There are huge energy resources in ocean power, but as yet few companies are actually producing electricity
The marine renewables industry is in its infancy compared to solar and wind, but the drive for clean energy is rapidly accelerating progress in this sector.
Harvesting energy from the ocean has advantages and disadvantages compared to other sources of renewable energy. Firstly, it’s much more predictable: tides and marine currents can be forecast years in advance. Secondly, water is over 800 times more dense than air so the energy potential is greater. And thirdly most of the hydrodynamic theory, engineering principles, and marine construction techniques are well studied. Drawbacks of marine renewables include the harsh marine environment and the challenges of delivering energy at a competitive price given the high cost of installing and maintaining equipment. Other hurdles including delivering the power to land, and the fact that the resource may be a long way from where it’s needed, or even a grid connection.
There are two main types of marine renewables, wave energy and tidal stream energy. Wave energy occurs near the surface, with the amount of energy available determined by the size of the waves and the time period between wave peaks. Wave energy systems are either off-shore in deeper water (where waves will tend to be bigger) or near-shore in shallower water (sometimes built into the shoreline). Tidal streams are caused by the regular rise and fall of the tides, with the amount of energy available determined by the speed of the flow and the size of the catchment area.
The amount of marine energy worldwide which can be practicably converted to electricity use is estimated at between 2000-4000 TWh/year for wave power, and 180-200 TWh/year for tidal power.Most of the work now taking place is development stage companies testing prototypes – only a handful of the new generation devices are so far in place generating grid-connected power. The exceptions are long-established tidal barrages, of which there are currently just two large-scale installations globally. The biggest is at La
Rance,
France (240 MW), and there’s another on the Bay of Fundy in
Nova Scotia (20 MW). The controversial Severn Barragein
Britain will follow the same principles.
The countries with the most significant developments are the
UK, US,
Australia,
Canada,
Norway,
Ireland and
Portugal. The UK is emerging as a world leader in marine renewables, largely thanks to a history of maritime engineering and the fact that long stretches of coastline (particularly in Scotland, Ireland and Cornwall) are exposed to North Atlantic waves and tides so there’s plenty of energy to harvest. The
UK’s lead is also attributable to Government support and the pioneering efforts of Professor Stephen Salter from the
University of
Edinburgh, who invented his famous device, the Duck, in the 1970s. Salter’s Duck achieved conversion efficiencies of close to 90%, a performance which hasn’t been matched by any wave device since. The
UK is home to a large number of wave and tidal device developers, including some of the early market leaders. The
UK marine renewables industry is also being supported by two major project testing centres. The first of these is the European Marine Energy Centre (EMEC) in the Orkneys, where prototype devices for both tidal and wave energy are being tested. The second is the Wave Hub in
Cornwall, which will be a test bed for arrays of wave energy converters (WECs) when it comes on-stream in 2010. It will be the world’s first proper wave farm.
The Carbon Trust estimates that marine renewables could potentially supply between 15-20% of the UK’s energy needs. For Canada, it’s about 25% and the United States 10%. Wave and tidal energy is undoubtedly an important emerging industry which could have a significant impact at some point in the future. At present, it’s comparable to the wind industry in the 1980s and private investors should tread with caution.
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