology has not yet been evaluated. ...
... Standard engineering principles were used to size the equipment and estimate the costs for stations using conventional design configurations. Assumptions for the submerged cryopump option were updated to account for the demonstrated field performance of a submerged pump including: energy use (kWh/kg); maximum flow rate (kg/h); boil-off losses (kg/d/pump) [6,7]. The configuration includes a cryotank, pump, vaporizer, dispenser and controls. ...
... Table 1 summarizes the performance and economics of the submerged cryopump system. Performance characteristics are obtained from published reports of operation under field conditions [6,7]. Relative to the default liquid H2 cryopump option in HDRSAM, which is based on aggregation of various industry inputs, the submerged pump offers higher flow suggesting fewer pumps may be needed to achieve a given target dispensing rate. ...
Recent progress in submerged liquid hydrogen (LH2) cryopump technology development offers improved hydrogen fueling performance at a reduced cost in medium- and heavy-duty (MDV and HDV) fuel cell vehicle refueling applications at 35 MPa pressure, compared to fueling via gas compression. In this paper, we evaluate the fueling cost associated with cryopump-based refueling stations for different MDV and HDV hydrogen demand profiles. We adapt the Heavy Duty Refueling Station Analysis Model (HDRSAM) tool to analyze the submerged cryopump case, and compare the estimated fuel dispensing costs of stations supplied with LH2 for fueling Class 4 delivery van (MDV), public transit bus (HDV), and Class 8 truck (HDV) fleets using cryopumps relative to station designs. A sensitivity analysis around upstream costs illustrates the trade-offs associated with H2 production from onsite electrolysis versus central LH2 production and delivery. Our results indicate that LH2 cryopump-based stations become more economically attractive as the total station capacity (kg dispensed per day) and hourly demand (vehicles per hour) increase. Depending on the use case, savings relative to next best options range from about 5% up to 44% in dispensed costs, with more favorable economics at larger stations with high utilization.
... These studies just focused on production sites. Some other researchers limited the scope of the study to the hydrogen refueling stations only (e.g., Ref. [20,46]). Studying the techno economics of the whole supply chain for hydrogen is still a research gap. In this study, we consider the whole hydrogen supply chain from the production site to the pump at the refueling station. ...
... They impact service provision and productivity. However, FCEVs for HDVS have advantages such as increasing range, sustained operation under extreme conditions, faster refueling, and low fuel cell degradation, unlike lithium-ion batteries [46]. The negative impact of such batteries used in BEV was studied, and results showed that it leads to an increase in weight (1400-1800 kg) of electric trucks [48]. ...
This study investigates the potential and economics of hydrogen as a clean energy to satisfy the energy demand and reduce emissions. Heavy-duty vehicles and hydraulic fracking processes, which consume significant amounts of diesel are introduced as pilot markets for hydrogen. The technical, economic, and environmental aspects of both markets are provided. Then, a case study of the Permian Basin is rendered to show the effects of hydrogen in the region. In this study, the HDSAM model is used to obtain the cost of hydrogen. A function to predict the hydrogen demand for hydraulic fracking is provided based on real data. The results obtained in this study are as follows.
First, the results for heavy-duty vehicles show that hydrogen demand is equal to 148 (tonnes/day), and hydrogen cost is 7.58 (/miles). If the payload and dwell time costs are considered, hydrogen trucks can even be cheaper than EV trucks. Second, the results for hydraulic fracking show that hydrogen demand is equal to 334 (tonnes/day) considering 1430 wells in the Permian Basin. The hydrogen cost is 4.22 ($/kg). If hydrogen is used instead of diesel in fracking,
3.41*10**6 kg-CO2-eq as well as 4.10*10**7 kg of NOx can be saved from emissions. The hydrogen cost is equal to or even less than the diesel cost to generate 1 horsepower-hour for hydraulic fracking.
This work can be expanded by investigating ammonia. Its features can be compared with hydrogen in terms of stability for long-term storage, transmission, and the globally established infrastructure. In addition, the tax credits of 45Q can be compared with 45 V and its effects can be analyzed.
... The liquid pump can provide hydrogen fuel directly or together with the HPSS. Jimmy et al. [50,51] have developed a hydrogen refueling solution with a submerged LP for heavyduty vehicle refueling. The volumetric efficiency of LP was studied, and the maximum value appears to be insensitive to the discharge pressure. ...
