1) Stationary

2) Mobile

Hydrogen stations are generally a stationary system. The main function of a hydrogen refuelling station is to act as a hydrogen storage system with hydrogen storage and refuelling technology. In most cases, hydrogen is currently delivered to the station in cylinders or in specialized hydrogen containers on trucks. Some stations produce hydrogen directly at the hydrogen station by electrolysis (from wind or sun). Pipelines would be another efficient way to deliver hydrogen to these stations in the future. Mobile hydrogen refuelling systems are much smaller and are used for emergency refuelling or for some special mobile use cases. The advantage of mobile refuelling stations is that the station can be designed as a functional unit, which will be brought to the site from the industrial gas filling plant and replaced by a full station when emptied, while the empty station will be taken away to be filled. This system is suitable, for example, for intra-company transport. [26]. Hydrogen for passenger cars requires hydrogen refuelling stations that provide H70 (700 bar) pressure, while trucks and other special vehicles nowadays typically require H35 (350 bar) hydrogen refuelling stations. Liquid hydrogen could also be used for truck applications in the future; the advantage is the higher energy density of liquid hydrogen. Liquid hydrogen is planned to be stored in a hydrogen tank using state-of-the-art technology. Fuel cell buses are becoming increasingly popular because these types of hydrogen vehicles have high hydrogen consumption that is predictable. A fleet of several hydrogen buses can justify the investment in its own hydrogen refuelling station. Hydrogen consumption can be calculated and the station can be regularly replenished.  Hydrogen fuel cell buses currently store hydrogen at 350 bar. Internal transport vehicles mainly use 350 bar technology because such a storage system requires less investment and, unlike cars, regular refuelling can be planned and carried out at a station built close to the general operating base (e.g. outside or inside the plant). Other modes of transport, such as trains, trams or even aircraft, can have hydrogen refuelling stations in a depot or hangar. [26]