In 1874, Jules Verne published The Mysterious Island and claimed:

"I believe that one day water will be a fuel, that the hydrogen and oxygen that constitute it, used alone or together, will provide an inexhaustible source of energy and light, with an intensity that coal cannot; since coal reserves will be exhausted, we will be heated by water. Water will be the coal of the future.

In the 70s of the last century, with the oil crisis, there was already talk of hydrogenEconomics , and it was seen that it could be profitable compared to traditional fuels. However, this paradigm shift did not take place, and today we continue with an enormous dependence on fossil fuels. In the 1970s, the market alone was not capable of making the change. Now it is clear that a public push is needed to make hydrogen a protagonist in the energy transition. This point has been made clear to the European Union.

A few weeks ago, agreement was announced between the governments of Spain, Portugal and France to build the so-called BarMar, the Barcelona-Marseille gas pipeline. It will first transport natural gas and later hydrogen, when this element has sufficient production and demand. It will take four to five years to build. Does this infrastructure make sense? It is not clear.

For a few years now, the possibilities of hydrogen have been revolutionizing the world of energy. It has in its favor that it is a non-polluting gas, since its combustion emits only water. It has been identified as an actor core topic in the fight against climate change because it perfectly fulfills the new commandment we have imposed on ourselves in Europe: thou shalt not emit CO₂ into the atmosphere.

However, it is not an energy source , and does not exist as such in nature, unlike current fuels such as oil, gas or coal. Producing hydrogen consumes energy, even more than the energy returned by its combustion. Therefore, hydrogen is said to be an energy carrier, the same as electricity: they are ways of transporting, storing and generating energy.

Hydrogen can be obtained in several ways, which are labeled with a color palette:

• Gray hydrogen. This is most of the hydrogen currently produced. It is generated by reacting natural gas with water vapor. It has the disadvantage that CO₂ is emitted into the atmosphere, so it is not valid to comply with this new commandment.

• Blue hydrogen. It is obtained as gray, but capturing the CO₂ produced.

• Green hydrogen or low-emission hydrogen. It is obtained by electrolysis of water, i.e., by breaking down the water molecule with renewable electricity.

Green and blue are the only colors that meet low-emission requirements. There are also other colors in the palette, such as pink hydrogen, produced by electrolysis of water from nuclear energy; or gold, produced from organic waste with CO₂ capture.

Once produced, the hydrogen must be transported to the place where it is consumed. As a matter of principle, the ideal is to locate the production of this gas as close as possible to where it will be used, but this is not always possible.

For short distances, hydrogen is transported in a similar way to butane cylinders: in cylindrical pressurized containers carried on trucks.

For longer distances, it is most efficient to have a network of pipelines, the so-called hydroproducts. deadline In the short term, network can be used to distribute natural gas by injecting some hydrogen into the network gas (so-called blending ). But to transport gas with high concentrations of hydrogen, it is necessary to modify the pipelines.

In addition, hydrogen, because of its leave density, requires a doubling of gas compressor stations, i.e., the distance between compressor stations would be half that of natural gas.

A pipeline such as BarMar, designed to transport hydrogen, could be used to transport natural gas and later replace it with hydrogen.

In a way, a hydrogen pipeline can be said to be similar to an electric cable: they are energy transport infrastructures. In other words, a hydrogen pipeline is a way to export solar and wind energy. This is where the question of whether the BarMar pipeline makes sense: it only makes sense if Spain and Portugal are able to produce enough renewable hydrogen to meet domestic demand and export the surplus through the pipeline.

There are two additional factors that must be taken into account: the increase in hydrogen production implies that it will be necessary to increase electricity production. The existing plants are not enough: more solar plants, more wind turbines and possibly more nuclear power are needed.

Moreover, in order to transport this electrical energy, it will be necessary to install more high-voltage lines. We are well aware of the difficulties of these new installations (solar parks, windmills or power lines) in the form of social rejection - notin my backyard -but we have to face them with a lot of pedagogy.