... Regarding thermal management, the cold energy of the LH 2 can be recovered [53] to precool the hydrogen flow from HPSS instead of the extra precooling chiller [34]. Jimmy et al. [50] employed a vaporizer and a heat exchanger to realize temperature control. Schafer and Klein [54] refueling processes with different thermal management systems. ...
... Petitpas et al. [3,5] conducted repetitive refueling experiments to test the cycling performance of a LH 2 pump rated for 100 kg/h and 87.5 MPa maximum pressure. Li et al. [6,7] tested the performance of a liquid pump-enabled hydrogen refueling system mounted on a trailer for heavy-duty vehicles in which a single-acting submerged pressure of the reciprocating LH 2 pump is acquired and analyzed. The motion characteristics of suction and discharge valves in the reciprocating LH 2 pump are obtained. ...
Reciprocating liquid hydrogen pumps are essential equipment for hydrogen refueling stations with liquid hydrogen stored. The valves play a crucial role in facilitating unidirectional flow and the pressurization of liquid hydrogen within the pump. This paper establishes a comprehensive numerical model to simulate the whole working cycle of a reciprocating liquid hydrogen pump. The influence of valve parameters and pump operating conditions on the motion characteristics of valves, including lift, closing lag angle, and impact velocity, is investigated. The results indicate that with the maximum lift of the suction valve at 10 mm and the discharge valve at 5 mm, the closing lag angle is minimal, and the impact velocity of the valve falls within an acceptable range. The optimal rotation speed range is between 200 and 300 rpm, within which both the closing lag angle and impact velocity of valves are minimized. Excessive maximum lift and low rotational speed lead to significant oscillations and high impact velocity in valve movement with the effects being more pronounced in the suction valve. The effects of the subcooling degree of inflow liquid hydrogen on the valve motion are further analyzed. The findings suggest that the subcooling degree of inflow liquid hydrogen helps inhibit the vaporization in the pump operation and ensures the valves work correctly. This work would contribute to pump optimization and valve collision failure analysis in reciprocating liquid hydrogen pumps.
... Li et al. [1] tested a submerged liquid hydrogen cryogenic piston pump applied to a refueling station. The pump was capable of reliable operation for a period of 6 months. ...
The process of liquefaction of gaseous fuels, such as natural gas or hydrogen, is an essential technology that helps reduce transportation costs over long distances. Cryogenic piston pumps play a critical role in these systems, as they compress the fuel up to 700 bar before vaporization and storage in high-pressure vessels. Due to the extreme temperatures and pressures involved, the design of these machines poses a significant challenge from the thermal and structural point of view. This work presents the application of a simplified numerical approach for evaluating the thermally induced stresses and deformations through a de-coupled thermo-structural three-dimensional analysis of a prototype cryogenic piston pump. Thermal simulations of the solid domain are carried out to assess the steady-state temperature distribution of the pump. The heat transfer between the pump and cryogenic liquid is computed using three-dimensional steady-state CFD simulations of the suction and discharge phases. Heat generated by friction during the working cycle of the pump and external natural convection are calculated and imposed as a heat source in the simulations. The steady-state temperature distribution is imposed in a finite-element steady-state three-dimensional structural simulation to evaluate the combined effect of thermal loads induced by the cryogenic temperatures and loads induced by the high working pressures. Results show how the proposed methodology can assist in the design of cryogenic piston pumps by offering valuable insights into the most critical aspects of these machines.
... The main components of the hydrogen filling system include the hydrogen fuel cell electric vehicle refueling receptacle (hereinafter referred to as the receptacle), filters, hydrogen transportation pipelines, pipeline solenoid valves, and one-way valve [8][9][10]. The pipeline solenoid valve can effectively prevent the gas from entering the battery when the cylinder is inflated, and the one-way valve can prevent the gas from leaking when the receptacle is damaged. ...
Hydrogen fuel cell vehicles (HFCVs) represent an important breakthrough in the hydrogen energy industry. The safe utilization of hydrogen is critical for the sustainable and healthy development of hydrogen fuel cell vehicles. In this study, risk factors and preventive measures are proposed for on-board hydrogen systems during the process of transportation, storage, and use of fuel cell vehicles. The relevant hydrogen safety standards in China are also analyzed, and suggestions involving four safety strategies and three safety standards are proposed.
