Power plant engineering is a branch of engineering which deals with conversion of various forms of energy into electrical energy. In this text we will discuss about thermal power, hydroelectric power, nuclear power, and non-conventional sources of energy. In thermal power plant, coal, diesel, petrol, natural gas, and kerosene oil are used as fuel and chemical energy of these fuels is converted into mechanical energy and then mechanical energy into electrical energy. In hydroelectric power plant the potential energy of water is converted into mechanical energy as shaft power and then mechanical energy into electrical energy. Similarly, in the case of nuclear energy, nuclear power is used to generate the heat required to produce superheated steam and then the heat energy is converted into mechanical energy and the mechanical energy is converted into electrical energy.
3.3.1 Thermal Power Plant
Thermal power plant may be coal based or gas based. In coal-based power plant, coal is used as burning fuel and the heat energy is transferred to water to convert it into superheated steam. The heat energy of the steam is converted into shaft power through expansion of steam in steam turbine. The shaft of steam turbine is coupled with generator where electricity is generated. The exhaust steam from steam turbine is condensed into condenser using cooling water. Condenser works just like a heat exchanger where heat energy of steam is transferred to cooling water and steam is condensed in the form of water which is then pumped into boiler. The cooling water is re-circulated through cooling tower to release the heat. A self-explanatory diagram is shown in Figure 3.1. The detail working of boilers and steam turbines is discussed in , respectively.
Figure 3.1 A Block Diagram of Steam Power Plant
In gas-based power plant or gas power plant, air is compressed to high pressure and heat energy is added to compressed air using combustion chamber by direct burning of fuel in compressed air or indirect heat transfer to compressed air. The high pressure and high temperature air is expanded in gas turbine which is coupled with generator generating electricity due to shaft rotation. The exhaust gas from turbine is released into atmosphere in the case of open cycle gas turbine and re-circulated to the compressor in the case of closed cycle gas turbine. The self-explanatory diagram of gas power plant is shown in Figure 3.2. The detail discussion about gas turbine and compressor is given in Chapters 5 and 10, respectively.
Figure 3.2 A Block Diagram of Gas Power Plant
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