According to the American Trucking Associations, more than 72% of goods and services moved in the U.S. travel by trucks. And more than 60% of the miles logged by the trucking industry come from heavy-duty diesel-powered, greenhouse gas-emitting semi-trailer trucks.
A smarter, cleaner way to maintain that interstate flow of goods while mitigating climate change would be to power the long-haul trucking sector with hydrogen fuel cells. Fuel cell vehicles (FCVs) have been around for a long time, but long-haul truckers still face the classic chicken-and-egg cost and infrastructure dilemma that other clean energy sectors have experienced.
Clean, Green Power
According to the Fuel Cell and Hydrogen Energy Association, a fuel cell is a device that generates electricity through an electrochemical reaction, not combustion. It combines hydrogen and oxygen to produce electricity, heat and water. In transportation applications, the electricity powers the electric motor that drives the vehicle’s propulsion system. And because fuel cells contain no moving parts, they operate silently with extremely high reliability.
“You can think of a hydrogen fuel cell vehicle as an electric vehicle where you’ve replaced the battery with a fuel cell, and the electric charge used for ‘fuel’ with compressed hydrogen gas,” explained Kenneth “K.C.” Neyerlin, an electrochemist with the Electrochemical Engineering and Materials Chemistry group at the National Renewable Energy Laboratory (NREL).
Depending on the current density being delivered, a typical fuel cell operates in the range of 0.6 to 0.95 volts. FCVs typically combine several hundred fuel cells into a so-called “stack” to achieve the voltage and power levels required to operate the vehicle.
Building on Success
Auto manufacturers such as General Motors, Toyota, Honda and Hyundai have been accumulating hydrogen cell research since the early 1990s. Toyota unveiled its first FCV in 1996, continued maturing and demonstrating its FCV technology through the 2000s, then began selling the Toyota Mirai, a mid-size fuel cell sedan, in the U.S. in 2015.
Jim Kast, a fuel cell business analyst with Toyota Motor North America (TMNA), explained that, today, the company is building on its Mirai experience to develop hydrogen fuel cell-powered Class 8 (semi-trailer) trucks as part of two company initiatives.
“In 2019, we partnered with the Kenworth Truck Company to develop 10 zero-emission Kenworth T680s powered by Toyota hydrogen fuel cell electric powertrains,” said Kast. “The collaboration is part of an initiative sponsored by the California Air Resources Board and the Port of Los Angeles to put zero-emissions cargo-handling equipment and hydrogen fueling infrastructure to work in the LA basin.”
Several of those Kenworth trucks are already built and expected to begin operating on trade routes in the greater Los Angeles area in 2021, he added.
TMNA is also working with Hino USA to develop a Class 8 fuel cell electric truck for the North American market. The new truck will use the Mirai hydrogen fuel cell technology — except that it will use two fuel cell stacks to power a Hino XL Series chassis.
According to Kast, a hydrogen fuel cell semi-trailer truck is similar in size, look and feel to a conventional diesel-powered Class 8 vehicle. However, it’s quieter, has zero-emissions and provides better performance.
“Our new fuel-cell trucks will deliver horsepower performance similar to a diesel truck, except you’ll have a bit more torque — which means faster, more immediate acceleration — coming from the electric powertrain,” he said. “The conventional diesel fuel tanks in the (semi-trailer) cab will be replaced with hydrogen fuel tanks.”
The initial Hino truck will have a range of about 300 miles (482.8 km) per tank of hydrogen, he added.
Less Weight, More Efficiency
For NREL’s Neyerlin, hydrogen fuel cells are particularly attractive as a fuel source compared with batteries for long-haul trucking.
“If you’re doing heavy-duty trucking with batteries, you not only have to carry your goods, but you also have to carry the weight of every battery you need,” he commented. “At some point, that Nth battery is only going to be carrying more batteries, not more goods.”
By comparison, he added, you can increase the size of pressurized hydrogen storage tanks on a truck for much less weight than adding a battery, and put more fuel cells in series to create higher-power stacks with an energy density higher than batteries.
Another advantage of using hydrogen fuel cells versus batteries for big rigs is that refueling a fuel-cell powered semi is comparable to filling up a similar diesel-powered truck (10 to 15 minutes). However, charging a semi’s batteries could require several hours, even with a fast-charging system. And any time spent charging batteries beyond 15 minutes is time spent not delivering goods and earning revenue.
For all the advantages of using hydrogen fuel cells for long-haul trucking, two distinct barriers to widespread adoption of this technology still remain: the cost of hydrogen and the availability of hydrogen fueling infrastructure.
