In 2005 Aquamarine Power Ltd. was formed to develop Oyster, a near shore flap which is hinge connected to the sea bed. With a combination of private equity and grant aid a 350kW Oyster module has been designed and it is planned to install a prototype module at the EMEC test site in Orkney when the nearshore test berth is available. In this version of Oyster high pressure sea water will be pumped ashore to drive a Pelton wheel. Ultimately it is envisaged that Oyster units will be arranged in clusters feeding power to a power take off unit of between 3.5 and 5 MW capacity. Arrays of clusters will form power stations of 20 to 100 MW capacity.
An extensive research and development programme has produced a very efficient structural form, which gives Oyster one of the highest power to weight ratios of all current technologies combined with high capture factors in the most commonly occurring seas. The sea bed foundations and installation technique developed enables Oyster to be easily removed and reinstalled for major maintenance when required. This is a feature normally associated with moored devices.
Although there are other bottom-hinged flap devices, Oyster is different in several ways and occupies a different part of the design space. For example, unlike the other systems it completely penetrates the water column from the water surface to the sea bed. Although it might be considered that such a system would be vulnerable in extreme seas, extensive wave tank modelling has shown that the flap intrinsically decouples from the wave as the oscillation increases and that the wave loads experienced are manageable in the three operational modes; generating, undamped and parked on the sea bed. However, model tests show that Oyster can remain generating in all sea-states including plunging breakers.
This paper charts the evolution of Oyster presenting some of the research that has led to the current design. An outline of the impending sea trials of a prototype demonstration unit is given along with the projected outcomes.