(i) (a) It is not available at all times.
(b) It requires a very large area of land.
(c) it is not possible to have a windmill everywhere as to run it, the minimum wind speed of 15 km/hr is required (only possible in open areas like the seaside).
(ii) (a) Wave energy would be a viable proposition only where waves are very strong.
(b) It is costly to set up devices to trap wave energy.
(iii) (a) Very few sea coasts in the world have suitable sites for the purpose of harnessing tidal energy.
(b) The rise and tall of tides happen only twice in a day and is not suffcient to generate electricity coutinuously.
