Fuel is an important source of energy. We use fuel in our daily life for different activities like petrol and diesel for driving vehicles, LPG for cooking, crude oil to fly an aeroplane, coal, and wood for burning that provides fire and warmth in the form of energy. All fuels burn to produce energy, but every fuel does not burn efficiently. For example, we can calculate the fuel efficiency of a vehicle by calculating the distance travelled by it with reference to the amount of fuel consumed by the vehicle to travel that distance.

The fuel efficiency of a vehicle is calculated in terms of kilometres/litre. Fuel efficiency is calculated based on its calorific value. This calorific value is defined as the amount of energy produced when complete combustion of \(1\,{\rm{kg}}\) fuel takes place. The calorific value of LPG is higher than that of wood so, LPG is considered a more efficient fuel than wood.

What is a Fuel?

Fuel is a substance that mainly consists of carbon which on combustion releases a considerable amount of thermal energy. Fuels produce a huge amount of energy that is used for different domestic as well as industrial purposes.

We all know that energy can never be created nor be destroyed. Rather, energy is transformed from one form to another. For example, a fuel like gasoline undergoes combustion in a car engine to convert its chemical energy to thermal energy. This thermal energy gets converted to mechanical energy that propels the car (kinetic energy). There are numerous types of fuels like coal, petrol, diesel, wood, etc., but we cannot use them anywhere we want. For example, we cannot use the combustion of wood to run a vehicle. Thus, there is a proper use of every fuel. The use of fuels is chosen based on the efficiency with which they work. Let’s learn about fuel efficiency in detail.

Fuel Efficiency Definition

Fuel efficiency is defined as the ability of a vehicle or any other device to extract energy from the fuel being used. In other words, we can say that fuel efficiency is the measure of how efficiently a fuel converts one form of energy to another. As we mention the word ‘measure,’ it means that combustion energy has some unit! This is measured in terms of ‘calorific value.’

Calorific Value

The amount of energy liberated or produced when complete combustion of \(1\,{\rm{kg}}\) fuel takes place is known as calorific value. It is measured in kilojoule/kilogram \(\left( {{\rm{kJ}}/{\rm{kg}}} \right).\) Fuel efficiency can be determined based on this calorific value. Like if two fuels of equal quantities are burnt, the one having a high calorific value will be considered as a more efficient fuel than the one having low calorific value.

Characteristics of an Efficient Fuel

1. Fuel Economy – It is the distance travelled per unit volume of fuel used in a vehicle. The farther a vehicle runs on a measured volume of fuel, the better is its fuel economy. It also depends on the engine performance. Better engines will make the combustion of fuel more efficient.
2. An efficient fuel should be environmentally friendly. This means it should not produce harmful gases as side products while burning.
3. A good fuel should have minimum ignition temperature, i.e., it should catch fire easily without wasting much energy.

Fuel Cell

A fuel cell is an electrochemical device that converts chemical energy into electricity through a chemical reaction between a source fuel and an oxidant. The source fuel could be any oxidant, including Hydrogen, methane, propane, diesel, or petrol.

A fuel cell consists of three adjacent segments: the anode, the electrolyte, and the cathode. At the interface of the three different segments, two chemical reactions (oxidation and reduction) take place. At the end of these two reactions, fuel is consumed, water or carbon dioxide is formed, and an electric current is created that is used to run electrical devices.

Fuel Cell Efficiency

A fuel cell has proved to be a more efficient conventional source of energy. For example, a conventional combustion-based power plant can generate \(33\% – 35\% \) electricity efficiently. On the other hand, fuel cell-based power plants generate around \(60\% \) efficient electricity.

Hydrogen Fuel Cell

A Hydrogen fuel cell is a special type of fuel cell that combines Hydrogen and oxygen to produce electricity along with water and heat as the by-products. Thus, it is an eco-friendly source of energy as the by-products are harmless. The energy generated by a Hydrogen fuel cell is in a huge amount that can even run power plants.

Working of a Hydrogen Fuel Cell

Hydrogen is the primary fuel in the hydrogen fuel cell. Oxygen is also used in this fuel cell to produce energy. The process by which a hydrogen fuel cell works can be explained as below:

1. Hydrogen atoms enter the anode, while oxygen is supplied to the cathode.
2. The hydrogen atoms lose an electron and get separated as protons and electrons at the anode.
3. The newly formed positively charged protons(hydronium ions) pass through the electrolyte to the cathode, and the negatively charged electrons flow through the circuit to generate electricity.
4. After passing through the circuit and the electrolyte accordingly, the electrons and protons meet at the cathode, where they combine with oxygen to produce heat and water as by-products.
5. These fuel cells are arranged into stacks to create enough power as the single fuel cells do not generate a large amount of electricity, as per the requirement.

Advantages of Fuel Cells

1. Though fuel cells work like batteries, unlike batteries, they will not get discharged or need recharging. Rather they can continue to produce electricity till the fuel source (For example, hydrogen in the case of hydrogen fuel cells) is supplied.
2. It is made up of an anode, cathode, and electrolyte membrane. There are no moving parts in a fuel cell, making them silent in operation and highly reliable and efficient.

