Pelamis Wave Energy Converter is Launched

Following six years of detailed design and development, UK-based Ocean Power Delivery has completed the build of the first full-scale Pelamis Wave Energy Converter. Similar in size and rating to a modern wind turbine the Pelamis is designed to harness the energy contained in ocean waves to produce electricity. The machine is the world’s first commercial-scale floating wave energy converter.

Port of Leith, Edinburgh, March 3, 2004 [] Jim Wallace MSP, Deputy First Minister of Scotland, and 75 members of the renewable energy sector attended an event to mark the launch of the Pelamis at OPD’s test facility in Leith Docks. Guests were given the opportunity to view the progression of the project, from the wave tank testing of the 50th scale machine and the Power Conversion Test Module to the final full-scale prototype machine moored at the quayside. The Pelamis is now being prepared for initial sea trials which will begin at the beginning of March. The 750 kW Pelamis machine measures 120m long by 3.5m wide (about the size of four train carriages) and weighs 750 tons fully ballasted. The machine was 100% assembled and fabricated in Scotland with over 90% of the machine’s content being sourced from the UK. The Pelamis is a semi-submerged, articulated structure composed of cylindrical sections linked by hinged joints. The wave-induced motion of these joints is resisted by hydraulic rams, which pump high-pressure oil through hydraulic motors via smoothing accumulators. The hydraulic motors drive electrical generators to produce electricity. Power from all the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected together and linked to shore through a single seabed cable. A novel joint configuration is used to induce a tuneable, cross-coupled resonant response, which greatly increases power capture in small seas, according to OPD’s Business Development Director, Max Carcas. Control of the restraint applied to the joints allows this resonant response to be ‘turned-up’ in small seas where capture efficiency must be maximised or ‘turned-down’ to limit loads and motions in survival conditions. The machine is held in position by a mooring system, for which a patent has been applied for, comprising of a combination of floats and weights which prevent the mooring cables becoming taut. It maintains enough restraint to keep the Pelamis positioned but allows the machine to swing head on to oncoming waves. Reference is achieved by spanning successive wave crests. The 750 kW full-scale prototype is 120m long and 3.5 m in diameter and will contain three Power Conversion Module, each rated at 250MW. Each module contains a complete electro-hydraulic power generation system. Ideally the Pelamis would be moored in waters approximately 50-60m in depth (often 5-10km from the shore). This would allow access to the great potential of the larger swell waves but it would avoid the costs involved in a longer submarine cable; if the machine was located further out to sea. Throughout the construction of the full-scale Pelamis, OPD has been working closely with WS Atkins who have independently verified the prototype design according to (DNV) offshore codes and standards.

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