Hydrogen Fuel Cells vs Hydrogen Combustion Engines

Investment in hydrogen vehicle technology is increasing across the globe - both in the form of hydrogen combustion, and hydrogen fuel cell vehicles.

The two are often confused, due to both utilising natural hydrogen gas for fuel. However, they’re actually incredibly different in terms of how they work, and the potential benefits they bring.

sopp+sopp are industry-leaders in technology-driven fleet management services - specialising in accident management, sustainable vehicle repair, and claims management. Here we discuss the key differences between hydrogen fuel cell (HFC) vehicles, and hydrogen combustion engines (H2-ICE).

HFC vs H2-ICE - What’s the difference?

Let’s start with the basics - what’s the difference between HFC and hydrogen combustion engine (H2-ICE) vehicles?

Hydrogen Combustion vs Fuel Cell Technology:

Hydrogen combustion engines work in a similar way to petrol/diesel engines. They ignite compressed hydrogen gas, which turns the engine, and delivers power to the wheels.

On the other hand, HFC vehicles are more comparable to EVs. They use the hydrogen gas to trigger an electrochemical reaction, which generates a current, charges the battery, and powers electric motors to drive the wheels.

Both HFC and H2-ICE vehicles are effectively carbon-neutral when it comes to everyday driving. However, both come with their unique considerations for manufacturers & drivers.

Are hydrogen vehicles classed as EVs?

Vehicles which utilise hydrogen fuel cells (HFC) are categorised as ‘FCEVs’, fuel cell electric vehicles. The only difference between HFC vehicles and standard EVs is that the latter uses a plug to charge the battery, while the former uses its onboard hydrogen fuel cell to generate a charge.

Hydrogen combustion (H2-ICE) vehicles, on the other hand, are classed as ‘low carbon vehicles’. They’re treated similarly to hybrids or AFVs like biofuel/LPG vehicles.

Read more: The Pros & Cons of Commercial EVs for Fleets

Hydrogen Fuel Cell (HFC) Vehicles explained…

Hydrogen fuel cells use pressurised hydrogen gas and oxygen to trigger an electrochemical reaction, which generates a current, and powers the vehicle’s electric drivetrain, which is similar to an EV.

The only waste products of this reaction are heat and water vapour - pure H2O - which are safely expelled through an exhaust system.

What are the benefits of HFC over Hydrogen Combustion?

Hydrogen combustion engines lose a lot of the energy they produce as heat, translating to average efficiency ratings of only 20-30%, compared to the 50-60% of hydrogen fuel cells.

This not only makes HFCs cheaper to run than H2-ICE, but also makes them more applicable to larger vehicles, like HGVs and buses, which require high fuel efficiency for long-distance driving.

What are the challenges of hydrogen fuel cells?

The uptake of HFC vehicles has been slowed significantly due to a lack of refuelling infrastructure, as well as the expensive nature of raw hydrogen gas.

There are currently just 15 hydrogen refuelling stations in the UK, making HFC vehicles incredibly difficult for fleets and their drivers to operate without investment in self-owned infrastructure.

Hydrogen fuel cells are also far less efficient than the lithium ion batteries found in EVs. HFC vehicles achieve efficiency of around 50-60% - higher than the 30-40% for ICE vehicles, but significantly lower than the near 80% for plug-in EVs.

Hydrogen Combustion Engines (H2-ICE) Explained…

Hydrogen combustion engines (H2-ICE) ignite pressurised gas within their cylinders, triggering a mechanical chain reaction which drives the engine, and delivers power to the wheels.

To put it in simpler terms - they work in a similar way to petrol/diesel vehicles, only they use gas instead of liquid fuel.

What are the benefits of hydrogen combustion engines?

Hydrogen combustion is a carbon-neutral process. In theory, the only side products are heat and water vapour. This makes hydrogen combustion engines more environmentally friendly than petrol/diesel engines, making the gas an attractive alternative to fossil fuels.

Hydrogen engines can also be more efficient, with BMW’s hydrogen-gasoline hybrid boasting 40% efficiency while running on hydrogen, compared with less than 30% for gasoline.

What are the drawbacks of hydrogen combustion?

While hydrogen engines are carbon-neutral, they aren’t emission-free. The excess heat generated by the combustion process can generate nitrogen oxides, an equally harmful and undesirable greenhouse gas.

They’re also less efficient than alternatives like hydrogen fuel cells. Combustion is never a completely efficient process, due to much of the fuel’s energy being lost to heat. The electrochemical reaction within fuel cells loses far less of this energy, delivering more of the hydrogen’s energy to driving the wheels.

The process of extracting, producing, and transporting raw hydrogen are also currently relatively carbon-intenstive, further lowering the environmental value of the gas as an alternative fuel.

What is the future for Hydrogen Combustion Engines?

Drawbacks in the efficiency of hydrogen combustion engines mean that investment & research is primarily focused on Hydrogen Fuel Cell vehicles, rather than developments in H2-ICE technology.

This means that, although they work in theory, we’re unlikely to see a vast increase in the number of hydrogen combustion vehicles on our roads.

In Summary - HFC vs H2-ICE

Types of hydrogen vehicles…

Hydrogen vehicles come in two main categories - Hydrogen Fuel Cells (HFC) and Hydrogen Internal Combustion Engines (H2-ICE).

Hydrogen combustion vs HFCs

H2-ICE vehicles ignite hydrogen within the engine to deliver mechanical power to the wheels. HFC vehicles, on the other hand, function much like EVs - they rely on an electrochemical reaction, which generates a current, and powers the electric drivetrain.

The benefits/challenges…

While hydrogen vehicles are generally more efficient than petrol/diesel, both HFC and H2-ICE are currently far less efficient than lithium-ion EVs.

Uptake of both HFC and H2-ICE vehicles has also been slowed significantly due to a lack of hydrogen refuelling stations in the UK, as well as the expensive nature of hydrogen gas.

In terms of the future of hydrogen vehicles, it’s far more likely that we’ll see further investment in HFC rather than H2-ICE, due to its increased efficiency, and absence of harmful emissions.