A large coal-fired power station produces 2000 MW of electrical energy. A wind turbine with 33 m blades can produce 300 kW.
(a) How many turbines would be needed to replace the power station?
(b) Why, in actual practice, this number of turbines could not replace the coal-fired power station?

(a) Electrical energy from the power station = 2000 MW = 2000000 kW (converted mega watt into kilowatt)

      Energy produced by the wind turbine  with 33 m = 300 kW

      So, number of turbines needed = $\frac {2000000}{300}$ = 6666.67

      Hence, 6667 turbines will be needed to replace the power station.

  

(b) In actual practice, this no. of wind turbines could not replace the coal-fired power plant because the efficiency of a wind turbine depends on the speed of the wind, which may vary from time to time, whereas the efficiency of steam turbines used in coal-fired power stations remains the same.