Development of Tidal, Ocean, Wave Energy
Ocean energy is mostly in an experimental stage. Many
ideas have been generated, and a lot of experimental projects are being
funded both by governments and commercially. These range from
technologies and schemes which produce small amounts of energy for
local, often dedicated use, to large-scale projects which can or will be
capable of supplying energy in quantities sufficient to feed into a
grid. The ocean can produce two types of energy: thermal energy from the
sun's heat and mechanical energy from the tides and waves. Energy can be
harvested from the oceans in four ways.
As the ocean energy technology develops, the industry is finding that
synergies and expertise exist in the offshore wind power and hydropower
industries. In the same way, the wind power industry found that the
offshore oil and gas industry had a valuable contribution to make in
helping with design of offshore wind plants.
Most countries which have investigated the potential exploitation of
tidal energy have concentrated on the use of tidal barrages that can be
used to control the natural tidal flow, which is directed to drive
turbines. Only around 20 sites in the world have been identified as
possible tidal power stations. Three countries have tidal energy schemes
in operation: France, with the 240 MW tidal barrage at Rance, the
largest tidal power station in the world and the only one in Europe,
built in 1966; Canada, with the 20 MW Annapolis tidal barrage; and
China, with an 11 MW scheme of small tidal plants. Experimental tidal
energy projects are being tested in Russia, UK, Australia, USA,
Argentina, Canada, India, Korea, and Mexico.
Potential sites for tidal energy stations are few and far between, but a
number have been identified in the UK, France, Eastern Canada, the
Pacific coast of Russia, Korea, China, Mexico, and Chile. Other sites
have been identified along the Patagonian coast of Argentina, Western
Australia, and Western India.
Tidal ranges along the west coast of England and Wales are unusually
large, averaging 7 to 8 metres on the spring tides in several estuaries
and as much as 11 metres in the Severn. The Severn estuary is the site
for the most ambitious tidal barrage that has been proposed for the UK
so far, and it has been discussed for many years.
Tidal energy is expensive to install, costing UKŁ1.5 /US$2.4 million per
megawatt, compared with about US$1 million per megawatt for wind
turbines. It also has environmental problems including effects on tidal
waters and ecosystems. On the positive side, it is cheap to maintain
once installed and the electricity output is completely predictable.
Tidal energy barrages would modify existing estuarine ecosystems to
varying degrees, and environmental considerations are some of the
barriers which have to be overcome to develop them.
Over 300 wave and tidal devices have been suggested to date, but of
these, very few are in an advanced state of development. A study in
early 2005 identified that one technology, Ocean Power Delivery's "Pelamis,"
was leading in terms of development, and a further 4 systems were
following closely behind.
There are many different wave energy devices on the drawing board or
undergoing tests. Wave energy is within sight of being able to provide
commercially viable electricity. The experience of onshore wind energy
costs, which have been seen to fall by a factor of five over 12 to 15
years, supports predictions that the cost of wave energy will fall to
3-4 cents/kWh in five to eight years.
Wave energy is generated by the movement of devices, stationary or
floating on the surface of the ocean and moved by waves, as opposed to a
large volume of tidal water that is used to drive motors. The highest
energy waves are concentrated off the western coasts in the 40°-60°
latitude range north and south, in the Atlantic SW of Ireland, the
Southern Ocean and off Cape Horn. The capability to supply electricity
from this resource is such that, if harnessed appropriately, 10% of the
current level of world supply could be provided.
Development is proceeding vigorously, and while little generating
capacity has yet been created, the technology is being explored with
many new ideas.
Experimental wave energy projects are being tested in Australia, UK,
USA, Argentina, Canada, China, India, Portugal, Sweden, Denmark, Greece,
Indonesia, Ireland, Japan, Maldives, and Norway. Benefits would
undoubtedly be gained from greater international collaboration on as
many as possible of the pre-competitive aspects of R&D. At present, the
EU funding opportunities provide a major incentive to encourage
collaboration, but there is room for other mechanisms to bring the
international wave community closer together and avoid duplication and
waste.
About the author
Euan Blauvelt is a co-founder of ABS Energy Research www.absenergyresearch.com