A hydrogen filling station (hereinafter referred to as HFS) is a relatively complex, dedicated technical facility that operates with hydrogen at high operating pressures of up to 900 bar. All the chemical and physical properties of hydrogen must be taken into account, and the safety of operations and the dispensing of hydrogen to road vehicles must be ensured.

The basic functional parts of a VPS are:

1. The source part of the VPS is where the operational hydrogen supply for the proper functioning of the VPS is stored. The usual pressure is around 25 bar.
2. Compressor unit for compressing hydrogen from an operating pressure of approx. 25 bar to pressure values in high-pressure buffers (VTB), which are designed for filling vehicles by transferring compressed hydrogen. However, the compressor unit can be connected at its inlet to the outlet of the first stage of the cascade and then compresses hydrogen from 300 bar to 500 and 900 bar. The aim is to reduce the energy consumption of compression and limit unwanted heating of hydrogen after compression (the equation of state for a reference temperature of 15°C also applies to filling pressure cylinders in the buffer).
3. VTBs connected in a multi-stage cascade. Each stage of the cascade consists of pressure cylinders connected to create the required volume. The product of the volume and pressure of hydrogen in all sections, taking into account the compressibility factor and temperature, forms the standby supply of the VPS for immediate and rapid filling of the vehicle after it is connected to the VPS. The client’s filling requirements include the types of vehicles to be filled (e.g., buses with a filling pressure of 350 bar and a tank capacity of approximately 30 kg of hydrogen, or passenger cars with a filling pressure of 700 bar and a tank capacity of approximately 6 kg) and the frequency of filling over time (e.g., the transport company has 15 buses and must fill them within 3 hours, and also expects 5 passenger cars per day). From this, the required hydrogen storage capacity in the VTB and the stratification of pressure levels, for example 300, 500, and 900 bar, are calculated.
4. The priority panel is a controlled valve block that controls the pressure output of the compressor unit and thus gradually fills the individual stages of the buffer pressure cascade. The control variables are the pressure in the section and the temperature of the pressure cylinders. At the same time, the priority panel controls the transfer of hydrogen through the dispenser from the individual pressure sections. The control variables are the pressure in the vehicle tank and the hydrogen flow rate measured by a mass flow meter (part of the dispenser; when the flow rate drops below the set minimum, it switches to a section with higher operating pressure), and in the case of filling to 700 bar, also the temperature of the filled tank.
5. A dispensing stand is a device for controlled dispensing of hydrogen into a vehicle tank. It performs several functions, in particular safety (tight connection to the vehicle, tightness of the system itself, prevention of hose rupture by a tear-off fuse, limitation of hydrogen flow rate to a maximum of 60 g/s, checking the pressure in the vehicle tank so that it does not exceed the reference temperature at 700 bar filling, and does not exceed the nominal value at 350 bar filling), furthermore, the priority control function of the panel for switching between buffer cascade sections, the commercial measurement function for determining the price of hydrogen consumed in kg of hydrogen, and hydrogen cooling in the case of filling at 700 bar, where mechanical cooling reduces the temperature of the filled hydrogen to -40°C. It includes a terminal unit for connection to a card payment bank or a system for recording drivers and filled vehicles.
6. The control system uniformly controls all station processes, evaluates the sensor system, and maintains the technology within the set operating limits. If any of the system parameters are exceeded, it activates an automatic sequence of station operations aimed at bringing it to a safe state. It communicates externally, provides signals for transmission to superior and monitoring systems, and supports teleservice and self-diagnostics.

Hydrogen filling stations and road vehicles are equipped with connectors that comply with internationally recognized technical standards. Among other things, this ensures compatibility for filling vehicles worldwide and at different dealers. From a safety perspective, the design of the connectors ensures proper functioning so that a vehicle with a 700 bar filling neck accepts a connecting hose with a filling pressure of 700 bar, but also a connecting hose with a filling pressure of 350 bar or even 250 bar.

Conversely, a filling hose with a filling pressure of 350 bar or 700 bar cannot be connected to a vehicle with a 250 bar filling neck. This is ensured by suitable mechanical locks.

