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Renewable Energy: Tidal Power

© Savithri Shimada

Tidal power is a particular kind of hydroelectric power that harnesses the energy contained in ocean tides. Turbines are set in motion when water flows through them. They take advantage of the natural movement of high and low tides that occur twice a day. In order to do so, current tidal turbines require a large tidal range, which is the difference in height between high and low tides. At the same time, turbines today cannot deal with extremely high-energy tides. That said, there is a large number of locations around the world which are suitable for tidal turbines.

There a few kinds of tidal power generation methods. The tidal fence involves a dam on the coast, and the environmental impact of these dams is similar to other hydroelectric schemes. Of major concern are siltation, algal blooms, salinity problems, and loss of mangrove and other coastal species' habitats. The main alternative to the tidal fence is the off-shore tidal turbine. Although the principle of making turbines rotate by means of tidal inflow is the same, these turbines are anchored in open waters and require no dams to build up water at high tide. Nearly all the environmental costs of the tidal fence are avoided with the tidal turbine, because there is no large constructions to change existing tidal and sedimentation patterns.

Tidal power plants have proven to be economically feasible, albeit at the threshold of economics viability, generating electricity at current rates of about US$0.05/kWh to US$0.10/kWh. Technology promises to advance to a level where tidal power plants compete with conventional power plants without the aid of subsidies.

Today tidal power plants are in use, or in construction, or being planned all over the world. Sites around Canada, France, and Australia are being used for experimental and commercial tidal plants. Unfortunately for conservationists, the more extensively studied and hence better trusted tidal fence is generally being installed instead of the off-shore tidal turbine. Conservationists and local land owners are continuing to keep environmental issues in the spotlight, to ensure that administrators and managers of the new power plants monitor and take responsibility for any side-effects on the environment.

Since the tidal turbine makes use of a pollution-free, renewable and abundant energy resource, it is very attractive to coastal countries, especially in the light of the recent Kyoto Accord, at which world nations agreed to minimise greenhouse gas emissions. Unlike solar and wind farms, tidal power plants are technically and economically feasible now, and in-depth studies on potential environmental problems have helped identify areas of weakness which must be considered.

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