Quantitative Risk Analysis of Scaled-up Hydrogen Facilities

Development of hydrogen facilities such as hydrogen refuelling stations (HRS) at scale is a fine balance between economy and safety, where an optimal solution would both prevent showstoppers due to cost of increased safety measures and prevent showstoppers due to hydrogen accidents. A detailed Quantitative Risk Analysis (QRA) methodology is presented where the aim is to establish the total risk of the facility and use it to find the right level of safety features such as blast walls and layout. With upscaled hydrogen facilities comes larger area footprints and more potential leak points. These effects will cause increased possible consequence in terms of vapour cloud explosions and increased leak frequencies. Both effects contributing negative to the total risk of the hydrogen facility. At the same time, as the number of such facilities is increasing rapidly, the frequency of incidents can also increase. A risk-based approach is employed where inherently safe solutions is investigated, and cost efficient and acceptable solutions can be established. The present QRA uses well established tools such as SAFETI, FLACS and Express which are fitted for hydrogen risks. By using the established Explosion Risk Analysis tool Express, the explosion risk inside the station can be found. By using CFD tools actively one can point at physical risk drivers such as equipment layout that can minimize gas cloud build-up on the station. The explosion simulations are further used to find the effects of e.g. blast wall on the pressures affecting on people on the other side of the wall. This is used together with the results from the SAFETI analysis to develop risk contours around the facility. Current standardized safety distances are discussed by considering the effects of scaling and risk drivers on the safety distances. The methodology can be used to develop certain requirement for how hydrogen facilities should be built inherently safe and in cost-efficient ways.