The overall efficiency of a steam power station is approximately 33 to 48%. There are two major reasons behind this low efficiency.
- Heat is lost in condenser when converted into mechanical energy
- Heat losses at various stages of the plant
Thermal efficiency of Steam Power Plant
It is defined as the ratio of corresponding heat of mechanical energy conveyed to the turbine shaft to the heat of combustion of coal. Mathematically thermal efficient is defined as:
Thermal efficiency = Corresponding heat of mechanical energy conveyed to the turbine shaft/Heat of combustion of coal
The overall efficiency of Steam Power Plant
It is defined as the ratio of heat equivalent of electrical output to the heat of combustion of coal is termed as overall efficiency of steam power station.
Overall efficiency = Heat equivalent of electrical output/Heat of combustion of coal
Relationship between Thermal efficiency, Overall efficiency and Electrical Efficient of Steam Power Station
Overall efficiency = Thermal efficiency × Electrical efficiency
Efficiency can also be defined as the energy produced by the plant divided by the heating value of the fuel consumed by it.