How to produce green hydrogen? | Science and Technology News (Amazings® / NCYT®)

Hydrogen has gained attention as a clean energy source, but how is green hydrogen made? As the world moves towards greater environmental awareness, more attention has been paid to use of renewable energy. This is where our protagonist comes into play.

Hydrogen is a powerful fuel because it is a very unstable element, which tends to combine with almost any element in nature.. Thus, chemical reactions are generated that emit a large amount of heat in most cases. However, as Antonie Lavoisier’s famous dictum indicates: “Energy is neither created nor destroyed, it is only transformed”, to get hydrogen we need to provide a lot of energy.

Types of hydrogen according to its origin

To date, hydrogen was produced for industrial processes, such as hydrotreating and the production of fertilizers, and for chemical processes. However, it was done using methods that generated a large amount of polluting emissionsmainly CO².

✓ gray hydrogen

gray hydrogen is obtained through the use of fossil fuels, among them natural gas is the most used. Large amounts of CO emissions are produced² to the atmosphere. However, it is currently the cheapest form of hydrogen product, which is why it is the most widely used.

✓ blue hydrogen

blue hydrogen it is obtained in the same way with the use of fossil energy. However, during production CO capture and storage techniques are used². This makes the hydrogen produced less polluting than gray. Although it is not possible to eliminate all toxic emissions, only reduce them.

✓ green hydrogen

Green hydrogen is obtained through procedures with zero emissions. The production process is carried out mainly through the electrolysis of water. In order to perform electrolysis electricity generated from renewable sources is injected, such as photovoltaic and the wind. For this reason it is the cleanest and most sustainable hydrogen.

Logically, green hydrogen is the ideal to accompany the rest of renewable energies in a new energy model. Nevertheless, its production cost is still high and the technology is not perfectly implemented.

New studies and new techniques

Interest in hydrogen is growing as problems with lithium batteries for storage surface. And it is that, to manufacture solar batteries, a great deterioration is generated to our planet, in addition to political disputes. This is one of the reasons why electromobility is receiving a lot of criticism and the number of people who do not support it is increasing.

That is why many companies and organizations continue to investigate improving and making the way of producing green hydrogen cheaper. An example of this is the polymer membrane for electrolytes and the simulation and control methods of green hydrogen manufacturing processes.

Green hydrogen production process

The basic process for the generation of renewable hydrogen is based on the electrolysis of water. To do this, a device is needed in which water is injected and a sufficient electric current is applied to break the water molecule. In this way it is possible to separate its elements, that is, hydrogen and oxygen.

This process must be carried out in an electrochemical cell formed by a cathode and an anode, with a proton exchange membrane, where the membrane, made of a special polymer, is between the anode and the cathode. this membranecalled PEM for its acronym in English, acts as a filter for the physical separation of particles that have been broken from the water molecule.

Thus, each basic element of the electrolytic cell has an important function:

➕ Anode

The anode is the positive pole that helps the circulation of electric current. Thanks to it, water is catalytically oxidized into Protons (H⁺), Oxygen (O₂) and Electrons (e-). Usually this anode is made with Iridium/Ruthenium.

⍈ PEM – Proton Exchange Membrane

As the name suggests, only H⁺ protons can pass through to reach the cathode. Unfortunately, a small amount of water is also entrained, overcoming the physical barrier of the polymer membrane. This happens by the so-called Electro-Osmotic Drag.

⚡ Electricity

The electricity necessary to carry out the process is provided by wind or solar photovoltaic power plants. These are usually installed in the vicinity of the green hydrogen plant, so that they provide the electrical current necessary to move the electrons from the Anode to the Cathode.

➖ Cathode

Protons and electrons combine at the cathode to produce hydrogen molecules. The cathode is usually made of platinum/palladium.

separators

At the outlet of the PEM electrolyser it has been possible to obtain hydrogen on the cathode side and oxygen on the anode side. However, at both sites the water that has not been broken into its components has been dragged. That is why the mixtures of water and hydrogen, and water with oxygen must be passed through separators.

It is there that the water separates from the Oxygen and Hydrogen flows. The recovered water is cooled and redirected back to the PEM Electrolyser, along with a new supply of water to complete the appropriate amount to be processed.

Renewable Hydrogen Uses

There is a lot of talk about hydrogen fuel cell vehicles, there have even been tests with hydrogen trains in Germany. Domestic boilers for heating that run on hydrogen have also been developed. Nevertheless, domestic use of hydrogen is not yet possible.

First, because the production of green hydrogen is currently very limited. In order to reach the domestic level, much more infrastructure would have to be created to generate that hydrogen.

There is the second drawback, and that is that if what we want is to use renewable hydrogen, instead of gray or blue, we need to generate a lot of electricity from renewable sources. But, if we already have that electricity, why not use it directly in our homes? For example, using heat pumps for air conditioning and obtain sanitary hot water, in lighting and other electrical appliances.

The third drawback would be the distribution of hydrogen. For this, the adaptation of the gas pipeline network and the distribution within the cities with the pipe network already installed have been considered. However, that takes time and should be progressive and somewhat expensive.