Oyster wave energy converter

1st May 2012

Client:

Aquamarine

Project:

The Oyster's wave power technology captures energy in near shore waves and converts it into clean sustainable electricity. Essentially Oyster is a wave-powered pump which pushes high pressure water to drive an onshore hydro-electric turbine.

Wave power is generated by wind blowing over the surface of the ocean far out at sea. The action of the wind transmits energy into waves. These waves can travel vast distances with little energy loss before breaking on the shore. The Oyster is designed to harness this energy and convert it into electricity.

The Oyster wave power device is a buoyant, hinged flap which is attached to the seabed at depths of between 10 and 15 metres, around half a kilometre from the shore.

Brief:

Oleo was commissioned to assist in the design of the Oyster by protecting the buoyant flap "door" and its associated hardware from damaging each other due to "slamming effect" (hard contact) in conditions arising from high amplitude wave and/or associated low water level conditions

Solution:

Oleo provided a "high tech" door closer using reciprocating buffers between the main moving elements. The velocity sensitive device limited the closing forces to acceptable levels within the design force limits of the Oyster. The Oyster application represents the harshest operating environment of all of Oleo's applications.

The main technical challenges were:

Submerged operation (corrosion / water ingress): This involved investigation of a new external sealing regime and use of corrosion resistant material and finishes. Corrosion is an everyday problem, but the use of a traditional solution such as stainless steel helped eliminate the problem of corrosion. However, stainless steel is not as robust as Oleo’s traditional high tensile steel and therefore additional design techniques needed to be factored in to take this into account.
Continuous operation caused by the movement of the sea generates high temperatures within the Oleo unit. The reason for greater heat generation is that mechanical energy in operation is converted into heat. This heat energy is transmitted away by the surrounding medium usually air or in this case water, normally temperature increase is minimal since the aggregate energy entering a buffer is much less than the heat leaving the buffer. However, the intensity and continuous nature of the energy input generated potentially damaging temperatures. To verify the solution Oleo instigated specialised immersion testing to investigate the absorption devices heat generation, heat transmission and the validity of the chosen high temperature sealing regime.

Oyster wave energy converter