Hydrogen, especially from renewable sources, is set to be a valuable energy carrier for the decarbonisation of the economy

Hydrogen (H2) is a molecule that functions as an energy carrier, i.e. it is not a primary energy source, but requires a certain amount of energy input to be produced. The potential of hydrogen is that it is able to store energy, which can then be released gradually when needed.

Hydrogen production

The cleanest way to produce hydrogen is by splitting water molecules into their two constituent elements: hydrogen and oxygen. However, for this reaction to take place, energy must be supplied in the form of an electric current, through a chemical process called electrolysis.

Depending on the raw material required and the level of CO2 emissions generated to obtain it, hydrogen is classified into different categories, or colours. Thus, black hydrogen is obtained thanks to the gasification of coal, grey hydrogen is produced from natural gas, and pink hydrogen from nuclear electricity.

Green hydrogen is obtained through the electrolysis of water, using electricity from renewable sources. It is therefore currently the most sustainable way to produce hydrogen.

Uses of hydrogen

Hydrogen, especially from renewable sources, is one of the solutions for the decarbonisation of some sectors of the economy. In particular, it is a valuable energy carrier for energy-intensive industry and high-temperature processes, long-distance heavy transport, and for seasonal energy storage and sectoral integration.

Hydrogen solutions

One of the main interests of this technology is the possibility of using surplus energy from a renewable installation (e.g. solar photovoltaic energy) for the generation and storage of hydrogen. In this way, energy that would otherwise be lost can be stored for a longer period of time than is possible with batteries, and then used in other applications when required.

How it is done

Hydrogen is obtained in equipment called electrolysers, which are fed with water and electricity to trigger the electrolysis reaction and produce H2. This must be pressurised in compressors in order to be stored. This is because, under normal conditions, hydrogen is in a gaseous state with a very low density. This means that it takes up a large amount of space, too much to be useful. For this reason, it is stored in tanks or cylinders as a gas at very high pressure.

To recover the energy from the hydrogen when it is needed, the process of hydrogen production is reversed in a fuel cell, where H2 is re-combined with oxygen to form water and a large part of the energy originally used to produce it is returned in the form of electricity.

Similar to an EV charging station, a hydrogen station is the same concept as a petrol station, but instead of supplying fossil fuels such as petrol or diesel, it supplies hydrogen to hydrogen vehicles (also called fuel cell vehicles or FCEVs).

Hydrogen vehicles are one of the alternatives to the more polluting conventional combustion vehicles. Although there are not yet many models on the market, as electric mobility is advancing mainly on the side of pure electric vehicles, some filling stations are already anticipating the possible future demand for this gas and are installing hydrogen production and storage systems and vehicle supply points.

This is particularly interesting for heavy vehicles such as buses and trucks.

Examples of completed projects