Environmental Engineering Reference
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largest waves without being damaged. Two operating wave power sta-
tions, one in Scotland and one in Norway, have already been damaged by
high waves. Wave energy was studied at the time of the French Revolution,
but there has not much progress in turning this motion into useful energy
until the last quarter century. A recent advance is the oscillating water
column (OWC). This is a column that sits on the seabed and admits the
waves through an opening near the base. As the waves rise and fall, the
height of the water inside rises and falls pushing air in and out of a turbine
which drives a generator. The turbine spins in the same direction regard-
less of the direction of the air flow.
Norway built a wave energy station on the coast near Bergen in 1985.
It combined an OWC with a Norwegian device called a Tapchan (TAPered
CHANnel). The waves move up a concrete slope where they fill a reser-
voir. As the water flows back to the ocean, it drives a turbine generator.
Wave power generators ranging from 100 kilowatts (kW) to 2 mega-
watts (MW) are now in use in more than a dozen countries. Scotland had
a trial 75-kW OWC on the island of Islay for 11 years. This has been re-
placed by a 500-kW unit with plans for a 2-MW seagoing device called the
Osprey. Portugal has been working on an OWC off the island of Pico in the
Azores. An American company has worked on a 10-MW system on buoys
3 kilometers off the south coast of Australia. China, Sweden and Japan are
also working on wave energy.
Wave energy is a capital-intensive technology, with most of the costs
for construction. But, after 3 decades major breakthroughs are in sight and
wave electricity should be part of the renewable mix in many countries
before long.
Another technique used to harness energy involves the difference
between sea levels. In Egypt, water running through an underground ca-
nal linking the Mediterranean to the El-Qattar depression could be used
to generate electricity. In Israel, the same principle could be used in a canal
between the Mediterranean and the Dead Sea which would descend 400
Solar power satellites (SPSs) have promised to provide cheap, clean
power for decades, but there has been very little progress on the concept
in over 30 years. In 2004, a conference about space based solar power
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