Wednesday, September 07, 2005

The Power of the Oceans

Tidal energy.

Thanks to our orbiting moon, twice a day the world’s oceans create powerful water currents and the rise and fall of tides. Humans have studied and used the tremendous power of water for over a thousand years. 10th century millwheels harnessed the energy of rivers to grind wheat into flour. 40 years ago, the first tidal dams were constructed, converting the tidal energy into electricity.

Today, new energy technologies that produce power from tidal currents could help supply as much electricity as the largest hydroelectric dam, or nuclear / fossil fuel generating power plants without negative side effects on our environment.

Science confers, huge advantages.

There are enormous advantages on this potential energy resource.

  1. The natural occurrence of the earth’s tides is a free renewable and reliable (FIRM)
  2. By Virtue of the physical characteristic of sea water’s density (832 time that of air) and it’s non compressibility. Its energy producing potential is far higher that of wind. For example a body of water moving at 8 knots has a wind speed equivalent of 390km/hour.
  3. Our environment is not damaged by greenhouse gas emissions.

Early tidal power plants.

As early as the 1930’s countries have been using tidal power with differing success and power output levels but what is notable is that all of these projects have stood the test of time the marine environment and still exist.

La Rance Tidal Brige France.

Tidal Barrage France In the 1960’s France began the construction of this Project. The system consists of a 330 meter long dam across a 22 square kilometre basin with an 8 meter tidal range. It was completed in 1967 and 24 5.5 meter wide turbines rated at 10MW were added to the 225kV French transmission network.

Using barrage bulb turbines, developed by Electricite de France allows this dam to generate power on both ebbs of the tide.

The turbines are rated at 10MW, therefore a total capacity of 240MW.
Maximum Electricity generated per annum (kWh) = 240000 * 8760 (hours in a year)

= 2102400000 kWh

Marine Turbines

These could be described as underwater wind farms and have the advantage of being much cheaper to build than tidal barrages. They also do not have the environmental problems that a tidal barrage would bring and there are many more suitable sites.

Array of marine turbines

These underwater turbines, which are generally rated at 750 to 1500kW per unit, (depending on the local tidal patterns and peak tidal velocities), are grouped in arrays or "farms" below the surface.

The rotors turn slowly (about 10 – 20 RPM) so risk to marine life is minimal as virtually all creatures which choose to swim in areas with strong currents have excellent perceptive powers and agility.

The Future.

With the obvious effects of global warming and climate change due to continued pumping of co2 gases into the atmosphere, marine turbines and tidal power are an indisputably clean renewable energy resource. We need to start now to help these alternative energies develop and for governments to harness the power of the oceans.

Written by Peter Young
Water Well - Watering the Future


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