“The price of hydrogen at the pump right now is $10 to $15 per kilogram in California,” said Mike Peters, a hydrogen infrastructure engineer with NREL. “That number needs to be closer to $3 to $5 per kilogram for fuel cell-based trucking to be cost competitive with diesel trucking. We have to continue pushing prices down, and we need to push for initiatives to produce green hydrogen, whether that’s through electrolysis coupled with wind or solar energy, steam methane reforming with carbon capture or capturing hydrogen as a waste product of certain processes.”
In October 2020, the Department of Energy (DOE) announced the formation of a new consortium, H2NEW, to reduce the costs of hydrogen production, transport, storage, distribution and use in multiple energy sectors. Co-led by NREL and the Idaho National Laboratory, H2NEW will focus on advancing both low- and high-temperature electrolysis techniques in hopes of achieving hydrogen production at $2 per kg.
The DOE also recently funded the Million-Mile Fuel Cell Truck consortium, which is a collection of national labs and academic and industrial partners focused on the improving the durability, performance and cost of fuel cells to enable long-haul, fuel-cell-powered trucks.
“Our hope is that by approaching the hydrogen fuel cell challenge from both the production and operation ends, we can solve some of the ‘chicken-egg’ dilemma that has stymied the growth of a hydrogen-based transportation segment so far,” suggested Neyerlin.
NREL’s and H2NEW’s work to reduce the cost of hydrogen will assist the broader goal of creating the hydrogen fueling infrastructure needed for a fuel-cell-based long-haul trucking industry.
The main push to retain hydrogen fueling stations is currently happening in California, where the California Energy Commission (CEC) is funding the development of a network of hydrogen fueling stations through its Clean Transportation Program. To date, the CEC has funded the development of 45 light-duty retail stations with 16 more under construction.
In December 2020, the CEC announced plans to invest in the development of 111 additional hydrogen fueling stations by 2027 to help meet California’s climate change goals. A portion of those stations will be dual-purpose stations that can serve both consumer and heavy-duty vehicles.
Same but Different
At first glance, a hydrogen fueling station might look similar to a conventional gasoline dispensing station, but its infrastructure is completely different.
“A hydrogen fueling station consists of three components: compression, storage and dispensing, and those components interact to fill the vehicle,” explained Peters. “The goal is to transfer hydrogen stored at high pressure (10,000 psi) from the station to a vehicle in a safe manner.”
To ensure a safe transfer, he added, hydrogen is cooled to a temperature of about -40 degrees Celsius. This compensates for the fact that hydrogen expands as it flows out of storage and heats up the vehicle tank. A series of communication checks and balances between the station and vehicle further ensure the safety of the fueling transaction.
“The dispensing of hydrogen is very similar to the process that drivers of gasoline vehicles are familiar with,” said Peters. “You just swipe your credit card, pull the nozzle from its dispenser, connect it to your car and squeeze the trigger. In three to five minutes, your car will be filled, and you’ll be back on the road.”
Starting Where It Makes Cents
California’s proactive approach to hydrogen fueling infrastructure is a good start, but it’s not enough to pay for the national fueling infrastructure that will be needed to power a fuel-cell based long-haul trucking industry.
Peters believes that the initial hydrogen fueling infrastructure could potentially be underwritten by fleet operators whose trucks operate on fixed routes and predictable schedules.
“If you had trucks coming and going from say, a port, on a set schedule, or going to the same city and back on a regular schedule, you could justify having a few hydrogen fueling stations,” he proposed. “The key driver of such an investment would be to make sure it has a high utilization rate.”
Such an approach might also work for Amazon, UPS or FedEx, added Peters, since their fleets typically operate on fairly fixed routes and return to a central warehouse at night.
Kast is also optimistic about the long-term willingness of ports and energy companies to invest in hydrogen fueling infrastructure. For example, TMNA has partnered with Shell Oil to develop three such stations in the Los Angeles region to support heavy-duty trucks.
“We’re working with Shell on matching supply and demand, not only for these first three stations but also for an additional 50 stations for light-duty vehicles,” said Kast. “That volume will help them bring down the cost of this infrastructure, and it potentially incentivizes them to also invest in renewable hydrogen production.”
Hydrogen fuel cells and related infrastructure are clearly a compelling environmental choice, especially as they grow in technical maturity and availability. But they still have a way to go.
As Kast noted, the good news is that “hydrogen is no longer the fuel of the future, as it has been for so long. With all the new targets for zero emission vehicles, and all the new funding coming through, it’s something we’re going to start seeing in trucks on the road in just a few years. It won’t be every truck, obviously, but the momentum is strong and continuing.”