Английский язык. Арланова Т.Л - 30 стр.

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30
This prototype wave-power plant on the Scottish island of Islay was
constructed by building a concrete water column across 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) which 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 scheme.
Source: Adapted from 'Inside out: Wave power'. Education Guardian
When a wave enters the gully, the
water column moves up and the
air above is forced out through the
turbine, making the rotors turn.
When the wave recedes, air is
drawn in through the turbine,
but because of their special
design the rotors keep turning
in the same direction.

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