Liquid Hydrogen as a Fuel and Hydrogen Economy: Fuel is a substance that burns to produce a considerable amount of energy. Most fuels are carbon compounds like coal and petroleum. They undergo combustion to release carbon dioxide gas, water vapours along with heat and energy that leads to global warming. But with time, these fossil fuels are overused, and before they get finished from the earth, we need to think of another option that would be a renewable source of energy.

A country’s economy is primarily determined by its infrastructure, transportation, and standard of life, and these factors depend upon the energy produced by the country. There is a great disparity between the consumption and the availability of energy at the global level. Presently, all nations are mostly dependent upon fossil fuels for energy production. But with the rapidly increasing global population, it is the need of the hour to upgrade ourselves to an alternative, sustainable energy source that does not adversely affect the environment. In this context, liquid hydrogen is widely taking the place of these fossil fuels. Hydrogen fuel cells are a good alternative to petrol and diesel vehicles.

Electric vehicles are also a good sustainable option, but the major drawback for these electric vehicles is that they soon get discharged due to the limited range and size of the battery. Instead of a battery that drains while it is used for electrical power appliances, internal combustion engines and fuel cells act as a continuous source of operational power if fuel is being provided to them. Hence, it can be inferred that the hydrogen fuel cell can overcome the disadvantages of Battery electric vehicles (BEVs), making hydrogen the future transportation fuel globally.

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What is Liquid Hydrogen?

Hydrogen elements exist in the liquid state known as ‘Liquid hydrogen’. Naturally, hydrogen exists in \({{\rm{H}}_2}\) form. It is cooled below its critical point of \(33\;{\rm{K}}\) to convert it into liquid hydrogen. This liquid hydrogen is used as a sustainable fuel in internal combustion fuel and in fuel cells.

Hydrogen as a Fuel

Hydrogen is a zero-carbon fuel that undergoes combustion with oxygen because it is from any carbon or hydrocarbons. Hydrogen \(\left( {{{\rm{H}}_2}} \right)\) reacts with oxygen \(\left( {{{\rm{O}}_2}} \right)\) to form water \(\left( {{{\rm{H}}_2}{\rm{O}}} \right)\) and releases an enormous amount of energy.

\({\rm{2}}{{\rm{H}}_2} + {{\rm{O}}_2} \to 2{{\rm{H}}_2}{\rm{O}} + {\rm{Energy}}\)

What is a Hydrogen Fuel Cell?

A fuel cell that combines hydrogen and oxygen across an electrochemical cell like that of a battery to produce electricity in the form of energy along with water and heat as the by-products are known as a hydrogen fuel cell. Thus, from the non-toxic by-products produced by this sustainable fuel cell, it can be understood that this is an eco-friendly fuel cell. The amount of energy generated by a Hydrogen fuel cell has the capacity to even run power plants. 

Production of Hydrogen Fuel

Hydrogen fuel can be produced by two common methods:

1. Steam Methane Reforming (SMR) – In this process, hydrogen is produced by heating methane from natural gas with steam, in the presence of a catalyst, to produce a mixture of carbon monoxide and hydrogen, which is widely used in organic synthesis and as a fuel. Obtaining hydrogen from this process has proved to be a viable way to produce it domestically at a low cost.
2. Electrolysis of water – In this method, a water molecule is split in the presence of electricity.

How does a Hydrogen Fuel Cell work?

Hydrogen and oxygen are the primary fuels also used in the hydrogen fuel cell to produce energy. The entire procedure by which a hydrogen fuel cell works can be explained as below:

1. Hydrogen atoms are supplied to the anode, while oxygen is supplied to the cathode.
2. At the anode, hydrogen atoms lose an electron and get separated as protons and electrons.
3. The protons formed to pass through the electrolyte to the cathode, and the negatively charged electrons flow through the circuit to generate electric current.
4. After passing through the entire circuit and the electrolyte, the electrons and protons collide at the cathode, where they react with oxygen to produce heat and water molecules as by-products.
5. Several such fuel cells are arranged into stacks to create enough power as per the requirement because single fuel cells do not generate a large amount of electricity.

Hydrogen Economy

The hydrogen economy is defined as the entire process that would include the production and use of hydrogen as the main fuel for vehicles, energy storage and transfer. In between production and use, any commercial product goes through the following processes: packaging, transportation, storage, and transfer. Similarly, for hydrogen in a “Hydrogen Economy”:

1. It must be packaged by liquefaction and compression.
2. It needs to be transported by vehicles or pipelines.
3. It must be stored in cryogenic containers under high pressure and transferred through various means.

