Oscillating water column

OWC are devices with a semi-submerged chamber or hollow open to the sea below, keeping a trapped air pocket above a water column.

This continuous movement forces a bidirectional stream of high-velocity air, which is channeled through a power take-off (PTO).

The Hanna design also drives two generators that operate outside of the enclosed air duct in a relatively dry environment.

These buoys used the air pressure generated in the collecting chamber to power a PTO system that consisted of a whistle or foghorn.

[3] The next major innovation occurred in 1947 when Yoshio Masuda, a Japanese naval commander, designed an OWC navigation buoy that used a turbine PTO system.

The PTO system generated electricity that recharged the buoy's batteries, allowing it to run with little maintenance.

Breakwaters are man made walls (built offshore) which block the coastline from wave activity (often used around harbors).

[10] The OE Buoy, currently under development by OceanEnergy, has been successfully tested in 2006 using a 28-ton 1:4 scale model anchored off the cost of Ireland.

The OE Buoy is designed to be anchored far off shore in deep water where storms generate wave activity.

It is powered by a Wells turbine and based on a 3-month test, full scale OE Buoys are expected to output approximately 500MW.

It has been tested at the Biscay Marine Energy Platform (BiMEP), near Armintza in the Basque Country, Spain.

The biggest concern is that OWCs cause too much noise pollution, and could damage the natural beauty of a seascape.