What is (Renewable) Hydrogen?
(Renewable) Hydrogen
What is Hydrogen?
Hydrogen is a chemical element with the symbol H and atomic number 1. It is the lightest and most abundant element in the universe. On Earth, however, hydrogen does not occur freely in significant amounts as it is highly reactive. Only small quantities of natural hydrogen are found in the Earth’s crust through geological water–rock reactions, and these occurrences are rare and localised.
Instead, hydrogen is abundantly found bound within other molecules, such as water (H2O) and hydrocarbons (e.g. CH4). To be used as a fuel, hydrogen must therefore be produced and separated into its gaseous form, dihydrogen (H2). Hydrogen gas is colourless, odourless, non toxic and highly combustible.
Why is hydrogen called an energy carrier?
Hydrogen is described as an energy carrier rather than a primary energy source because it does not occur freely on Earth in significant, usable quantities. As hydrogen is almost always bound within other molecules (e.g. H2O & CH4), energy must first be used to separate it into its gaseous form (H2).
Via the separation process, hydrogen stores energy. H2 then can be transported from where it is generated to where it is needed. Like a battery, hydrogen delivers energy that was created by other means rather than providing energy directly as a primary fuel.
How is hydrogen produced?
One common method is electrolysis, where electricity is used to split water (H2O) into hydrogen (H2) and oxygen (O2). When the electricity used for this process comes from renewable sources, the resulting hydrogen is considered renewable hydrogen.
Another widely used method is steam methane reforming, in which natural gas (CH4) is heated with steam (H2O) to release hydrogen (H2). This process (CH4 + 2H2O = 4H2 + CO2) produces hydrogen efficiently at large scale but also generates carbon dioxide (CO2). When this carbon dioxide is captured and stored, the resulting hydrogen is considered low carbon hydrogen*.
What is renewable hydrogen?
Renewable hydrogen*, often called green hydrogen, is hydrogen gas produced using renewable energy sources. While hydrogen itself is always the same molecule (H2), the term renewable refers to how it is produced, not to the hydrogen gas itself.
What do the different colours of (renewable) hydrogen mean?
The different “colours” of (renewable) hydrogen are a way to describe how (renewable) hydrogen is produced, not a difference in the (renewable) hydrogen molecule (H2) itself, which is always colourless. These colour labels are not standardized but help indicate for how the gas is produced and its environmental impact, ranging from high-emission fossil fuel-based (grey/black/brown) to low-carbon (blue/turquoise) and renewable (green) or nuclear (pink/purple) methods.
Some examples for (renewable) hydrogen colours further explained:
- Green: Produced via electrolysis using renewable electricity (wind, solar).
- Blue: Created from natural gas reforming with carbon capture and storage (CCS) to reduce emissions.
- Pink/Purple: Produced through electrolysis powered by nuclear energy.
- Turquoise: Produced via methane pyrolysis, splitting methane into hydrogen and solid carbon.
- Yellow: Produced specifically via electrolysis powered only by solar energy.
- White or gold: Naturally occurring, geological hydrogen found in underground deposits
- Grey: Produced from natural gas via steam methane reforming without capturing emissions.
- Black/Brown: Produced from coal (bituminous/lignite) gasification, with high environmental impact.
What are the current applications of (renewable) hydrogen?
- Oil Refining & Chemicals: to treat fossil fuels, produce ammonia and methanol.
- Industrial Processes: Used in steel making, metal processing, glassmaking, and producing electronics like circuit boards.
- Transport sector: as a fuel for vehicles.
- Aerospace: as a fuel for space shuttles and rocket launches.
- Energy Storage & Power: Used for storing electricity from renewable sources (power-to-hydrogen)
- Aviation & Shipping: Testing in ships and aircraft
Why (Renewable) Hydrogen in Transport?
How is (renewable) hydrogen offered as a fuel at a refuelling station?
How does refuelling work for (renewable) hydrogen?
Gaseous hydrogen vehicles are refuelled using a secure nozzle system that is similar in use and refuelling time to conventional fuels.
Where Can you Refuel (Renewable) Hydrogen at TotalEnergies?
You can refuel (renewable) hydrogen at a network of public stations operated by TotalEnergies and its partners.