The filling nozzle is a sophisticated component whose function is defined by an international technical standard and which has certification confirming that it complies with this international technical standard. User-friendliness was a fundamental consideration that was respected during the development of the component. The filling hose nozzle is simply inserted into the nozzle on the vehicle and secured in this position by turning the lever on the nozzle. There is a great analogy here with CNG, for example, where nozzles have been tested for many years all over the world.

In addition, the automatic filling sequence first checks the tightness of the connection between the filling hose and the vehicle connector. This is done using the residual hydrogen pressure in the vehicle and in the filling hose. The hydrogen pressure in the connected nozzle is measured for a certain period of time, and the next step in filling the road vehicle with hydrogen can only continue if the pressure does not drop. If this is not the case, the control system stops the process and reports an error – a leak in the hose connection.

Such an error may occur if the seal on the filling nozzles has been damaged or if dirt has entered the connection. A leaky connection will also be indicated if the nozzle is connected to the wrong counterpart. A leaky connection can be easily repaired by a hydrogen filling station service technician.

Yes, it is possible. The necessary condition is a compatible connection in accordance with international standards and corresponding technical parameters for the hydrogen pressure vessel in the mobile device. According to findings from abroad, these “specials” are usually filled to 350 bar.

For this purpose, APT, spol. s r. o. has developed small hydrogen filling stations with the necessary capacity to fill emission-free forklift trucks. These stations are easily movable and can therefore respond quickly to the needs of different users. These small stations are designed for filling with hydrogen at pressures of 250, 350, or 700 bar. Individual specifications are always specified by the user at the time of ordering.

The pressure levels given refer to standard gas conditions, i.e., a temperature of 15°C. We also encounter hydrogen volume in Nm3, which is defined at a temperature of 15°C and a pressure of 101.325 kPa. From the user’s point of view, we most often talk about kilograms of hydrogen consumed. The conversion ratio between Nm3 and kg of hydrogen is 11.2 Nm3 = 1 kg.

The current market price of hydrogen at public hydrogen filling stations in Western Europe ranges from around €10 to €15 per kilogram of hydrogen filled into a vehicle. Hydrogen prices are expected to fall in the future.

Hydrogen filling station equipment shall be located outdoors so that any hydrogen leaks cannot accumulate in a dangerous manner in enclosed structures. Some parts of the filling station may be installed in enclosed spaces, which must be ventilated in accordance with the regulations and conditions specified in the Certified Methodology for the Construction and Operation of Compressed Hydrogen Filling Stations for Mobile Equipment in the technical rules issued by the Czech Gas Association TPG 304 03. Automatic valves must always be installed to ensure automatic closure of hydrogen sources in the event of a dangerous situation. The technological parts of the station must be secured against access by unauthorized persons.

APT, spol. s r. o. has developed hydrogen filling station assemblies whose basic components are housed in attractive containers. This not only protects the station components from atmospheric influences, but also simplifies on-site installation and project preparation. An example of such a station located on the premises of ÚJV Řež is shown in the photo below. APT, spol. s r. o. designs the containers individually according to the investor’s requirements.

The fundamental difference is that non-public hydrogen filling stations serve a closed group of customers, such as corporate stations or even private stations. At such stations, hydrogen consumption by mobile vehicles is usually only recorded. Therefore, there is no need for commercial measurement of the hydrogen consumed for the purpose of accurate pricing. In such cases, private stations are much cheaper to purchase. High-pressure compressed hydrogen storage tanks can be optimized according to the station’s usage regime, which may also be slow filling.

Public hydrogen filling stations serve the general public and must be equipped with commercial meters to measure the amount of hydrogen dispensed and must always have valid metrological verification (see Act No. 505/1990 Coll.). Public stations must also be equipped with a large supply of compressed hydrogen so that they are able to satisfy the needs of the public arriving at irregular intervals. These are usually fast-fill stations. Public hydrogen filling stations are subject to Act No. 311/2006 Coll.

In terms of operational safety, both filling station variants are equivalent. The principles of maximum safety and operational reliability are always observed in the design and delivery.

