The oceans are vast and full of energy produced by the sun and wind. This makes wave energy a potential power platform. So, how does wave energy work?

How Does Wave Energy Work

Waves, particularly those of large amplitude, contain large amounts of energy. Wave energy is in effect a stored and concentrated form of solar energy, since the winds that produce waves are caused by pressure differences in the atmosphere arising from solar heating. The strong winds blowing across the Atlantic Ocean create large waves, making the west coast of Europe ideally suited to wave energy schemes.

A wide variety of countries have pursued wave energy technologies, but haven’t coordinated there research. As a result, there are a wide variety of technological strategies for attacking wave energy as a power source. The three most common are Shoreline Device, Near Shoreline Devices and Offshore Devices.

Shoreline devices actually come in three forms: the oscillating water column (OWC), the convergent channel (TAPCHAN) and the Pendulor.

* The OWC comprises a partly submerged concrete or steel structure, which has an opening to the sea below the water line, thereby enclosing a column of air above a column of water. As waves impinge on the device, they cause the water column to rise and fall, which alternately compresses and depressurizes the air column. This air is allowed to flow to and from the atmosphere through a turbine which drives an electric generator.
* The Tapchan consists of a gradually narrowing channel with wall heights typically 9 to 10 feet above mean water level. The waves enter the wide end of the channel and, as they propagate down the narrowing channel, the wave height is amplified until the wave crests spill over the walls to a reservoir which provides a stable water supply to a conventional low head turbine.
* The Pendulor device consists of a rectangular box, which is open to the sea at one end. A pendulum flap is hinged over this opening, so that the action of the waves causes it to swing back and forth. This motion is then used to power a hydraulic pump and generator.

Nearshore devices are situated in shallow waters, typically 25 to 75 feet of water. Again the OWC is the main type of device, with several designs having been deployed world-wide.

Offshore devices are deployed in water of more than 100 feet of depth. As with shoreline devices, there are a number of different approaches:

* The Swedish Hosepump has been under development since 1980. It consists of a specially reinforced elastomeric hose (whose internal volume decreases as it stretches), connected to a float which rides the waves. The rise and fall of the float stretches and relaxes the hose thereby pressurizing sea water, which is fed to a central turbine and generator unit.


* The McCabe Wave Pump consists of three rectangular steel pontoons which move relative to each other in the waves. The key aspect of the scheme is the damper plate attached to the central pontoon, which ensures that it stays still as the fore and aft pontoons move relatively to the central pontoon by pitching about the hinges. Energy is extracted from the rotation about the hinge points by linear hydraulic pumps mounted between the central and two outer pontoons near the hinges. The device was developed to supply potable water (by reverse osmosis) but can also be used to generate electricity (via a hydraulic motor and generator).
* The floating wave power vessel is a steel platform containing a sloping ramp, which gathers incoming waves into a raised internal basin. The water flows from this basin back into the sea through low-head turbines. In these respects it is similar to an offshore Tapchan but the device is not sensitive to tidal range.
* The Danish Wave Power float-pump device uses a float which is attached to a seabed mounted piston pump; the rise and fall motion of the float causes the pump to operate driving a turbine and generator mounted on the pump. The flow of water through the turbine is maintained as uni-directional through the incorporation of a non-return valve.

The viability of any of these platforms as a wave energy producer is iffy at best. At this time, it seems the solution lays in future technology breakthroughs.

How does wave energy work? Not very well at the moment.