My link wouldn't work, so I've copied the whole L.A. Times article below. Enjoy!
GLOBAL REPORT
Using Ocean Waves to Power Desalination
Two Australian companies are claiming they can turn ocean waves into drinking water at very little cost, thanks to a combination of their technologies.
Energetech Australia's initial aim was to generate cheap electricity using wave power, but it realized that in teaming up with desalination specialist H2AU it could use the same power to produce potable water at a low cost.
Ocean waves, so abundant and consistent, are a source of energy — and energy is the main expense of any desalination process.
Most desalination installations use electricity to create the pressure needed to drive a reverse osmosis system, but the two Sydney-based, privately owned companies' combined technologies use wave pressure directly to power a reverse osmosis desalination plant. This unusual project avoids the multiple energy losses in converting wave energy to electricity before using the electricity to drive pressure pumps.
The entire operation can be run off the coastline, where the residual concentrated brine is released harmlessly back into the ocean and the only land connection is a pipe carrying potable water ashore. The process involves no fossil fuels, greenhouse gases or waste, the companies say.
The pressure source is an innovative wave energy system, the Energetech Wave Energy Plant, developed by Energetech.
"Essentially, we use the same principle as a car headlight, but in reverse. With a headlight, light is generated at the focus of a parabolic reflector, which then projects the light energy out in an almost parallel beam. As we want to capture energy, we have simply reversed the same process," said Tom Denniss, technical director at Energetech.
At the focus is a vertical shaft that is open at the base to allow free water entry and that tapers at the top, where there is a turbine that is usually used to generate electricity but that also can be used to generate pressure for the desalination stage.
As the water rises and falls inside the shaft, it drives air back and forth through the turbine, generating electricity or pressure. Because the shaft is narrower at the turbine, a "blow hole" effect is created as the air is accelerated through the narrowing shaft.
The system's other novelty is a turbine with reversible blades, so it always spins the same way despite any reversal in air-flow direction. Turbine performance has been optimized by installing pressure sensors inside the shaft; by combining the pressure data with a software program developed to reverse the blades at the right moment, designers ensure that the turbine operates at maximum efficiency.
The prototype is being tested offshore at Port Kembla, south of Sydney, and indications are that it will deliver electricity at a price competitive with coal-fired power. In full-scale production, each unit could cost as little as $1.6 million and could at times deliver power for as little as 5 cents a kilowatt-hour.
Although Energetech's device was designed as an electrical power generator, its suitability for desalination was realized during early testing. Energetech sought a collaborator with experience in reverse osmosis desalination, a well-established process used in thousands of installations worldwide wherein pure water is produced by forcing saline or impure water through a semipermeable membrane across which salts or impurities cannot pass.
This led it to H2AU, which specializes in desalination plants for cruise liners and other marine structures such as oil platforms.
"The power generation capability of this technology offers great potential, but we feel the direct 'wave to water' model offers even more potential," said Tom Engelsman, chief executive of Energetech.
Energetech is investigating projects at sites including Rhode Island, Spain, England and Australia.
Energetech Australia's initial aim was to generate cheap electricity using wave power, but it realized that in teaming up with desalination specialist H2AU it could use the same power to produce potable water at a low cost.
Ocean waves, so abundant and consistent, are a source of energy — and energy is the main expense of any desalination process.
Most desalination installations use electricity to create the pressure needed to drive a reverse osmosis system, but the two Sydney-based, privately owned companies' combined technologies use wave pressure directly to power a reverse osmosis desalination plant. This unusual project avoids the multiple energy losses in converting wave energy to electricity before using the electricity to drive pressure pumps.
The entire operation can be run off the coastline, where the residual concentrated brine is released harmlessly back into the ocean and the only land connection is a pipe carrying potable water ashore. The process involves no fossil fuels, greenhouse gases or waste, the companies say.
The pressure source is an innovative wave energy system, the Energetech Wave Energy Plant, developed by Energetech.
"Essentially, we use the same principle as a car headlight, but in reverse. With a headlight, light is generated at the focus of a parabolic reflector, which then projects the light energy out in an almost parallel beam. As we want to capture energy, we have simply reversed the same process," said Tom Denniss, technical director at Energetech.
At the focus is a vertical shaft that is open at the base to allow free water entry and that tapers at the top, where there is a turbine that is usually used to generate electricity but that also can be used to generate pressure for the desalination stage.
As the water rises and falls inside the shaft, it drives air back and forth through the turbine, generating electricity or pressure. Because the shaft is narrower at the turbine, a "blow hole" effect is created as the air is accelerated through the narrowing shaft.
The system's other novelty is a turbine with reversible blades, so it always spins the same way despite any reversal in air-flow direction. Turbine performance has been optimized by installing pressure sensors inside the shaft; by combining the pressure data with a software program developed to reverse the blades at the right moment, designers ensure that the turbine operates at maximum efficiency.
The prototype is being tested offshore at Port Kembla, south of Sydney, and indications are that it will deliver electricity at a price competitive with coal-fired power. In full-scale production, each unit could cost as little as $1.6 million and could at times deliver power for as little as 5 cents a kilowatt-hour.
Although Energetech's device was designed as an electrical power generator, its suitability for desalination was realized during early testing. Energetech sought a collaborator with experience in reverse osmosis desalination, a well-established process used in thousands of installations worldwide wherein pure water is produced by forcing saline or impure water through a semipermeable membrane across which salts or impurities cannot pass.
This led it to H2AU, which specializes in desalination plants for cruise liners and other marine structures such as oil platforms.
"The power generation capability of this technology offers great potential, but we feel the direct 'wave to water' model offers even more potential," said Tom Engelsman, chief executive of Energetech.
Energetech is investigating projects at sites including Rhode Island, Spain, England and Australia.
5 comments:
Another positive...we've been having a lot of trouble with erosion caused by wave energy in the last few decades because we keep removing the plants and animals along our coastlines that usually attenuate it. Here seagrass beds are deterriorating because the oyster reefs are not protecting them any more. Other places, cities, towns, and villages are being wiped out by hurricains and tsunamis because they've lost their mangroves.
Now, I'm not saying that it's an excuse to keep destroying those systems, but maybe power plants like this one could have the same protective effect that we've already removed.
What do you think?
How do you figure the power plant would have a protective effect?
The energy used to move the turbine would not be hitting the shore. It would slow down the waves the same way a reef or mangrove does.
A whole lot of water would need to be stopped to have a real impact. And would one of these plants even survive a hurricane? They wouldn't even bother building them down here because there's essentially no wave action.
It's not really about stopping water, it's about slowing down the directional flow. Mangroves and reefs do this by converting it to turbulant flow. I can only assume that a power plant large enough to produce a useful amount of power would be as large as some reefs, but instead of turning it into turbulance, it would use the energy to move a turbine. I have no idea about hurricaine survival, but it can't be worse than that of oil rigs, can it? As for the amount of wave energy needed, if you think in terms of tides (not surf), I would think there's plenty of energy in the gulf, especially if these plants are able to capture energy moving in both directions as they claim in the article.
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