The filling quick coupling must comply with the provisions of ČSN EN ISO 17268 Hydrogen gas – Filling interfaces for land vehicles. It must ensure differentiation between filling pressures. Only filling hoses whose design ensures a conductive connection to the mobile equipment being filled and which are resistant to flowing hydrogen and its operating pressure may be used for filling connections. The filling connection shall not be shorter than 3 m or longer than 5 m. The design of the filling quick coupling must prevent its use for purposes other than filling the tanks of hydrogen mobile equipment. It must also ensure that hydrogen flow is only possible when it is tightly connected to its counterpart on the vehicle being filled and prevent its unintentional disconnection. It must only be possible to disconnect the quick-release coupling after it has been depressurized. If the mechanical stress on the filling connection exceeds a certain limit, it will be disconnected by a mechanical disconnect device and the hydrogen supply from the dispensing equipment will be shut off, as will the return flow of hydrogen from the tank of the vehicle being filled. The force required for disconnection is significantly lower than the tensile strength of the filling connection hose itself, or the force required to tear out the quick-release coupling or damage the dispensing equipment.

The filling hose has defined electrical conductivity. This is necessary to bring the filled vehicle and the filling station to the same potential and thus prevent the transfer of electrical charges as a possible source of ignition.

A hazardous area is defined as a space in which an explosive atmosphere is present or may occur in such quantities that special measures must be taken in the design, installation, and use of a compressed hydrogen filling station.

A hazardous area may include spaces classified as Zone 0, in which an explosive gas atmosphere is present continuously, or for long periods of time, or very frequently. Such spaces do not occur at hydrogen filling stations in areas where customers and their vehicles are present.

Zone 1 represents the area in which it is necessary to take into account that an explosive atmosphere may occur occasionally. Such an area is present at a hydrogen filling station around the quick coupling at the moment of connection, filling, and disconnection. Zone 1 is in the form of a sphere with a radius of 25 centimeters.

Zone 2 represents the area in which there is no need to expect an explosive atmosphere to occur. However, if it does occur, it will most likely be rare and short-lived. Zone 2 is around the dispenser to a distance of 20 centimeters from its surface in all directions.

An explosive area is an area in which the presence of an explosive atmosphere is not expected in such quantities that special measures must be taken in the design, installation, and use of a hydrogen filling station. These are all other areas used by customers at the filling station, with the exception of the small zones mentioned above. However, the ban on smoking, the ban on the use of open flames, and the ban on activities that could initiate combustion in the filling station area remain in place as a precaution against dangerous situations. Prevention also includes sophisticated design principles, the use of high-quality materials, and thorough functional testing during the design and construction of APT hydrogen filling stations, which guarantee that the station is safe under normal operating conditions. Instructions for the correct use of the filling station by customers are posted in multiple languages in the station area.

In general, hydrogen as a gas obtained by a suitable production process (there is very little free hydrogen on Earth, barely 10% of helium) will always be a mixture of substances that participate in the process or influence it due to marginal conditions. We then talk about the degree of purity, which expresses the proportion of individual components of residues in the composition of hydrogen. For example, we can distinguish between a degree of purity of 3.0, which means that hydrogen is three 9s, i.e., 99.9%, and the remaining 0.1% is other substances. We are also able to distinguish between these, and so we know that the remainder consists of water vapor, nitrogen, oxygen, hydrocarbons, sulfur compounds, and the like.

Some residues in hydrogen have a negative effect on the fuel cell membrane in particular. This reduces the performance of the fuel cell and shortens its service life. These substances include, among others, carbon monoxide, sulfur compounds, formaldehyde, ammonia, formic acid, and halides. The maximum concentration of these and other substances in hydrogen for fuel cells is defined by the ČSN ISO 14687-2 standard in the table at the end of the answer. The above-mentioned residual substances enter the hydrogen during its production process. The method of hydrogen production has a significant impact on the composition of undesirable residues. For example, the production of hydrogen by steam reforming from natural gas carries the risk of higher levels of CO₂, CH₄, or halides. Hydrogen produced by oil cracking may contain increased amounts of sulfur compounds. Hydrogen produced by water electrolysis may contain higher amounts of water or oxygen. Special filtration equipment can remove unwanted substances and prepare the hydrogen for use in fuel cells. In technical practice, it is not a problem to achieve hydrogen purity of 5.0, i.e., 99.999% purity. However, even in the small remainder below 100%, there must be no substances that limit or degrade the fuel cell.

Hydrogen quality requirements for hydrogen fuel cells

Total proportion of hydrogen and contaminating gases

Maximum concentration of individual contaminating gases