Future Fuels: What SAE J2601-5 Means for Industry Amidst Growing Interest in Hydrogen
Guest Post by Steve Mathison, SAE J2601-5 Document Sponsor
Posted: March 1, 2024
A recent well-written and informative SAE Media news article entitled “Time for Hydrogen” notes that hydrogen holds much promise in decarbonizing the transportation sector, and there is a flurry of R&D activity in bringing hydrogen powered mobility applications to market.
And nowhere is this interest and activity more prominent than in the heavy-duty (HD) truck market.
Many truck manufacturers, both big and small, are developing hydrogen fuel cell and hydrogen ICE powered trucks. Production light-duty (LD) fuel cell vehicles have been available from several manufacturers since 2014; just recently truck manufacturers have released production HD fuel cell Class 8 trucks. This trend is growing and the number of production Class 8 truck offerings along with other offerings in the LD, medium-duty (MD) and HD segments is expected to grow exponentially in the coming years. 
To prepare for this growth and to ensure that hydrogen stations can fuel these vehicles safely and as quickly as possible, the SAE Fuel Cell Standards Committee Interface Task Force (ITF) spent the last two years developing hydrogen fueling protocols for these vehicles. This work culminated in the publication of a new SAE Technical Information Report (TIR) J2601-5, entitled “High-Flow Prescriptive Fueling Protocols for Gaseous Hydrogen Powered Medium and Heavy-Duty Vehicles.”
The ITF previously developed hydrogen fueling protocols for LD vehicles contained in SAE J2601 “Fueling Protocols for Light Duty Gaseous Hydrogen Surface Vehicles”, which SAE first published in 2014 with subsequent revisions published in 2016 and 2020. This standard is the hydrogen fueling protocol standard referenced worldwide and is used in nearly every retail or public access hydrogen station in the world.
However, the fueling protocols in J2601 are designed for LD vehicles and are constrained to a maximum mass flow rate of 60 g/s (3.6 kg/min). This maximum mass flow rate is not sufficient to facilitate fast fueling times (less than 10 minutes) for larger MD and HD class vehicles.
This was the impetus for the ITF to develop the new TIR J2601-5.
What’s New in SAE J2601-5
The hydrogen fueling protocols in SAE TIR J2601-5 are designed for Pressure Classes H35 (35 MPa) and H70 (70 MPa) and Flow Rate Maximum (FM) Classes of FM90 (90 g/s), FM120 (120 g/s), and FM300 (300 g/s).
The H35 FM120 hydrogen fueling protocol is capable of filling vehicles with on-board storage capacities up to 50 kg in less than 10 minutes, and the H70 FM300 protocol is capable of filling vehicles with storage capacities up to 120 kg in less than 10 minutes.
The FM Class is associated with a specific nozzle/receptacle coupling – the FM90 is to be used with the H70 coupling, the FM120 is to be used with the H35HF coupling and the FM300 is to be used with an H70HF coupling, which is not yet standardized but is expected to be within the next couple of years. These coupling types are defined in the SAE J2600 and ISO 17268 standards.
The H35 FM120, H70 FM90 and H70 FM300 protocols are based on an improved version of the MC Formula control structure first introduced in the 2016 version of SAE J2601 and named MC Formula High-Flow General (MCF-HF-G).
The MCF-HF-G fueling protocol measures the hydrogen fuel delivery temperature and accumulated mass to precisely determine an appropriate pressure ramp rate for each point in time during the fueling period. This formula-based control algorithm facilitates the fastest fueling which is safely possible under the current conditions of the fueling period.
The MCF-HF-G fueling protocol also allows for a wide range fuel delivery temperature, from 20 °C to -40 °C for the H35 FM120 protocol and from 0 °C to -40 °C for the FM300 protocol. In addition to the MCF-HF-G protocol, TIR J2601-5 also includes an FM90 table-based fueling protocol named Category D HF, which is a modified version of the CHSS Capacity Category D fueling protocol from the 2020 SAE J2601.
The hydrogen fueling protocols in SAE TIR J2601-5 are “general purpose” protocols, meaning they are designed to be appropriate for all types of vehicles using compressed hydrogen storage systems (CHSS) with capacities from 248.6 L to 5000 L (or 10 kg to 201 kg) for the H70 pressure class and from 248.6 L to 7500 L (or 6 kg to 180 kg) for the H35 pressure class. These CHSS may contain individual hydrogen storage tanks with capacities up to 800 L (or 32 kg) for the H70 pressure class and up to 1000 L (or 24 kg) for the H35 pressure class.
These limits were established through an industry survey which was conducted in late 2022. This survey was developed by the ITF and sent to a wide swath of industry stakeholders, including vehicle manufacturers, CHSS manufacturers, and hydrogen station manufacturers and operators. The survey queried these respondents on several important CHSS design parameters which the ITF used to establish appropriate assumptions and boundary conditions for development of the fueling protocols.
Because these fueling protocols are general purpose, they can be used for all types of hydrogen stations, including retail and commercial public access stations as well as private access stations intended for vehicle fleets.
A Vision for the Future
The ITF decided to initially publish J2601-5 as a TIR because, although the ITF conducted extensive computer fueling simulations, only limited real world testing of the fueling protocols has been conducted to date. After field testing / verification of the fueling protocols, along with any feedback from these efforts, the ITF intends to publish a subsequent revision of J2601-5 as an SAE standard.
This work is an integral part of alternative fuel’s practical application at a large scale. Standardization is needed to achieve the mobility industry’s sustainability goals, and as efforts evolve, we envision the ITF at the forefront of progress.