Ocean power breakthrough close ...

Excerpt from ABC News:

Researchers close to ocean power breakthrough

17 October 2007

Commercial wave-powered water desalination and electricity generation is one step closer to reality, according to Australian developers.

Trials of a technology called CETO have yielded promising results, says Dr Michael Ottaviano of Carnegie Corporation, which is developing the system in the southern hemisphere.

The tests, carried out in Fremantle, Western Australia, verify predictions of how much electricity and water the technology could produce under various wave conditions.

"We've found a perfect correlation between the results our models predicted and what we've actually measured in the ocean, which is a major technical milestone," Dr Ottaviano said.

The CETO technology, first conceived by Perth-based inventor Alan Burns in 1975, consists of submerged buoys connected to seawater pumps fixed to the seabed.

As each buoy moves back and forward with the swell, it generates energy to pump seawater onto land at high enough pressures to drive a reverse osmosis desalination plant as well as hydroelectricity turbines.

The company has just spent two years developing a computer model of the buoy and pump system, which calculates how much power and water it can deliver back on shore according to different wave conditions.

The computational fluid dynamics model uses the same software used to design racing cars and boats for the America's Cup.

"We can also now go to any number of sites, measure the wave conditions there, plug those conditions into our models and then tailor a design of the unit to each specific site that we go to," Dr Ottaviano said.

He says tailoring the units to particular sites would involve changing the buoyancy of the buoy and the design of the pump.

Kelp forest design

Dr Ottaviano says one of the challenges of wave farms is designing them to survive the massive force of storms.

While most wave farms float on the surface of the water and try to resist storms, he says CETO is fully submerged, avoiding the highest force of storms, which is at the surface of the ocean.

It is also designed to be flexible and to go with the flow of the sea.

"The way it moves in the water mimics a kelp forest," he said.

Demonstration plants

Dr Ottaviano says he has just been negotiating with state governments about possible sites in South Australia, Victoria and New South Wales for commercial scale demonstration wave farms.

These will be 50 megawatt power stations, producing 15-50 gigalitres of desalinated water per year. About 300 buoy and pump units will be used for each farm.

Energy from the farms is expected to cost $80 per megawatt hour, around the cost of wind energy.

And the cost of water will be comparable to other desalination plants at around $1.50-2 per kilolitre.

The company wants to start building the first plant in 2009 and wants to manufacture the components in Australia, using skills from the automotive industry.

Challenges ahead

Before a demonstration plant can be built the company needs to increase the size of the buoy and pump units.

The prototypes currently work in eight metres of water but will eventually operate in 25 metres, and sit two metres beneath the ocean's surface.

"There are some mechanical and engineering challenges to work through here," Dr Ottaviano said.

The company will also have to test that the units can operate over an extended period of time.


They will run them at faster than normal speed over around one year to simulate a 20-year period of operation.

An independent view

Professor David Harries of the Research Institute for Sustainable Energy at Murdoch University, which evaluates new technologies, views the CETO technology favourably.

Although he has not seen the results of the latest trial, he thinks CETO is among the best wave energy-capturing technologies in the world.

He says one advantage over other designs is that there are no electrical wires and generators underwater.

"As soon as I saw it I thought it was very smart and sensible technology by minimising what actually goes in the water," Professor Harries said.

"That simplifies it, makes it cheaper and stops the corrosion."

Another advantage of CETO is that it is less susceptible to storm damage because it is tied to the sea floor.

Professor Harries says units can be added in a modular fashion to increase the size of the wave farm as required.

The balance of water and electricity produced can also be altered as required.

"In some areas, the water is going to be more valuable than the electricity so that's a huge advantage," he said.

Environmental effects?

One concern about the desalination plants is the production of hypersaline water - water with high levels of salt - which is returned to the sea.

Dr Ottaviano says the preferred site for energy production will be naturally turbulent and therefore more easily disperse the hypersaline water.

He says the wave farms should not be built in sensitive marine areas because construction would disrupt the sea floor.

See - Researchers close to ocean power breakthrough.

Also see Stuart Khan's thoughts - Wave Energy to Power Desalination?

Great concept and hopefully it will go ahead but bolting it onto a commercial desalination plant is some time away ...