Correct Answer - Option 2 :
\(\frac{{heat\;equivalent\;of\;electrical\;output}}{{heat\;of\;combustion\;of\;coal}}\)
The efficiency of Steam Power Station:
- The overall efficiency of a steam power station is low (about 29%) due mainly given reasons.
- Firstly, a huge amount of heat is lost in the condenser.
- Secondly, heat losses occur at various Stages of the plant.
- We cannot avoid the heat lost in the condenser. It is because heat energy cannot be converted into mechanical energy without temperature difference.
- The greater the temperature difference, the greater is the heat energy converted into mechanical energy.
- Therefore we have to keep the steam in the condenser at the lowest temperature. But the greater temperature difference causes a greater amount of heat lost.
\(Thermal\;Efficiency = \frac{{Heat\;equivalent\;of\;mechanical\;energy\;transmitted\;to\;turbine\;shaft}}{{Heat\;of\;combustion\;of\;coal}}\)
Thermal Efficiency: The ratio of heat equivalent of mechanical energy transmitted to the turbine shaft to the heat of combustion of coal is known as thermal efficiency of the steam power station.
The thermal efficiency of a modern steam power station is about 30%.
Overall efficiency: The ratio of heat equivalent of electrical output to the heat of combustion of coal is known as the overall efficiency of the steam power station.
\(Overall\;Efficiency = \frac{{Heat\;equivalent\;of\;electrical\;output}}{{Heat\;of\;combustion\;of\;coal}} \)
The overall efficiency of the Thermal Power Plant is about 29% because there is an approximation of 1% loss in the Alternator.
