What is H2?
Hydrogen is the simplest chemical element (made up of only one proton and one electron) and the most abundant in the universe. It is found mainly in the form of hydrogen gas (H2) in stars and gaseous planets, and it also appears together with other elements forming a great variety of chemical compounds, such as water (H2O) and most organic compounds.
Hydrogen gas is, under normal conditions of pressure and temperature, colorless, odorless, non-toxic and flammable, with a boiling point of -252.77ºC and a melting point of -259.13ºC. It can react with oxygen (O2), releasing energy and forming water. This reaction is known as combustion and in it hydrogen is the fuel (1).
There are other combustible materials, such as coal, natural gas, gasoline (oil), which are known as fossil fuels because they come from compounds formed by the activity of living things millions of years ago. All of them can also react with oxygen and produce energy. For example, for methane (natural gas) it would be (2).
Our energy system is based on the use of these fuels. We therefore live in what has been called the ‘fossil fuel society’. Much of the activities carried out by human beings are possible thanks to the energy of these fuels; for example for transport (cars, airplanes, ships), heating of buildings, machine work, in industry, etc.
There are two main reasons why it is desirable to substitute hydrogen for fossil fuels:
— The combustion of hydrogen does not pollute, it only produces as a by-product water (reaction 1), while fossil fuels produce CO2 (reaction 2) that remains in the atmosphere as a pollutant and is one of the main responsible for what is called the “greenhouse effect. “.
— Fossil fuel reserves will sooner or later be depleted, while hydrogen will remain inexhaustible.
However, this substitution is complicated at the present time. In the first place, because, unlike fossil fuels, hydrogen is not found in a free state on our planet, but rather forming compounds such as water or most organic compounds; therefore, it is necessary to develop systems capable of producing it efficiently. On the other hand, it would be necessary to set up new infrastructures for the supply of hydrogen; in other words, a complete network of hydrogen service stations or “hydrogenerators” would have to be built, which implies a heavy investment.
Hydrogen, therefore, is a means of transporting energy, which is why it is called an energy vector. In this way, the hydrogen will be transformed into energy and heat in an efficient and clean way, through a chemical process achieved in equipment called a “fuel cell”.
How is it obtained?
To obtain hydrogen in its pure state, it is necessary to extract it from the compounds in which it is combined, mainly water, fossil fuels and organic matter (biomass).
From water – Electrolysis
Through electrolysis, water breaks down to form hydrogen and oxygen. It is really about carrying out the reverse process of the hydrogen combustion reaction (3).
As can be seen, this reaction requires an energy supply, which will be supplied by electrical energy. The electrolysis mechanism is as follows: in an electrochemical cell there are two electrodes (cathode and anode) joined by a conductive medium formed by H + ions (protons) dissolved in water. The passage of electrical current between cathode and anode causes the water to dissociate, forming hydrogen at the cathode and oxygen at the anode. Later we will see another type of electrochemical cells (“fuel cells”) that act just in reverse, consuming hydrogen and oxygen to produce electricity and water.
From fossil fuels – Grey H2, Blue H2
As mentioned above, fossil fuels are “hydrogen carriers” because they contain it in their molecule. To obtain it as hydrogen gas, it would be enough to make them react with water using a catalyst to facilitate the reaction. This chemical process is called “steam reforming” and requires energy input because it is an endothermic process, in which hydrogen and carbon monoxide (CO) are obtained as main products.
This energy input can be reduced by introducing oxygen (or air) to the reactor at the same time as the water is fed. In this way, the process becomes a slightly exothermic process – it releases heat – which is called ‘autothermal reforming’. In addition to hydrogen and carbon monoxide, carbon dioxide (CO2) can also be formed by combustion with oxygen. The end result is a lower hydrogen production, but it is of interest in some cases due to the lower energy consumption.
In both cases, it is necessary to eliminate the carbon monoxide that has formed in the reforming stage, in order to obtain hydrogen free of impurities. The first purification step is often the so-called “water gas shift reaction”, in which carbon monoxide reacts with water to form carbon dioxide and hydrogen. Depending on the final application in which the hydrogen is going to be used and the level of purity required, a final purification stage will be necessary, for which both chemical (selective oxidation of carbon monoxide) and physical processes can be used. Separation by adsorption, cryogenic methods.
Currently, the largest production of hydrogen on an industrial scale is carried out by reforming from natural gas (blue H2).
To create a mixed technological space for the generation of clean Energy and Hydrogen, where to develop a national supply chain for the production, transport, storage and use of hydrogen, focusing on innovative research, technologies, infrastructures and services. The project will be developed in collaboration with universities, research institutes, associations and companies, with the aim of promoting the energy transition and decarbonization.
“It is a multifunctional and inclusive platform in which we will treat hydrogen at 360 degrees, to accelerate research and innovation and make high-tech infrastructures available to industry to bridge the gap between the laboratory and the industrial scale.”
The project involves the construction of a set of high-tech infrastructures for research and experimentation throughout the entire hydrogen supply chain and its applications in the energy, industry sectors and mobility.
These are just some examples of the potential of a totally transformative energy project for the country and the region, which would give companies the opportunity to produce innovation, experimenting and validating their technologies in a dedicated environment and with the support of qualified personnel and laboratories.
Among the most interesting applications that will be carried out and studied within the Hydrogen Energy Hub, is power-to-gas, a process that, through electrolysis, allows the production of hydrogen from electricity generated from renewable sources, solar energy and water to produce H2.
The hydrogen thus produced is Green and can be converted into e-methane, e-ammonia, enter the internal natural gas network (“blending”) or transform gas-to-power using – totally or partially – 100% green fuel (Synthetic gas).
In this way it is possible to accumulate the energy produced from renewable sources, also perform a function of ‘stabilization’ of the electrical network and act as a connecting element between the different technologies responsible for the Energy Transition, as well as act as a catalyst between the key sectors of this process: Industry, Mobility and Energy, towards the great Global Goal ZeroEmission – FreeCO2.