Hydrogen, the first element of the periodic table, is the oldest and most abundant element in the universe. 75% of the mass of the universe is made up of hydrogen. Two hydrogen atoms combine with each other and give rise to gaseous molecules (H2). The gas is colourless and odourless.
Hydrogen can be used as an “energy vector”, thanks to its ability to accumulate energy within itself. Hydrogen can be stored and then transformed as needed into thermal electrical energy for seconds, minutes, weeks or even months as on of the most green, energy source.
This happens in fuel cells. Electricity is generated thanks to the reaction of hydrogen with oxygen in the air. Since the only by-product of this reaction is water, when hydrogen is made using energy from renewable sources, this process has a very low environmental impact.
Hydrogen has been used industrially for a long time, mainly in the production of ammonia, fertilizers and in the processing of petroleum derivatives. Although the potential benefits of hydrogen have been known for decades, several factors have slowed down its adoption: mainly the cost of production, the lack of suitable systems for transportation and distribution and the limitation of commercial markets.
But the global urgency to slow down climate change is calling and leading the world’s largest energy companies to see hydrogen as a cleaner alternative to oil and gas. Additionally, hydrogen can be adopted by properly reconverted, existing production plants and distribution networks. The importance of hydrogen-based energy technologies has been recognized by governments and industry leaders around the world and in countries such as the United States, Germany, France, Italy and the United Kingdom, as well as China, Japan and Korea. In principle, all the countries led by industry have not only understood the role that hydrogen can play in achieving climate goals, but have also begun to support projects that see its use.
Hydrogen does not exist in a free state on our planet. There are no hydrogen fields. It is found associated with other elements, in molecules, such as water (H2O). The reason why we think of hydrogen for decarbonization is precisely because when it is converted to generate energy, “burned” so to speak, it emits water and not CO2.
It can be produced through several processes.
It can be “burned”, reacting with oxygen and producing thermal energy or placed in a fuel cell, where it produces electricity. The first system can be useful for converting vehicles (cars, trucks, trains, ships, planes) that are currently powered by diesel or gasoline, especially those that could not be conveniently powered with batteries (especially trucks, ships, planes).
Despite the fact that molecular hydrogen is colourless, we hear about green, blue, grey and purple hydrogen… The color attributed depends on the way in which the hydrogen is produced.
It is the one made or through the so called “steam reforming”, that is through the reaction of a hydrocarbon (normally methane) and water vapour, or through electrolysis of water using electricity produced from fossil sources. Currently, over 96% of the hydrogen produced is “grey”.
It is also made through the “steam reforming” but the considerable quantity of CO2 inherent to this process is “captured” and stored, normally in depleted hydrocarbon fields( this is called “CCS”: Carbon Capture and Storage), however this is a complex, expensive and inefficient process.
It is the one made by electrolysis using the electricity supplied by nuclear power plants, usually when the demand for electricity is reduced (for example at night) and the power plants in question continue to produce the same amount of energy.
“Green” Hydrogen is made – usually by electrolysis of water – using electricity produced from renewable sources (wind, photovoltaic …). This method has the lowest environmental impact which is given by the energy incorporated in the components of the production process and by that of the renewable sources. Today about 4-5% of hydrogen is produced in this way, however, in light of the progressive reduction of the cost of solar and wind energy and of electrolyzers, this production method can prove to be a game-changer for the energy transition”, explains Marco Alverà, CEO of SNAM.
IT is highly adaptable and CAN BE USED TO SATISFY THE DEMAND FOR ENERGY IN DIFFERENT SECTORS all the while helping to REDUCE CARBON EMISSIONS.
The benefits can be summarized as follows:
The energy is produced from renewable sources, leading to the storage and distribution of clean energy.
High investments in new distribution infrastructures may be avoided by using existing infrastructures (for example natural gas pipelines) that can be properly adapted for transmission and distribution.
A large storage capacity is currently available, which is necessary to decouple fluctuating energy production from energy consumption.
Enables the reduction of carbon emissions in various sectors, such as transport, industrial production or buildings.
HOW IS IT TRANSPORTED?
Hydrogen is suitable for transport in existing gas pipelines and can be a more efficient and economical mean than batteries for storing electricity. It can favour decarbonization in various industrial sectors, in particular those where electrification is difficult to apply, such as heavy transport. “It has a lower transport cost than electricity”, explains SNAM, the Italian methan gas network main player, whose gas transmission networks are compatible with the transport of liquid or pressurized hydrogen.
Today, the transportation of pure hydrogen takes place through “hydrogen pipelines”, which are a few kilometres long. Generally, hydrogen is mixed with methane gas. When it reaches its destination it can be used as a fuel mixture (in some cases it can improve the efficiency of engines or turbines) or it can be separated. To separate large quantities of hydrogen, however, new technologies are needed, which are under development.
Hydrogen can also be transported in the gaseous state by tank wagons or as a cryogenic liquid, for long distances and in large quantities. “Recently LOHC (Liquid Organic Hydrogen Carriers) have been proposed, organic compounds capable of transporting hydrogen at low costs”, explains Marcello Baricco, professor of Metallurgy and Chemical Plants at the University of Turin and a member of the scientific committee of FCH JU and H2IT and coordinator of the HyCARE project.
The simplest and cheapest storage method is in the form of compressed gas in cylinders. In automotive applications, very high pressures are used (up to 700 atmospheres) for smaller tanks. Tanks made with composite materials can be up to three to four times lighter in weight. The hydrogen stored in liquid form is less voluminous, in suitable tanks, but must be kept at -253°C, with a great expenditure of energy.
Other technologies exploit the ability of hydrogen to bind to chemical compounds or metal alloys (hydrides) to allow their accumulation. Also, the phenomenon of hydrogen absorption in highly porous structures, such as MOFs (Metallic Organic Framework), can be exploited and in this context. Also carbon nanotubes and nano fibres are being developed.
Hydrogen is a fundamental resource, which allows for a substantial reduction of the environmental impact in energy production and distribution.
However, to achieve this goal, the obstacles regarding hydrogen storage, transport and distribution must be overcome.
Perhaps the biggest challenge in using hydrogen energy is that this gas has an extremely low density: 3.2 times lower than that of natural gas and 2,700 times lower than that of gasoline. Hydrogen must therefore be compressed or liquefied to be economically competitive compared to other forms of energy.
Thus, achieving this goal presents a number of technical challenges and difficulties:
The key here is all about lowering the cost of hydrogen production. There is open competition between the different technologies for electrolyzers while there is a big margin for cost reduction, in particular thanks to process industrialization and market scale up. Combined with the present supporting policies of industrialized countries, these aspects leads us to hope that by 2030 the hydrogen market will begin to replace an increasingly growing part of the fossil fuel based energy system.