Hydrogen Basics - Hydrogen101

Hydrogen Basics - Hydrogen101

Hydrogen Basics Explained - Hydrogen101

Here we cover some of the basics of Hydrogen in railways, in a simple bite-sized way.

We cover topics such as explaining where the hydrogen comes from, the different ways hydrogen can be used to power trains, (yes there is more than one), and discuss some of the potential pros and cons of hydrogen powered rail vehicles. These articles are not going to be detailed - just enough to give a basic overview.  If you'd like to see a topic covered or more detail added, then let us know via the form.

Hydrogen Basics

Where does Hydrogen Fit?

Diesel has many good points which is why its use is so common, but also some uncomfortable problems in terms of air-quality and CO2 emissions. With an increasing focus on climate change and decarbonisation of transport, people, companies, and countries increasingly wish to seek out lower carbon fuels as alternatives and Hydrogen is one option which you will increasingly see as well as battery power. Which choice for traction is right?

A key factor for many in choosing Hydrogen over battery for rollingstock, is that it is more energy dense than battery power. Where space or weight is constrained, as is typical on a vehicle, you can go further per kilogram or per cubic meter on hydrogen than you can on battery power.  In practice this means that where routes are longer and services not frequent enough to justify overhead electrification that hydrogen becomes a good alternative to diesel powered vehicles. For freight locomotives the energy density becomes even more apparent and battery power over any significant distance usually becomes impractical.

Hydrogen Generation - Deciphering Hydrogen Colour Codes

There are many sources from which hydrogen can be generated - and this process is critical to how carbon intensive that hydrogen is. If you want to understand the difference between Blue and Green Hydrogen then take a look at our Hydrogen T-Rainbow blog below to get an overview and explore other colours you may not have come across before such as Turquoise and Pink. There really is quite a spectrum of hydrogen generation options.

Discover the Hydrogen T-Rainbow

Discover the Hydrogen T-Rainbow

Explaining Hydrogen colours, sources and how they are grouped Read more

How can hydrogen power trains and locomotives?

Whilst this may seem like a trick question - it is not. Although many immediately think of fuel cells when talking about Hydrogen powered trains, Hydrogen can be also be used to power internal combustion engines to power railway rollingstock. Each type of power generation process has its merits and limitations.

Hydrogen fuel cells


Fuel cells are like a battery in that they provide electrical power. However, unlike a battery they generate electricity from combining hydrogen stored in high pressure tanks with oxygen (often from the air) inside the fuel cell. So long as fuel is supplied, electrical power is produced. The electricity produced is either used directly, stored via a battery, or in rail vehicles a combination of both to provide traction power via electric motors with the necessary flexibility in power output needed for operational use.

Hydrogen Fuel Cell emissions in use are typically only pure water and they can offer higher efficiencies than combustion engines, so they are clearly attractive from an environmental point of view. Ricardo teams played a key part in bringing the first hydrogen powered train to the mainline in the UK.

Key benefits:

  • Higher energy efficiency than combustion engines - 50%+ 
  • Emits only water in use
  • Quiet

Key challenges:

  • Requires energy storage to provide flexible traction power (battery hybrid)
  • Needs high cleanness fuel and air
  • Cost


Hydrogen Internal Combustion Engines (ICE / H2ICE)

These engines operate like conventional internal combustion engines mixing hydrogen fuel with air and then burning it inside the engine to produce mechanical power via pistons and a crankshaft.

Whilst fuel cell technologies lead in energy efficiency, hydrogen combustion engines do have significant merits too. Combustion engines are a well-developed, proven and understood technology and are more tolerant of fuel and air contaminants and non-ideal running conditions. 

In many countries there is a significant drive, or even legal requirement, to remove diesel fuelled vehicles to achieve decarbonisation and air-quality targets.  Hydrogen Internal combustion engines offer significant potential to repurpose fossil fuel (diesel) burning rollingstock avoiding replacement of the entire vehicle which may have significant useful life remaining.

Furthermore there is also the exciting potential to modify original diesel engines to burn hydrogen rather than require a whole new engine. These key aspects are likely to prove attractive to existing diesel rollingstock fleet owners allowing them to decarbonise by repurposing existing assets relatively quickly and extend their rollingstock useful life whilst avoiding entire new fleet capital purchases along with the cost and carbon impact that has.

Key benefits:

  • Potential to re-use existing vehicle
  • Potential to re-engineer existing engine 
  • Tolerant of fuel and air contaminants
  • Lower costs

Key challenges:

  • Noise/Vibration (lower than existing diesel engines)
  • Lower efficiency than fuel-cell ~44%
  • Exhaust emissions to manage (lower than other combustion engines but still some control required). 
Hydrogen Internal Combustion Engines (H2ICE)

Hydrogen Internal Combustion Engines (H2ICE)

More information on retrofit hydrogen solutions to decarbonise current rollingstock Read more

Download our handy hydrogen guide

Introducing Hydrogen in Railways
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