Hydrogen Cars: Hot Air or Cool Ride?

August 24, 2024 RE Update

If you think you will soon be driving a hydrogen-powered vehicle, think again.

The hype over hydrogen as a transportation fuel is reaching a fevered pitch. Governments, automakers, and oil companies are investing hundreds of millions of dollars to make the concept more attractive.

On paper, hydrogen looks good. You can make it through water electrolysis using excess wind and solar renewable energy. When hydrogen is used in a fuel cell, it can power an electric vehicle (EV), emitting only water vapor, making it a zero-carbon fuel. It can be pumped directly into an on-vehicle storage tank in a few minutes, less time than it takes to recharge an EV battery.

As always, the devil is in the details, and hydrogen used to power everyday personal vehicles and light trucks has multiple problems.

Hydrogen fuel cell truck concept. Image used courtesy of Honda Motors

Hydrogen Fuel: Not That Simple

First, although it’s possible to make green hydrogen from renewable energy sources, more than 90 percent of industrial hydrogen is still produced by steam-reforming methane, a fossil fuel. This produces large amounts of carbon dioxide (CO2), which hydrogen proponents say can be captured and stored, creating blue hydrogen. However, despite huge efforts, large-scale capture and storage of CO2 hasn’t yet been demonstrated on the colossal industrial scale necessary to make blue hydrogen a viable fuel.

If creating clean hydrogen is a challenge, it’s only the beginning. Storing and distributing hydrogen isn’t easy. Due to low density, hydrogen must be compressed to thousands of pounds per square inch (psi) or liquified at temperatures below -253° (-423°F) and stored in special vessels. Compressing and liquifying hydrogen takes significant energy, reducing the overall fuel efficiency. Distributing hydrogen is also problematic as it embrittles welds in ordinary steel pipelines, causing them to fail. At a hydrogen refueling station, the cryogenic hydrogen often freezes the nozzle used to put the fuel into a vehicle’s tank, which must be either able to withstand liquid hydrogen’s extreme cold or gaseous hydrogen’s pressure, which can be as high as 10,000 psi (700 bar).

Creating Hydrogen Motion

Once the hydrogen is on board the vehicle, it must be converted into motion. One method is to convert the hydrogen into electrical energy with a proton exchange membrane (PEM) fuel cell. The converted fuel can then power an electric motor. A fuel cell uses a platinum electrode as a catalyst to combine hydrogen with oxygen to make electricity and water vapor.

Protein exchange fuel cell. Image used courtesy of Wikimedia Commons

Because a fuel cell operates at slightly elevated temperatures and much lower pressures than stored hydrogen, the hydrogen in the vehicle’s fuel tank must be warmed and regulated to a pressure the fuel cell can accept. Reducing the fuel’s pressure also decreases its temperature, requiring additional warming before it can enter the cell. In addition, the oxygen from the atmosphere and the hydrogen from the tank must be extremely pure to avoid degradation of the PEM fuel cell. PEM fuel cells using platinum are also expensive, although new designs with reduced amounts of expensive catalyst metals are bringing costs down.

Another issue for a hydrogen fuel cell vehicle is the escape of hydrogen molecules over time. Hydrogen is the smallest element and comprises a single proton and a single electron. As such, it leaks from storage systems with relative ease, reducing the fuel in the onboard storage tank over a relatively short time.

Hydrogen Efficiency Problems

A PEM fuel cell can use around 60% of the energy within the hydrogen fuel, which is significantly better than a typical gasoline internal combustion engine (ICE) with a 20% efficiency. While this is attractive, the additional energy required to create the hydrogen, compress or liquify it, transport it, reduce pressure and temperature for fuel cells, and then convert it into electricity is where energy efficiency starts to go sideways.

Here is the reality:

Producing 1 kg of green hydrogen via electrolysis requires around 50 kWh of renewable electricity, which accounts for a 60 percent efficiency loss from the original renewable energy input.
Compressing hydrogen gas to 700 bar (10,000 psi) for storage requires additional energy, around 10-15 percent of the energy content of the hydrogen.
Liquefying hydrogen by cooling it to -253°C is even more energy-intensive, requiring around 30 percent of the hydrogen’s energy content.
Transporting compressed or liquefied hydrogen over long distances incurs further energy losses and costs.
In a fuel cell vehicle, converting the hydrogen back to electricity has an efficiency of around 60 percent.