... An alternative solution is to store the hydrogen in liquified form. Although studies show that this configuration reduces the stations' footprint, capital and operating costs, the lack of a global assessment over the entire liquefaction chain and the poor performance of existing pumps slow down its application [9,10]. The compressed gas delivery is conducted either by tube trailers, in which the hydrogen is generally stored at a pressure of 200 bar or is transported from the point of production until the distribution point through pipelines at pressures between 30 and 80 bar [11,12]. ...
Worldwide about 550 hydrogen refueling stations (HRS) were in operation in 2021, of which 38%. were in Europe. With their number expected to grow even further, the collection and investigation of real-world station operative data are fundamental to tracking their activity in terms of safety issues, performances, costs, maintenance, reliability, and energy use. This paper shows and analyses the parameters that characterize the refueling of 350 bar fuel cell buses in four HRS within the 3Emotion project. The HRS are characterized by different refueling capacities, hydrogen supply schemes, storage volumes and pressures, and operational strategies. From data logs provided by the operators, a dataset of three years of operation has been created. In particular total hydrogen quantity, the fill amount dispensed to each bus, the refueling duration, the average mass flow rate, the number of refueling events and the daily number of refills, the daily profile, the utilization factor, and the availability are investigated. The results show similar hydrogen amount per fill distribution, but quite different refueling times among the stations. The average daily mass per bus is around 12.95 kg, the most frequent value 15 kg, the standard deviation 7.46. About 50% of the total amount of hydrogen is dispensed overnight and the refueling events per bus are typically every 24 hours. Finally, the station utilization is below 30% for all sites.
Hydrogen is being presented and adopted as a carbon-free alternative to traditional fossil fuels in the transportation sector. Carbon emissions from hydrogen production have been well characterized, but hydrogen emissions themselves interfere with chemical processes that serve to check concentrations of atmospheric greenhouse gases. Recent published analyses suggest a 100-year global warming potential of approximately 10 for hydrogen, so that direct hydrogen emissions are of concern in quantifying climate change benefits. This is similar to concerns that methane emissions diminish the benefits of natural gas as a low carbon fuel. Our review and study have gathered the scattered literature and data relevant to hydrogen emissions, employed analogies from natural gas deployment, and derived realistic estimates of hydrogen emissions for the pump-to-wheels (PTW) transportation sector. Our results demonstrate that losses depend on the type and scale technology in place and can be substantial as a percentage. The results should be combined with existing upstream climate change emissions for hydrogen production and upstream distribution to improve quantitative assessment of the net environmental benefit offered by hydrogen in the transportation sector. This in turn should guide future investment and policy decisions. A direct implication of the results is that effort should be made to abate pump-to-wheels hydrogen emissions through adoption of best technology and practice, through improvement of hydrogen recovery, and through sizing of fueling infrastructure that is appropriate for vehicle fleet size.
This chapter reviews pumps used with liquid cryogens, followed by an excursion on possible high temperature superconducting pump designs. Furthermore, we gauge the present status of hydrogen pumps and where we need components to improve this technology to make them aircraft worthy, followed by general tank safety concerns.
While battery-electric vehicles already account for almost 100 % of all alternative drive concepts in the passenger car sector today and in the medium term, the medium- to long-term future is open in other transport sectors. Here, concepts of purely battery-electric drives as well as hydrogen-based drives with fuel cells and hydrogen combustion engines continue to be discussed. One of the most important factors for the success of a drive technology, especially in commercial applications, is the total cost of ownership (TCO).
