Numerical modeling for analysis and improvement of hydrogen refueling process for heavy-duty vehicles

This paper presents the development, validation, and application of a numerical model to simulate the process of refueling hydrogen-powerd heavy-duty vehicles, with a cascade hydrohen refueling station design. The model is implemented and validated using experimental data from SAE J2601. The link between the average pressure ramp (APRR) and flow rate, which is responsible for the dynamic evolution of the refueling process, was analyzed. Various simulations were conducted, with a vehicle tank of 230 L and nominal pressure of 35 MPa typical of tanks adopted in heavy-duty vehicles, varying the ambient temperature between 0 and 40 °C, the cooling temperature of the hydrogen by the system cooling between −40 and 0 °C and the APRR between 2 and 14 MPa/min. The study found that if the ambient temperature does not exceed 30 °C, rapid refueling can be carried out with not very low pre-cooling temperatures, e.g. -20 °C or − 10 °C, guaranteeing greater savings in station management. Cooling system thermal power has been investigated, through the analyses in several scenarios, with values as high as 38.2 kW under the most challenging conditions. For those conditions, it was shown that energy savings could reach as much as 90 %. Furthermore, the refueling process was analyzed taking into account SAE J2061/2 limitations and an update was proposed. An alternative strategy was proposed such that the settings allow a higher flow rate to be associated with a given standard pressure ramp. This approach was designed to ensure that the maximum allowable pressure downstream of the pressure control valve, as specified by the refueling protocol, is reached exactly at the end of the refueling process. It has been observed that the adoption of this strategy has significant advantages. In the case of refueling with higher APPR, refueling is about 20 s faster with a single tank, with limited increases in temperature and pressure within it.