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    Wave Energy 

    The use of devices which harness wave energy to make electricity is becoming increasingly popular in the UK. The RYA explains how these devices work and how they can affect recreational boating.

    Marine renewable energy covers a range of technologies including wave, tidal and ocean thermal energy conversion. Unlike the three-bladed turbines used to capture wind energy, there is a large range of technologies used to harness wave energy. The process by which the most popular technologies work can be seen below, but in practice, they could look very different both in size and shape.

    How do wave energy devices work?

    The Government is legally committed to meeting 15% of the UK's energy demand from renewable sources by 2020. As a result, exploiting renewable energy resources by harnessing wave energy is becoming increasingly important in the UK. Wave energy may have a crucial role to play in the UK energy mix, with many of these innovative technologies already being trialled in UK waters.

         
     
    Attenuators are floating devices that are aligned perpendicular to the waves.  These devices capture energy from the relative motion of the two arms as the wave passes them.   Surface point absorbers are floating structures that can absorb energy from all directions. They convert the motion of the buoyant top relative to the base into electrical power.
         
     
    Oscillating wave surge converters are near-surface collectors, mounted on an arm which pivots near the sea bed.  The water particles in the waves cause the arm to oscillate and generate power.   Oscillating water column technologies convert the rise and fall of waves into movements of air flowing past turbines to generate power.
         
     
    Overtopping devices have a wall over which waves break into a storage reservoir which creates a head of water.  The water is released back to the sea through a turbine to generate power.   Submerged pressure differential devices capture energy from pressure change as the wave moves over the top of the device causing it to rise and fall.
       
     
    Bulge wave technology consists of a rubber tube filled with water, moored to the seabed heading into the waves. The water enters through the stern and the passing wave causes pressure variations along the length of the tube, creating a ‘bulge’. As the bulge travels through the tube it grows, gathering energy which can be used to drive a standard low-head turbine located at the bow, where the water then returns to the sea.   Two forms of rotation are used to capture energy by the movement of the device heaving and swaying in the waves. This motion drives either an eccentric weight or a gyroscope causes precession. In both cases the movement is attached to an electric generator inside the device.

     

    Images and descriptions courtesy of Aquatic Renewable Energy Technologies (Aqua-RET) www.aquaret.com 

    Wave Energy Sites in the UK

    There are a number of wave energy sites already leased within UK waters. The Crown Estate website lists information about each project, including test sites, and where each site is in the planning process. You can also click on the image below for a larger view of The Crown Estate map.

    Wave and Tidal Energy Map

    This map is courtesy of The Crown Estate.

    The RYA Position

    Whilst the RYA acknowledges the Government's desire to promote renewable energy, it is keen to ensure that the navigational safety of recreational craft is safeguarded around the coast.

    The RYA has developed a detailed position statement on offshore renewable wave energy developments, based on recreational craft data, which it provides to every developer during the consultation process. The RYA believes that the impact that wave energy devices have on recreational boating can be minimised provided developers fully consider the following key points:

    • Collision risk. The RYA believes that the collision risk to recreational craft can be minimised by specifying a minimum safe water clearance over submerged structures, moving components and associated infrastructure determined in accordance with the MCA Under Keel Clearance policy paper.
    • Charting, marking and lighting. The RYA supports the guidance provided by the MCA, UKHO and GLAs and works with them to identify site specific issues that may occur.
    • Navigational and communication equipment. Any proposed development should account for any effect on small craft navigation and communication equipment in detail.
    • Location. Recreational routes, general sailing area, racing areas and access to boating facilities and anchorages must be considered when examining the impacts of wave energy devices and arrays and their associated infrastructure. Poorly sited wave energy devices and arrays and those built within the 12nm limit may increase the risk to navigational safety and discourage visiting boaters to the area.  This would have an adverse effect not only on the visitors but also on the local economy.
    • Sailing and racing areas. Any interference or adverse impact caused by a wave energy device or array that encroaches into a racing or sailing area would create a significant negative impact on boating and diminish its value for recreation.
    • Cumulative and in-combination effects. The RYA expects development site plans to include all adjacent developments that may have cumulative and in-combination effects on shipping and navigation.

    The RYA position statement on offshore renewable wave energy developments is downloadable from the list on the right. 

    The RYA has also carried out an extensive mapping project to identify the main cruising routes, sailing and racing areas to better inform the management process. Initially this culminated in a detailed description of cruising routes, racing and sailing areas for the three strategic wind farm development areas in 2004 and is reported in the document 'Sharing the Wind'.

    This project then evolved to cover the whole of the UK following considerable demand from the offshore renewable energy industry. In 2005, with funding from Trinity House, the RYA produced the first UK Coastal Atlas of Recreational Boating. This dataset has since been updated and is now regularly incorporated into developers’ consultations and navigational risk assessments.

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