April 12, 2005 The power of ocean waves has long been recognised as one of the great untapped energy resources with more than 1,000 patents filed for technologies to harness that energy in the last two hundred years and none that have yet reached commercial realisation. When that goal is reached, it will be a day worth celebrating as the World Energy Council believes that enough energy could be extracted from waves to meet the world's entire electrical energy needs. One company on the verge of commercialisation of wavepower-derived energy is Australian company Energetech. Energetech Australia is working on a new and commercially efficient system for extracting energy from ocean waves and converting it to electricity as a cheap, sustainable source of power. The company has a pilot installation in Port Kembla, NSW and has just received an investment of AUD$500,000 from the Centre for Energy and Greenhouse Technologies (CEGT) for the deployment of the first commercial wave energy converter off the Victorian coast.
In June 2004, a report by the U.S. Electric Power Research Institute (EPRI) identified Energetech’s wave technology device as the one of a few ocean energy technologies around the world that had overcome most of its technical challenges.
According to Mr Jan Dekker, Managing Director of CEGT, Energetech will use the $500,000 for the development and deployment of its first commercial unit based on testing and performance results from the first prototype. The prototype at Port Kembla weighs 485 tonnes and stands 40 metres high by 35 metres long by 18 metres wide.
"In particular, the funds will be applied to the development of a more compact commercial Energetech wave energy converter to be located in Victoria that is targeted to generate up to four times the electrical output of the existing prototype plant," Mr Dekker said.
"We will also provide support for the deployment of a Victorian pilot plant, and several potential sites along the Victorian coastline will be investigated. The Victorian installation will support the local economy through the supply of manufacturing, construction and maintenance services."
Mr Dekker said ocean power had many advantages over other renewable energy forms, including that waves are more consistent than wind and sunshine and hence can improve on the intermittency of renewable energy sources such as wind and solar; and because water has 835 times the density of air, more energy is available from moving water (tides, currents, waves) than from moving air (wind).
The Energetech wave energy converter is described as an oscillating water column wave energy type device, as it harnesses energy from the vertical movement of ocean waves. The key innovation in the converter is a variable pitch blade turbine that operates in combination with a concentrator that increases the amount of energy that can be extracted from the water movement. Animations of the system that clearly demonstrate how the technology works can be viewed as either flash or AVI here.
The variable pitch turbine blades allow the turbine to extract power from both the wave peak and the wave trough under the concentrator. During the wave peak, air is pushed up and compressed in the concentrator chamber to drive the turbine, which is connected to a generator.
As the wave trough occurs, a vacuum is created and the air is drawn backwards through the turbine, with the turbine blades adjusting to the reverse air flow. This innovation is known as the Denniss-Auld Turbine after its Australian inventors.
Specially developed systems management software accepts inputs such as wave height, wave frequency, turbine speed and generator output to adjust performance on a wave-by-wave basis to maximise operational efficiency.
"CEGT sees this as another exciting area of renewable energy technology," Mr Dekker said. "Many areas of Australia, particularly along the western and southern coastline, have wave conditions that can be efficiently converted to clean renewable energy by the Energetech system.
"The Energetech technology can easily be deployed in any suitable location around the world. With greater focus and more attractive energy policy and regulation for renewable energy in the UK and Europe, a significant export opportunity exists.”
The power of ocean waves has long been recognised as one of the great untapped energy resources and has been the subject of numerous patent applications over the last 200 years. The first wave power patent was filed in 1799, a proposal by a Parisian father and son team named Girard, for a device using direct mechanical action to drive pumps, saws, and other mechanical machinery.
Since that first patent, more than 1,000 patents related to obtaining useful energy from ocean waves have been filed in various countries though significant effort only really began in the 1970s when the oil crises provoked the exploitation of a range of renewable energy sources.
Based on various energy-extracting methods, a wide range of systems has been proposed but only a few reached the demonstration stage.
Wave energy can be considered a concentrated form of solar energy. Winds are generated by the differential heating of the earth, and, as a result of their blowing over large areas of water, part of their energy is converted into waves. The amount of energy transferred, and hence the size of the resulting waves, depends on the wind speed, the length of time for which the wind blows and the distance over it blows (the “fetch”).
Energy is concentrated at each stage in the conversion process so that the original solar power levels of typically 100 W/m2 (watts per square metre) can be converted into waves with power levels of typically 10 to 50 kW per metre of wave crest length.
Within or close to the generation area, the storm waves known as “wind sea” exhibit a very irregular pattern. These waves will continue to travel in the direction of their formation even after the wind turns or dies down. In deep water waves lose energy only slowly so they can travel out of the storm areas with minimal loss of energy, progressively becoming regular, smooth waves or “swell”, which can persist at great distances (i.e. tens of thousands of kilometres) from the origin.
Therefore, coasts with exposure to the prevailing wind direction and long fetches tend to have the most energetic wave climates, i.e. the western coasts of the Americas, Europe and Australia/New Zealand and the south coast of Australia.
The global wave power potential was estimated to be 1012-1015 J (1-10 TW), which is the same order of magnitude of the world consumption of electrical energy (Isaacs and Seymour, 1973; WEC,1993).
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