Question

ocean thermal energy

Answer 1

Ocean Thermal Energy Conversion (OTEC) is a process that can produce electricity by using the temperature difference between deep cold ocean water and warm tropical surface waters. OTEC plants pump large quantities of deep cold seawater and surface seawater to run a power cycle and produce electricity.

Answer 2

Ocean thermal energy is derived from the solar energy that is absorbed by the oceans. Given that almost two-thirds of the planet’s surface is covered by the oceans, the majority of solar radiation hitting Earth is absorbed and stored here. In terms of heat energy, the amount of solar radiation absorbed by the oceans on an average day equates to about 250 billion barrels of oil. This means that if even a small amount of the heat energy stored in the oceans could be harnessed, it would have the potential to produce billions of watts of electrical power.

The sunlight that hits the ocean is stored as though the ocean was a giant solar panel. The ultraviolet radiation from sunlight excites the water molecules at the surface of the ocean, causing a rise in temperature. The ocean has a low ‘albedo’ (albedo is a measure of how well a surface reflects sunlight) of around 0.6. This means that the majority of solar radiation that hits the surface, around 94%, is absorbed. The warm water stays near the surface of the water as it is less dense than the cold water at depth.

As the ocean surface is heated by the sun, the depths of the ocean remain cold, thus creating a temperature gradient between the top of the ocean and the bottom. These differences in temperature can be used to drive turbines which can convert the thermal energy into electrical power.

Generally, the optimum situation for the conversion of ocean thermal energy to electrical power is when the temperature difference between surface and deep water is around 36oF (20oC). These conditions are usually found between the Tropic of Cancer and Tropic of Capricorn. Favourable conditions for ocean thermal energy conversion (OTEC) can be found off the coast of over 80 countries worldwide.