Oyster Wave Energy

Control Techniques Inverters Chosen for Aquamarine Power’s Flagship Technology – The Oyster Marine Energy Generator

The world’s largest and most successful working hydro-electric wave energy device, known as ‘Oyster’, has, at its heart, a 315kW high-efficiency grid connected inverter system from Control Techniques.

Aquamarine Power’s Oyster marine energy generator, sits just off shore, in Orkney, and comprises a large buoyant steel flap hinged to a base that sits on the sea bed. As waves roll over the device, the flap oscillates backwards and forwards, driving two hydraulic pistons attached to each side. High pressure water from these two pumping cylinders – clean, salt-free water in an enclosed system – is pumped ashore, driving a Pelton wheel with spoon-shaped buckets that harness the energy of the high pressure water. This is attached to a flywheel (to smooth out variations), powering a standard induction generator. Control Techniques inverters take the generated power and provide an interface with the grid.

Testing of the demonstration scale wave energy device commenced at NaREC in March last year and it is now installed and working offshore at Billia Croo near Stromness, in Orkney . The Oyster was officially turned on in November 2009 to generate power for the national grid and local homes in Orkney and beyond.

The more powerful the wave action, potentially the more electricity that can be generated from such devices, with the maximum output being in the winter months, coinciding with maximum demand – it has been estimated that big waves incorporate potential energy amounting to 200kW per metre!! Long term, marine energy has the potential to meet up to 20% of the UK’s energy demands.

Control Techniques was involved in the development at an early stage, because of its close working relationship with the New and Renewable Energy Centre (NaREC) at Blyth, where the Oyster concept was under test in their dry dock facility.

Now, Oyster is installed at the European Marine Energy Centre’s test site in Orkney, where two Control Techniques inverters provide a clean supply to the grid, with low harmonic distortion.