The movement of water in the world’s oceans creates a vast store of kinetic energy. Marine Renewable Energy (MRE) can be harnessed to generate electricity to power homes, transport and industries. MRE encompasses both wave power — power from the movement of surface waves, tidal power — power from the kinetic energy of large bodies of moving water, and ocean thermal energy conversion (OTEC) — power from the heat differential of different thermal layers within a body of water.
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Ocean surface waves are generated by wind passing over the ocean surface. The friction between the wind and ocean surface causes energy to be transferred from the faster moving air to the surface layer of the ocean. Wave development depends on the length of ocean, or “fetch,” over which the wind blows in a constant direction. Longer fetches with higher wind velocities will produce larger waves. Waves can travel thousands of miles with little energy loss and can combine with waves from storms and other wind-driven events to create very energetic seas. The energy of ocean waves is concentrated at the surface and decays rapidly with depth.
Tides are the rise and fall of the ocean surface height primarily caused by the gravitational interactions of the earth, moon and sun and the rotation of the earth. Tidal current used for power production typically occurs between two bodies of water connected by a narrow land passage.
Ocean currents can be a renewable energy source that uses technology similar to under water tidal turbines but is less constrained by channel geometry. It has been researched primarily in the United States, where potential resource has been identified in the Florida Straits, in the Gulf Stream east of Miami.
Ocean thermal energy conversion (OTEC) technology converts solar energy stored in the layers of the tropical and subtropical oceans. Thermal heat engines use the temperature difference between the sun-warmed surface water and cold water in the deep ocean.
Cold water source cooling is not an energy source, but it can enable significant energy savings by providing a cooling source for regions with high air conditioning loads. It is considered a potentially viable option if cold water from the ocean exists in close proximity to large load centers.