A certain form of energy which is not sourced directly or indirectly from the sun and does not cause any pollution is very easily converted into electricity. This form of energy is however, not available everywhere. Moreover, it is technically very difficult and expensive to obtain it. Name the form of energy.

Since the given source of energy is not sourced directly or indirectly from the sun, chances of solar energy are eliminated.

Since the energy is pollution free and at the same time technically difficult and also costly which implies that the energy is tidal energy.

Tidal energy is not available everywhere and also the initial cost for tidal energy is very high as compared to other forms of energy. Tidal energy is difficult to construct and it is also pollution free.