Hydro-electric power plants use dam to retain water in a natural or artificial lake or sometimes a watercourse, and divert the same to a turbine that generates mechanical energy. This is attached to an alternator for generating electricity (Czisch 2011).
Hydropower plants are costly to install but cost-effective to operate. The key advantage of hydroelectric power is the ability to store energy and the flexibility of its use during peak load periods (Planning Commission, 2002).
Types of hydro power plants (Czisch 2011):
Run-of-river hydropower plants utilize the inflow directly for electricity supply without significant storage capacity. In some cases changes in water level can be utilized for storage purposes to a limited degree. This operating mode is referred to as hydropeaking.
Impoundment hydropower plants collect the inflow in reservoirs with capacities that, in many cases, are large enough for generating at full load for several months. Inflow and generation can thus largely be decoupled. The storage hydropower plants only use part of the water impounded immediately.
Pumped storage hydropower plants have no significant inflow but have a reservoir that is filled from a lower reservoir using pumps. The potential energy of the water stored at the higher level is used for electricity supply, usually to cover peak demand.
India is endowed with economically viable hydro potential. The Central Electricity Authority (CEA) has assessed India's hydro potential to be about 148,700 MW of installed capacity (Planning Commission, 2002). The total installed capacity of large hydro-electric power plants in India is 48,038 MW, including 4935 MW of pumped storage hydropower plants as on March, 2018. Naptha Jhakri Hydro Power Plant over Sutlej River in Himachal Pradesh is the largest hydro-electric power plant in India with an installed capacity of 1,500 MW. Illustration 1 shows the very high resolution satellite image of Tehri Dam in Uttarakhand with 1000 MW Hydro Power Plant. Illustration 2 shows Pong Dam in Himachal Pradesh with 396 MW Installed Capacity Hydro Power Plant.
The hydro-power plants smaller than 25 MW Installed Capacity are called Small Hydro Power Plants. The total installed capacity of small hydropower plants in India is around 4000 MW as on March, 2018.
Illustration 1: Tehri Dam, Uttarakhand
Illustration 2: Pong Dam, Himachal Pradesh
Czisch, G., 2011, Scenarios for a Future Electricity Supply, The Institution of Engineering and Technology, London, United Kingdom.
Planning Commission, 2002, Tenth Five Year Plan 2002-07, Government of India, New Delhi.