Hydroelectric and Wind Energy

Question 1 What is meant by non-conventional source of energy? Give few examples?

Question 2 What is hydroelectricity? Explain the principle of generation of hydroelectricity with the help of a diagram?

Question 3 State few advantages of producing hydroelectricity?

Question 4 State few disadvantages of producing hydroelectricity?

Question 5 What type of energy is possessed by wind?

Question 6 How wind energy can be used to generate electricity?

Question 7 State few advantages of using wind energy for generating electricity?

Question 8 State few limitation of wind energy for generating electricity?

Question 9 How was the traditional use of energy of flowing water been modified for our convenience?

Non-Conventional Sources of Energy

Those sources of energy which are not based on the burning of fossil fuels or the splitting of atoms of nuclear fuels, are called alternative sources of energy (or non-conventional sources of energy).

The examples of alternative sources of energy are : Hydroelectric energy, Wind energy, Solar energy, Biomass energy, Energy from the sea (Tidal energy, Sea-wave energy, Ocean thermal energy), and Geothermal energy.

 

The scientists have started showing renewed interest in exploring and using the alternative sources of energy due to two reasons because

(1) the fossil fuels and nuclear fuels in the earth are limited which may not last for long, and (2) because of the undesirable effects of pollution both from the burning of fossil fuels and from the radioactive nuclear wastes of nuclear power plants.

Hydroelectric energy

Flowing water possesses kinetic energy. The energy of flowing water is used for rotating the water-wheels and drive water-mills to grind wheat to make flour. The traditional use of energy of flowing water has been modified by improvements in technology and used to generate electricity.

At hydro-power plants, the energy of falling water is trapped by using a water turbine and then made to drive generator.

Hydro-Power Plant (or Hydroelectric Power Plant)

A power plant that produces electricity by using flowing water to rotate a turbine (which drives the generator), is called hydro-power plant (or hydroelectric power plant).

The electricity produced by using the energy of falling water (or flowing water) is called hydroelectricity.

Working of Hydro Power Plant

To produce electricity, a high-rise dam is built to stop the flowing river water. Due to this, a large lake or reservoir builds up behind the dam. As more and more water collects in the reservoir, the level of water behind the dam rises to a large height. In this way, the kinetic energy of the flowing river water is converted into the potential energy of water stored behind the dam. Thus, the water stored behind a tall dam has a lot of potential energy (due to its great height).

 

The sluice gates (sliding gates) at half the height of dam are opened to allow some of the stored water to escape. This water is taken through pipe to the turbine installed at the bottom of the dam. Since the water falls down through a large height from the dam, it flows very fast (its potential energy is changed into kinetic energy). A high pressure jet of fast flowing water pushes on the blades of turbine with a great force and makes the turbine rotate rapidly. The turbine is connected to generator through its shaft. When the turbine rotates, its shaft also rotates and drives the generator. The generator produces electricity.

When the hydroelectric generator works and produces electricity, water flows out of the dam continuously and the level of water in the reservoir falls slowly. The reservoir is filled up again by the rain water brought in by the rivers. Hydroelectric power is a renewable source of energy. It will never get exhausted.

A hydro-power plant converts the potential energy of water stored in the reservoir of a tall dam into electric energy.

Advantages of Generating Hydroelectricity

(1) The generation of electricity from flowing water does not produce any environmental pollution.

(2) Flowing water is a renewable source of electric energy which will never get exhausted.

(3)The construction of dams on rivers helps in controlling floods, and in irrigation.

Disadvantages of Generating Hydroelectricity

(1) Large areas of agricultural land, a vast variety of flora and fauna (plants and animals) as well as human settlements (or villages) get submerged in the water of reservoir formed by the dam. Due to this many plants and trees are destroyed, animals get killed and many people are rendered homeless.

(2) Large eco-systems are destroyed when land is submerged under the water of reservoir of a dam. The construction of dam on a river also disturbs the ecological balance in the downstream area of the river. Due to the construction of dam there are no annual floods in the river. And because of this the soil of downstream region does not get nutrient-rich silt. This decreases the fertility of soil in the downstream area and finally the crop yields also decrease.

 

(3) Due to the construction of dam on the river, the fish in the downstream area do not get sufficient nutrient materials due to which the production of fish decreases rapidly.

(4) The vegetation which is submerged under water at the dam site rots under anaerobic conditions and produces a large amount of methane which is a greenhouse gas.

The energy of flowing water is called hydro energy. The energy of flowing water is in fact an indirect source of solar energy. This is because it is the solar energy which recirculates water in nature in the form of water-cycle. It is this water which then flows in the rivers and makes water available to us.

Wind Energy

Moving air is called wind. The energy possessed by wind is due to its high speed (or motion). The wind possesses kinetic energy. Solar energy (or sun’s energy) is responsible for the blowing of wind. Wind blows due to the uneven heating of earth by the sun in different regions. 

The energy of wind is harnessed by using a windmill. A windmill consists of big sized, table fan like blades which are fixed over the top of a tall pole in such a way that they are free to rotate. When the fast moving wind strikes on the blades of windmill it makes them rotate continuously. The rotatory motion of the windmill is then used to do mechanical work through a shaft connected to the rotating blades.

Wind energy was used through windmills to pump water (or lift water) from a well and to grind wheat into flour. When the blades of windmill rotate by the force of wind, a shaft connected to them also rotates. This rotating shaft was made to run a water pump to lift water from a well by a suitable mechanism. It could also turn the mill-stones of a flour mill.

Wind Generator

 

The windmill used for generating electricity is called a wind turbine, and the complete set-up of generating electricity by using wind energy is called wind generator.

When the fast moving wind strikes the blades of wind turbine, then the wind turbine starts rotating continuously. The shaft of wind turbine is connected to a small generator. When the wind turbine rotates, its shaft also rotates and drives the generator. The generator produces electricity.In order to generate a large amount of electricity , a large number of wind turbines are erected over a big area of land. Such a set-up of having a large number of wind turbines working at a place to generate electrical energy on a large scale is called a wind energy farm. The small electricity generated by each wind generator is combined together to obtain electricity on a large scale.

Advantage of using wind energy for generating electricity

(1) Its use does not cause any pollution.

(2) Wind energy is a renewable source of energy which will never get exhausted. As long as the sun keeps shining, the wind will keep blowing and provide us energy.

(3) Wind energy is available free of cost.

Limitations of harnessing wind energy for generating electricity

(1) Wind energy farms cannot be established everywhere. The wind energy farms can be established only at those places where wind blows for most part of the year

(2) The wind required for generating electricity should be strong and steady to maintain the desired level of generation.

(3) The wind energy farms require a large area of land.

(4) The setting up of wind energy farms is very expensive.