Sources of Energy

Synopsis

Sources of Energy

• According to the law of conservation of energy, the energy can neither be created nor be destroyed it can just transform from one form to another, whereas the amount of work done will be directly proportional to the amount of energy it contains.
• By applying the principle of conservation of energy we can do work by converting one form of energy to another.
  Example: In a hydroelectric power plant when water is dropped from some height, the gravitational energy is used to rotate the turbine. i.e., Gravitational potential energy is used to do mechanical work, as a result, we get electric energy
  Gravitational potential energy ⇒ Mechanical energy ⇒ Electric energy.
• Because of this, it is very important to study and explore these sources of energy which can provide an adequate amount of energy over a long time.

An Important Characteristic of Energy Sources.

It's very important to understand the characteristics of different energy sources to select the correct source of fuel according to our requirement, based on this following are the important characteristics of good energy sources.

1. Safety and convenience: a good fuel source must be safe and easy to use also it can be safely transported without any risk.
   Example: Petrol & coal are easy to use, unlike nuclear fuel.
2. Cost-effective: A fuel has to be cost-effective to make it viable for all and can be used in our day-to-day life.
3. Accessibility: An energy source must last longer at any time of day so that it can be accessed for many years without any need to search for a new source of energy.
   Example: Because of the limited amount of fossil fuel we are shifting slowly towards renewable sources of energy like solar, wind, etc. 
4. Total energy output: The cost-effectiveness of a fuel source also depends on the total output energy provided per unit volume of mass.
   Example: A energy per unit weight of nuclear fuel is 16000 times when compared with coal. 

A good energy source must have all the following characteristics and it can be summarised as

Also, all the sources of energy can be classified as 

Conventional or Non-conventional Sources of Energy: 

• Based on the method of energy production, the energy sources can be classified as a conventional source of energy or a non-conventional source of energy, 
• As we can see below generally all non-conventional sources of energy are renewable sources of energy (except nuclear energy since nuclear fuel is limited on earth and cannot be reproduced).
• In India, the major source of energy is conventional sources, and among those fossil fuels contribute the most but are gradually reducing our dependence on fossil fuels and moving towards renewable sources of energy.
  
  

 

Non-renewable or renewable Sources of Energy: 

• Based on the availability of energy sources or fuel we can classify all energy sources as renewable sources (inexhaustible sources of energy) and non-renewable sources of energy (exhaustible sources of energy).

 

And the examples for each of the following renewable and non-renewable sources of energy are as shown below:

 

 

 

Sources and Methods of Energy Production

Hydropower Plant

• Water at a height has potential energy stored in it. When this water stored in a reservoir is dropped from a height, its potential energy is converted to kinetic energy which is utilized to generate electricity.
• Thus, these plants are built around dams so that water from a high level in the dam is carried through pipes, to the turbine at the bottom of the dam and used for the production of electric energy.
  
  
  

 

The advantage and disadvantages of such hydroelectric power projects are:

 

 

Thermal Power Plant

• In thermal power plants, we use fossil fuels like coal to produce heat energy which converts water into steam, and this high-pressure steam is passed through a turbine to converted heat energy into electrical energy.
• Such a power plant is easy to construct and maintain as a result many countries still use this method for the production of electricity.
• These types of power plants are the major contributor to air pollution and heavily rely on the continuous supply of fossil fuels.

 

Geothermal Power Plant

• Just like a thermal power plant, a geothermal power plant also uses hot water for the production of electricity. 
• But unlike thermal power plants, the water is heated because of magma which is trapped between the surface of the earth (such area of earth’s crust is also known as hot spots).
• Such places are also known as geysers or hot spring and electricity produced from these sources are known as geothermal energy.
• These type of power plants are very cost-effective and easy to construct, whereas it can only be constructed near hot spring hence not much county uses this type of power supply because of less availability of such hot spots.

 

Nuclear Power Plant

• Nuclear fission is a process in which, a nucleus of a heavy atom splits into lighter nuclei when bombarded with a low-energy neutron.
  
  
• This process releases a large amount of energy due to mass defects which can be predicted by the famous mass-energy relation given by Albert Einstein.
  
  
• Just like the thermal power plant, the nuclear power plant produces electricity with the help of nuclear fuel through a self-sustaining fission chain reaction that releases energy at a controlled rate.
• This energy is used to heat water and generate electricity by passing the steam through the turbine.
• The fission of one uranium atom releases approximately 10 times the energy released by the combustion of one atom of carbon in coal.
• The major disadvantage of nuclear power is the storage and disposal of used fuel since it is very dangerous for us and our ecosystem and takes huge time for decay. 
• Hence improper storage and disposal of the nuclear waste result are considered environmental contamination.
• Also, nuclear radiation can leak from the reactors in case of emergencies like the Chernobyl disaster that occurred on 26th April, 1986 in Ukrainian because of a design flaw, Fukushima Daiichi nuclear disaster occurred on 11th March, 2011 in Japan due to earthquake and tsunami.

