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a natural gully on the shoreline. Waves flowing in and out of the
gully cause water in the column to move up and down. As the
water moves up it compresses the air above and forces it through a
wide tube at the back of the water column. As the water moves
down air is drawn into the water column. The moving air passes
through a turbine coupled to a generator. Both the turbine and
generator are unusual. The turbine is a Wells turbine (named after
its inventor) that keeps turning in one direction even though the air
flow is constantly changing direction. It has two rotors, each with
four blades.
The generator is a wound rotor induction motor, which acts
as a generator when it is turning at speeds greater than 1,500 rpm.
Below that speed it operates as a motor and takes power from the
grid. This motor/generator is used because the turbine takes some
time to build up to a speed where it can generate electricity. When
the turbine slows down due to a lull in wave activity, the generator
becomes an electric motor and keeps the turbine running at a
minimum speed so that it is ready to accept the power from the
next batch of waves.
The plant is controlled by a computer. It includes a PLC
(programmable logic controller), which monitors the operation of
the motor/generator and the amount of electricity going to or being
taken from the grid. There is also testing equipment to monitor
how much electricity the plant is producing and the efficiency of
the water column, turbine, and generator.
This experimental plant generates 150 kW. Plans have been
approved for the construction of a 1 MW.

Sources scheme: Adapted from “Inside out; Wave power.”
Education Guardian.

High hopes for wave power project.
The world’s first power station in the open sea is to be
stationed off do unreal in Scotland. The machine, called Osprey
(Ocean Swell-Powered Renewable Energy), will stand in 18
meters of water a kilometer out and not only harvest the larger
waves, which produce higher outputs, but also gain power with

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