What is green hydrogen and how does it work?

Green hydrogen: an alternative for reducing emissions in industrial processes

Decarbonising the planet is one of the targets that countries around the world have set themselves for 2050. The production of green hydrogen – a technology based on the conversion of this element through electrolysis – is emerging as an alternative to other types of fossil fuels.

Green hydrogen, an alternative when electrification is not possible.

Our way of life requires an ever-increasing number of watts to function. This has brought terms such as security and energy resilience to the forefront, as they are fundamental pillars for the development of any region. The aim, therefore, is to eliminate dependence on fossil fuels, particularly imported ones that could be jeopardised by any geopolitical event. Instead, the focus is on strengthening the commitment to alternative energy sources whose production is closely linked to the region to promote greater energy independence. Here, renewable sources become an asset that not only aids the process of electrifying the economy but also acts as an energy shield.

In this journey towards decarbonisation by 2050, a new technology is emerging that will be particularly important for industry: green hydrogen.

What is green hydrogen an how is it obtained?

This technology is based on the generation of hydrogen — a universal, light and highly reactive fuel — through a chemical process known as electrolysis. This method uses an electrical current to separate the hydrogen from the oxygen in water. If this electricity is obtained from renewable sources we will, therefore, produce energy without emitting carbon dioxide into the atmosphere.

How is green hydrogen obtained?

Producing green hydrogen by electrolysis from renewable sources involves breaking down water molecules (H₂O) into oxygen (O₂) and hydrogen (H₂).

1 The water used in the electrolysis must contain salts and minerals to conduct the electricity 2 Two electrodes are immersed in the water and connected to a power source and a direct current is applied 3 The dissociation of hydrogen and oxygen occurs when the electrodes attract ions with an opposite charge to them 4 During the electrolysis, an oxidation-reduction reaction occurs due to the effect of the electricity Hydrogen Oxygen Cathodic reaction 4H+ + 4e- → 2H2 Anodic reaction 2H2O → O2 + 4H+ + 4e- Membrane

Source: U.S. Department of Energy and Wood Mackenzie.

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Hydrogen as clean energy

Hydrogen is the most abundant chemical element in nature. Global demand for it as a fuel has tripled since 1975, as noted by the IEA, and is following the same upward trend as electricity. The problem is that the main sources of hydrogen are fossil fuels, which generate air pollution when burnt.

The commitment to decarbonising and electrifying the global economy calls for solutions to replace these types of fuels with cleaner alternatives. This shift is particularly relevant in the industrial sector, which has a long-standing relationship with hydrogen. This gas has been used as a fuel since the early 19th century for cars, airships and spacecraft.

Although their development is complex and progressing slowly, projects are emerging around the world that are beginning to incorporate it as an option that can gradually reduce the need to rely on fuels that are more harmful to the environment.

Pioneers in the
development of hydrogen

Advantages and disadvantages of green hydrogen

This energy source has both pros and cons that we need to be aware of. Let's take a look at some of its most significant advantages:

100% sustainable: green hydrogen emits no polluting gases, either during combustion or during the production process.
Storable: hydrogen is easy to store, allowing it to be used later for other purposes and at times other than when it was produced.
Versatile: hydrogen can be converted into electricity or synthetic fuels and used for commercial, industrial or transport purposes.

Nevertheless, green hydrogen also has some drawbacks that are worth bearing in mind:

Higher cost: energy from renewable sources, which is essential for producing green hydrogen through electrolysis, is more expensive to generate, which in turn makes hydrogen production more costly.
Higher energy consumption: the production of hydrogen in general, and green hydrogen in particular, requires more energy than other fuels.
Safety considerations: hydrogen is a highly volatile and flammable element, so it requires stringent safety measures to prevent leaks and explosions.

Impact of green hydrogen

This emerging technology possesses some of the qualities needed to become a very promising source of clean energy. Below we explain what its future impact will be:

Electricity and drinking water generator

These two elements are obtained by reacting hydrogen and oxygen together in a fuel cell. This process has proved very useful on space missions, for example, by providing crews with water and electricity in a sustainable manner.
Energy storage

Compressed hydrogen tanks are capable of storing energy for long periods of time and are also easier to handle than lithium-ion batteries because they are lighter.
Transport and mobility

Hydrogen's great versatility allows it to be used in those consumption niches that are very difficult to decarbonise, such as heavy transport, aviation and maritime transport. There are already several projects under way in this area, such as Hycarus and Cryoplane, which are promoted by the European Union (EU) and aim to introduce it in passenger aircraft.