Fuel Cell Vs Hydrogen Combustion Engines for Trucks

This is not intended to be a technical piece aimed as a discussion about which technology is best for the future of long distance transportation. We hope to simplify and explain the basis of the technologies that may help to hitting our net zero targets whilst still making long distance haulage a reality.

What makes the issue confusing is that the same fuel can power a truck, yet use two totally different approaches. You could think of it this way – you put petrol in a car internal combustion engine (ICE) to power it along, but you could equally use petrol to heat up a steam engine to power it along. Same fuel, different technologies.

Why are hydrogen trucks necessary?

In order to reach our climate target diesel trucks will have to be a thing of the past. The trouble is that they are very good at carrying heavy loads over long distances before refuelling AND there is usually a refuelling network around to fill up quickly and get under way again. Battery electric trucks are suited to local and regional work where trucks can return to base each day and cover shorter overall daily distances, but for triple shift operations or long distance transport they cannot carry sufficient power and take too long to recharge – even if there were a refuelling network.

This is where hydrogen comes in, as the refuelling time is relatively fast and the energy available vs the weight is an acceptable compromise compared to diesel.

Fuel Cell Vs Hydrogen Combustion Engines

Both technologies utilize hydrogen, a clean energy source that, in principle, emits only water vapor when used, but they operate in fundamentally different ways.

Hydrogen Fuel Cell Trucks (FCEVs)

Fuel cell electric vehicles (FCEVs) use the same electric motors that we see in battery electric trucks. They even have a similar type battery fitted. The difference is that the battery is relatively small and is continually charged by the hydrogen fuel cell which generates the electricity.  The battery is used simply to make the power supply reliable and constant.

HVS Hydrogen Fuel Cell Prototype 4x2 tractor unit RTX 2024
HVS Hydrogen Fuel Cell Prototype 4×2 tractor unit

The fuel cell process involves hydrogen gas reacting with oxygen in the fuel cell to produce electricity, water, and heat. FCEVs are known for their high efficiency, especially at lower loads, and their ability to capture energy through regenerative braking charging the battery, further enhances their efficiency. They have zero tailpipe emissions, emitting only water vapor, unlike the ICE hydrogen engines.

Advantages of FCEVs include:

  • Quick refuelling, similar to conventional vehicles.
  • Longer driving range compared to battery electric vehicles (BEVs).
  • High energy-to-weight ratio, beneficial for heavy loads and long distances.
  • No emissions besides water vapor.

Hydrogen Combustion Engine Trucks

On the other hand, hydrogen combustion engine trucks burn hydrogen in an internal combustion engine, much like traditional petrol engines, (note diesel engines are compression rather than combustion engines). These engines are nearly identical to conventional spark-ignition engines and can operate without the need for a battery pack.

Volvo Hydrogen Truck
“Trucks where the traditional internal combustion engine remains but runs on hydrogen will have the same performance and reliability as our diesel trucks, but with the added benefit of potentially net zero CO2 emissions.”

Hydrogen combustion engines are most efficient under high load conditions, such as when hauling heavy loads, making them suitable for heavy-duty trucking applications. There is a downside in so far as existing technology requires the use of a pilot fuel to aid the combustion process.

Volvo Trucks will be testing these hydrogen ICE trucks with customers as early as 2026 and will feature High Pressure Direct Injection (HPDI), a technology where a small amount of ignition fuel is injected with high pressure to enable compression ignition before hydrogen is added. The advantages of this technology include higher energy efficiency with lower fuel consumption, and increased engine power.

Due to the low CO2 emissions from hydrogen combustion, these trucks are categorised  as “Zero Emission Vehicles” under the agreed new EU CO2 emission standards. Hydrogen combustion engines will also emit very small amounts of nitrogen oxides and particles.

Advantages of hydrogen combustion engines include:

  • High efficiency under heavy loads.
  • Familiar technology for manufacturers and mechanics.
  • Ability to handle transient response demand effectively.
  • Standalone powertrain solution without the need for battery packs.

Comparing Emissions and Use Cases

Both FCEVs and hydrogen combustion engines have near-zero emissions profiles. However, while FCEVs produce no emissions other than water vapor, hydrogen combustion engines can emit trace amounts of CO2 and nitrogen oxides (NOx), although these are significantly lower than those from diesel engines.

The choice between FCEVs and hydrogen combustion engines often comes down to the specific use case. For instance, vehicles that frequently operate without any load, such as tow trucks or concrete mixer trucks, may find fuel cells more efficient. Conversely, heavy trucks that spend most of their time under heavy loads benefit from the efficiency of internal combustion engines.

Mercedes Hydrogen Truck
BP is planning to work with Mercedes Trucks’ parent company, DaimlerAG to open 25 hydrogen refuelling stations for trucks in the UK by the end of 2030

The Cost

The elephant in the room is the cost of the technology as it is in its early stages, but also the cost of manufacturing green hydrogen. This is a process that requires a lot of electricity. The whole process from electricity generation to manufacture of the fuel to transporting it to the trucks, which then convert it to electricity or set fire to it, is relatively inefficient. This means that you have to make more green electricity using hydrogen trucks than if you could get by using battery electric trucks.

The Road Ahead

As the industry progresses, both hydrogen fuel cells and combustion engines are expected to play vital roles in achieving a carbon-neutral future. Specialist manufacturers such as Hydrogen Vehicle Systems based in the UK are developing a 4×2 fuel cell electric tractor unit, whilst DAF won an award for their H2 ICE truck as far back as 2022. MAN are planning a small series run of hydrogen trucks in 2025 and Volvo Trucks will have hydrogen trucks available for customers to buy by 2030. Mercedes believe that we will need hydrogen powered trucks and are working on their fuel cell solution. Iveco have taken over their European joint venture with Nikola which includes a fuel cell battery electric vehicle.

Iveco S Way FCEV
The Iveco HD FCEV boasts a range of up to 800 km