Enhancing heavy duty vehicle hydrogen refueling by alternative approach to SAE J2601/2 protocol and flow dynamics

Abstract

This paper analyzes the hydrogen refueling process for heavy-duty vehicles according to the SAE J2601/2 protocol. Attention is paid to two key aspects of the protocol that affect the refueling process: treatment of the storage system from a thermodynamic and geometric point of view and the maximum deliverable flow rate of the station in the refueling process. The effect of the ratio of the inner diameter to the inner length of the total volume on the refueling process was then analyzed, and it was shown how far the new approach results deviate from the results obtained by applying the SAE protocol. A total supply of 28 kg was simulated but with three different configurations: 14∗2 kg tanks, 7∗4 kg tanks, and 4∗7 kg tanks. When analyzing the effect of varying the ratio of inner diameter to inner length, it was noted that in the most conservative case, there is an overestimation in terms of final temperature for the three configurations of about: 2.1 °C, 1.4 °C and 1.1 °C, respectively. This aspect has a significant impact on the refueling time, which could be reduced by about 9.9% in the first case and about 7.1% and 5.4% in the other two. In addition, refueling using the multi-tank approach was simulated for some case studies assimilated to heavy vehicles currently on the market in terms of the amount of hydrogen stored. These refuelings were carried out with stations capable of delivering a maximum flow rate of 120 g/s, 180 g/s, and 240 g/s. It is inferred that increasing the flow rate from 120 g/s to 180 g/s results in time savings for the three cases of: 35%, 34% and 37%. On the other hand, running up to 240 g/s results in time savings of: 54%, 52% and 55%.