Future of heavy-duty hydrogen trucks is promising

As the culmination of two years of work on the Innovating High Throughput Hydrogen Stations (IHS) Project, NREL researchers have successfully demonstrated high-flow-rate hydrogen fueling into a heavy-duty (HD) vehicle system at the Energy Systems Integration Facility as part of the Advanced Research on Integrated Energy Systems environment.

The accomplishment adds to U.S. Department of Energy (DOE) and industry goals for high-density fuel cell electric vehicles (FCEVs) and infrastructure, which supports decarbonization advances in the transportation sector. NREL has supported cutting-edge research on hydrogen fueling methods for light-duty FCEVs for well over a decade. However, HD trucks and machinery represent a whole different scale of endeavor.

“To design and build these first-of-its-kind systems, it’s a significant technical accomplishment,” said project leader Shaun Onorato. “This research is instrumental to characterizing hydrogen HD fueling and opens the door for new protocols that shape the future of decarbonized transportation.”

The IHS project, a cooperation with Air Liquide, Honda, Shell, and Toyota, tackles research issues and technology gaps in the development of high-flow-rate hydrogen fuelling systems, including applications for Class 8 semi-trucks, marine vessels, and rail and mining vehicles.

The project is partially supported by the Hydrogen and Fuel Cell Technologies Office of the Department of Energy in order to promote the H2@Scale goal for clean hydrogen across many applications and economic sectors. The ultimate objective is to compete with typical diesel vehicle refueling durations (about 10 minutes), which requires an ambitious hydrogen gas mass flow rate of 10 kg/min average (20 kg/min peak) based on a maximum onboard vehicle storage capacity of 100kg hydrogen gas. This pace is approximately 10 times the current average mass flow rate for FCEVs.

On April 26, 2022, the IHS team surpassed this mass flow rate target by exhibiting an average mass flow rate of 14 kg/min (highest mass flow rate of 21 kg/min) with a 40.3 kg fill into a bank of eight hydrogen storage tanks—similar to those used by HD vehicles—in 2.87 minutes. This intermediate milestone will pave the path for the project’s completion of a 60-80 kg fill in under 10 minutes at high mass flow rates, the final milestone.

Building a bigger hydrogen fuel system

To construct a brand-new hydrogen filling station, researchers used the Hydrogen Filling Simulation (H2FillS) model developed by NREL. H2FillS is a quick, versatile, and cost-free thermodynamic model that mimics the hydrogen delivery from a hydrogen station to a light-duty FCEV. In 2021, researchers made significant modifications to the H2FillS model to bring it in line with HD and IHS specifications. The current version of the model computes 20–40 times quicker than its predecessor, and the pressure ramp rate parameter has also been adjusted. In addition, H2FillS now investigates the entire hydrogen fuelling process in order to determine the appropriate filling rate for heavy-duty vehicles.

To analyze the temperature distribution within a vehicle’s hydrogen storage tanks (essential for creating novel fuelling methods), researchers used NREL’s supercomputer Eagle to conduct 3-D computational fluid dynamic modeling to identify possible hot spots and improve mixing properties. Throughout the course of the study, the team performed a number of full and partial fills using computational fluid dynamic modeling to investigate factors such as the impact of tank size, injector diameter, and injector angle on gas mixing. Researchers weighed these data with experimental testing to continue validating their method and enhancing H2FillS for HD applications.

This integrated procedure influenced the extension of the Energy Systems Integration Facility’s hydrogen infrastructure in order to establish a new research area for the installation and assessment of large-scale equipment. These improvements included a new concrete pad that was attached to the underlying bedrock to accommodate bigger research components having vibrational properties, such as hydrogen compression devices. To ensure compatibility with HD-FCEVs and trucks, researchers added 300 kg of additional high-pressure hydrogen stationary storage, designed and constructed new medium- and high-pressure gas management panels, an HD hydrogen fueling dispenser, a new hydrogen precooling system, and an HD vehicle storage simulation device.

New station heavy-duty capabilities

The demonstration of high-flow-rate hydrogen fueling by NREL paves the way for increased study into high-density (HD) hydrogen systems, including protocols for fueling (which do not exist at present) and safety, codes, and standards. As the first facility of its kind, NREL’s HD station enables researchers to evaluate hardware devices for HD hydrogen fueling—such as high flow rate nozzles, receptacles, hoses, and breakaways—at a controlled site to ensure the safety and reliability of these devices, which are not yet commercially available. Future partnerships will exploit the capabilities of the new station to aid in the development of HD-FCEV fueling infrastructure.

“We see a bright future for heavy-duty fuel cell vehicles, especially where companies are faced with complex logistics that demand tough duty cycles, long ranges, and fast refueling,” Onorato said. “This milestone signifies new opportunities to develop and validate best-practices for hydrogen fueling to support the adoption of heavy-duty fuel cell trucks.”

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