Thermodynamic modeling of hydrogen refueling for heavy-duty fuel cell buses and comparison with aggregated real data

The foreseen uptake of hydrogen mobility is a fundamental step towards the decarbonization of the transport sector. Under such premises, both refueling infrastructure and vehicles should be deployed together with improved refueling protocols. Several studies focus on refueling the light-duty vehicles with 10 kg_H2 up to 700 bar, however less known effort is reported for refueling heavy-duty vehicles with 30–40 kg_H2 at 350 bar. The present study illustrates the application of a lumped model to a fuel cell bus tank-to-tank refueling event, tailored upon the real data acquired in the 3Emotion Project. The evolution of the main refueling quantities, such as pressure, temperature, and mass flow, are predicted dynamically throughout the refueling process, as a function of the operating parameters, within the safety limits imposed by SAE J2601/2 technical standard. The results show to refuel the vehicle tank from half to full capacity with an Average Pressure Ramp Rate (APRR) equal to 0.03 MPa/s are needed about 10 min. Furthermore, it is found that the effect of varying the initial vehicle tank pressure is more significant than changing the ambient temperature on the refueling performances. In conclusion, the analysis of the effect of different APRR, from 0.03 to 0.1 MPa/s, indicate that is possible to safely reduce the duration of half-to-full refueling by 62% increasing the APRR value from 0.03 to 0.08 MPa/s.     

Design proposal for hydrogen refueling infrastructure deployment in the Northeastern United States

Fuel cell vehicles (FCVs) are expected to be commercially available on the world market in 2015, therefore, introducing hydrogen-refueling stations is an urgent issue to be addressed. This paper proposes deployment plan of hydrogen infrastructure for the success of their market penetration in the Northeastern United States. The plan consists of three-timeline stages from 2013 to 2025 and divides the designated region into urban area, suburban area and area adjacent to expressway, so that easy to access to hydrogen stations can be realized. Station is chosen from four types of stations: off-site station, urban-type on-site station, suburban-type on-site station and portable station, associated with growing demand. In addition, on-site station is used as hydrogen production factory for off-site station to save total investment. This deployment plan shows that 83% of urban residents can reach station within 10 min in 2025, and that more than 90% people especially in four major cities: Boston, New York City, Philadelphia, and Washington, D.C. can get to station within 10 min by Geographic Information System (GIS) calculation.     

Design of a future hydrogen supply chain: A multi period model for Turkey

There is no doubt that energy will have one of highest priorities in agendas of strategic plans of countries. Since fossil fuels are running out and carbon emissions are more important than ever, researchers seek alternative clean and efficient energy sources. One of the best alternatives is hydrogen. The systems in which hydrogen flows from its production to end users are called hydrogen supply chains (HSC). Since hydrogen is not in active use, its HSC infrastructure is not complete and should be planned very carefully. We study the design of HSC of Turkey to meet the hydrogen demand of the period between 2021 and 2050. Our aim is to minimize total cost of the HSC while meeting the demand of the transportation sector. We address the problem by using a mixed integer programming (MIP) model and derive several insights for the future HSC. The results show that while decentralization (being able to fulfill the demand from local production facilities) is 12% in the first period, this rate raises up to 48% by the end of the planning horizon. Analysis also reveal that almost all grids do not produce and import hydrogen simultaneously, i.e., they either produce or import hydrogen. The results are robust in the sense that solutions of different optimality gaps have minor differences in terms of established facilities.     

Development of Ti1.02Cr2-x-yFexMny (0.6≤x≤0.75, y=0.25, 0.3) alloys for high hydrogen pressure metal hydride system

To save compressor investment and promote operation efficiency of hydrogen refueling station, the hydrogen storage alloys for high-pressure hydrogen metal hydride tank is developed. Ti_1.02Cr_2-x-yFe_xMn_y (0.6 ≤ x ≤ 0.75, y = 0.25, 0.3) alloys with main structure of C14 type Laves phase and low dehydrogenation enthalpy were prepared by plasma arc melting and heat treatment. Pressure-composition-temperature measurements show that hydrogen desorption plateau pressures increase with Cr substituted by Fe increasing. The maximum and reversible hydrogen storage capacities are more than 1.85 and 1.65 wt% at 201 K respectively. The hydrogen desorption plateau slopes are all less than 0.5. The symmetry weakening of 2a sites may deteriorate the plateau slop characteristic. Ti_1.02Cr_0.95Fe_0.75Mn_0.3 and Ti_1.02Cr_1.0Fe_0.75Mn_0.25 alloys are suitable for high pressure hybrid tank which can supply the effective hydrogen (more than 70 MPa) about 40.0, 44.2, 46.9 kg/m³ with 45, 70, 90 MPa compressor, respectively.     

Research on sealing performance and self-acting valve reliability in high-pressure oil-free hydrogen compressors for hydrogen refueling stations

Piston ring sealing and valve design play an important role in high-pressure oil-free reciprocating compressors for hydrogen refueling stations. The severe non-uniformity of the pressure distribution was suggested to be the root cause of the premature failure of the sealing rings, and therefore a mathematical model was established to simulate the unsteady flow within the gaps of piston rings, based on which the pressure distribution was obtained and the mechanism of the non-uniform abrasion of the rings was disclosed. The method to equalize the pressure difference through each ring was proposed by re-distributing the cut size of each ring, and it was validated experimentally. Aiming at the problem that the self-acting valves in hydrogen compressors could be easily destroyed by severe impact, this paper investigated the motion and impact of valves theoretically and experimentally, based on which the methodology was explored to design the parameters of valves for hydrogen compressors.     

Dynamic simulation for optimal hydrogen refueling method to Fuel Cell Vehicle tanks

A dynamic simulation approach to investigate an optimal hydrogen refueling method is proposed. The proposed approach simulates a transient temperature, pressure and mass flow rate of hydrogen flowing inside filling equipment in an actual station during the refueling process to an Fuel Cell Vehicle (FCV) tank. The simulation model is the same as in an actual hydrogen refueling station (HRS), and consists of a Break-Away, a hose, a nozzle, pipes and an FCV tank. Therefore, we can set actual configurations and thermal properties to the simulation model, and then simulate the temperature, pressure and mass flow rate of hydrogen passing through each position based on the supply conditions (temperature and pressure) at the Break-Away. In this study, the simulated temperature, pressure and mass flow rate are compared with the corresponding experimental data. Therefore, we show that the dynamic simulation approach can accurately obtain those values at each position during the refueling process and is an effective step in proposing the optimal refueling method.     

Queuing-based approach for optimal dispenser allocation to hydrogen refueling stations

Dispenser allocation to hydrogen refueling stations aims at minimizing the number of dispensers while ensuring satisfactory performance of vehicle queues during the peak hour of a peak day. A queuing model is developed in this study to evaluate the queuing performance at such stations by incorporating the statistical and thermodynamic characteristics of refueling. An optimization framework is proposed to determine the minimal number of dispensers required to meet the upper limits imposed on two important performance measures: mean waiting time and mean queue length. Reasonable upper limits are provided for 70 MPa stations according to the effects of dispenser allocation and station capacity on queuing performance. Server (dispenser nozzle) utilization under the optimal dispenser allocation generally increases with an increase in station size and tends to exceed 50% for large stations. The proposed approach can offer significant performance improvements for small stations and considerable savings in the number of dispensers for large ones.