Sources of Energy

The energy of flowing water is utilised to produce electricity on a large scale at hydroelectric power plants. This is another conventional source of energy derived from flowing water. Dams are constructed across the waterfalls to derive electrical energy from it.

Principle
The water flowing in a river is collected by constructing a high rise dam. This stored water is then allowed to fall from the top of the reservoir on to a water turbine located at the bottom of the dam. The fast moving water rotates the blades of the water turbine, which in turn rotates the armature of the generator and produces electricity.

Construction and Working

Water flowing in high altitude rivers is stored in a man-made reservoir as shown in the figure. The kinetic energy of the flowing water is transformed into potential energy as the water level rises. This water is carried through pipes to the turbine situated at the bottom of the dam. The water turbine has cup-shaped discs around its circumference. A jet of moving water rotates the water turbine rapidly which in turn rotates the shaft which is attached to its centre. The other end of the shaft is connected to the coil of an electric generator. The generator coil rotates and produces electricity.

It has been estimated that the total hydroelectric power potential in India is about 4 x 10¹¹ kilowatt-hours but only 11% of this total potential has been utilized so far.

Advantages of Hydroelectricity

• The generation of electricity from water does not produce any environmental pollution
• Water is a renewable source of energy
• The construction of dams on rivers helps in controlling floods and also helps in irrigation
  
  Disadvantages of Hydroelectricity
• A vast variety of flora and fauna as well as human settlements get submerged in the water of the reservoir. Thus, animals and people are rendered homeless
  
  
• It disturbs the ecological balance in the downstream area of the river. As there are no annual floods due to construction of the dam. This downstream region does not get nutrient rich silt and decreases the fertility of the soil and finally the crop yields also decrease
  
  
• The fish in the downstream area do not get sufficient nutrient materials and they die
  
  
• The vegetation which is submerged rots under anaerobic conditions and gives rise to large amounts of methane which is a green- house gas
  
  
• It creates the problem of satisfactory rehabilitation of displaced people