Monday, May 18, 2009

CETO Wave Power combined with Desalination

In Greek mythology, Ceto was a sea goddess. Ceto was a daughter of Gaia and Pontus, and she personified the power of the sea.

In a current incarnation, CETO is the name of a wave power technology that uses air-filled buoys that float in the sea. As the waves go up and down, the buoys pull pistons up and down inside underwater pipes, pushing the seawater onshore. The buoys are fully submerged and permanently anchored to the sea floor, so they don't spoil the seascape.

CETO units are manufactured from steel and rubber. The buoys are like bladders, they are made from Hypalon. CETO components have a known subsea life of over 30 years. No new technology needs to be developed and all such components are relatively cheap and simple to manufacture, without making countries dependent on imports of scarce resources.

Another advantage of this technology is that it can deliver a relatively steady supply of electricity at times when there is little or no wind or sunshine.


The electricity thus generated can be sent either to the grid, or used for other purposes such as desalination. Up to 100% of the electricity can go into the grid during periods of peak demand on the grid, while desalination can take place during periods when there's little or no demand for more electricity on the grid.

Australian company Carnegie Corporation plans to build a CETO wave farm on Garden Island, off the coast of Perth, Australia. Managing Director Mike Ottaviano says: "We'll generate electricity at around about the cost of a wind farm." The plans include installation of a Pelton Turbine, supplied by Swiss company Calder AG, and a Desalination Plant, supplied by Australian company Citor Pty Ltd.

Since 60% of the world's population lives within 40 miles (about 60 km) of the sea, the electricity and water can thus be produced where they are consumed. There no need to first build pipelines from dams to cities. Nor is there a need to first build high voltage direct current (HVDC) lines. Electricity from wind farms and solar concentrators often needs to be brought to cities over HVDC lines. There's little or no need to expand the electric grid or to upgrade the water distribution network. This technology can replace coal-fired power plants and secure water supply relatively swiftly, easily and without much extra cost.

While wave power levels may differ from place to place (see image left), the potential for wave power clearly is huge, especially when combined with applications such as water desalination. CETO can operate efficiently in swell in the 1 to 2 meter wave height range, greatly increasing the number of potential base-load sites globally.  For example, much of Southern Australia always has significant waves more than 1 meter high.

The article Desalination with zero sea discharge, by CSIRO Australia, describes how the residue of desalination can be used as industrial input. Of particular interest is recovery of lithium and magnesium from brine. The lithium could be used to manufacture batteries, while magnesium could be added to concrete to offset emissions of carbon dioxide.

For years, CETO has claimed it can generate zero emission base load electricity at a cost comparable to existing wind power. For years, GE has also claimed for years that, with a cost of approximately 3.5 to 4 cents per kilowatt-hour and declining, wind is a low-cost renewable energy source that is less expensive than coal, oil, nuclear and most natural gas-fired generation.

When looked at in isolation, wind power, hydrogen, desalination and wave power may each not seem commercially attractive at the moment. Combined, however, they can be more viable. Surplus power from wind turbines can be used to produce hydrogen, which could be assisted by the availability of clean water. Hydrogen produced offshore could power ships. In combination, such new industries can become successful as they complement each other. Turning trash into treasure, what was previously regarded as waste can become the input of entire new industries.

In July 2007, the Singapore Government offered S$4 million worth of research funds to a desalination proposal that consumed 1.5 kilowatt-hour (kWh) energy or less per cubic meter of potable water produced from seawater. Almost one year later, a team of Siemens researchers won the challenge with a proposal to remove salt from seawater by using a novel electricity-based method that includes electrodialysis and ion exchange.

Only if we allow such new industries to develop will they reveal their full potential. Moreover, when the pollution and environmental harm of fossil fuel is taken into account, there should be even less doubt that such renewable energy and production methods can be more than price-competitive, even before economies of scale and innovation will bring costs down further.

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