Impact of hydrogen refueling configurations and market parameters on the refueling cost of hydrogen

The cost of hydrogen in early fuel cell electric vehicle (FCEV) markets is dominated by the cost of refueling stations, mainly due to the high cost of refueling equipment, small station capacities, lack of economies of scale, and low utilization of the installed refueling capacity. Using the hydrogen delivery scenario analysis model (HDSAM), this study estimates the impacts of these factors on the refueling cost for different refueling technologies and configurations, and quantifies the potential reduction in future hydrogen refueling cost compared to today's cost in the United States. The current hydrogen refueling station levelized cost, for a 200 kg/day dispensing capacity, is in the range of $6–$8/kg H₂ when supplied with gaseous hydrogen, and $8–$9/kg H₂ for stations supplied with liquid hydrogen. After adding the cost of hydrogen production, packaging, and transportation to the station's levelized cost, the current cost of hydrogen at dispensers for FCEVs in California is in the range of $13–$15/kg H₂. The refueling station capacity utilization strongly influences the hydrogen refueling cost. The underutilization of station capacity in early FCEV markets, such as in California, results in a levelized station cost that is approximately 40% higher than it would be in a scenario where the station had been fully utilized since it began operating. In future mature hydrogen FCEV markets, with a large demand for hydrogen, the refueling station's levelized cost can be reduced to $2/kg H₂ as a result of improved capacity utilization and reduced equipment cost via learning and economies of scale.     

Developing an infrastructure for hydrogen vehicles: a Southern California case study

We have examined the technical feasibility and economics of developing a hydrogen vehicle refueling infrastructure for a specific area where zero emission vehicles are being considered, Southern California. Potential hydrogen demands for zero emission vehicles are estimated. We then assess in detail several near term possibilities for producing and delivering gaseous hydrogen transportation fuel including: (1) hydrogen produced from natural gas in a large, centralized steam reforming plant, and truck delivered as a liquid to refueling stations; (2) hydrogen produced in a large, centralized steam reforming plant, and delivered via small scale hydrogen gas pipeline to refueling stations; (3) by-product hydrogen from chemical industry sources; (4) hydrogen produced at the refueling station via small scale steam reforming of natural gas; and (5) hydrogen produced via small scale electrolysis at the refueling station. The capital cost of infrastructure and the delivered cost of hydrogen are estimated for each hydrogen supply option. Hydrogen is compared to other fuels for fuel cell vehicles (methanol, gasoline) in terms of vehicle cost, infrastructure cost and lifecycle cost of transportation. Finally, we discuss possible scenarios for introducing hydrogen as a fuel for fuel cell vehicles.     

Development of a Hydrogen Refueling Station Design Tool

In the last couple of decades, there has been a growing concern in what effects fossil fuels are having on the environment, resulting in governments and governing organizations issuing stringent emission standards in an effort to curve their environmental damage. To meet these new standards, the transportation industry has been conducting research into alternative fuels, such as hydrogen, but one critical problem utilizing hydrogen is that there is almost no infrastructure. A network of hydrogen refueling stations similar to modern gasoline stations will be required to be constructed to meet future demand. The hydrogen refueling station model was created to aid in designing hydrogen facilities, thus accelerating their development while reducing design cost. A model was created using Simulink consisting of an electrolyzer that generates hydrogen, a compressor, numerous storage tanks, a dispensing unit that transfers hydrogen, and a vehicle component that consumes hydrogen fuel. The model was validated using data from existing hydrogen refueling stations, and the data obtained from testing the previous version of the hydrogen refueling station model to determine model accuracy and if the model has improved. The model has demonstrated that it can produce reasonable results for a station's performance and has improved compared to the previous version.     

Energetic evaluation of hydrogen refueling stations with liquid or gaseous stored hydrogen

The future success of fuel cell electric vehicles requires a corresponding infrastructure. In this study, two different refueling station concepts for fuel cell passenger cars with 70 MPa technology were evaluated energetically. In the first option, the input of the refueling station is gaseous hydrogen which is compressed to final pressure, remaining in gaseous state. In the second option, the input is liquid hydrogen which is cryo-compressed directly from the liquid phase to the target pressure. In the first case, the target temperature of −33 °C to −40 °C [1] is achieved by cooling down. In the second option, gaseous deep-cold hydrogen coming from the pump is heated up to target temperature. A dynamic simulation model considering real gas behavior to evaluate both types of fueling stations from an energetic perspective was created. The dynamic model allows the simulation of boil-off losses (liquid stations) and standby energy losses caused by the precooling system (gaseous station) dependent on fueling profiles. The functionality of the model was demonstrated with a sequence of three refueling processes within a short time period (high station utilization). The liquid station consumed 0.37 kWh/kg compared to 2.43 kWh/kg of the gaseous station. Rough estimations indicated that the energy consumption of the entire pathway is higher for liquid hydrogen. The analysis showed the high influence of the high-pressure storage system design on the energy consumption of the station. For future research work the refueling station model can be applied to analyze the energy consumption dependent on factors like utilization, component sizing and ambient temperature.     