In the case of TCO in long-distance transport, fuel costs play a decisive role and account for the largest share of the cost per km. Therefore, in the use of hydrogen-based propulsion concepts, the cost of hydrogen procurement plays a central role, which in turn is determined in equal parts by hydrogen production costs and distribution costs (including the refueling station). The existing hydrogen refueling station network is essentially based on on-site liquid storage and uses high-capacity compressors to fill the high-pressure gas storage tanks (350 or 700 bar) of current hydrogen vehicles. The capital and operating costs of the compressors significantly determine hydrogen costs and have a corresponding impact on TCO performance. Storage systems based on in-vehicle liquid hydrogen storage can positively influence overall cost performance by modifying the refueling system accordingly and have an impact on the capital cost of the storage systems. This analysis examines and compares these cost effects in comparison to battery electric drives
Recovering the cryogenic cold energy of liquid hydrogen (LH2) for precooling high-pressure hydrogen gas before refueling can significantly reduce the electricity and energy consumption of liquid hydrogen refueling stations. Existing methods, such as blending, require continuous cryogenic pump operation and are not suitable for various operating conditions. This work proposes a novel method to recover LH2 cryogenic cold energy using a double-pipe heat exchanger, which can decouple the compression and refueling process and meet the fluctuating demand for the cryogenic cold energy required by the hydrogen dispenser. The lumped parameter method and temperature partition method were adopted to design the heat exchanger structure. Numerical simulations of a 2D axisymmetric swirl model were done to verify the accuracy of the temperature partition method applied to high-pressure cryogenic hydrogen. Due to the low temperature of LH2, the secondary refrigerant dichloromethane (CH2Cl2) risks freezing. Comparing the outer wall surface temperature of the inner pipe with the CH2Cl2 freezing point temperature, the optimal anti-freezing condition is that the outer pipe nominal diameter should be selected as 0.032 m and CH2Cl2 mass flow rate should be at least 1.72 kg s−1. Recovery efficiency can reach over 75.39% without freezing.
Reciprocating liquid hydrogen pump operates under alternating pressure, temperature, and flowrate with dramatic changes in the thermodynamic states of liquid hydrogen. The thermodynamic state in the pump is influenced by the dynamic interactions between fluid flow, heat transfer, piston motion, and valve dynamics. This paper presents a numerical study for reciprocating liquid hydrogen pumps based on a coupled simulation of the dynamic processes between the alternating flow, unsteady heat transfer, and valve dynamics with a given piston motion as the input. A pump for hydrogen refueling stations with a nominal flowrate and delivery pressure of 50 kg/h and 87.6 MPa is selected as the research object. The appropriate design parameters of the pump and its valves are determined to avoid cavitation in the cylinder and oscillation of the valves. The effects of the frequency and delivery pressure on the valve motion and pump performance are further analyzed. Finally, the in-cylinder heat transfer leads to an extra evaporation loss of 0.012 kg/day, and the isentropic and volumetric efficiencies of the liquid hydrogen pump are 97.30% and 90.76% respectively. The work presented here would be beneficial for the design and optimization of reciprocating liquid hydrogen pumps.
Modeling and optimization of liquid hydrogen (LH2) pumps require accurate in-cylinder heat transfer correlations. However, the applicability of existing correlations based on gas mediums to LH2 remains to be verified. In this paper, the unsteady heat transfer and fluid flow in a closed LH2 pump cylinder are numerically studied by adopting the gas spring model. The phase shifts and temperature distribution in the closed pump cylinder are investigated. LH2 is less affected by in-cylinder heat transfer and has a more uniform temperature distribution compared to nitrogen gas, while a low-temperature zone appears near the piston face at 120 rpm. Finally, the validity of Lekic's correlation in predicting the heat flux of the LH2 compression process in the closed pump cylinder is verified, and the efficiency decrement versus rotational speed is analyzed based on the correlation. This work would be useful for selecting a proper in-cylinder heat transfer model for predicting the thermodynamic process in reciprocating LH2 pumps.
Worldwide about 550 hydrogen refueling stations (HRS) were in operation in 2021, of which 38% were in Europe. With their number expected to grow even further, the collection and investigation of real-world station operative data are fundamental to tracking their activity in terms of safety issues, performances, maintenance, reliability, and energy use. This paper analyses the parameters that characterize the refueling of 350 bar fuel cell buses (FCB) in five HRS within the 3Emotion project. The HRS are characterized by different refueling capacities, hydrogen supply schemes, storage volumes and pressures, and operational strategies. The FCB operate over various duty cycles circulating on urban and extra-urban routes. From data logs provided by the operators, a dataset of four years of operation has been created. The results show a similar hydrogen amount per fill distribution but quite different refueling times among the stations. The average daily mass per bus and refueling time are around 14.62 kg and 10.28 min. About 50% of the total amount of hydrogen is dispensed overnight, and the refueling events per bus are typically every 24 h. On average, the buses' time spent in service is 10 h per day. The hydrogen consumption is approximately 7 kg/100 km, a rather effective result reached by the technology. The station utilization is below 30% for all sites, the buses availability hardly exceeds 80%.
