Hydro - Electric Power Plant

• Hydro - electric power plant utilize the potential energy of water to move hydraulic turbines which are coupled to electric generators. Therefore, these plants have to be located where the water resources are available in abundance at sufficient head.
• The first hydro power plant was set up in 1897 at Darjeeling of 200KW capacity and the first major hydro-power plant was commissioned in 1902 of 4.5MW capicity of Sivasamudram scheme in Mysore. 
• A large amount of water is collected during rainy season in a reservoir will not be able to meet the maximum load, therefore, the present trend is to use hydro-electric power plant with steam power plant in an interconnected system. 

The main components of the hydro-electric power plant and their function are as follows:

1. (Reservoir) : A reservoir is provided to store water during rainy season and supplies the same    in dry season. The water from the reservoir is used to run hydraulic turbine.
2. (Dam) : A dam is structure of considerable height built across the river. Its function is to provide working head of water for power plant and to increase the storage-capacity of reservoir.
3. (Trash rack) : These are made up of steel bars. Trash rack is provided to prevent entry of debris into the intakes from dam or from the forebay. Any debris into the intake water pipe may damage the turbine runners or choke the nozzles of an impulse turbine.
4. (Gate) : The gate is provide for controlling of flow of water from reservoir to hydraulic turbine through penstock. It is closed when maintenance of system is required.
5. (Waterway and Penstock) : A waterway is used to carry water from the dam to the power house. It include canal and penstock or a tunnel. The penstock are made up of steel of reinforced concrete which are designed to withstand high pressures. penstock are supported by Anchors. Sharp bends in penstock are avoided in order to reduce hydraulic losses.
6. (Power house) : A power house consists of hydraulic and electric equipment's where the water energy is converted into electrical energy. usually the power house is located underground whenever possible e.g as in case of Koyana power house in Maharashtra stare.
7. (Hydraulic turbines) : These are used to convert the kinetic energy of water into mechanical energy.
8. (Spillway) : A spillway is provided to discharge the flood water and to keep the level of water below the disigned maximum level in the reservoir. Thus a spillway saves the dam from damage during floo

                                                                                                                                                               

                                          

Classification of Steam Turbines

1. According to principle of action of steam :                                                                                     (A)  Impulse     (B)  Reaction
2. According to direction of steam flow :                                                                                           (A)  Axial     (B)  Radial     (C)  Tangential   
3. According to number of pressure stages :                                                                                       (A) Single stages with one or more velocity stages.                                                                       (B) Multistage
4. According to method of governing :                                                                                               (A)  Throttle     (B)  Nozzle     (C)  By-pass                                                                                   (D)  Combination of Throttle-bypass or Nozzle-bypass
5. According to heat drop process :                                                                                                     (A)  Non-condensing     (B)  Condensing     (C)  Regeneration
6. According to steam conditions at inlet :                                                                                         (A)  Low pressure up to 2 bar                                                                                                         (B)  High pressures above 50 bar                                                                                                     (C)  Medium pressure up to 50 bar                                                                                                 (D)  Super critical pressure above 225 bar 
7. According to their usage :                                                                                                               (A)  Stationary with constant speed                                                                                                 (B)  Stationary with variable speed                                                                                                 (C)  Non-stationary used in steamers, ships, railways locomotive etc.

Steam Power Plant

• Generally, a Thermal power plant is one which is used to produce electrical power on a large scale. Usually, the steam power plant are used in which the chemical energy of a fuel is utilized to generate high pressure, high temperature steam in a boiler.
• This steam is used in a turbine to produce mechanical power which is finally converted into electrical energy by a alternator.                                                                                                                                                                                                                                                                
   
• In a steam power plant, various heat recovery systems like air preheat-er, economizer are used to improve the thermal efficiency of the steam power plant.                                                                                                                                                                                                                     Various components of a steam power plant with their function                                                                                                                                                                                                      (1) Blower : The function of the blower is to draw the surrounding air needed for combustion of fuel. The air drawn by  blower is supplied to air preheat-er.                                                        (2) Air preheat-er: It is a heat transfer device in which the air drawn from surrounding is heated with the help of hot flue gases before discharging to atmosphere through the chimney. The heated air is supplied to the furnace. It improves the combustion efficiency of the fuel.        (3) Furnace: Heated air from air preheat-er is supplied to the furnace where fuel is burnt. The products of combustion of fuel and air are called flue gases.                                                          (4) Economizer : The feed water before supplied tot he boiler tubes is heated with the help of flue gases. It reduce the energy needed for formation of steam.                                                      (5) Boiler : It consists of boiler shell, water, tubes and super heater. Feed water supplied from the economizer is first converted into wet steam in water tubes and then into super heated steam in the super heater due to the heat supplied by the hot flue gases. Steam is generated at high pressure in the boiler.                                                                                                                 (6) Steam Turbine and Generator : High pressure, super heated steam of the boiler expands in the produces the mechanical work. This work is utilized to drive a generator which convert the mechanical energy into electrical energy.                                                                                  (7) Condenser and condensate extraction pump: Steam from steam turbine is exhausted to the condenser where the steam is condensed by rejecting heat to circulated cooling water.The condensed steam is called the condensate which is drawn with the help of condensate extraction pump and supplied to hot-well.                                                                                       (8) Feed pump: The condensate collected in the hot well with make up water is fed back with the help of feed pump at boiler pressure to the economizer.                                                           (9) Cooling tower: Cooling water from cooling is circulated into the condenser and absorbs heat from the exhaust steam of the stem turbine. The resultant heated water from condenser is supplied at the top of cooling tower.                                                                                                (10) Condenser water circulating pump: This pump circulates the cooling water from the cooling tower to the condenser and the heated water from the condenser back to the cooling tower.