Consequence-based Safety Distances and Mitigation Measures for Gaseous Hydrogen Refueling Stations

With the rapid development of hydrogen vehicle technology and large scale fuel cell vehicle (FCV) demonstration project worldwide, more hydrogen refueling stations need to be built. Safety distances of hydrogen refueling stations have always been a public concern and have become a critical issue to further implementation of hydrogen station. In this paper, safety distances for 35MPa and 70MPa gaseous hydrogen refueling station are evaluated on the basis of the maximum consequences likely to occur. Four typical consequences of hydrogen release are considered in modeling: physical explosion, jet fire, flash fire and confined vapor cloud explosion. Results show that physical explosion and the worst case of confined vapor cloud explosion produce the longest harm effect distances for instantaneous and continuous release, respectively, indicating that they may be considered as leading consequences for the determination of safety distances. For both 35MPa station and 70MPa station, safety measures must be implemented because the calculated safety distances of most hydrogen facilities can not meet the criteria in national code if without sufficient mitigation measures. In order to reduce the safety distances to meet the national code, some mitigation measures are investigated including elevation of hydrogen facilities, using smaller vessel and pipe work, and setting enclosure around compressors. Results show that these measures are effective to improve safety but each has different effectiveness on safety distance reduction. The combination of these safety measures may effectively eliminate the hazard of 35MPa station, however, may be not enough for 70MPa station. Further improvements need to be studied for compressors inside 70MPa station.