02/05/08
A variety of technologies have been proposed to capture the energy from waves. Some of the more promising designs are undergoing demonstration testing at commercial scales.
Wave technologies have been designed to be installed in nearshore, offshore, and far offshore locations. The OCS Alternative Energy Programmatic EIS is concerned primarily with offshore and far offshore wave technologies. Offshore systems are situated in deep water, typically of more than 40 meters (131 feet).
While all wave energy technologies are intended to be installed at or near the water's surface, they differ in their orientation to the waves with which they are interacting and in the manner in which they convert the energy of the waves into other energy forms, usually electricity. The following wave technologies have been the target of recent development.
Terminator devices extend perpendicular to the direction of wave travel and capture or reflect the power of the wave. These devices are typically onshore or nearshore; however, floating versions have been designed for offshore applications. The oscillating water column is a form of terminator in which water enters through a subsurface opening into a chamber with air trapped above it. The wave action causes the captured water column to move up and down like a piston to force the air though an opening connected to a turbine. Oscillating Water Columns are partially submerged, hollow structures open to the seabed below the water line. The heave motion of the sea surface alternatively pressurizes and depressurizes the air inside the structure generating a reciprocating flow through a turbine installed beneath the roof of the device.
A point absorber is a floating structure with components that move relative to each other due to wave action (e.g., a floating buoy inside a fixed cylinder). The relative motion is used to drive electromechanical or hydraulic energy converters.
..
..
..
..
..
Attenuators are long multisegment floating structures oriented parallel to the direction of the waves. The differing heights of waves along the length of the device causes flexing where the segments connect, and this flexing is connected to hydraulic pumps or other converters.
Overtopping devices have reservoirs that are filled by incoming waves to levels above the average surrounding ocean. The water is then released, and gravity causes it to fall back toward the ocean surface. The energy of the falling water is used to turn hydro turbines. Specially built seagoing vessels can also capture the energy of offshore waves. These floating platforms create electricity by funneling waves through internal turbines and then back into the sea.
--seokting
Edited and reviewed by: yuwei, 15/06/08
--
--
--
--
24/05/08
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
There are many wave energy conversion techniques patented worldwide. Some main concepts for wave energy converters can be classified within a few basic types:
• Heaving devices (floating or submerged), which provide a heave motion that is converted by mechanical and hydraulic systems in linear or rotational motion for driving electrical generators.
• Pitching devices that consist of a number of floating bodies, hinged together across their beams. The relative motions between the floating bodies are used to pump high-pressure oil through hydraulic motors, which drive electrical generators.
• Surging devices that exploit the horizontal particle velocity in a wave to drive a deflector or to generate pumping effect of a flexible bag facing the wave front.
An economically viable design with a simple geometrical construction but strong enough to withstand against the waves with different heights and different wave periods and directions is essential. The design would usually consist of a rectangular chamber and a pyramidal top which is installed on top of the chamber. A conical duct is erected on the pyramidal top to reciprocally move the air from the chamber and into the chamber during the process of wave approach and wave leaves the chamber. A turbine which is mounted on top of the duct is subjected to turn in one direction as the airflow moves bi-directional. A generator is coupled to the turbine that produces electricity by rotating it's armature shaft which is coupled with the turbine shaft.
--yuwei
No comments:
Post a Comment