Portugal to house world¹s first commercial wave farm

Paul Boughton

A Portuguese consortium is to build the initial phase of the world¹s first commercial wave farm to generate renewable electricity from ocean waves. The initial phase will consist of three of Ocean Power Delivery¹s (OPD)Pelamis P-750 machines located 5km off Portugal¹s northern coast, near to Póvoa de Varzim.

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 seabed. Several devices can be connected together and linked to shore through 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.

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, 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 model is 120m long and 3.5m in diameter and contains three power conversion modules, each rated at 250kW. Each module contains a complete electro-hydraulic power generation system.

The E8m Portuguese project will have an installed capacity of 2.25MW, and is expected to meet the average electricity demand of more than 1500 households while displacing more than 6000 tonnes per year of carbon dioxide emissions from conventional generating plant.

The consortium is lead by Enersis, part of the Semapa Corporation which is one of Portugal¹s leading renewable energy companies with 100MW of mini hydro, 500MW of wind farms under operation/construction and a further 500MW under development. A letter of intent has also been issued to order a further 30 Pelamis machines (20MW) before the end of 2006 subject to satisfactory performance of the initial phase.

The project is being supplied by Ocean Power Delivery Portugal, a wholly owned subsidiary of OPD with full rights to manufacture Pelamis machines in Portugal. Construction of the project will begin immediately.

Richard Yemm, md of OPD, said: ³This is a significant milestone for our company and for wave energy. We see this order as just the first step in developing the Portuguese market, which has the potential to be worth up to a billion Euros over the next 10 years.² Gonçalo Serras Pereira, chairman of Enersis, commented: ³After 17 years of experience developing, constructing and operating mini hydro schemes, and nine years with wind farms, we believe wave energy will be the new Portuguese endogenous renewable resource.

This move in conjunction with other potential partners may win significant industrial economic benefits for Portuguese companies as the market is developed and wave energy gains competitive advantage with other renewables.² Camcal on the Isle of Lewis, Scotland, is to fabricate the main tube segments for the Portuguese contract.

The company will provide 12 main tube segments, four per machine, with each section being similar in size and length to a train carriage. The segments will then be delivered to Portugal for final assembly utilising Camcal¹s deep water access for seabornetransport.

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