Energy and the Environment-A Coastal Perspective

 

How does an attenuator work?

Attenuators are situated parallel to the force and direction of a wave. They are held in place by mooring on the seabed. The motion of the device from the crest and trough of the wave exerts force on a turbine that then feeds energy into the grid.

The Image below shows the inner structure of the most common attenuators design:

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The Pelamis Wave Energy Converter:

 

 

• The Pelamis Wave Energy Converter is the result of many years of engineering development by Pelamis Wave Power. It was the world’s first commercial scale machine to generate electricity to the grid from offshore wave energy and the first to be used commercially (1).
• The Pelamis device was developed in Scotland and was the first commercially viable wave energy attenuator device.
• The Device was originally intended to produce 2.5 MW.
• Real world applications showed the first devices in Portugal had a rated power 750 kilowatts.
• A typical Pelamis ‘farm’ would span one square kilometer, providing 30 megawatts of power in an optimal setting
• 20 megawatts is more likely for a location near North Carolina
• The second generation of Pelamis devices, known as P2, has been tested in Orkney Scotland and shows considerable improvement over the first device.
• The combined P2 test program – which also involves testing by an E.on-owned machine – has now accumulated 7500 grid connected operating hours, and exported 160MWh of electricity to the national grid. (1)

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Anaconda Wave Energy Converter

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source: http://www.guardian.co.uk/environment/2009/may/06/anaconda-wave-power

• Instead of hinged segments, the Anaconda is made up of one large rubber tube.  Bulge waves form inside the tube when it is squeezed by a passing wave.   The action of the bulge waves turn a power-generating turbine at the far end of the device.
• The full scale device was proposed to be about 200m in length and produce 1MW of power
• Could have potentially been used in any area where wave power exceeds 25 KW/m  (5).
• Cheaper to produce and easier to maintain than the hard-surfaced attenuators
• The company Checkmate Seaenergy ltd., appears to no longer exist, casting doubt on the Anaconda’s viability.

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Potential for use worldwide and in the United States and North Carolina:

Optimal locations for the Pelamis wave energy device are circled on the map. Note that offshore of the United States East Coast there is potential for wave power.

Photo: http://hydropower.inel.gov/hydrokinetic_wave/pdfs/day1/09_heavesurge_wave_devices.pdf

The following graph is from a study which was conducted using buoys at various offshore locations to determine the amount of potential power which could be generated by a wave energy device such as the Pelamis.

The following graph shows global wave power density estimates.  Based on current predictions, sites in the yellow to red range would likely be compatible with the Anaconda device (5).

The following chart shows the wave power potentials for several states as determined in a 2004 study (6):

State	Wave Power Density	Estimated Annual Energy Production	Assumed Capacity Factor
Maine	12.4 kW/m	1076 MWh	40%
Oregon	21.2 kW/m	1337 MWh	40%
Washington	26.5 kW/m	1587 MWh	40%
Hawaii	15.2 kW/m	1143 MWh	40%

Attenuators are a feasible technology in many areas, requiring less wave power than many other wave power converters, such as point absorbers.  One potential issue for wave energy in the future is the variability of the resource.  Wave power fluctuates seasonally and there may be some annual fluctuation, though in some areas this fluctuation is negligible (7.)  Wave attenuators have environmental impacts which are in line with other renewable energy devices (Boehlert and Gill.)

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Works Cited:

Munro, Alistair. “Year of Pelamis Wave Power Testing Hailed Success.” The Scotsman. 05/21/2013

Boehlert, George and Andrew Gill. “Environmental and Ecological Effects of Current Renewable Energy Technology: A Synthesis.” Oceanography (2010): 68-81. Electronic Document.

 

 

This page has the following sub pages.

• How it Works

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