Answer:
Answer depends upon the conditions like type, quality and class of turbines but majorly it lies in between 30% to 40%. But if we choose from the given options we can not select a single option but range from 25% to 50% which is explained below.
Explanation:
Turbines have different types. Turbines converts Thermal Energy to Mechanical Energy. Then this energy is converted to Electrical Energy. Both of these steps has losses in them.
<u>The first step:</u>
Turbines, which converts Thermal Energy to Mechanical Energy has following types and efficiencies:
- Gas Turbines = 35% to 40%
- Steam Turbines = 36% to 42%
which means average efficiency of the step is 35% to 42%.
<u>Second Step:</u>
It is the generation portion which converts Mechanical to Electrical. Usually these generators are of greater efficiencies ranging from 88% to 97%.
So,
Overall the efficiency range we have is:
Minimum = 0.35x88 = 30.8%
Maximum = 0.42x97= 40.74%
Hence energy efficiency of the turbines widely depends upon the quality, type and specifications of the turbines and their associated generators. But usually it ranges in between 30.8% to 40.74%
Exceptional Case
Exhaust gases from turbines can be used in other applications too, for example to generate steam or heating effects, which can improve overall efficiency up to some extent. Furthermore if an economizer is installed with this waste heat boilers, efficiency can be improved further more but, again, it doesn't exceed from 45% to 50% practically.