Uses of Hydrogen Fuel

Hydrogen can be used in fuel cells for power generation using a chemical reaction instead of combustion. It produces only water and heat as by-products. Various uses of hydrogen fuel are:

1. Due to its high energy content, it is used as a fuel in applications such as fuel cells and rockets.
2. Many research works are going on to make liquid hydrogen a successful fuel in the development of Fuel Cell Vehicles. 

Advantages of Hydrogen Fuel Cell

1. Unlike batteries, hydrogen fuel cells will not get discharged or need recharging again and again. Rather they continuously produce electricity till the fuel source, i.e., hydrogen is supplied.
2. It is a renewable source of energy that is readily available.
3. Hydrogen fuel produces energy in a clean and efficient manner to support zero-carbon uses strategies.
4. Hydrogen fuel is more powerful and efficient than fossil fuels. It is highly efficient when compared to other sources of energy.
5. It leads to almost zero emission of toxic gases to the environment.
6. It consists of an anode, cathode, and an electrolyte membrane. There are no moving parts in a hydrogen fuel cell, making them silent in operation and highly reliable and efficient.

Summary

In a nutshell, a substance that undergoes combustion to release a huge amount of energy in the form of heat and light is known as a fuel. Some of the fuels that we use in our daily lives are coal, wood, gasoline, diesel, LPG, etc., used for different jobs like running vehicles, cooking food, and many more. Many fuel cells are also used to produce energy instead of fossil fuels. A device that transforms chemical energy into electrical energy by certain chemical reactions going inside it is known as a fuel cell. Among various fuel cells, hydrogen fuel cells are upcoming as a great alternative to fossil fuels. Liquid hydrogen is used as a fuel to produce an immense amount of energy.

A Hydrogen fuel cell is a special and sustainable fuel cell that combines hydrogen and oxygen to produce electrical energy and water and heat as by-products. It should be promoted because of zero-carbon release, which can minimise global warming to a great extent as carbon dioxide release will be stopped into the atmosphere. The main target is to use hydrogen fuel cells to minimise the use of fossil fuels, such as coal and petroleum, and replace them with renewable energy sources. Hydrogen fuel cells provide a huge amount of energy or power and help reduce atmospheric pollution as the by-products are non-toxic gases like water and heat.

FAQs on Liquid Hydrogen as a Fuel and Hydrogen Economy

Q.1. Is liquid hydrogen a good fuel source?
Ans: Liquid hydrogen is a good and useful fuel source because it has a high calorific value, i.e., energy content per unit of weight. This is the reason why it is used as a fuel in rocket fuel and in spacecraft to produce electricity. Though liquid hydrogen is not widely used as fuel now, it has great potential to be used in future aspects.

Q.2. Why can liquid hydrogen be used as a fuel in spacecraft?
Ans: For several decades, liquid hydrogen has been used as a fuel in spacecraft and other space technologies. It is very light in weight, and has a higher density and lowers potential risks in terms of storage pressure when compared with compressed gas. Liquid hydrogen is widely used as a fuel for an internal combustion engine or fuel cell.

Q.3. How does liquid hydrogen work as a fuel?
Ans: In most rocket engines and spacecraft, liquid hydrogen is used as a fuel. It works in the following manner: Firstly, Hydrogen atoms are supplied to the anode, while oxygen is supplied to the cathode. Secondly, at the anode, hydrogen atoms lose an electron and get separated as protons and electrons. The protons formed to pass through the electrolyte to the cathode, and the negatively charged electrons flow through the circuit to generate electric current. Finally, once the electrons pass through the entire circuit and the electrolyte, the electrons and protons meet at the cathode, where they react with oxygen to produce heat and water molecules as by-products.

Q.4. How does hydrogen help the economy?
Ans: The hydrogen economy is defined as the entire process that would include the production and use of hydrogen as the main fuel for vehicles, energy storage and transfer. In between production and use, any commercial product goes through the following processes: packaging, transportation, storage, and transfer. Hydrogen helps the economy as it can be used as a feasible source of power for transportation in small storage tanks by being compressed. The costs of production, distribution and product manufacturing will become cheaper with an increase in the use of hydrogen fuel. One of the major benefits of a hydrogen economy is that hydrogen fuel can replace the fossil fuels used to convert chemical energy into kinetic or electrical energy, eliminating greenhouse gas emissions and pollution from the engine and promoting sustainable development.

Q.5. What are the disadvantages of hydrogen fuel cells?
Ans: There are disadvantages to using hydrogen fuel cells as follows: (i) It is difficult to store hydrogen in cars because it exists in the gaseous state at room temperature and pressure, so it is difficult to store in the car. (ii) Hydrogen fuel cells are less durable than petrol and diesel engines, so they are not very durable. (iii) This is a very expensive fuel cell. While widely available, hydrogen is expensive. (iv) Hydrogen is highly flammable, which is quite risky. (v) Fossil fuels like natural gases are mostly used to produce them.

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