Ocean energy is a form of renewable energy that uses the ocean's tides, waves, winds, currents and thermal elements to generate energy.
Oceans cover over 70% of the Earth’s surface, making them the world’s largest solar energy collectors. The oceans constitute the largest powerhouse on Earth.
There are three basic ways to tap the ocean for its energy. We can use the ocean's waves (Ocean Wave Power), we can use the ocean's high and low tides (Ocean Tidal Power), or we can use temperature differences in the water (Ocean Thermal Energy Conversion – OTEC).
Ocean energy is mostly in an experimental stage but some of its component technologies have the potential to become mainstream energy sources and are now being trialed.
Ocean tides constitute a clean and inexhaustible energy source, free from the climatic irregularities which are a constraint on wind and solar power.
One of the world’s most suitable sites is the estuary of the river Rance, in western France, where the difference between high and low tides averages 8.17 metres, peaking at 13.5 metres during the equinoxes.
In order to disseminate knowledge and promote sharing of information on Ocean Energy conversion, the Co-ordinated Action on Ocean Energy was launched in October 2004 with scheduled duration of 3 years, in continuation to the European Wave Energy Network, which proved very successful in meeting these targets.
Ocean energy is preferable to wind because tides are constant and predictable and water’s natural density requires fewer turbines than are needed to produce the same amount of wind power.
Of all the emerging alternative technologies, ocean energy is perhaps the least advanced, but with great potential. Some says that ocean energy is where wind was 20 years ago because ocean energy is currently undeveloped compared to other conventional and renewable energy technologies.
The biggest problem in developing renewable ocean energy is obtaining the necessary capital to prove the technology.
The cost of electricity from ocean energy is of the order of about a factor two compared to other electricity renewable energy sources.
The largest but most experimental form of ocean energy is ocean thermal energy conversion, which taps heat stored in the ocean to generate electricity.
Ocean Energy is recognized in the new US Energy Bill. The US Department of Energy is focusing its hydro capacity toward ocean energy.
Using current technologies, most ocean energy is not cost-effective compared to other renewable energy sources, but the ocean remains and important potential energy source for the future.
Over the past few decades ocean energy has been tested with the commercial viability receiving varying successes; yet, the physics are proven.
Ocean energy has the potential to deliver ten million terra-watt hours of electricity per year.
In recent years ocean energy has started to receive funding for R&D in European Union that is significantly larger than at any time in its history.
According to the survey of United Nations Educational Scientific and Cultural Organization (Ho, 2003), the global reserve of ocean energy was 73.6 TW, in which around 40 TW was OTEC.
The cost of ocean energy systems will reduce as the numbers of devices produced, per offshore development, increase. However, unless the devices can be arranged effectively in an array, large scale deployment will not be commercially viable.
The ocean can produce two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves.