In the planet’s new energy landscape, electricity is likely to play the leading role. But it has a major flaw: storing and transporting it is difficult, expensive and polluting.
New ways of storing electricity are therefore emerging, such as converting it into hydrogen...
Hydrogen is the most abundant chemical element in the universe. It is in the molecular form H2 (dihydrogen), which it takes in a gaseous state, that this element is exploitable from an energy point of view.
H2 is not found in its natural state on Earth. There is therefore no source or 'sink' for hydrogen. To obtain hydrogen, it has to be manufactured.
Hydrogen is nothing new. This gas was used to inflate Zeppelins in the 1920s. Today it is widely used in the chemical and petrochemical industry.
|Belgium has 613 km of underground hydrogen pipelines, the longest network in Europe. It passes through Antwerp, Zeebrugge, Ghent, Brussels and Charleroi, among others. And this network is connected with those of our neighbouring countries.|
If hydrogen is the focus of all the debate today, it’s because it is the ultimate decarbonated gas: it contains no carbon at all, and its combustion generates only water, therefore no pollutants
As a fuel, hydrogen can:
Today we differentiate between:
Currently, hydrogen is 95% manufactured from non-renewable, fossil-based natural gas. Hydrogen can also be produced with electricity, by electrolysis. This is a process that separates water into its two components: oxygen and hydrogen.
If the electricity used is not from renewable sources, the hydrogen produced is not renewable either. And its manufacture therefore indirectly releases CO2. For example, in the gas or coal-fired power plant that was used to make electricity for electrolysis.
|Blue hydrogen is produced in the same way but this time with CO2 recapture stored in empty gas fields.|
If hydrogen is made from green, renewable energy, hydrogen does not pollute during its manufacture. And we already know that it never pollutes when consumed.
Hydrogen offers a very promising answer to the big issue of renewable energy sources (solar, wind, hydroelectric): they are intermittent, variable and unpredictable. But the amount of energy available is far greater than anything we can consume.
It would therefore 'suffice' to:
|In short, hydrogen is not an energy source, it is an energy carrier, like a battery or a reservoir.|
Simply mix the hydrogen with natural gas from the distribution network and it can be used in regular equipment. At about 6% hydrogen, no changes need to be made to the network or equipment. With adaptations, we could go as high as 20%.
Hydrogen thus allows a bridge to be created between the electricity and gas networks. It allows you to switch from one form of energy to another. Above all, it provides a response to the problems of intermittent renewable energy sources.
Many projects are being developed around the world, and the European Union is actively supporting research in this area.
We are still a long way from seeing more hydrogen filling stations in our country. It’s even hard to buy a hydrogen-powered car and they’re very expensive. But in Germany, a country of car manufacturers, some 60 stations are already in operation.
The technique for producing hydrogen with electricity has been known for more than 200 years. But there’s a big difference between a successful lab experiment and profitable economic use.
Storing hydrogen is difficult: its atom is so small that it passes through metal tanks. In addition, it makes the metal brittle.
Moreover, hydrogen is so light that it has to be stored under enormous pressure to build up a large enough stock. Or it has to be liquefied at -253 °C. Pressurising or liquefying requires energy – so there is additional energy consumption at this level.
When hydrogen is produced with electricity, or vice versa, the process results in significant losses: the original amount of electricity is not recovered after the two operations.
|More than half of it is actually lost: 25% in electrolysis and around 50% in the fuel cell, at least with existing technologies.|
This loss will only be acceptable when very large quantities of renewable electricity are available at very low cost. Or when we’ve managed to cut those losses.
Hydrogen can ignite in a very wide range of mixtures with air (between 4 and 75%), which is not the case with natural gas, for example: natural gas only burns in a mixture with air between 5 and 14%).
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