Hydrogen-powered (H2) fuel cell vehicles are enabling emission-free electromobility with long ranges and short refuelling times. Depending on the manufacturing process or on transport to the filling station, however, hydrogen may contain impurities which can damage the fuel cells. In order to be able to guarantee the required long service life of fuel cells in vehicles, it is necessary to check the hydrogen quality regularly to make sure that it meets the demands. The ZSW has developed tools for cost-effective checks on hydrogen quality at refueling stations (HRS) and filling points.
Fuel cell vehicles (FCEV) are refueled at hydrogen refueling stations (HRS). The refueling process is comparable to that of gasoline or diesel vehicles. In 2009, the first HRS was opened to the public in Germany. Currently (2021), there are around 100 operational HRS for fuel cell cars (700 bar tanks) in Germany, and more are on the way. The development of a filling station network for fuel cell commercial vehicles (350 bar tanks) started in Germany last year (2020), six filling stations are currently (09/21) already in operation. Real-time information on the HRS network in Germany and neighboring countries is shown at h2.live.
In Germany, DIN EN 17127 (guideline for H2 refueling technology and quality assurance) is legally binding under the European Alternative Fuel Infrastructure Directive (AFID). Therefore, hydrogen refueling stations in Germany must pass a series of acceptance tests defined in SAE J2601 and ISO 19880-1 before being approved. The tests check for safe shutdown when limits are exceeded or not met, correct compliance with refueling ramps or refueling protocols, and response to signals from the vehicle. For the test reports, a report template is used in Germany and in the future worldwide, which was largely created by the ZSW.
Hydrogen refueling stations (HRS) in Germany must pass a series of acceptance tests defined in SAE J2601 and ISO 19880-1 before they can be released. With the "Fueling Station Test Module" (FSTM), ZSW has developed a mobile test system in 2018 to perform these tests for PWK-HRS. So far, 26 fueling station acceptance tests have been performed (09/2021). For the acceptance of hydrogen refueling stations for heavy-duty vehicles, no suitable test equipment is currently available in Europe. Therefore, the tests have to be carried out with commercial vehicles, which is time-consuming. In order to reduce the time required and simplify the logistics for the tests, the ZSW has applied for funds to expand the existing FSTM for the acceptance of HeavyDuty-HRS.
An open challenge in refueling is determining the exact amount of hydrogen dispensed. For liquid fuels, this process is established and relatively simple. In the case of gaseous hydrogen, it still requires completely new methods and measuring equipment. The devices approved by the PTB (Physikalisch-Technische Bundesanstalt) so far are based on gravimetric measurements and require unacceptably long on-site measurement times. The ZSW has therefore applied for funds to qualify a transfer meter available on the market as a standard for hydrogen quantity measurement with short measuring times. Positive preliminary tests have already been carried out together with the PTB.
To protect fuel cells in vehicles from impurities in the hydrogen, the hydrogen delivered to filling stations must meet the international quality standards ISO 14687, SAE J2719 and, in Germany, the legally binding DIN EN 17124. Verifying these standards is time-consuming and requires an appropriate fleet of equipment.
ZSW's own HyLaB (Laboratory for Hydrogen Quality) is equipped for this and can provide this proof - and has already done so in many projects. In 2019, the HyLaB was one of only three laboratories worldwide in the "Interlaboratory Comparison for hydrogen purity analysis" of the MetrohyVe project that was within the maximum permitted measurement deviations in all measurements.
However, the hydrogen quality standards mentioned are based on work that is more than 17 years old and can be transferred to the requirements of today's and future fuel cell systems and operating conditions only to a limited extent. In order to create the data basis for an urgently needed update of the standards, around 300 long-term measurements with various pollutants, pollutant concentrations, fuel cell components and load cycles are therefore currently being carried out at the ZSW and partner institutes as part of the H2Fuel project.
The proof of hydrogen quality according to the standard is time-consuming and thus expensive and can therefore not be continuously represented by offline analysis in the laboratory. In addition, pollutants not included in the standard can also cause lasting damage to fuel cells (e.g. pollutants from modified manufacturing processes, other means of transport or new filling station technology).
Detecting these unknown substances with the highly specialized analysis technology in the laboratory is hardly possible. The ZSW is thus developing a simple, safe and relatively inexpensive procedure based on "fuel cell as quality sensor" for permanent quality monitoring of hydrogen.