Fuel Efficiency: Definition, Properties, Factors, Applications and Sample Questions

Fuel Efficiency is the efficiency of fuel with which the energy is transformed from one form to another form. Whenever someone buys a new vehicle like a car or bike the first thing that a person enquires about is its mileage. We can calculate how far any vehicle could travel by consuming one litre of petrol or diesel based on its Fuel Efficiency. 

Fuel

According to the law of the conservation of energy, energy can neither be created nor be destroyed. It can only convert from one form to another form. Any substance that is burned to produce heat and release energy is known as fuel. When the fuel is burnt, the energy stored in it is converted into another form. There are different types of fuel. It can be in any state i.e. solid, liquid or gaseous. The table below has few examples of different types of fuels.

The video below explains this:

Fuel Efficiency Detailed Video Explanation:

Properties of an Ideal Fuel

• A good fuel is inexpensive, readily available, transportable, and flammable.
• It has a high calorific value.
• It does not emit any polluting gases or residues into the environment.
• It should be easy to store and transportable.
• It should burn easily in the air at a moderate rate.

 

Fuel Efficiency Definition

Whenever a fuel undergoes combustion, it converts the energy stored in it in the form of chemical energy to kinetic energy. This energy is used to perform any task. The efficiency with which a fuel converts energy is referred to as fuel efficiency.

Fuel efficiency is measured in kilometers per litre.

The amount of heat produced by different types of fuels varies. The calorific value of a fuel is used to measure and express the amount of heat it produces. The higher the calorific value, the more heat it will produce on burning, and vice versa. 

So, in other words, the quantity of energy released per unit mass of the fuel can be characterized as fuel efficiency.

Mentioned below are the calorific values of different types of fuels in KJ/Kg.

Factors Affecting Fuel Efficiency

Many factors affect fuel efficiency negatively or positively. Some of them are:

• Type of vehicle or engine performance- The cost and efficiency of fuel are determined by the performance of the engine. For Example; bikes are more fuel-efficient than cars. 
• Weather- Cold weather can reduce fuel efficiency significantly. The car engine takes a long time to warm up in cold weather. If the engine is cold, it will take a longer time to start and if the weather is cold, the process even takes more time to start. 
• Maintainance of the vehicle or device - When the maintenance of the vehicle is neglected, all of the systems, including those directly related to fuel efficiency, run less efficiently. For example; a blocked air filter might have an impact on engine performance and as a result, more fuel is consumed.
• Calorific value- Higher the calorific value more efficient a fuel will be. For example- Hydrogen is a more efficient fuel than cow dung as it has a higher calorific value.

Applications of Fuel efficiency

Here are some of the applications of fuel efficiency-

• Fuel efficiency provides significant environmental benefits.
• Fuel-efficient driving tactics consume less fuel and emit fewer greenhouse gas (GHG) emissions.
• It helps in reducing the cost of travel.
• It helps in reducing the loss of energy.

Things to Remember based on Fuel Efficiency

• Energy can neither be created nor be destroyed. It can only transform from one form to another. 
• The efficiency with which a fuel converts energy is called fuel efficiency.
• The efficiency of each fuel varies depending on the equipment. 
• Fuel efficiency is also determined by the energy efficiency of a specific device. 
• In villages, a variety of fuels are used for heating and cooking, including coal, wood, cow dung, etc. These fuels are inefficient and release greenhouse gases that contribute to global warming.

Important Questions based on Fuel Efficiency 

Ques.1: What are the characteristics of a good fuel? (All India 2015, 1 Mark) 

Ans: The characteristics of good fuel are- 

1. It should have a high calorific value.
2. It should be non-polluting.
3. It should be easy to transport and easily available.
4. It should have a moderate ignition temperature.

Ques.2: State any three reasons to justify that LPG is considered as an ideal fuel. (All India 2014, 3 Marks)

Ans: LPG is considered an ideal fuel because

1.  It is easy to store and transport.
2.  It produces a large amount of heat on burning.
3.  No residue is left on burning.

Ques.3: (a) How does the construction of dams across the river get linked with the production of greenhouse gases?

(b) How do technological inputs improve the efficiency of biomass fuels? (All India 2012, 2 Marks)

Ans: (a) A vast variety of plants get submerged in water, rot under anaerobic conditions and produce large amounts of greenhouse gases such as methane.

(b) Traditional uses of biomass fuels are not only efficient but also produce a lot of pollutants that are hazardous to health. Therefore, technological inputs are necessary to improve the efficiency of these fuels and make them environment-friendly. With the help of technology, smokeless chulhas and biogas plants have been designed.

Ques.4: (a) Charcoal is a better fuel than wood. Why?

(b) How does the biogas plant help to reduce the problem of pollution? (All India 2011, 3 Marks)

Ans: (a) Charcoal is considered to be a better fuel than wood because:

1. It has a higher calorific value which means it can generate heat more efficiently than wood.
2. It burns without flames.
3. It is comparatively smokeless.

(b) Biogas plant helps to reduce the problem of pollution in the following ways.

1. It provides better sanitation due to the safe disposal of bio-waste and sewage material.
2. Biogas obtained from the biogas plant produces less smoke on burning. 
3. The residue left can be used as manure.