Hydrogen Fuel Cells vs Hydrogen Combustion Engines
Investment and research in hydrogen-powered vehicles is increasing across the globe - both in the form of hydrogen combustion engines, and hydrogen fuel cell (HFC) vehicles.
But which of the two is more viable for the low-carbon future of transportation? Do hydrogen fuel cells, or hydrogen combustion engines, have the most potnetial to power the fleet & commercial vehicles of the future?
sopp+sopp are industry-leaders in technology-driven fleet management solutions, having worked with some of the UK’s best-known fleets and commercial insurers since our conception in 2003.
We share our clients’ commitments for an environmentally-conscious, low-carbon future for commercial transportation. That’s why we partner with leading researchers in sustainable vehicle technology, helping us to understand, navigate, and support our customers to implement the latest low-carbon fleet initiatives.
Here we discuss some of the key contrasts between hydrogen combustion (H2-ICE) and hydrogen fuel cell (HFC) vehicles, including around how they work, their benefits, and their operational challenges for fleets.
HFC vs H2-ICE - What’s the difference?
Before we get into the considerations for fleets, let’s start with the basics - what’s the difference between HFC and H2-ICE vehicles?
Hydrogen Combustion vs Hyrdogen Fuel Cells
H2-ICE (Hydrogen Combustion) Vehicles:
Hydrogen combustion engines work in a similar way to petrol/diesel engines. They ignite compressed hydrogen gas in the engine cylinders, which turns the engine, and delivers power to the wheels. They’re filled up with hydrogen in the same way you’d fill a conventional car with fossil fuels, and emmit waste products (mainly water and nitrgoen oxides) through an exhaust.
HFC (Hydrogen Fuel Cell) Vehicles:
On the other hand, HFC vehicles are more comparable to EVs than fossil fuel vehicles. 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. Unlike lithium-ion EVs, they still have an exhaust, but the only waste product produced from the reaction is pure H2O.
Are hydrogen vehicles classed as EVs?
Vehicles that utilise hydrogen fuel cells (HFCs) are categorised as ‘FCEVs’, fuel cell electric vehicles. This means they’re treated similarly to EVs in terms of taxation, insurance, and repair practices.
Hydrogen combustion (H2-ICE) vehicles, on the other hand, are classed as ‘low carbon vehicles’. They’re treated similarly to hybrids, or alternative fuel vehicles, such as those powered by biofuels or LPG.
Read more: The Pros & Cons of Commercial EVs for Fleets
Hydrogen Fuel Cell (FCEV) Vehicles explained…
Hydrogen fuel cells use pressurised hydrogen gas, along with oxygen, to trigger an electrochemical reaction - which generates a current, and powers the vehicle’s electric drivetrain, which is similar in design 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 - like you’d find on a conventional car, but much cleaner!
What are the benefits of Hydrogen Fuel Cells over Hydrogen Combustion?
Hyrdrogen Fuel Cell (HFC) vehicles achieve impressive efficiency, usually of around 40-60%, compared to just 20-30% for Hydrogen Combustion engines. This makes HFC technology far more applicable for larger vehicles, like HGVs or buses, which require high fuel efficiency for long distance driving, usually while bearing weight.
They’re also considered more environmentally friendly. HFC vehicles are effectively emmission free in day-to-day driving, aside from carbon emissions generated from braking and tyre wear. Hydrogen combustion vehicles, on the other hand, are known to produce emissions like nitrogen oxisdes - a greenhouse gas equally as ecologically undesirable as CO2.
What are the challenges of using hydrogen fuel cells in vehicles?
The uptake of hydrogen fuel cell vehicles has been slowed significantly due to a lack of investment in public 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 40-60% - 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 - much like a petrol or diesel vehicle.
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 far more environmentally friendly than petrol/diesel engines, making the gas an attractive alternative to fossil fuels.
Hydrogen engines can also be more efficient than fossil fuels, 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 variety of greenhouse gas.
They’re also less efficient than hydrogen fuel cells (HFCs). Combustion of any form is never an entirely efficient process, due to much of the fuel’s energy being lost to heat. The electrochemical reaction within fuel cells dissepates far less of the hydrogen’s potential energy, delivering more of its power to driving the wheels.
The process of extracting, producing, and transporting raw hydrogen is also, currently, immensely carbon-intenstive - further clouding any potential environmental value of the gas as an alternative fuel.
What is the future: FCEVs, or Hydrogen Combustion?
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 - Hydrogen Fuel Cells vs Hydrogen Combustion Engines
Types of hydrogen vehicles…
Hydrogen vehicles come in two main categories - Hydrogen Fuel Cells (HFCs) 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.