(359a) Dynamic Simulation and Optimization of Hydrogen Fueling Operated By Real-Time-Responding without Look-up Tables: 3-Bank Cascade Fueling Method

In Korea, since 2017, more than 19,000 hydrogen fuel cell electric vehicles (HFCEV) have been supplied with the rapid commercialization of HFCEV, annual average increase of 235%. On the other hand, the expansion of hydrogen fueling stations is about 110 units, showing a relatively slow progress with an annual average growth rate of 116%. The current status of the supply of fueling stations also affects the sales of hydrogen electric vehicles, delaying the implementation of the hydrogen economy. Nevertheless, according to the "Hydrogen Infrastructure and Fueling Station Construction Plan" announced in Korea in 2019, the government plans to build 660 hydrogen fueling stations by 2030 and 1,200 by 2040, and also aims to upgrade core components and fueling technology of fueling stations.

The advancement of fueling technology is based on fast and safe fueling. The fueling of the HFCEV is a method of fueling it with the pressure difference between the fueling station tank (about 90 MPa) and the vehicle’s hydrogen storage tank. At this time, heat is generated inside the tank due to the Joule-Thompson effect by the expansion, so the faster the fueling speed, the higher the temperature increase rate. However, if the hydrogen storage tank’s temperature rises above 85°C, the durability of the tank may collapse and lead to hydrogen leakage and explosion. In order to be competitive with ordinary cars, fast and safe fueling technology must be equipped. Currently, a regular vehicle fuels in about 3 minutes, but a HFCEV takes about 5 minutes to fully fuel under smooth conditions, and sometimes takes more than 30 minutes due to variables such as gas remaining pressure in a storage tank. The smooth condition here refers to a technology that can safely fuel hydrogen in a short time, and the hydrogen fueling protocol standardizes this technology. Currently, the hydrogen fueling protocols include SAE J2601 in the United States, JPEC-S 0003 in Japan, and EN 17127 in the EU, and most countries require SAE J2601 to be compliant. On the other hand, KGSFP-216 in Korea has only two provisions: to fuel below the maximum fueling pressure based on SAE J2601 and to prevent the temperature inside the tank from exceeding 85°C. Therefore, it is necessary to develop its own hydrogen fueling protocol in Korea, and related research is being actively conducted.

This research developed a dynamic simulation of hydrogen fueling as a tool for design of sustainable hydrogen economy, without using the Look-up Table of SAE J2601 by calculating the temperature and pressure inside the storage tank in seconds using the thermodynamic model to develop a hydrogen fueling protocol. The model composition includes 1-bank fueling method and 3-bank fueling method, so it is possible to compare the efficiency of the two fueling methods and, through this, it is possible to confirm the expected effect of the 3-bank cascade fueling method. In addition, it is possible to check changes in temperature and pressure inside the tank according to various parameter changes.

When fueling a HFCEV, change of the storage tank can be obtained by communicating with the fueling station through a sensor, but it is difficult to measure the fueling line. Therefore, the change of the fueling line is another important component of the simulation model. The designed model considers pressure loss due to internal friction and temperature increase due to external heat transfer. In this process, the physical property values of austenitic stainless materials were used to calculate more accurate values. As a result, the developed model calculates the mass flow rate first, and then calculates the temperature and pressure of the fueling line. Thereafter, the temperature and pressure inside the storage tank are calculated using the calculated temperature and pressure values of the fueling line until the SOC reaches about 100%. The simulation model was developed based on Python and was released as an opensource on GitHub. Opensource users can check the mass flow rate, temperature, and pressure inside the storage tank during the fueling process by inputting the gas supply temperature, storage tank initial pressure, storage tank capacity, and external temperature for operating simulation. The developed model was designed to have higher sensitivity by receiving communication data from the hydrogen fueling station in consideration of future scalability. Through this, it is expected that factors affecting the development of domestic hydrogen fuel protocol standards can be identified.