In a recent article posted on the US Department of Energy (DOE) website, Jesse Schneider (BMW), the lead of the SAE hydrogen fueling standards SAE J2601, noted the importance of releasing the standards now, due to the impending deployment of fuel cell electric vehicles (FCEVs) by the automotive companies.

Seven automakers have announced plans to sell or lease FCEVs—some as early as this year—and several of these auto companies have also entered partnerships to support this launch—e.g., BMW-Toyota, Daimler-Ford-Nissan, and Honda-GM.

Schneider said that Japan, Europe and North America are the three main areas with hydrogen infrastructure plans to support fuel cell vehicles. More than 230 hydrogen stations are expected to be in operation by 2016 and more than 1,400 additional hydrogen stations will be in operation by 2025 (totaling roughly 1,680 new stations announced to date).

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Internationally, there are a number of government and industry initiatives to support the initial development and commercialization of hydrogen infrastructure as well as FCEVs. In the United States, DOE, along with industry stakeholders, announced the public-private partnership H₂USA in May 2013 to address hydrogen infrastructure and assist in deployment of FCEVs in the United States. (Earlier post.) H₂Mobility (earlier post) is supporting the development of hydrogen infrastructure throughout Europe and the Fuel Cell Commercialization Project (FCCJ) (earlier post) and HySUT are actively supporting the build out of hydrogen infrastructure and the introduction of FCEVs into the market in Japan. These organizations have supported SAE in the standardization of hydrogen fueling.

Schneider noted that the H₂ fueling standardization activities at both SAE and the ISO have taken lessons learned from experience with AC and DC charging standards and harmonized the hydrogen nozzle-receptacle coupling connection. SAE J2600 and its ISO equivalent for the hydrogen nozzle and FCEV vehicle receptacle are essentially identical and are harmonized worldwide for both 35 MPa and 70 MPa.

Comparison between EV charging in SAE J1772 with a Battery Electric Vehicles (BEVs) and SAE J2601 with Fuel Cell Electric Vehicles. Source: Jesse Schneider. Click to enlarge.

Fueling of FCEVs to the SAE J2601 Hydrogen Fueling Standard requires only 3–5 minutes and gives a high state of charge (SOC) equaling a range of 300 miles or more (500 km+). This is on par with gasoline internal combustion vehicles.

To further optimize fueling and provide a consistent high (95%–100%) SOC, the recently published SAE J2799 standardizes wireless communications between FCEVs and hydrogen stations. This optional technology utilizes Infrared Data Association technology to transfer vehicle and tank information to the hydrogen dispenser.

Developing J2601. SAE J2601, was created by an SAE Technical Committee and was validated over 12 years in both the laboratory and the field to produce a robust method for fueling worldwide, Schneider said. The SAE Technical Committee first developed a model to simulate fueling. Seven automakers shared information pertaining to their FCEV tank components and four hydrogen suppliers shared their station dispenser properties to support the development of the model. The first lookup tables were then generated by the model. The tables were then tested in the laboratory under extreme conditions with a range of tanks from the automaker, representing all expected tank volume categories.

The J2601 standard hydrogen fueling protocol was validated in the field with real FCEVs and hydrogen stations in Europe (Denmark, Germany), North America (US), and Asia (Japan) by five original equipment manufacturers (OEMs). The tests resulted in a state of charge between 90%–100% within the specified 3–5 minutes. The fueling data from the J2601 validation on OEM FCEVs and hydrogen stations in addition to extreme case studies were documented in the SAE Technical Report “Validation and Sensitivity Studies for SAE J2601.” Click to enlarge.

The SAE J2601 standard for light duty FCEVs uses a pressure targeted fueling or a “lookup table” approach for 35 MPa and 70 MPa fueling. These lookup tables can be programmed into the hydrogen dispenser’s programmable logic control (PLC) to control the fueling process. There are three types of dispensers used for the J2601 lookup tables which use different hydrogen gas cooling temperatures or “T-ratings” to offset the heat of hydrogen compression. These tables use the initial gas pressure from the FCEV when it pulls up to a station, the ambient temperature, and the dispenser’s T-rating to determine the fueling rate and target pressure at which the dispenser stops fueling.

In the example given on a recent webinar, a vehicle pulls up to a H70-T40 dispenser (70 MPa nominal working pressure, -40˚C rated gas category) with a pressure of 10 MPa remaining in the tank on a 20˚C day. The SAE J2601 standard lookup table is used to determine a 21.8 MPa/minute average pressure ramp rate (APRR) and an 86.8 MPa stop pressure for the fueling. This results in a 4 minute fueling time. If the dispenser is cold due to multiple back-to-back fuelings, a separate “cold dispenser” table can be used; the resulting fueling time can be reduced to as low as 3 minutes in this example.

It is important to standardize and establish a baseline protocol for fueling at all hydrogen stations to not exceed the storage limits and to ensure that the customer gets a consistent fast fueling. The SAE J2601 tables accomplish this. At the same time, it is important to keep the door open for innovations in hydrogen fueling, which is the reason for allowing development fueling such as the “MC Method” to continue.

—Jesse Schneider

“MC Default” is a non-normative fueling protocol defined in Appendix H of SAE J2601. The MC Method, developed ny Honda R&D, is a mathematical construct which quantifies heat absorption capability of the tank and is analogous to SAE J2601 Lookup Tables. MC can be thought of as a heat sink or thermal mass.

As with the J2601 protocol, the MC Fill fast-fill protocol, developed by Honda R&D, is designed for fuel systems that store hydrogen at a pressure of up to 700 bar (70MPa or 10,000 psi). The primary differentiator between the current J2601 approach and Honda’s MC Fill is that Honda offers dynamic control of the refueling rate based on the measured gas temperature rather than a lookup table to control the pressure ramp rate. Click to enlarge.

The MC Default Fill is a dynamic method which offers many benefits. It has fast fueling times and offers consistency in fueling time.

—Steve Mathison

Due to MC Fill’s adaptive qualities, it allows more flexibility in station design and better station utilization Currently testing of this method is underway in both field and lab validations; the method may be included in future revisions of SAE J2601.

To validate that dispensers meet the performance and communication standards specified in SAE J2601 and J2799 , organizations such as the California Air Resources Board (CARB) and DOE in the United States, ENAA and HySut in Japan, and CEP in Germany are in the process of developing and implementing Hydrogen Station Test Apparatus (HSTA). In addition, both ISO and CSA are working on hydrogen station validation standards.