Estimation of consequence and damage caused by an organic hydride hydrogen refueling station

Organic hydride hydrogen refueling stations are currently being developed in Japan. For these stations, we estimate the consequence and damage caused by explosions and heat radiation after a hydrogen leak, and the acute toxicity caused by the leakage and dispersion of methylcyclohexane and toluene energy carriers. First, the organic hydride hydrogen refueling station is defined, and an accident scenario for four leak sizes of hydrogen and chemical leak accidents is set. Next, simulations of the blast wave pressure and heat radiation after the hydrogen leak and of atmospheric dispersion for the evaporation after liquid methylcyclohexane and toluene leaks are performed. Probit functions or threshold values are created for each type of effects caused by the explosion, heat and the inhalation effect on humans of toluene acute toxicity. Population data for the area surrounding the station are created in a 10-m mesh. The consequence and damage are estimated for each leak size. The results show that although the explosion and chemical leak affects the area around the refueling station, the effects are small in all of the accident scenarios. In contrast, although the area of the heat effect is limited to inside the refueling station, the burn damage is large, and there is a need for conducting quantitative risk assessment.     

An advanced framework for leakage risk assessment of hydrogen refueling stations using interval-valued spherical fuzzy sets (IV-SFS)

The extensive population growth calls for substantial studies on sustainable development in urban areas. Thus, it is vital for cities to be resilient to new situations and adequately manage the changes. Investing in renewable and green energy, including high-tech hydrogen infrastructure, is crucial for sustainable economic progress and for preserving environmental quality. However, implementing new technology needs an effective and efficient risk assessment investigation to minimize the risk to an acceptable level or ALARP (As low as reasonably practicable). The present study proposes an advanced decision-making framework to manage the risk of hydrogen refueling station leakage by adopting the Bow-tie analysis and Interval-Value Spherical Fuzzy Sets to properly deal with the subjectivity of the risk assessment process. The outcomes of the case study illustrate the causality of hydrogen refueling stations' undesired events and enhance the decision-maker's thoughts about risk management under uncertainty. According to the findings, jet fire is a more likely accident in the case of liquid hydrogen leakage. Furthermore, equipment failure has been recognized as the most likely cause of hydrogen leakage. Thus, in order to maintain the reliability of liquid hydrogen refueling stations, it is crucial that decision-makers develop a trustworthy safety management system that integrates a variety of risk mitigation measures including asset management strategies.     

Liquid pump-enabled hydrogen refueling system for heavy duty fuel cell vehicles: Pump performance and J2601-compliant fills with precooling

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.     

Determining the lowest-cost hydrogen delivery mode

Hydrogen delivery is a critical contributor to the cost, energy use and emissions associated with hydrogen pathways involving central plant production. The choice of the lowest-cost delivery mode (compressed gas trucks, cryogenic liquid trucks or gas pipelines) will depend upon specific geographic and market characteristics (e.g. city population and radius, population density, size and number of refueling stations and market penetration of fuel cell vehicles). We developed models to characterize delivery distances and to estimate costs, emissions and energy use from various parts of the delivery chain (e.g. compression or liquefaction, delivery and refueling stations). Results show that compressed gas truck delivery is ideal for small stations and very low demand, liquid delivery is ideal for long distance delivery and moderate demand and pipeline delivery is ideal for dense areas with large hydrogen demand.     

