Renewable Alternative Energy From Tidal Power

New Technologies Generate Green Electricity From Ocean and Sea Tides

Nov 4, 2009

A sustainable source of clean electrical power is the energy in the tides. Several companies are pioneering green generation of electricity with various types of turbine.

Tides as an alternative energy source could supply all of the world's needs for electricity. The U.K. Government’s Marine Foresight Panel estimates that if less than even 0.1% of the energy available from oceans were harnessed, it would supply more than five times the current global demand.

Tides have advantages as a source of green electricity, compared to wind power and solar generation:

In the past, tidal power has been harnessed with dams and barrages, but without great success. Recent developments have been focused on turbines that sit on the seabed or are mounted on pillars or float. Current projects in Europe, North America, and Australia are testing their environmental impact and effects on marine wildlife.

Technologies for Sustainable Tidal Power

The first to produce electricity was installed by Marine Current Turbines, Bristol, U.K., off the coast of north Devon, England, in 2003. This company’s turbines uses twin propeller-type rotors on a wing-like structure. The rotors can be pitched through 180 degrees to operate in either direction of the tide. The wing is mounted on a steel pillar on the sea bed and can be raised above the surface for maintenance.

Several companies have developed turbine generators that sit on the seabed with no structure above the sea surface. An advantage is that no preparation is needed of the sea floor.

OpenHydro, Dublin, Ireland, has developed a seabed turbine in which the rotors are in a ring with the outer ends of the blades concealed in a housing and a circular aperture in the center for marine life to swim through. It is said to protect marine life from being damaged by the blades.

Verdant Power, U.S.A., has a Free Flow System with turbine blades on a torpedo-shaped body that automatically aligns with tide flow and is suitable for waterways to improve sustainability of urban centers, as in New York's East River. It can complement wind power for buildings and solar generators.

Electricity Generation in Low Speed and Shallow Water

Swanturbines, a consortium based in Swansea University, Swansea, U.K., has developed a fully-submerged gearless low-speed generator with only one moving part that operates with high efficiency over a range of speeds with low maintenance requirements. A yawing mechanism rotates the turbine to the direction of water flow.

Pulse Tidal, Sheffield, U.K. has developed a shallow-water generator in which tidal streams move horizontal blades up and down.

Two companies, Tidal Energy, Gold Coast, Queensland, Australia, and Lunar Energy, Aberdeen, U.K., have developed turbines with venturi-tube housings. A venturi tube is tapered from the inlet to outlet, accelerating the water flow so that increased energy is obtained from the turbine. The Lunar Energy venturi housing straightens tidal flow so that the angle of flow to the turbine blades is optimized without a yawing device.

Renewable Electrical Generation in Bridge Pillars

A generator developed by Blue Energy Canada, Richmond, BC, Canada, houses its turbine in a concrete caisson on the sea floor. A vertical shaft is driven by vertical hydrofoil blades that move faster than the water flow so that electricity can be generated in low-speed streams. The shaft drives a generator above the surface of the water. Several caissons can be stacked to form pillars to support a bridge.

Tidal Power Energy, St. John's, NF, Canada, has developed the concept of a series of caissons that contain paddle-wheels to drive a generator. It proposes to use them for a bridge between the island of Newfoundland and the Labrador mainland.

Turbines on pillars require foundations to be constructed on the seabed but take advantage of the faster streams closer to the surface. Another type that does this is a floating turbine tethered to the seabed, as developed by Tidal Stream, Southam, Warwickshire, U.K.

Inexhaustible Clean Energy

Some of these generators are already delivering power to utilities. What they have all demonstrated is that the tides are an inexhaustible source of clean energy.

The copyright of the article Renewable Alternative Energy From Tidal Power in Environmental Engineering is owned by Thomas Kelly. Permission to republish Renewable Alternative Energy From Tidal Power in print or online must be granted by the author in writing.