Major tidal turbine contract

Paul Boughton
ABB Ltd has secured an order in excess of £2 million for the engineering, supply, installation and commissioning of an electrical generating system for two tidal turbines, rated at 2.4MW.

The first full-scale Neptune tidal stream device is the design of Edinburgh’s Aquamarine Power Ltd. The Neptune demonstration design is on schedule for delivery in 2010 at the UK tidal test centre, known as the European Marine Energy Centre (EMEC), located in Orkney, as a precursor to commercial deployment.

The entire Neptune generating system is based on proven wind turbine technology and sources energy from the flood and ebb of the tides, converting tidal energy into electrical power to supply to the grid.

The device comprises two horizontal axis tidal turbines, which will be mounted on a single monopile for the commercial demonstrator. The device features bi-directional (flood and ebb) generation, with its design heavily influenced by wind turbine technology and as such gives predicted efficiencies of up to 45 per cent. This is achieved through both variable speed operation and pitch control. Close integration of electrical and mechanical systems ensures fault tolerant design and UK grid code compliance.

The design is simple and robust, aimed at achieving high levels of reliability through low component count and use of duty/standby components at critical points.

Among ABB’s scope of supply includes two ABB industrial drives, two 1.6 MVA Midel filled transformers, two 1.2 MW induction generators, an 11 kV switchboard and two pitch control and supervisory controllers. In addition ABB is responsible for the grid connection engineering, interface engineering, nacelle electrical engineering and containerisation of all the equipment. The system will include a custom-designed control system, which will allow remote monitoring, fault prevention and continuous grid quality power output.

Neptune’s mechanical and electrical systems have been designed from the outset for large scale array deployments. For example, the electrical system is similar to some of the latest developments in off-shore wind turbine designs. This allows for a rapid transition from commercial demonstrator to commercial farms without major re-engineering. Also, the ‘steel can’ design of the Neptune nacelles enables the use of different power train components, to match any site specific requirements without major re-design.

The mechanical engineering and design is by Babcock Strachan & Henshaw with the build and installation being carried out by Aquamarine Power.
The Neptune technology is a joint venture combining the strengths of the UK’s largest renewable generator, Scottish and Southern Energy, and a major Scottish-based engineering firm. Aquamarine Power brought the Neptune system into its portfolio in October 2007, and is now continuing to develop this device.

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