Correct Answer - Option 2 : 32.3%
Concept:
The overall efficiency of the power plant is given as
\(Overall\;Efficiency\;\; = \frac{{Electrical\;energy\;output}}{{chemical\;energy\;input}}\)
Overall efficiency is also expressed as
\({\eta _0} = \;\frac{{Thermal\;Energy}}{{Chemical\;Energy}} × \frac{{Mechanical\;Energy}}{{Thermal\;Energy}} × \frac{{Electrical\;Energy}}{{Mechanical\;energy}}\)
So, the overall efficiency of the power plant is equal to the multiplication of the efficiencies of the boiler, turbine, and generator.
Overall Efficiency = Boiler efficiency × turbine efficiency × generator efficiency
ηpower plant = ηboiler × ηturbine × ηgenerator
Where,
Boiler efficiency = Thermal efficiency
Turbine efficiency × Generator efficiency = Electrical efficiency
∴ Overall Efficiency = Thermal efficiency × Electrical efficiency
Calculation:
Given that, Boiler efficiency = 85%
Turbine efficiency = 40%
Alternator efficiency = 95%
Overall efficiency = 0.85 × 0.4 × 0.95 = 0.323 = 32.3%