Overall, when all the energy losses are added up, the full cycle efficiency of green hydrogen is only around 20-30 percent. This is significantly lower than using renewable electricity directly in a battery electric vehicle, which has an end-to-end efficiency of 70-90 percent.

Instead of using a fuel cell, a modified ICE can use hydrogen as a combustion fuel. This appears attractive because the only emissions are oxides of nitrogen emissions and no CO2 emissions, as would occur if the engine were to run on a fossil fuel like gasoline.

Unfortunately, efficiency raises its head again. With an ICE’s 20 percent efficiency instead of the fuel cell’s 60 percent, the overall end-to-end efficiency falls below 10 percent. This means nearly the entire passenger and luggage space in an ordinary vehicle would need to be filled with hydrogen storage tanks to achieve a couple hundred-mile range between hydrogen refueling stops.

Why the Interest in Hydrogen?

The challenges for green hydrogen make it less suitable for light-duty vehicles than battery electric options when renewable electricity is available. However, some applications for hydrogen as a transportation fuel do look promising. Hydrogen’s high energy density could provide superiority over battery electric systems for heavy freight transport. This makes it a promising option for long-haul trucking, particularly along known specific routes where hydrogen refueling stations could be placed in strategic locations.

Getting Started With Hydrogen Trucks

Developing affordable, reliable fuel cells for heavy-duty trucks is one key to the eventual acceptance of hydrogen. General Motors and Honda have established a joint venture called Fuel Cell System Manufacturing (FCSM) to produce hydrogen fuel cells for various applications.

Here are the key details about this joint venture:

FCSM was formed in 2017 with an $85 million investment from Honda and GM to build a manufacturing facility in Brownstown, Michigan.
The 70,000-square-foot facility has begun commercial hydrogen fuel cell production after development work, dating back to 2013, by engineers from both companies.
GM plans to initially use the fuel cells for backup power generators and heavy-duty trucks like those from Autocar.
FCSM claims it can produce the fuel cells at one-third the cost of Honda’s previous system used in the Clarity fuel cell vehicle. Design improvements, reducing precious metal use, and production automation reduced costs.
The joint venture has also doubled the fuel cell system’s durability compared to the Clarity by using corrosion-resistant materials and improving low-temperature operation.
Honda aims to produce around 2,000 fuel cell systems annually by 2025, ramping to 60,000 units by 2030. The company aims to make a few hundred thousand units annually in the late 2030s.

GM will supply Autocar with its fuel cells for integration into heavy-duty vocational trucks, such as cement mixers, dump trucks, refuse trucks, and terminal tractors, which are expected to go into production in 2026 at the Autocar manufacturing plant in Birmingham, Alabama.

Meanwhile, Honda has partnered with Isuzu Motors to develop and commercialize hydrogen fuel cell-powered heavy-duty trucks that Isuzu plans to release in 2027. With this arrangement, Honda aims to leverage its fuel cell expertise to enable zero-emission solutions for the heavy-duty commercial vehicle segment, which has traditionally been challenging for battery-electric powertrains due to range and weight limitations.

Next-gen fuel cell technology. Image used courtesy of Honda Motors

To further showcase its hydrogen fuel cell ambitions, Honda has also developed a Class 8 hydrogen fuel cell truck concept.

The Honda Class 8 truck concept is fully operational and powered by three Honda fuel cell systems produced at the FCSM plant in Michigan. Honda has identified four core targets for its fuel cell systems: fuel cell electric vehicles, commercial fuel cell vehicles, stationary power stations, and construction machinery.

Class 8 hydrogen fuel truck concept. Image used courtesy of Honda Motors

Hydrogen Vehicles’ Future

Some applications for green hydrogen are promising. It can dramatically reduce carbon emissions in steel-making. In some regions, it could be used to store renewable energy for later conversion back into electricity to improve power grid reliability. It has been successfully used to power forklifts and other industrial machinery.

As a transportation fuel, hydrogen might be viable for long-distance heavy-duty trucks and some other heavy-duty trucks. However, if you are waiting for a hydrogen-powered fuel cell or ICE vehicle to be parked in your driveway, you are in for a long wait.