 

Bioenergy

• Bioenergy is one of the easiest, renewable, and most cost-effective ways of fulling the rising demand for energy by converting biomass into biofuel such as biogas, ethanol, methanol, biodiesel, etc.
• Biomass: it is defined as the parts of plants and the waste material of animals that can be used to produce heat or electricity.
• Wood or cow dunk is the simplest example of biomass which is used for the production of heat although the amount of heat produced from such source is very less compared to coal, it also produces lots of smoke and is considered harmful for daily use.
• Biogas plants are used to obtain biogas when cow dung and various plant materials such as sewage, vegetable waste, and residue of crops after harvesting are decomposed by anaerobic micro-organisms in the absence of oxygen. 
• In India biogas is also known as the Gobar gas plant, and from such plants, we get gases like CH₄, CO₂, H₂, H₂O these gases are known as biogas, and among these approximately 75 percent are methane gas.

The components and working of the biogas plant are as shown below:

 

Solar Energy

• Sun is the most ancient and powerful source of energy. It has been radiating energy for the past 5 billion years and will continue to do so for the next 5 billion years or so. India receives approximately 5000 trillion kWh of energy per year.
• An enormous amount of energy produced is produced in the interior of the sun by fusing hydrogen and helium into heavier nuclei. Such a nuclear reaction is known as a fission reaction.
• Whereas energy travels from the sun to earth in a form of electromagnetic radiation and among those radiation one third is infrared radiation which is majorly responsible for heating the earth’s atmosphere.
• Any device that gets heated by solar energy is called a solar heating device.
• Solar cooker: A device that helps in collecting as much solar energy as possible by using a black-painted surface, a glass sheet cover, and a reflector is termed a solar cooker.

 

 The below figure shows the simple representation of the solar cooker.

 

 

• Solar water heater: Based on a similar principle a device that is used to heat water by utilizing the energy radiated by the sun is known as the solar water heater. 
• Solar power plant: Solar power plants are used to produce electricity by converting solar energy into electrical energy. 
• Solar cells: it is a device used to convert solar energy directly into electrical energy using photoelectric effect. The solar cells are made of thin wafer of semiconductor elements such as Silicon and Germanium.
  A typical solar cell develops about 0.5 V and can produce about 0.7 W of power when exposed to the Sun.
  A large number of cells can be connected to form a solar panel.

 

Wind Energy

• The motion of air is known as wind and this motion is because of convection and air currents.
• This motion of wind has kinetic energy also known as wind energy which is harnessed using a device known as windmills, it is used to produce electricity from wind energy. 
• A windmill is a simple machine with a structure similar to a large fan erected at some height. It uses the motion of wind for its rotation and the rotatory motion of the windmill is utilized to run the turbine of an electric generator.
• Throughout our history windmills are used to draw water from the ground, river, or to run a flour mill to grind grain.

 

The below image shows the advantages and disadvantages of wind power plants.

 

 

 

Energy from Sea or Ocean

The oceans act as a storehouse of solar heat energy because they cover almost 71% of the earth’s surface. The following ways are used to generate energy from the sea.

 

Tidal Energy

• Due to the gravitational pull of the moon by the spinning earth, the level of water in the sea rises and falls. This phenomenon is called high and low tides, and the difference in sea levels gives us tidal energy. 
• Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. A turbine fixed at the opening of the dam converts tidal energy to electricity.

Ocean Wave Energy (OWE)

• The kinetic energy possessed by huge waves near the seashore can be trapped by a dam to generate electricity.
• The waves are generated by strong winds blowing across the sea. Wave energy would be an efficient source of energy only where waves are very strong.

Ocean Thermal Energy (OTE)

• The Sun heats the water at the surface of seas or oceans. However, the water deep under the ocean is much colder.
• This temperature difference provides energy through ocean thermal energy conversion plants.
• These plants can operate when the temperature difference between the water at the surface and water at depths of 2 km is 20 K (20°C) or more.
• In these plants, warm surface water is used to boil volatile liquid like ammonia. The vapors evolved from the liquid are used to run the turbine of the generator.
• The vapors are condensed by the cold water and pumped up from the depth of the ocean which can be reused again.