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User:Paulecotricity/Snapper (Wave Power)

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Snapper (Wave Power) Snapper is a novel rare-earth magnet based wave energy conversion system. Snapper is a Seventh Framework Programme funded by the EU, including partners from Norway, Sicily, Lithuania, and the UK[1].

History

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The concept of the Snapper electrical generator arose during attempts to overcome a fundamental difficulty of wave power generation[2].

The inventor, Ed Spooner has previously worked in the development of direct-drive (gearless) generators for wind turbines and tidal power turbines. However, wave power systems present a much more difficult challenge. Electrical generators produce power as a result of the movement of an applied force. The size, weight and cost are all related to the magnitude of the force but the power is related to speed as well. Sea waves have very low vertical velocities but can produce very high forces and so normal types of electrical generator would be very heavy, expensive and inefficient.

Technology

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Snapper works like a typical linear alternator in which a set of magnets mounted in a translator is moved up and down inside multiple coils of wire of an armature[3]. However, there is a crucial difference with Snapper: alongside the armature coils is a second set of magnets of alternating polarity.

These armature magnets prevent the translator magnet assembly from moving up and down smoothly in relation to the armature. Instead magnetic forces between the armature and translator repeatedly couple the two sub-assemblies together until the external force is able to overcome it. This results in a series of faster movements (faster relative movements between armature and translator) more suited to classical electrical generation.

Principles

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Instead a new approach was conceived where the continuous slow movement of the wave power machine is divided into a sequence of rapid bursts. The maximum force applied during each burst is well defined according to maximum force that can be transmitted by a coupling. Varying drive speeds are accommodated by the variation in the delay between bursts of motion.

The diagram illustrates an example of how slow continuous motion giving a total movement of 2m can be subdivided into a set of short bursts. It is analogous to a common electronic technique for converting power in the form of low current at high voltage to high current at low voltage.

Energy must be stored during the waiting periods. The Snapper machine uses a spring and a magnetic coupling in the force transmission path. As the applied force increases, the spring stretches and stores energy. When the force exceeds a certain threshold the magnetic coupling can no longer transmit the force and it snaps allowing the energy stored in the spring to be released quickly and efficiently[4].

See Also

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References

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  1. ^ http://cordis.europa.eu/fetch?CALLER=FP7_PROJ_EN&ACTION=D&DOC=1&CAT=PROJ&RCN=91915 "European Commission CORDIS"
  2. ^ http://www.narec.co.uk/media/published_papers/ "Narec published papers: Snapper An efficient and compact direct electric power take-off device for wave energy convertors"
  3. ^ http://www.youtube.com/watch?v=46raxrQgNXk "YouTube Snapper Wave Energy Convertor – Dry testing of prototype linear test rig"
  4. ^ http://www.youtube.com/watch?v=cAPmX_BdYK0 "YouTube Snapper Wave Energy Convertor"
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