Technology Types Of Ocean Energy Conversion (Jenis Teknologi Konversi Energi Laut )

Ada 4 Jenis Sistem Konversi Energi Kelautan,  yaitu (1). energi ombak atau gelombang laut, (2). energi pasang surut,  (3). energi arus laut, dan (4). OTEC, Ocean Thermal Energy Conversation, yaitu konversi energi perbedaan temperatur yang terjadi antara permukaan laut dan dasar laut. Permukaan laut jelas memiliki temperatur lebih panas jika dibandingkan dengan dasar laut. Perbedaan temperatur yang tinggi dapat mudah ditemukan di perairan tropis. Perbedaan ini mampu mencapai 20⁰-25⁰ C. Air panas dan air dingin kemudian dialirkan ke permukaan melalui pipa terpisah yang kemudian bisa dimanfaatkan.( Abstraksi Indonesia )

For further detail study can see here : Ocean energy technology  and here : Ocean energy : Global tecnology development status.

Four types of ocean energy conversion exist:

(1). wave energy, (2). tidal energy, (3). marine current energy, and (4). ocean thermal energy conversion.

Ocean Treader

Wave Energy

Wave energy is generated by the movement of a device either floating on the surface of the ocean or moored to the ocean floor. Many different techniques for converting wave energy to electric power have been studied. Wave conversion devices that float on the surface have joints hinged together that bend with the waves. This kinetic energy pumps fluid through turbines and creates electric power. Stationary wave energy conversion devices use pressure fluctuations produced in long tubes from the waves swelling up and down. This bobbing motion drives a turbine when critical pressure is reached. Other stationary platforms capture water from waves on their platforms. This water is allowed to runoff through narrow pipes that flow through a typical hydraulic turbine. Wave energy is proving to be the most commercially advanced of the ocean energy technologies with a number of companies competing for the lead.

Tidal Energy 

The tidal cycle occurs every 12 hours due to the gravitational force of the moon. The difference in water height from low tide and high tide is potential energy. Similar to traditional hydropower generated from dams, tidal water can be captured in a barrage across an estuary during high tide and forced through a hydro-turbine during low tide. To capture sufficient power from the tidal energy potential, the height of high tide must be at least five meters (16 feet) greater than low tide.  There are only approximately 20 locations on earth with tides this high. The Bay of Fundy between Maine and Nova Scotia features the highest tides in the world, reaching 17 meters (56 feet). This area has the potential to produce 10,000 MW

Current Energy

Marine current is ocean water moving in one direction. In the U.S., it is found primarily off the coast of Florida. This ocean current is known as the Gulf Stream. Tides also create currents that flow in two directions. Kinetic energy can be captured from the Gulf Stream and other tidal currents with submerged turbines that are very similar in appearance to miniature wind turbines. As with wind turbines, the constant movement of the marine current moves the rotor blades to generate electric power. 

Ocean Thermal Energy Conversion

 Ocean thermal energy conversion, or OTEC, uses ocean temperature differences from the surface to depths lower than 1,000 meters, to extract energy. A temperature difference of only 20°C (36°F) can yield usable energy. Research focuses on two types of OTEC technologies to extract thermal energy and convert it to electric power: closed cycle and open cycle. In the closed cycle method, a working fluid, such as ammonia, is pumped through a heat exchanger and vaporized. This vaporized steam runs a turbine. The cold water found at the depths of the ocean condenses the vapor back to a fluid where it returns to the heat exchanger. In the open cycle system, the warm surface water is pressurized in a vacuum chamber and converted to steam to run the turbine. The steam is then condensed using cold ocean water from lower depths

Illustration of OTEC plant ( Xenesys Inc.)

Sumber : http://www.nrel.gov/docs/fy09osti/44200.pdf