As a clean energy source, hydrogen has attracted much attention due to its high thermal conversion efficiency, recyclability and non-polluting properties. Recently, hydrogen fuel cell vehicles have become a global research hotspot, and the number of hydrogen refueling stations is steadily increasing. But the biggest problem holding them back is that the filling of high-pressure hydrogen causes a rapid increase in the internal temperature of the storage tank. In order to make hydrogen fuel cell vehicles fully popular, the principle of temperature rise is systematically elucidated, the influence of refueling parameters on the tank state is summarized and appropriate mitigation measures and solutions to limit or mitigate the effects of temperature rise are proposed in this review, such as pre-cooling the hydrogen in advance, reducing the initial hydrogen content in the tank and ensuring that the ambient temperature and the initial tank temperature are at a low level. In addition, a number of safe refueling strategies and methods are presented. Through the comprehensive study in this paper, the important relationship between the refueling parameters and the temperature rise in the tank is refined, which is very useful in promoting the development of new refueling strategies and hydrogen fuel cell vehicles.
Battery electric vehicles (BEVs) and hydrogen fuel cell vehicles (HFCVs) will predominate in near future, and the new energy vehicle (NEV) charging station which provides charging services for aforementioned NEVs could grow rapidly. The reliability of the NEV charging station would be the primary concern for early construction and NEV users. This study investigates the reliability evaluation of NEV charging station considering the impact of charging experience and analyzes the influence of various factors by comparing the evaluation results. The explicit modelling of the station considering power generation system, coupling devices and hydrogen storage is presented and an optimal revenue model is established to coordinate the operation of the station. A reliability index system is established to evaluate the charging reliability of the NEV charging station and reflect the charging experience. In addition, an amount model estimating the number of vehicles accessed in the coming days is proposed to address the impact of driver charging experience on the reliability evaluation. The results show that it is necessary to consider the charging experience in reliability evaluation. The comparison and analysis of reliability evaluation results reveal that the charging reliability and profit of the charging station are influenced by the initial hydrogen in tank, the price of hydrogen/electricity and the sizes of electrolyzer, hydrogen tank and fuel cell. The reliability evaluation provides guidance for determining the parameters of these factors.
We have demonstrated a hydrogen (H2) refueling solution capable of delivering precooled, compressed gaseous hydrogen for heavy duty vehicle (HDV) refueling applications by refueling transit buses over a three-month period under real-world conditions. The system uses a submerged pump to deliver pressurized liquid H2 from a cryogenic storage tank to a dispensing control loop that vaporizes the liquid and adjusts the pressure and temperature of the resulting gas to enable refueling at 35 MPa and temperatures as low as −40 °C, consistent with the SAE J2601 standard. Using our full-scale mobile refueler, we completed 118 individual bus filling events using 13 different vehicles, involving a total of 3,700 kg of H2 dispensed. We report filling statistics from the entire campaign, details on individual fills (including fill times, final state of charge, benefits of pre-cooled fills, and back-to-back filling capabilities), and discuss transit agency feedback on technology performance. In our final test, the system successfully completed an endurance test using a single dispenser involving 52 consecutive individual fills over an 11.5-h period, dispensing 1,322 kg of H2 with an average fill rate of 3.4 kg/min and peak rate of 7.1 kg/min, and reaching an average SOC of 97.6% across all fills.
The cost of delivered H2 using the liquid-distribution pathway will approach $4.3–8.0/kg in the USA and 26–52 RMB/kg in China by around 2030, assuming large-scale adoption. Historically, hydrogen as an industrial gas and a chemical feedstock has enjoyed a long and successful history. However, it has been slow to take off as an energy carrier for transportation, despite its benefits in energy diversity, security and environmental stewardship. A key reason for this lack of progress is that the cost is currently too high to displace petroleum-based fuels. This paper reviews the prospects for hydrogen as an energy carrier for transportation, clarifies the current drivers for cost in the USA and China, and shows the potential for a liquid-hydrogen supply chain to reduce the costs of delivered H2. Technical and economic trade-offs between individual steps in the supply chain (viz. production, transportation, refuelling) are examined and used to show that liquid-H2 (LH2) distribution approaches offer a path to reducing the delivery cost of H2 to the point at which it could be competitive with gasoline and diesel fuel.