Operating experience with a liquid-hydrogen fueled buick and refueling system

An investigation of liquid-hydrogen storage and refueling systems for vehicular applications was made in a recently completed project. The vehicle used in the project was a 1979 Buick Century sedan with a 3.8.1, displacement turbocharged V6 engine and an automatic transmission. The vehicle had a fuel economy for driving in the high altitude Los Alamos area that was equivalent to 2.4 km/l of liquid hydrogen or 8.9 km/l of gasoline on an equivalent energy basis. About 22% less energy was required using hydrogen rather than gasoline to go a given distance based on the Environmental Protection Agency estimate of 7.2 km/l of gasoline for this vehicle. At the end of the project the engine had been operated for 138 h and the car driven 3633 km during the 17 months that the vehicle was operated on hydrogen. Two types of onboard liquid-hydrogen storage tanks were tested in the vehicle; the first was an aluminium Dewar with a liquid-hydrogen capacity of 1101.; the second was a Dewar with an aluminium outer vessel, two copper vapor-cooled thermal radiation shields, and a stainless steel inner vessel with a liquid-hydrogen capacity of 1551. The Buick had an unrefueled range of about 274 km with the first liquid-hydrogen tank and about 362 km with the second. The Buick was fueled at least 65 times involving a minimum of 8.1 kl of liquid hydrogen using various liquid-hydrogen storage Dewars at Los Alamos and a semiautomatic refueling station. A refueling time of 9 min was achieved, and liquid-hydrogen losses during refueling were measured. The project has demonstrated that liquid-hydrogen storage onboard a vehicle, and its refueling, can be accomplished over an extended period without any major difficulties; nevertheless, appropriate testing is still needed to quantitatively address the question of safety for liquid-hydrogen storage onboard a vehicle.     

Near-term location planning of hydrogen refueling stations in Yokohama City

Establishing hydrogen refueling stations is key to transition into a hydrogen economy. To achieve this, a near-term, city-level roll-out plan is required, as Japan is shifting from the demonstration to implementation stage of a hydrogen economy. The aim of this study was to devise a plan to identify near-term locations to build hydrogen refueling stations in Yokohama City, Japan. Our plan provides information on the potential location of hydrogen refueling stations for 2020–2030. We considered mobile and parallel-siting type refueling stations; the locations of these stations were determined by matching the supply and demand estimated from hybrid vehicle ownership data and the available space in existing gas stations based on a safety perspective. The results reaffirmed the importance of planning the locations of hydrogen refueling stations and highlighted the suitability of using mobile-type stations. This was based on the uncertainty in fuel demand for fuel cell vehicles during the implementation stage of the hydrogen economy.     

Review on the research of hydrogen storage system fast refueling in fuel cell vehicle

A comprehensive review of the hydrogen storage systems and investigations performed in search for development of fast refueling technology for fuel cell vehicles are presented. Nowadays, hydrogen is considered as a good and promising energy carrier and can be stored in gaseous, liquid or solid state. Among the three ways, high pressure (such as 35 MPa or 70 MPa) appears to be the most suitable method for transportation due to its technical simplicity, high reliability, high energy efficiency and affordability. However, the refueling of high pressure hydrogen can cause a rapid increase of inner temperature of the storage cylinder, which may result not only in a decrease of the state of charge (SOC) but also in damages to the tank walls and finally to safety problems. In this paper, the theoretical analysis, experiments and simulations on the factors related to the fast refueling, such as initial pressure, initial temperature, filling rate and ambient temperature, are reviewed and analyzed. Understanding the potential relationships between these parameters and the temperature rise may shed a light in developing novel controlling strategies and innovative routes for hydrogen tank fast filling.     

Addition of hydrogen refueling for fuel cell bus fleet to existing natural gas stations: A case study in Wuhan,China

Hydrogen refueling is an essential infrastructure for fuel cell vehicles, and currently, it appears to be a critical service needed to initiate the highly anticipated hydrogen economy in China. A practical selecting procedure of adding hydrogen refueling service to existing natural gas (NG) stations is proposed in this study. A case study in Wuhan, China, is established to assess the feasibility and future planning. The demand for hydrogen fuel and initial supply chain of hydrogen in Wuhan are estimated based on the deployment objective of fuel cell buses. The existing NG stations are evaluated based on 300 kg/day to determine whether they meet the hydrogen safety requirement using Google map or field investigation. The safety space requirement of the hydrogen refueling area on existing NG station is determined as 25.9 × 27.1 m². The optimal hydrogen refueling plan for fuel cell buses is calculated with multi‐objective analysis in economic, environmental, and safety aspects from the view of the hydrogen refueling supply chain. It is shown that adding hydrogen refueling stations to existing NG stations is feasible in technology, economics, regulation, and operation considerations. This study provides guidelines for building the hydrogen infrastructure for fuel cell buses at their early stage of commercial operation.     

