M5 Production of hydrogen and safety
Topic outline
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Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Education and Culture Executive Agency (EACEA). Neither the European Union nor EACEA can be held responsible for them.
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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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Objectives
- To name primary characteristics of hydrogen and its isotopes;
- To recognize hydrogen colours and to compare its means of acquisition;
- To define the temperature at which hydrogen becomes liquid.
Keywords
Hydrogen, hydrogen colours, hydrogen isotopes, critical temperature
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- Define hydrogen as a chemical element, its chemical symbol and its protonic number.
- How many isotopes are there in hydrogen, and what are they called?
- At what temperature does hydrogen become liquid?
- In what year has Henry Cavendish discovered hydrogen
- Which French chemist named hydrogen?
- What colours are used to label hydrogen, and which are acquired from fossil fuels?
- Describe the process during which green hydrogen is made.
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Objectives
- To define hydrogen as an energy vector;
- To recognize the differences between steam reformation and partial oxidation technologies for acquiring hydrogen to describe the process of acquiring hydrogen from refinery gas
- To name other technologies for acquiring hydrogen from refinery gas
Keywords
Energy vector, steam reformation, partial oxidation, cryogenic separation, absorption, diffusion, plasma reforming.
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- Explain the concept of hydrogen as an energy vector.
- From which substances is hydrogen acquired during the steam reformation?
- What chemical substances form in substance transformation during a steam reformation?
- During partial oxidation, in what temperatures and pressure does hydrogen form?
- Is a steam reformation of partial oxidation more convenient for hydrogen production?
- What are the three primary processes used to produce hydrogen from refinery gas?
- Name three other possibilities to produce hydrogen from fossil fuels.
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Objectives
- To define the principle of water electrolysis;
- To describe the difference between alkaline water electrolysis, high-temperature electrolysis and thermochemical water splitting;
- To name other alternative technologies of hydrogen production;
- To explain the principle of hydrogen production using biotechnological processes.
Keywords
Water electrolysis, high-temperature electrolysis, Westinghouse sulphur cycle, solar-powered hydrogen powerplant, pee power, biomass, photolysis, fermentation, dark fermentation
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- Describe the main principles of water electrolysis.
- What chemical substance is used as an electrolyte during alkaline water electrolysis?
- What chemical substance is used as an electrolyte during polymer membrane water electrolysis?
- What are the operating temperatures during high-temperature electrolysis?
- What energy is used during thermochemical water splitting?
- What is the Westinghouse sulphuric cycle?
- Where is the use of solar-powered hydrogen powerplants most common?
- Explain the term Pee Power.
- Name and explain the most known technologies used to produce hydrogen from biomass.
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Objectives
- To explain the principles of fuel cells;
- to divide cells by their operating temperatures;
- to define cells by the electrolyte type;
- to name other components of a vehicle with fuel cells.
Keywords
Fuel cell, electrolyte.
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- What chemical reactions take place in a fuel cell?
- What voltage value is generated by fuel cells?
- What temperatures are high-temperature fuel cells operating?
- What chemical substance forms the electrolyte of alkaline fuel cells?
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Objectives
- To define safety guidelines when handling hydrogen and its biological effects;
- To explain the differences between hydrogen storage in liquid form and as a gas;
- to explain the principles of storing hydrogen as a hydride;
- to explain the terms absorption and adsorption.
Keywords
Hydrogen storage, cryogenic chambers, hydrides, absorption, adsorption
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- What chemical substances can cause combustion when mixed with hydrogen?
- Describe the states in which hydrogen can be stored.
- Explain the term hydrogen storage in the form of hydrides.
- What is absorption?
- What is adsorption?
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Hydrogen as an energy source is an important current topic. It is referred to as the fuel of the 21st century. Hydrogen production is a crucial process coming from various resources. Currently, 48% of hydrogen is produced from natural gas, 30% from oil, 18 % from coal, and 4% from electrolysis. It is evident that fossil fuels dominate hydrogen production, and only a small fraction is produced by electrolysis. Thermochemical, biochemical, and photochemical production processes are still at the beginning and without industry use. In the automotive industry, only hydrogen produced by alternative methods makes sense as fossil fuels can be used as a fuel directly. That is the main reason to search for alternatives.
Water electrolysis recently cannot challenge traditional methods due to its high energy demand. Its use is suitable for countries with an abundancy of water and inexpensive electricity. Island is such country, sourcing its energy from geothermal springs. Another interesting method for hydrogen production is generators of the fourth generation. A heated cooling medium has a high enough temperature to conduct chemical cycles or high-temperature electrolysis. The most relevant method that could challenge fossil fuels in near future is hydrogen production using biomass. Biomass belongs to promising renewable sources of energy. Except for hydrogen production, it also holds large-scale energy use. The remaining issue of hydrogen use lies in its storage. Storage capacity needs to be improved for the global spread of hydrogen use due to its high weight and large volume. The cost of hydrogen still over-exceeds the cost of fossil fuels. The energetic efficiency (high energetic demand on compression, liquifying or reprocessing of chemical compounds) is another aspect needing to be increased.
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