What are the limitations of extracting enegry from :
(a) the wind
(b) waves
( c) tides ?

Explanation

Limitations of extracting energy from various sources are following:
(a) Wind energy is harnessed by windmills. A windmill requires wind of speed more than 15 km/h to generate electricity from wind energy. Also, large numbers of windmills are required to get feasible output which covers a large area.
(b) Very strong ocean waves are required in order to extract energy from waves. But these are not available all the time.
(c) Very high tides are required in order to extract energy from tides. Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. But tides depend on the relative positions of the Sun, the Moon and the Earth.