Hydrogen infrastructure for fueling vehicles has progressed in the last decade from stations with restricted access and limited operating hours to customer-friendly retail stations open to the public. There are now 121 retail hydrogen stations around the world. In California, the number of public retail hydrogen stations has increased from zero to more than 30 in less than two years, and the annual amount of hydrogen dispensed by retail stations has grown from 27,400 kg in 2015 to nearly 105,000 kg in 2016 and more than 440,000 kg in 2017—an increase of about four times year over year. For more than a decade, government, industry, and academia have studied many aspects of hydrogen infrastructure, from renewable hydrogen production to retail hydrogen station performance. This paper reviews the engineering and deployment of modern hydrogen infrastructure, including the costs, benefits, and operational considerations (including safety, reliability, availability), as well as challenges to the scale-up of hydrogen infrastructure. The results identify hydrogen station reliability as a key factor in the expense of operating hydrogen systems, placing it in the context of the larger reliability engineering field.
This paper reports the results of a comprehensive test of liquid hydrogen (LH2) pump performance and durability conducted while cycle testing a prototype thin-lined cryogenic pressure vessel 456 times to 700 bar. This extensive LH2 pump experimental data set provides a wealth of information vital for a complete evaluation of the future potential of this promising technology for ambient temperature and cryo-compressed vessel refueling. The experiment was conducted at Lawrence Livermore National Laboratory (Livermore, CA)'s hydrogen test facility, specifically built for this experiment and including a containment vessel for safe testing of the prototype vessel and a control room for efficient monitoring. Original pump and storage instrumentation was complemented with an electric power analyzer and a boil-off mass flow meter for more complete pump characterization.
The results of the experiment confirm most of the expected virtues of the LH2 pump: rapid (3 min) refueling of the 65-liter prototype vessel at high flow rate (1.55 kgH2 per minute on average), unlimited back to back refueling, low electricity consumption (1.1 kWh/kg H2), no measurable degradation, and low maintenance. High cryogenic vessel fill density is another key performance metric that was demonstrated in an earlier publication. These virtues derive from the high density of LH2 enabling pressurization to high density with relatively little energy consumption and high throughput from a small displacement pump. Boil-off losses as high as 27.7% of dispensed hydrogen were measured, at experimental conditions not representative of operation at a hydrogen refueling station. These losses drop to 15.4% for operation that may be representative of a small station (332 kg/day), while we anticipate less than 6% boil-off with the existing pump and Dewar with improved LH2 delivery truck operations and a more favorable arrangement of the LH2 pump relative to the Dewar.
Several alternative vehicle and fuel options are under consideration to alleviate the triple threats of climate change, urban air pollution and foreign oil dependence caused by motor vehicles. This paper evaluates the primary transportation alternatives and determines which hold the greatest potential for averting societal threats. We developed a dynamic computer simulation model that compares the societal benefits of replacing conventional gasoline cars with vehicles that are partially electrified, including hybrid electric vehicles, plug-in hybrids fueled by gasoline, cellulosic ethanol and hydrogen, and all-electric vehicles powered exclusively by batteries or by hydrogen and fuel cells. These simulations compare the year-by-year societal benefits over a 100-year time horizon of each vehicle/fuel combination compared to conventional cars. We conclude that all-electric vehicles will be required in combination with hybrids, plug-in hybrids and biofuels to achieve an 80% reduction in greenhouse gas emissions below 1990 levels, while simultaneously cutting dependence on imported oil and eliminating nearly all controllable urban air pollution from the light duty vehicle fleet. Hybrids and plug-ins that continue to use an internal combustion engine will not be adequate by themselves to achieve our societal objectives, even if they are powered with biofuels.There are two primary options for all-electric vehicles: batteries or fuel cells. We show that for any vehicle range greater than 160 km (100 miles) fuel cells are superior to batteries in terms of mass, volume, cost, initial greenhouse gas reductions, refueling time, well-to-wheels energy efficiency using natural gas or biomass as the source and life cycle costs.