Tidal Power

The energy from the movement of water in tides can be used as the source of energy to generate electrical energy. A dam can be built across a river mouth or inlet. As the tide comes in the water is stored in the dam. When the tide goes out the water in the dam is channeled through pipes to turn the blades of a turbine. The turbine then turns a generator shaft and electricity is generated.

Tidal generation differs from hydroelectric plants where water flows only in one direction. The aim of tidal generators is to take advantage of both incoming and outgoing tides.

In Australia

There are no tidal energy facilities currently operating in Australia. A million dollar grant was given to Derby Hydro Power to assist in building a $100 million 48 MW tidal hydro plant outside Derby in the north west of WA, however a gas fired generator was built instead. Tidal generators are extremely expensive.

Environmental concerns relating to both living populations and coastal systems are significant. Research into the impacts of tidal power generation is limited. Recently research has tested tidal generators located off shore. These operate like wind generators, where the moving tidal flow turns the turbines. Local impacts are not entirely known.

A Tidal Turbine

Generating electricity from tides is similar to hydroelectric generation. Tidal plants take advantage of the incoming and outgoing tides. This is where they differ from hydroelectric plants where water only flows in one direction. When tides come into the shore, the water can be trapped in reservoirs behind dams created by using sluice gates. Then when the tide drops the water behind the dam can be let out, just like in a regular hydroelectric power plant.

A Tidal Turbine

Generating electricity from tides is similar to hydroelectric generation. Tidal plants take advantage of the incoming and outgoing tides. This is where they differ from hydroelectric plants where water only flows in one direction. When tides come into the shore, the water can be trapped in reservoirs behind dams created by using sluice gates. Then when the tide drops the water behind the dam can be let out, just like in a regular hydroelectric power plant.



There are no tidal energy plants currently operating in Australia. However, a million dollar grant has been given to Derby Hydro Power to assist in building a $100 million 48 MW tidal hydro plant outside Derby in the north west of WA. This plant is expected to have a lifespan of approximately 120 years and will not generate any greenhouse emissions. There are however, concerns about its effect on the mangroves located at the proposed construction site. (Australian Energy News, Issue 12, June 99. http://www.isr.gov.au/resources/netenergy/aen/aen12/index.html)

There is a 240 MW generator at La Rance, Brittany, France and a 16 MW plant in Nova Scotia, Canada.

Advantages and disadvantages of tidal power Advantages:

• Tidal power does not produce greenhouse emissions.
• Tidal power is a renewable energy resource.
• Tidal power can provide secondary benefits such as bridges and roads, which are built over the tidal generators.

Disadvantages:

• Tidal power plants are expensive to construct.
• Dams used in the production of tidal power can raise tide levels.
• Tidal power changes the sedimentation and turbidity (how clear the water is) of the water system.
• Raised tide levels can flood the shoreline affecting the marine population
• The affect on the plants and animals in the local environment in uknown.

Tidal power and the environment

Research into the environmental impacts of tidal power is limited. There is concern that the use of tidal power can result in the silting up of waterways and fish are killed as they swim through the turbine blades. History has shown that there are always consequences for an ecosystem when humans alter the natural balance of an environment.

Costs and benefits of tidal power

Benefits:

• Tidal power does not produce greenhouse emissions.
• Tidal power is a renewable energy resource.
• Tidal power can provide secondary benefits such as bridges and roads, which are built over the tidal generators.

Costs:

• Supply can be intermittent and unreliable
• Tidal power plants are expensive to construct.
• Dams used in the production of tidal power can raise tide levels.
• Tidal power changes the sedimentation and turbidity (how clear the water is) of the water system.
• Raised tide levels can flood the shoreline affecting the marine population
• The affect on terrestrial populations is unknown.

Technologies

The technologies associated with tidal power are very similar to those of hydro power: - earthmoving, dam building, flooding land, placing turbines in dams. The set up costs are significant.

Concerns about the impacts of tidal power technologies have caused recent endeavours to focus on tidal turbines and tidal fences. Tidal turbines can operate with tides and currents some distance from land, like underwater wind farms. These may have less impact.

All of these technologies are situated where tides and currents dictate rather than where the need arises. At the time of writing these forms of power generation are still very much in the developmental stage.