The forms of energy that can be obtained from the ocean are tidal energy, wave energy, and ocean thermal energy. There are several limitations in order to harness these energies.
- Tidal energy depends on the relative positioning of the Earth, moon, and the Sun.
- High dams are required to be built to convert tidal energy into electricity.
- Very strong waves are required to obtain electricity from wave energy.
- To harness ocean thermal energy efficiently, the difference in the temperature of surface water (hot) and the water at depth (cold) must be 20ºC or more.