INTRODUCTION
The potential for hydrogen uses in industry and energetics is significant. Even though, for a long time, it was overlooked. However, one of its disadvantages is that it can mostly be found only in chemical compounds in nature as it is a highly reactive gas, and it must be derived from water or methane.
The advantages outweigh the disadvantages significantly, which is why its use is becoming more common. Hydrogen can store energy effectively for an extended period without considerable energetic losses. It is one of the important differences from batteries which can store electric energy only for days. For that reason, hydrogen is considered the right direction for storing energy gained from renewable resources, which offer unstable electricity production.
There are many benefits of hydrogen. It is the most common element in the universe, the third most common element on Earth, and it can be found in many substances. An unlimited amount of hydrogen is in water, it is also the basic element of organic matter, and most importantly, it is a part of all used hydrocarbon fuels. Hydrogen has a high energy density (for one unit of mass) and can be transported and stored. When used as a fuel, the advantage is zero-emission combustion. Suppose it is used to produce energy in engines with inner combustion or fuel cells. In that case, it emits heat, electric power, or mechanical power and an unharmful byproduct – water, leaving out CO2 and other waste substances, which are a common part of burning any hydrocarbon fuels in any form. Carbon is the main part of greenhouse gases, and Hydrogen energy should reduce its production. The prevailing problem is nitrogen oxide emitted inside of the hydrogen engine. Its amount depends on the oxygen surplus, temperature, pressure, and the time when the flue gases are kept in the combustion engine at high temperatures.[1]
Colours of Hydrogen
Hydrogen is resourced in different ways; therefore, it is divided into groups labelled by different colours.
Brown and Grey Hydrogen
One means of hydrogen production is resourcing them from fossil fuels (brown) and natural gas (grey).
Hydrogen is generated as a byproduct of different industrial processes. The most common hydrogen generation is by "steam-reforming", meaning the source is heated with water at a high temperature. Grey hydrogen is the most produced one nowadays. However, steam-reforming is dependent on fossil fuels, and a large amount of CO2 is generated during this process; therefore, it is not considered for future hydrogen production.
Blue Hydrogen
Grey and Brown hydrogen can be improved by capturing produced CO2 using Carbon Capture and Storage (CCS) technology and Carbon Capture and Use (CCU) technology. This way, so-called blue hydrogen is produced. Total CO2 production in this process is lower even though the source is natural gas or methane, as significant part of the emissions is captured.
Pink Hydrogen
Pink hydrogen is produced by nuclear energy and is low emission. Sometimes, it is labelled ad purple or yellow. The labelling is still undecided.
Green Hydrogen
The primary purpose of hydrogen technology is to cut the dependency on fossil fuels and produce “Green hydrogen”. This type of hydrogen is produced during an electrolysis process when water molecule is split into two atoms of hydrogen and one atom of oxygen using electricity. When the source of energy for this process comes from renewable resources, it is considered "green" and therefore "green hydrogen".
Hydrogen has the significant potential to decarbonize the use of energy. To fulfil its potential, there are a few barriers we have to overcome, mostly associated with storage, transportation and distribution. [2]
[2] Plyn budoucnosti. Jak daleko je Česko na cestě k jeho využití? - Ekolist.cz. Ekolist.cz: životní prostředí, příroda, ekologie, klima, biodiverzita, energetika, krajina, doprava i cestování [online]. Available at: https://ekolist.cz/cz/zpravodajstvi/zpravy/vodik-v-cesku.jak-daleko-jsme-na-ceste-k-vyuziti-plynu-budoucnosti
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