The Efficiency of Fuel Cell Formula

The thermodynamic efficiency or the maximum efficiency of a fuel cell can be calculated using this equation:
\({\eta _{\max }} = \frac{{\Delta {\rm{G}}}}{{\Delta {\rm{H}}}} \times 100\)
Where \({\Delta {\rm{G}}}\) is the change in Gibbs Energy and \({\Delta {\rm{H}}}\) is the change in enthalpy.

Corporate Average Fuel Efficiency / Economy (CAFE)

The Corporate Average Fuel Cell Efficiency / Economy standards were implemented by the U.S. government to regulate the distance a vehicle must run by using a gallon of fuel. In order to reduce the use of fossil fuels and promote the use of renewable sources of energy, for example, electric vehicles, certain rules and regulations are implemented by the Indian Government. CAFE regulations in India came into effect on April \(1, 2017.\)

Certain Norms of CAFE are:

1. CAFE (Corporate Average Fuel Efficiency/Economy) norms aim at improving fuel efficiency or lowering the fuel consumption of vehicles.
2. It is mainly achieved by lowering carbon dioxide emissions by vehicles.
3. Thus, it serves the dual purposes of reducing dependence on crude oil for fuel, which is a non-renewable source of energy, and controlling pollution.
4. Corporate Average is the sales-volume weighted average for every automobile manufacturer. These norms are relevant for petrol, diesel, LPG, and CNG passenger vehicles.
5. Under this, average corporate carbon dioxide gas emission must be less than \(130\,{\rm{gm}}\,{\rm{per}}\,{\rm{km}}\) till \(2022\) and below \(113\,{\rm{gm}}\,{\rm{per}}\,{\rm{km}}\) after that.
6. In other words, cars should be \(10\% \) or more fuel-efficient between \(2017\) and \(2021\) and \(30\% \) or more fuel-efficient from \(2022\) in terms of carbon dioxide emission.

Summary

In short, fuel is a substance that undergoes combustion to release a huge amount of energy in heat and light. Coal, wood, gasoline, diesel, LPG, etc., are some examples of fuels that we use in our daily lives, like running vehicles, cooking food, and many more. The use of these fuels is based on their efficiency. Fuel efficiency is the ability of a fuel to extract the maximum amount of energy from a given fuel which is measured in terms of calorific value. Nowadays, fuel cells are used to produce energy more efficiently.

A fuel cell is a device that converts chemical energy into electrical energy by certain chemical reactions going inside it. A Hydrogen fuel cell is a special type of fuel cell that combines Hydrogen and oxygen to produce electric energy along with water and heat as the by-products. The Government has formed various laws to regularize fuel consumption in recent years. The main target is to minimize the use of fossil fuels like coal and petroleum and replace them with renewable sources of energy. One of the best examples of this is electric vehicles. Efficient fuel cells not only provide a good amount of energy or power but also help to reduce pollution as the by-products are non-toxic gases.

FAQs on Fuel Efficiency

Q.1. What is fuel efficiency?
Ans: Fuel efficiency is defined as the ability of a vehicle or any other device to extract energy from the fuel being used. This is measured in terms of ‘calorific value’.

Q.2. What do you understand about fuel efficiency?
Ans: Fuel efficiency is measured as the attempt or work done by a fuel to convert chemical energy to mechanical energy, followed by kinetic energy. Such as diesel, when it is used as a fuel to run vehicles, the distance it can travel in each volume of fuel will give an idea about the efficiency of the fuel.

Q.3. How to test fuel efficiency?
Ans: To test fuel efficiency, we can take two different fuels in the same quantity and burn them. The one that releases more energy will be more efficient than the one that releases a lesser amount of energy calculated in its calorific value.

Q.4. How efficient are hydrogen fuel cells?
Ans: A hydrogen fuel cell is more efficient than other fuels. Like, a conventional combustion-based power plant can generate \(33\% – 35\% \) electricity efficiently. On the other hand, hydrogen fuel cell-based power plants generate around \(60\% \) efficient electricity. It combines hydrogen and oxygen to produce electricity along with water and heat as the by-products.

Q.5. How to calculate fuel efficiency?
Ans: The fuel efficiency can be calculated using this equation: \({\eta _{\max }} = \frac{{\Delta {\rm{G}}}}{{\Delta {\rm{H}}}} \times 100.\) Where \({\Delta {\rm{G}}}\) is the change in Gibbs Energy and \({\Delta {\rm{H}}}\) is the change in enthalpy.

Q.6. Why is natural gas an efficient fuel?
Ans: Natural gas is an efficient fuel as it produces maximum electricity as compared to coal. Also, it does not release harmful greenhouse gases on combustion. Transportation of natural gas is also easy as it can be transported through pipelines.

Study Structure Of Cell Here

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