Ocean-based energy:

Wave energy
Oceans cover a little more than 70 per cent of the earth’s surface. They are the largest collectors of solar energy or sunlight, according to the National Renewable Energy Laboratory (NREL) in the United States. The NREL has calculated that if less than one-tenth of 1 per cent of this stored solar energy could be converted into electric power, it would supply more than 20 times the total amount of electricity used in the USA on any given day. As well as being a destructive force, the kinetic energy from waves can be turned into electrical energy. As wind blows across the surface of the ocean, it creates waves. Wave motion in deep water is up-and-down; near the shore, a surge of water results. Consequently, waves represent a large renewable flow of energy and no greenhouse gas emissions.

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In 2003, the World Energy Council estimated that global wave resources contained sufficient energy for more than twice the world’s electricity production. In favourable locations, the energy density of surface waves can average 40 megawatts per kilometre of coastline, according to the Australian Greenhouse Office . But ocean energy remains an untapped resource due to the high cost of generating electricity from the power of waves. Less than 0.1 per cent of the world’s electricity is produced by ocean energy. Over the years, a number of schemes have been proposed to capture the energy of waves.

The strongest winds create the highest waves and the higher waves contain more energy. Long, uninterrupted distances are needed to get waves of good length and force. The strongest winds and consequently, the greatest wave energy potential are found in areas that are mainly between the 40 degree and 60 degree latitudes which exclude Australia.

The use of waves as a source of power is a recent occurrence. In 1909, the California Wave Power Company used wave energy to produce electricity for lamps on wharves. At about the same time, an “electric” ball was installed near Sorrento, south of Melbourne. Little else is known about its operation. This device generated electricity as it rose and fell on incoming waves. In the 1970s, research into wave power was mainly being conducted in the United Kingdom with other programs in Japan, Norway, Sweden and the USA. The vertical motion of deep water waves can be captured by mechanical devices such as Cockerell’s rafts (which create a store of compressed air which drives a generator) or Salter’s ducks (which impart a twisting motion to a mechanical drive).

To view diagrams of the Cockerell’s rafts and Salter’s duck, go to “ocean-based energy” at:
http://www.sustainable.energy.sa.gov.au

The wind-generated waves off the Western Australian coast have a high concentration of energy, creating opportunities to generate electricity.  Western Australia’s southern coast has attracted the attention of renewable energy scientists and engineers. The State Energy Commission of Western Australia (the SEC of WA) began researching wave energy in the state in 1982. It was identified that possible locations for a wave energy generator include Esperance, Yanchep and Fremantle. Research into efficiently harnessing wave energy is increasing in response to the escalating demand for emissions-free renewable energy.

An innovative wave energy system has been developed by Western Australian company Seapower Pacific Pty Ltd. Seapower installed a new wave energy generator in the Fremantle Harbour in May 2005. The CETO wave energy generator is situated about 250 metres from the shore off Rous Head, North Fremantle. This generator  pumps high-pressure seawater through a small diameter pipe to the shore. It is intended that the wave energy will drive a turbine to produce 100 kilowatts of electricity, enough for 100 homes. The system also includes a desalinisation process, converting seawater into fresh water. It is expected to produce about 300,000 litres of fresh water a day. It is believed that the CETO system is the first wave power converter to sit on the seabed, where it is invisible, safe from storms and ocean forces, and self contained. The company that owns the technology is Renewable Energy Holdings (REH), a company listed on the London Stock Exchange specifically to invest in cutting-edge renewable energy technology.

For more information, go to:
http://www.seapowerpacific.com/WHAT-IS-CETO.htm

On a small scale, there are hundreds of wave-powered navigational buoys in use around the world. The oscillating wave motion drives an air turbine and can generate about 60 watts.

In other parts of Australia, there are plans to develop and install new wave-energy systems that will generate electricity. One trial is being conducted by Ocean Power Technologies (Australasia) Pty Ltd (also known as OPTA), which is an Australian subsidiary of a United States company, Ocean Power Technologies, Inc.

The purpose of the OPTA trial is to install a wave-energy generation system, to be moored to the seabed several kilometres off the Victorian coast near Portland. A wave energy converter, called the PowerBuoyTM, will generate up to 20kW of electricity. The PowerBuoyTM looks like an ocean buoy and it will be fully submerged under water. Electricity will be sent along an underwater cable to the shore.

Following the trial, OPTA intends to install more PowerBuoyTM units, which will be fixed to the ocean floor to minimise the risk of interfering with migrating whales in this region.

For more information about the OPTA wave-energy system, go to:
http://www.greenhouse.gov.au/renewable/recp/wave/two.html

Energetech Australia Pty Ltd is building a demonstration wave energy system on the breakwater at Port Kembla on the New South Wales south coast. The demonstration system includes a revolutionary all-Australian designed turbine that always spins in the same direction, regardless of the flow direction.

The Energetech Wave Energy System will provide sufficient power for about 150 households. The system will produce a maximum capacity of 500kW of electricity, which will save about 1,000 tonnes of greenhouse gas emissions annually.

For more information about the Energetech Wave Energy System, go to:
http://www.greenhouse.gov.au/renewable/recp/wave/one.html

Tidal energy.
The tidal rise and fall of the oceans is caused by the varying gravitational pull of the sun and moon. Larger and smaller tidal ranges occur from season to season and from year to year. The coastline and sea floor topography can also affect the tidal range which can be 15 metres or more.

The potential of tidal power has been recognised for hundreds of years. There are records of tidal-powered mills in Ireland in the seventh century and in the lagoons of Venice before 1050. The mills, however, could only operate for a few hours a day and they were vulnerable to storm damage.

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As our knowledge of oceans and tides has increased, so have efforts by engineers to use tidal energy for generating electricity. The world’s first tidal power station was completed in St Malo on the Brittany coast in France in 1966. The St Malo power station is still operating. The second tidal power plant, a prototype, was built near Murmansk, Russia, between 1964 and 1968. It was known as the Kislogubskaya tidal power plant. The pilot plant was restored and put into operation in December 2004.

The only potential for tidal power in Australia is along the north-west coast, near the Kimberleys in Western Australia. The potential of Kimberley tidal power can be compared with the capacity at St Malo, France. However, there are no large requirements for electricity in this area and there would be a significant cost (including losses) in transmitting power long distances to more populous areas of Western Australia.

For more information, go to:
http://www.rise.org.au/info/Res/tidal/index.html

Thermal Energy
Energy can be extracted from the temperature difference between the warmer and cooler layers of the ocean. This process is known as Ocean Thermal Energy Conversion (OTEC).

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