Friday, June 23, 2006

By the power of Greyskull...

The other day I stumbled upon some kick arse ideas for renewable energy production. The source of this energy is from the sun but they have let nature do the conversion and concentration from light/heat into kinetic energy in the form of waves. With WA having waves with some of the highest energy content in the world. Seems like a perfect solution for us.

Seapower Pacific

With the test unit based in Fremantle, this method is a fairly novel approach to desalination of seapower, with the added benefit of electricity production.

From the FAQ:
Unlike other wave energy systems, the CETO wave power converter designed and developed in Western Australia , is the first unit to be fully submerged and resting on the seabed in up to 20 metres of water. It produces highly pressurised seawater from the power of waves.

The process: As a wave moves over the top of the CETO unit it is enhanced, the wave crest depresses a disk and the force is transmitted to reciprocating pumps which deliver water at 7000kpa (1000psi). The high-pressure seawater comes ashore in a 125mm pipe to a turbine to produce electricity, or to a reverse osmosis filter to produce fresh water.

The appeal of wave power includes the vast natural resource world-wide, the dual capability to produce electricity and fresh water, and the exceptionally clean/green result without fossil fuel inputs. The specific advantages of CETO include being the first wave power converter to sit on the seabed, where it is invisible, safe from storms and ocean forces, and self contained. Unlike other wave energy technologies that require undersea grids and costly marine qualified plant, CETO requires only a small diameter pipe to carry high pressure seawater ashore to either a turbine or a reverse osmosis filter, and CETO can be employed in any location that geographical and wave conditions permit.

Pretty interesting idea. I don't know about the long term viability of the rubber membrane and the piping to deal with 1000psi of pressurised seawater. If they can get it to work reliably, this would be good for WA, fresh water and electricity.


From the technology info page:
Ocean waves contain enormous amounts of energy, but the energy in each crest is generally spread out along it. If all the energy could be transported to one point it could be harnessed far more readily.

It is possible to focus all the energy of a plane surface gravity wave crest, the type you see breaking on the beach, on to a single point using a parabolic wave focusser. The section of the wave is reflected by a parabolic wall and converges on the focus of the parabola. As the wave converges, the crest height grows to a maximum in the focus area. Atop the focal region is a chamber that extends deeper than any likely wave trough. The oscillatory wave motion causes a similar oscillatory airflow through the chamber .

At the narrowest point of the chamber, the airflow accelerates and a revolutionary turbine, outlined later, converts the energy in the airflow into mechanical energy which drives an electrical generator. The parabolic wall, chamber and turbine are the essence of the Energetech Australia Wave Energy System.

The Parabolic Wall - Focussing The Waves

The conditions that must be met to maximize the wave focussing are:

Ideally, the crests will propagate parallel to the axis of symmetry of the parabola. While slight variations will result in little energy loss, the greater the angle between the axis of symmetry and the propagation direction, the more the energy will be spread out.

The sea bottom should be reasonably flat, so it does not disturb the wave direction, and deep enough so that when wave section enters the parabola, the crests do not steepen and break as they grow.

A very choppy scattered incoming wave will scatter some energy away from the focus. The energy loss arising from the above-mentioned conditions can be minimized by choosing the appropriate focal length of the parabola, so that the waves do not have the time or space to vary greatly.

The wave which converges on the focus will not be a full circle as there will be a missing section on the open ocean side. At the edges of this missing section, there will be some diffraction of energy.

The Energy Extracting Device

At the focus, the water will rise and fall periodically with amplitude of approximately 3 times that of the incoming waves. All the energy of the section of the incoming plane wave converges on this point.

The Denniss-Auld Turbine in conjunction with a chamber in which the air flow is oscillatory is the best way to convert the potential energy of the water into mechanical energy. The centre of the chamber should be located above the focus of the parabolic wall.

The only problem with this method is the massive structure that is required above the waterline creating something a bit unsightly. Nice way of harnessing the wave energy with the minimum of moving parts though.

The really good thing about this method of power generation is the efficiency of the conversion from wave energy to electrical energy. Seas conditions having a 1m swell can produce 1-2 MW of power... As a comparison, a coal fired power station produces 500MW.

:Where do you think renewable energy should come from?

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