Oceanic Energy Sources

Energy can be harnessed from tidal waves.

While not nearly as popular as an energy source as fossil fuels, ocean energy contains much potential for a future renewable energy resource. Scientists are working on technology to harness energy from ocean winds, currents and salinity gradients. Tidal and wave power are the most developed technologies to date.

Wave Energy

There are multiple systems for drawing power from ocean waves. Because wave energy is an "irregular and oscillating low-frequency energy source," it must be converted to a 60 Hz frequency before it can be used in an electric grid, according to the California Energy Commission. These systems can convert power from surface waves or pressure changes beneath the ocean's surface. Depending on how the system draws power, it is either submerged completely or is partially above water. Issues that concern naysayers of wave energy include the decrease in scenic ocean views or possible disturbance of marine life.

Tidal Energy

Tidal energy has been in use since the eleventh century. It works by trapping tides behind a dam when water comes to shore, then slowly releasing the water back into the ocean. This process produces electric energy, just as in a typical hydroelectric power plant. Most systems require an increase of at least 16 feet between low tide and high tide. Many areas stay away from tidal energy because it requires large investments at first.

Ocean Thermal Energy Conversion

Ocean Thermal Energy Conversion (OTEC) saw its origins in 1881. French engineer Jacques D'Arsonval gathered the plans from the idea that temperature varies depending on level in the ocean. Power plants use the differences in ocean water temperature to produce electricity. A difference of "at least 38 degrees Fahrenheit is needed" between the warm surface water and cold deep water, according to the California Energy Commission. OTEC plants must have a large diameter intake pipe that submerges a mile or more into the ocean.

Applications

An example of an OTEC system is located in Hawaii at the Ocean Thermal Plant. This power plant is capable of producing 210 kilowatts of power. The most advanced wave power system is the Pelamis Wave Energy Converter. This system has a total capacity of 2.25 megawatts and is located off the coast of Portugal. Because tidal energy systems are expensive to build, only a few exist currently. Ninety percent of the worldwide ocean energy production comes from the La Rance Tidal Power Plant in Brittany, France.

References

• The California Energy Commission: Ocean Energy
• National Renewable Energy Laboratory: What is Ocean Thermal Energy Conversion?
• Ocean Energy Council: Tidal Energy
• U.S. Department of Energy: Ocean Thermal Energy Conversion

Resources

• Renewable Energy Development: Strangford Lough
• Renewable Energy Development: CORE Project