Cogeneration
- Co-generation means the sequential conversion of energy of fuel into two or more forms.
- With regard to thermal power plants, the co-generation can be defined as the simultaneous generation and utilization of both power and heat.
- In a conventional power plant, the efficiency of power generation is about 35% and the remainder of 65% energy is lost as heat.
- By utilizing the lost heat energy in various applications, in a co-generation system, we can improve upon the overall efficiency of the system.
Topping and bottoming cycles in cogeneration :
- In inplant co-generation system can use either the topping cycle or bottoming cycle.
- In a topping cycle co-generation, plant generates electrical or mechanical power first followed by the heat recovery boiler to create low pressure process steam or to drive a secondary steam turbine alternately the exhaust of gas turbine and diesel power plant is used to provide low pressure process steam.
- In a bottoming cycle co-generation plant, heat energy is used first and the waste heat energy is used in a boiler to generate process steam.
- Such systems are used only in heavy industries where very high temperature furnaces are used e.g. in iron and steel industry. Such cycles are not commonly used.