A GIS-based risk assessment of hydrogen transport: Case study in Yokohama City

Highlights

• Risk assessment method of hydrogen transport considering spatial features was proposed.

• Case study for the risk assessment in Yokohama City was conducted.

• Our results indicated that hydrogen transport risks were acceptable level in Yokohama City.

• Hydrogen transport risks were affected by spatial features.

Abstract

This study proposes a method of assessing the risk of hydrogen transport via road considering spatial features of a transport route, based on a geographic information system (GIS); a case study of Yokohama, Japan was considered in the assessment. The risk determined by multiplying the frequency of accidents with their consequences was estimated using road segments constituting the entire transport route. The effects of road structure, traffic volumes, and population information were reflected in the estimation of the risk for each road segment by using GIS. In the case study, the risks of transport route were assessed at an acceptable level under risk criteria. The results indicated that the risks fluctuated according to the road segments, indicating that spatial features of a transport route significantly affect the corresponding risks. Analyzing this importance indicates the transport routing to avoid high risk road segments as countermeasures.

Introduction

In recent years, efforts to realize a hydrogen society in Japan have been accelerating. In this society, hydrogen is transported in trucks from the production and storage plants to the consumption areas. Hydrogen has dangerous physicochemical properties that include the risk of explosions or fires. Therefore, when an accident occurs, it can severely impact the surrounding area. In addition, it is predicted that as hydrogen consumption increases in the future, the quantity to be transported will increase, thereby increasing the demand that the hydrogen be transported safely. The hydrogen transport safety must be verified through risk assessments.

Owing to topographical restrictions, logistics in Japan are dependent on road transport. Therefore, hydrogen transport is mainly conducted via roads. A major characteristic of road transport is that, unlike spatial fixed facilities (e.g. chemical plants) as a risk source, the surrounding environment changes constantly by the spatial movement. As a result, spatial features of a transport routes must be reflected in the hydrogen-transport risk assessment.

The hydrogen transport risk is recognized as the risk associated with the spatial movement of risk source for hydrogen. As the typical spatial fixed risk source, there is hydrogen fueling station. Many previous studies focused on risk assessment for hydrogen fueling stations; these were compressed hydrogen type [[1], [2], [3], [4], [5], [6]], liquid hydrogen type [7,8], liquid organic hydrogen type [[9], [10], [11]], on-site type [12], hydrogen power plant type [13], and dispenser type [14] fueling stations. Kim J et al., Kim E et al., and Honselaar et al. compared hydrogen fueling station risks for various types of stations [[15], [16], [17]]. The usefulness of a Bayesian network to represent a complex accident process was verified through the case study of an on-site hydrogen fueling station [18]. The HAZID method [19] detected hazards of hybrid gasoline-hydrogen fueling stations for risk assessment. To realize the efficient and detailed risk screening of large areas, Huang developed a grid-based risk mapping method based on the Bayesian network for hydrogen fueling stations [20].

Although many risk assessments for hydrogen fueling stations from the spatial fixed perspective are available, risk assessments of hydrogen transport from the spatial moved perspective are limited. Previous studies have assessed the risks of hydrogen transport via roads in the case of compressed hydrogen [21,22], using a qualitative approach, including the accident frequency and consequence. Moreover, the risks in terms of the transport of liquid hydrogen [7] and of compressed hydrogen and liquid hydrogen [14] have been assessed based on the risk matrix. A spatial moved perspective needs to consider the spatial features of transport routes in the risk assessment of hydrogen transport. However, previous studies on hydrogen transport risk assessment have not focused on the spatial features of the transport routes [7,14,20,21].

In risk assessments of the transport of hazardous materials, except for hydrogen, some spatial features are considered by mainly linking a geographic information system (GIS) [[23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33]]. Spatial features affect the frequency and the consequence, respectively, which constitute the risk assessment. In the consequence estimation, the population density along the transport routes on the GIS is utilized as the spatial feature [[23], [24], [25],[27], [28], [29], [30], [31], [32], [33]]. Population density information can be easily handled using the GIS, and thus, can be automatically reflected in the consequence estimation. In the frequency estimation, the importance of spatial features with respect to a variety of road structures (e.g., road type, road configuration, and topography surrounding the road) and traffic volume (e.g., travel velocity) is known. Some previous studies have successfully quantified the effect of spatial features on the frequency by statistically analyzing traffic accident information; however, these studies have targeted limited spatial features, mainly for the road type [[23], [24], [25], [26]]. Other studies have followed comprehensive spatial features, while those studies depended on expert judgment to assess the effect of the spatial features [[27], [28], [29], [30],32,33]. The information for frequency-related spatial features cannot be easily handled using the GIS, and thus, cannot be automatically reflected in the frequency estimation.

With reference to previous literature, to the best of our knowledge, no studies have been published focusing on hydrogen transport risk assessment considering the spatial features. Previous studies targeting hazardous material transport have explored spatial features using the GIS. However, limitations related to the coverage of spatial features, the quantification method of spatial features, and the linkage of spatial features into the GIS were observed.

To overcome these limitations, the present study develops a hydrogen transport risk assessment method that considers spatial features, using the GIS and traffic accident information. It considers the road structure, road traffic volume on transport routes, and population density along these transport routes as the spatial features with high linkage to the GIS. In addition, this study includes a risk assessment case study for the city of Yokohama, Japan.