A thermodynamic analysis of refueling of a hydrogen tank

A thermodynamic analysis of refueling of a gaseous hydrogen fuel tank is described. This study may lend itself to the applications of refueling a hydrogen storage tank onboard a hydrogen fuel-cell vehicle. The gaseous hydrogen is treated as an ideal or a non-ideal gas. The refueling process is analyzed based on adiabatic, isothermal, or diathermal condition of the tank. A constant feed-rate is assumed in the analysis. The thermodynamic state of the feed stream also remains constant during refueling. Ideal-gas assumption results in simple closed-form expressions for tank temperature, pressure, and other parameters. The non-ideal behavior of high-pressure gaseous hydrogen is addressed using the newly developed equation of state for normal hydrogen, which is based on the reduced Helmholtz free energy formulation. Sample calculations are presented using initial tank and feed stream conditions commensurate to practical vehicular applications. Comparing to the non-ideal analysis, the ideal-gas assumption always results in under-prediction of the tank temperature and pressure irrespective of the filling condition. For a given target tank pressure, the refueling time is the shortest under adiabatic condition and is the longest under isothermal condition with the tank being maintained at the initial tank temperature. The adiabatic and isothermal conditions can be viewed, respectively, as the lower and upper bounds of the refueling time for a given final target tank pressure.     

Single-tank storage versus multi-tank cascade system in hydrogen refueling stations for fuel cell buses

Many countries in Europe are investing in fuel cell bus technology with the expected mobilization of more than 1200 buses across Europe in the following years. The scaling-up will make indispensable a more effective design and management of hydrogen refueling stations to improve the refueling phase in terms of refueling time and dispensed quantity while containing the investment and operation costs. In the present study, a previously developed dynamic lumped model of a hydrogen refueling process, developed in MATLAB, is used to analyze tank-to-tank fuel cell buses (30–40 kg_H2 at 350 bar) refueling operations comparing a single-tank storage with a multi-tank cascade system. The new-built Aalborg (DK) hydrogen refueling station serves as a case study for the cascade design. In general, a cascading refueling approach from multiple storage tanks at different pressure levels provides the opportunity for a more optimized management of the station storage, reducing the pressure differential between the refueling and refueled tanks throughout the whole refueling process, thus reducing compression energy. This study demonstrates the validity of these aspects for heavy-duty applications through the technical evaluation of the refueling time, gas heating, compression energy consumption and hydrogen utilization, filling the literature gap on cascade versus single tank refueling comparison. Furthermore, a simplified calculation of the capital and operating expenditures is conducted, denoting the cost-effectiveness of the cascade configuration under study. Finally, the effect of different pressure switching points between the storage tanks is investigated, showing that a lower medium pressure usage reduces the compression energy consumption and increases the station flexibility.     

Estimation of final hydrogen temperature from refueling parameters

Compressed hydrogen storage is currently widely used in fuel cell vehicles due to its simplicity in tank structure and refueling process. For safety reason, the final gas temperature in the hydrogen tank during vehicle refueling must be maintained under a certain limit, e.g., 85 °C. Many experiments have been performed to find the relations between the final gas temperature in the hydrogen tank and refueling conditions. The analytical solution of the hydrogen temperature in the tank can be obtained from the simplified thermodynamic model of a compressed hydrogen storage tank, and it serves as function formula to fit experimental temperatures. From the analytical solution, the final hydrogen temperature can be expressed as a weighted average form of initial temperature, inflow temperature and ambient temperature inspired by the rule of mixtures. The weighted factors are related to other refueling parameters, such as initial mass, initial pressure, refueling time, refueling mass rate, average pressure ramp rate (APRR), final mass, final pressure, etc. The function formula coming from the analytical solution of the thermodynamic model is more meaningful physically and more efficient mathematically in fitting experimental temperatures. The simple uniform formula, inspired by the concept of the rule of mixture and its weighted factors obtained from the analytical solution of lumped parameter thermodynamics model, is representatively used to fit the experimental and simulated results in publication. Estimation of final hydrogen temperature from refueling parameters based on the rule of mixtures is simple and practical for controlling the maximum temperature and for ensuring hydrogen safety during fast filling process.     

Final hydrogen temperature and mass estimated from refueling parameters

The final temperature and mass of compressed hydrogen in a tank after a refueling process can be estimated using the analytical solutions of a lumped parameter thermodynamic model of high pressure compressed hydrogen storage system. The effects of three single refueling parameters (ambient temperature, initial pressure and mass flow rate) and three pairs of the refueling parameters on the final hydrogen temperature are studied, for both 35 MPa and 70 MPa tanks. Overall expressions for the final hydrogen temperature, expressed as a function of the three factors, are obtained. The formulae for the final hydrogen temperature provide an excellent representation of the reference data. The effects of the refueling parameters (mass flow rate, initial pressure and inflow temperature) on the final hydrogen mass are determined from the physical model. An overall expression of the final hydrogen mass is also obtained. The final hydrogen temperature can be controlled by reducing the ambient temperature or the mass flow rate, or increasing the initial pressure. The final hydrogen mass can be maximized by reducing the mass flow rate or the inflow temperature, or increasing the initial pressure. This study provides simple engineering formulae to assist in establishing refueling protocols for gaseous hydrogen vehicles.     

