King Canute’s Tides
King Canute, once monarch of Denmark, England, Norway and parts of Sweden, famously commanded the tides to halt in order to prove his power to courtiers. Sadly, Canute was unsuccessful in this regard. Almost 1500 years later man has now been able to harness tidal energy for his own purposes.
What is Tidal Energy?
The energy contained within the sea’s tides - caused by the gravitational pull of the moon on water on the surface of the earth - is amongst the most powerful and reliable sources of renewable energy on the planet. Indeed, man has been making the most of its effects since at least the Middle Ages, when tidal mills were a common feature around the coast of Europe.
Tidal generators are used to convert the tide’s energy into electricity. Generally, tidal energy is only available to countries with large coastal areas.The amount of energy extracted with each individual tide depends on the changing positions of the Moon and Sun relative to the Earth, the effect of the Earth’s rotation and local conditions. As a source of energy, tidal power is practically inexhaustible.
How tidal energy works
Two different systems of converting the power of tides into electricity exist:
- The first of these is ‘tidal stream generator’ or ‘TSD’ which harness the kinetic energy of tides. This is achieved with large underwater turbines turned by the incoming or outgoing tide.
- The second method is through use of ‘tidal barrages’, effectively damns preventing tides from running out of coastal areas, allowing for huge releases of energy at a later time. Such systems are much rarer than tidal stream generators because they rely on specific local geographical conditions, e.g. coastal inlets appropriate for damning.
Advantages of tidal energy
Tidal power is a renewable, yet predictable form of energy – a particular rare phenomenon. Once initial building costs have been undertaken, tidal energy is also practically free, aside from very small maintenance costs for incurred for dams and turbines which can last for 100 years or more. Tidal energy – particularly tidal barrage systems –allow for enormous releases of energy at one time, usefulfor areas with heavy industries and mining. No other form of renewable energy can match tidal for the sheer volume of production.
Disadvantages of tidal energy
Environmental concerns have plagued recent tidal energy projects, with many questioning the effects they have on sea-life and local aesthetics. The high capital investment puts many developers off, particularly as building underwater is notoriously expensive. Locations are also limited; even countries with vast coastal areas do not always have the inlets, bays and coastal rivers providing the ideal conditions for tidal energy to be effective.
Future of Tidal Energy
Engineers are currently in the process of developing new systems to enhance the efficiency of tidal energy. The most advanced of these systems, ‘dynamic tidal power,’ involves the construction of huge, t-shaped dams jutting out to sea. These would create different tidal depths on either side, allowing for energy to be mined along the dividing wall.
Projects are planned, or underway, in areas as diverse as Scotland, South Korea and India. Most involve tidal barrage systems, although tidal generators are equally popular due to their less harmful effects on the environment.
Tidal power around the World
The list of countries able to pursue tidal energy projects is fairly limited due to geographical limitations and expense. Even those with vast coastlines, such as Australia, have seen little development, although the federal government has begun investing more heavily in such projects on both the Western and South Eastern coasts. Asian governments have also been particularly keen on investing, with huge constructions in Korea, Japan and India.
Leading companies involved in tidal energy production include:
- Atlantis Resources Company
- Open Hydro
- Voith Hydro Ocean Current Systems
- Tidal Power Competitiveness
- Hammerfest Strom
- Sea Current Generators.
Tidal energy’s scope for development will always be limited by geographical and environmental concerns. Nonetheless, the sheer size and reliability of energy produced means that, for those who have the option, tidal energy will remain a useful resource.
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