The Limpet 2 OWC generator. Image (c) Wavegen, Ltd.

Oscillating Water Column Generator
Tech Level: 11
Wave Pitch Generator
Tech Level: 11

In some parts of the world, energy density from waves can exceed 65 megawatts per mile of coastline. There is an estimated 3000 gigawatts of untapped energy lying along the world’s coastlines in the form of waves breaking on shore.

Wave energy in general is not a high-density form of electric power. Even if all eco-friendly available spots along the US coastline were developed with wave generators, for example, combined they would still only provide a few percentage points of the country’s current energy needs. However, because of their location, they are ideal for use as power sources for shoreline and near-shore facilities where a constant flow of uninterrupted power would be ideal, such as desalinization plants and factories that extract hydrogen from seawater for fuel cells.

Tech Level: 11

These are also called OCW or breakwater generators, as they are designed to work on or near shore, utilizing surface waves.

These devices channel airflow through a narrow raised tunnel, as the constant rising and falling of the water in the device from the waves pushes air out and then sucks it back in. It has a large opening for the wave which it channels into a narrow tunnel. The water rises dramatically, which forces the air above it to blow through the generator above, spinning the counter-rotating turbine blades. When the water recedes, the water level drops, sucking in air in the other direction across the turbine blades. This constant back-and-forth spinning of the turbine blades generates electricity.

At a test facility constructed by Wavegen Inc. on Islay creates an optimal power output of 15 to 15 kilowatts per minutes.

OCW generators are sometimes cited as being deployed in conjunction with wave-amplifying breakwalls. These are basically an array of specially-constructed vertical concrete columns located, from several dozen to several hundred meters away, that help to channel and narrow a wave before it hits the generators, helping to increase the amount of energy delivered.

OCW generators do have some downsides. They would have to be used in large clusters and groups along a shoreline, no doubt incurring the wrath of local residents who would fear environmental damage or a threat to their property value. OCW generators as currently designed also tend to be noisy at times, another threat to their potential popularity.

Tech Level: 11

The Pelamis Wave Pitch Generator. Image (c) Ocean Power Delivery, Ltd.

These floating devices resemble large, segmented tubes that undulate and bob over the surface of the waves as they pass. The tubes are filled with hydraulic fluid. The constant up and down motion of the tube drives this liquid through turbines, generating electricity.

Like with OCW Generators, Wave Pitch Generators will be deployed in large clusters. But unlike their OCW cousins, wave pitch generators would be placed a good ways offshore, to take advantage of the constant rolling motion of deep water waves. An experimental group of three of the Pelamis Wave Pitch Generators, developed by Ocean Power Delivery Ltd, are being deployed offshore of Portugal. Each of the Pelamis generators are about as thick and long as a twenty-car railroad train, and combined will provide 2.25 megawatts of power.






Article added 2006