Experimental and numerical study on temperature rise within a 70 MPa type III cylinder during fast refueling

The fast refueling of hydrogen results in a temperature rise, which may lead to the failure of the hydrogen storage cylinder. Hence, study of temperature rise during refueling is a significant concern regarding hydrogen safety. In this research, a well-design system for 70 MPa hydrogen refueling was developed. Several refueling experiments on a type III cylinder have been conducted to study the temperature rise during the refueling process on this system. The experimental results show that the gas in caudal region and the aft domes junction surface achieved the maximum temperature rise. A Computational fluid dynamics (CFD) model was also validated by the experimental results. Finally, effects of initial pressure and ambient temperature on temperature rise were studied using this model. The results show that with the increase of initial pressure and the decrease of the ambient temperature, the final gas temperature decreases approximately linearly. This pilot research can provide invaluable guidance in developing advanced refueling standard.     

Proposed model of potential accident process at hydrogen refueling stations based on multi-level variable weight fuzzy Petri net

Hydrogen is becoming more popular as a fuel for vehicles. It is stored and dispensed at hydrogen refueling stations. Once the hydrogen in hydrogen refueling stations leaks, it easily forms a combustible cloud, and can explode by encountering a spark. It is therefore important for the safe and stable operation of hydrogen refueling stations to analyze the evolution of a leakage and explosion accident, clarify the causes and processes of the accident, and prevent the spread of risks. This paper proposes a model using multi-level variable weight fuzzy Petri net. On the basis of hierarchical consideration of the development of the accident, it adds a variable weight factor, which can quantify information in the development of the accident. According to the calculated results, the evolutionary path of risk and the most likely initial cause of the accident are deduced. Finally, taking the leakage and explosion accident of an urban hydrogen refueling station as an example, the usability and effectiveness of the model are verified.     

Quantitative risk assessment of a mobile hydrogen refueling station in Korea

Hydrogen infrastructure is expanding. Mobile hydrogen refueling stations are advantageous because they can be moved between locations to provide refueling. However, there are serious concerns over the risk of various accident scenarios as the refueling stations are transported. In this study, we conduct a quantitative risk assessment of a mobile hydrogen refueling station. Risks that may occur at two refueling locations and the transport path between them are analyzed. Our evaluation reveals that risks are mostly in an acceptable zone and to a lesser degree in a conditionally acceptable zone. The greatest single risk factor is an accident resulting from the rupture of the tube trailer at the refueling site. At sites with no tube trailer and during the transport, the risk is greatest from large leaks from the dispenser or compressed gas facility. The mobile hydrogen refueling station can be safely built within acceptable risk levels.     

Development of efficient hydrogen refueling station by process optimization and control

Development of efficient hydrogen refueling station (HRS) is highly desirable to reduce the hydrogen cost and hence the life cycle expense of fuel cell vehicles (FCVs), which is hindering the large scale application of hydrogen mobility. In this work, we demonstrate the optimization of gaseous HRS process and control method to perform fast and efficient refueling, with reduced energy consumption and increased daily fueling capacity. The HRS was modeled with thermodynamics using a numerical integration method and the accuracy for hydrogen refueling simulation was confirmed by experimental data, showing only 2 °C of temperature rise deviation. The refueling protocols for heavy duty FCVs were first optimized, demonstrating an average fueling rate of 2 kg/min and pre-cooling demand of less than 7 kW for 35 MPa type III tanks. Fast refueling of type IV tanks results in more significant temperature rise, and the required pre-cooling temperature is lowered by 20 K to achieve comparable fueling rate. The station process was also optimized to improve the daily fueling capacity. It is revealed that the hydrogen storage amount is cost-effective to be 25–30% that of the nominal daily refueling capacity, to enhance the refueling performance at peak time and minimize the start and stop cycles of compressor. A novel control method for cascade replenishment was developed by switching among the three banks in the order of decreased pressure, and results show that the daily refueling capacity of HRS is increased by 5%. Therefore, the refueling and station process optimization is effective to promote the efficiency of gaseous HRS.