Hydrogen power is gradually making its mark on the motorsport scene. This year, we have already witnessed hydrogen race cars competing in the Fuji 24 Hours, hillclimbs, and the Dakar Rally. Looking ahead to 2025, the world’s first hydrogen championship, Extreme H, will debut, and by 2027, hydrogen prototypes are expected to race at the Le Mans 24 Hours.

So, why are teams shifting towards hydrogen? Which technology is more suitable for motorsport—hydrogen fuel cells or hydrogen combustion? Technical experts at Ricardo provide insights.

The Benefits of Hydrogen Power

As an alternative to fossil fuels, hydrogen offers several advantages. It is the most abundant element in the universe, releases about three times more energy per unit weight compared to gasoline, and emits only water and heat when used in vehicles.

“Hydrogen engine efficiency is comparable to conventional combustion engines,” says Richard Osborne, Global Technical Expert – Sustainable Engines at Ricardo. “Hydrogen fuel cells achieve higher efficiencies at low-load operating conditions, but at high loads, fuel cells and hydrogen engines are quite similar in overall traction efficiency.”

“The most significant advantage of hydrogen is that it produces no carbon emissions at the tailpipe,” Osborne continues. “Even sustainable liquid fuels, which can be carbon-neutral over their lifecycle, still emit CO2 at the tailpipe. That’s why hydrogen is considered a crucial alternative.”

How Hydrogen Combustion Works

Hydrogen combustion employs a spark ignition engine to burn a fuel-air mixture, driving reciprocating pistons to generate mechanical power. Instead of liquid fossil fuels like gasoline or diesel, it uses liquid or gaseous hydrogen fuel.

“Hydrogen is an excellent fuel for combustion due to its high flame speeds and fast combustion, which is ideal for motorsport applications,” explains Osborne. “It also has a broad flammability range, allowing for a wide range of air-fuel ratios. Although it requires slightly different materials and compression ratios, many of the mechanical, injection, and emission systems are similar to conventional internal combustion engines.”

How a Hydrogen Fuel Cell Works

A hydrogen fuel cell functions similarly to a battery, consisting of an electrolyte, an anode, and a cathode. Hydrogen fuel is supplied to the anode, while air is supplied to the cathode. At the anode, a catalyst separates hydrogen molecules into protons and electrons, which take different paths to the cathode. The protons pass through the electrolyte, while the electrons flow through an electrical circuit. At the cathode, the electrons and protons combine with oxygen from the air, producing water and heat.

“Hydrogen fuel cell vehicles retain an electric powertrain, with inverters providing AC power to motors that drive the wheels through a transmission,” says Temoc Rodriguez, Global Technical Expert – Electrified Solutions at Ricardo. “However, power is generated by the stacks within the hydrogen fuel cell, rather than a battery.”

Despite this, batteries or supercapacitors are still crucial. The rapid accelerations and decelerations in racing require quick energy discharge. Fuel cells cannot react fast enough because they are limited by the speed of chemical reactions within the stacks.

“Fuel cells cannot split the electrons from hydrogen molecules quickly enough for motorsport,” Rodriguez adds. “It can take a fuel cell 2-3 seconds to reach 100% power capacity, while a race car needs to accelerate from 0 to maximum speed in 2-3 seconds. Therefore, peak power must come from another energy storage system, such as a battery or supercapacitor.”

This is why hydrogen fuel cells are often combined with a battery or supercapacitor. The battery provides consistent power, while the supercapacitor delivers the instantaneous power needed for rapid acceleration and braking.

The Challenges of Storing Hydrogen on a Race Car

Hydrogen, being the lightest gas in the universe, has a high energy density per unit weight. However, its high expansion ratio results in poor energy density per unit volume, making storage on a vehicle challenging.

“Liquid hydrocarbons are hard to beat in terms of energy density per unit volume, so alternatives like batteries or gaseous fuels struggle to compete,” says Osborne. “For instance, compressed hydrogen gas occupies about 12 times the volume and liquid hydrogen about six times the volume compared to gasoline for the same energy content.”

Currently, most hydrogen fuel cells store hydrogen gas at 400 bar, with newer vehicles reaching up to 700 bar. However, hydrogen gas occupies about twice the volume compared to its liquid state. Could liquid hydrogen be the solution?

“This is one of the biggest challenges with fuel cells—how much hydrogen can you realistically store on board?” Rodriguez highlights. “Using liquid hydrogen instead of gas could store around 100% more hydrogen, but it requires maintaining cryogenic temperatures and additional equipment, increasing the vehicle's overall volume and mass.”

“Another storage method under research is solid hydrogen,” Rodriguez continues. “Hydrogen is chemically mixed with a hydride molecule and stored as a solid, achieving similar volumetric densities as liquid hydrogen without the need for cryogenic temperatures. A heating element in the tanks releases hydrogen gas from the solid for use in the stacks.”

Is Hydrogen a Good Solution for Motorsport?

There are no perfect solutions in engineering, so hydrogen in motorsport has both advantages and challenges.

Performance-wise, there is minimal difference between hydrogen combustion and hydrogen fuel cell race cars on the track. Although fuel cells are typically suited for lower-load applications, integrating a battery or supercapacitor makes the hydrogen fuel cell package as competitive as hydrogen combustion.

“There is also a weight advantage compared to fully electric race cars,” says Rodriguez. “Battery packs are heavy, which limits acceleration. A hydrogen fuel cell combined with a small capacitor bank reduces the car's base weight, allowing faster acceleration for similar power capacity, which could lead to more overtaking.”

This fuel cell and supercapacitor/battery setup also introduces a strategic element to races. Similar to energy management in Formula E, teams will need to balance energy from the fuel cell with that from the supercapacitor/battery, optimizing the blend for each circuit.

“Another benefit of hydrogen power, particularly for combustion, is noise,” Osborne adds. “Fans often criticize the quietness of hybrid and electric championships, but hydrogen combustion race cars produce sounds similar to conventional internal combustion engines.”

“Refueling hydrogen is also much faster than recharging batteries,” Osborne continues. “Although there are safety considerations for hydrogen refueling, the technology is available; it’s a matter of integrating it into pitstops.”

Conclusion

Overall, whether through fuel cells or combustion, hydrogen can serve as an effective alternative to fossil fuels in motorsport. The key is ensuring that hydrogen comes from sustainable sources and that regulations drive innovation in storage solutions.

“In motorsport, new technologies are seen as challenges, not restrictions,” concludes Stuart Cooper, Market Head of Motorsport for Ricardo. “Racing offers a unique platform to address new technologies in a competitive environment that captivates spectators.”

“That’s why Ricardo is actively involved in hydrogen discussions with the FIA and ACO and in hydrogen projects across various sectors,” Cooper adds. “We have invested in test, manufacturing, assembly, and simulation facilities to develop hydrogen powertrains, whether for combustion or fuel cells. Integrating these technologies into motorsport championships accelerates development, and we are ready to support our customers in this endeavor.”

This article was originally published on the Ricardo website.

Image: Fuel cell cut out. Credit: Ricardo and Gemma Hatton

References

All About Hydrogen [Online]. IFP Energies Nouvelles.

2001. Module 1: Hydrogen Properties [Online]. Department of energy.