Why is there a need for harnessing non-conventional sources of energy? How can energy be harnessed from the sea in different ways?

(N/A) The need for harnessing non-conventional sources of energy arises because:
$1$. Fossil fuels are finite and are depleting rapidly due to high consumption.
$2$. The global population is increasing, leading to a higher demand for energy.
$3$. There is a need to improve the quality of life and reduce environmental pollution caused by burning fossil fuels.
Energy can be harnessed from the sea in the following ways:
$1$. Tidal Energy: This is harnessed by constructing dams across a narrow opening to the sea. The rise and fall of sea levels during high and low tides rotate turbines to generate electricity.
$2$. Wave Energy: This is harnessed by trapping the kinetic energy of waves near the seashore to rotate turbines or drive other mechanisms.
$3$. Ocean Thermal Energy Conversion $(OTEC)$: This utilizes the temperature difference between the warmer surface waters of the ocean and the colder deep waters to operate heat engines and generate electricity.