Pelamis Wave Energy Converter
The Pelamis Wave Energy Converter is a technology that uses the motion of ocean surface waves to create electricity. The machine is made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity.
Developed by the Scottish company Pelamis Wave Power (formerly Ocean Power Delivery), the Pelamis became the world’s first offshore wave machine to generate electricity into the grid, when it was first connected to the UK grid in 2004. Pelamis Wave Power have since gone on to build and test five additional Pelamis machines: three first-generation P1 machines, which were tested in a farm off the coast of Portugal in 2009, and two second-generation machines, the Pelamis P2, which started tests off Orkney in 2010.
The Pelamis machine is an offshore wave energy converter, operating in water depths greater than 50m. The machine consists of a series of semi-submerged cylindrical sections linked by hinged joints. As waves pass along the length of the machine, the sections move relative to one another. The wave-induced motion of the sections is resisted by hydraulic cylinders which pump high pressure oil through hydraulic motors via smoothing hydraulic accumulators. The hydraulic motors drive electrical generators to produce electricity. Electricity from all the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected and linked to shore through a single seabed cable.
The Pelamis is an attenuating wave energy converter designed with survivability at the fore. The machine's long thin shape and low drag profile minimises hydrodynamic forces, namely inertia, drag, and slamming, which in large waves give rise to large loads. The machine responds to the curvature of the waves rather than the wave height. As waves can only reach a certain curvature before naturally breaking, this limits the range of motion through which the machine must move but maintains large motion at the joints in small waves.
The Pelamis has a novel joint configuration used to induce a tunable cross-coupled resonant response. 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.
P2 Pelamis Testing at EMEC
The P2 Pelamis design is Pelamis Wave Power's second generation Pelamis machine. The Pelamis P2 is 180m long, 4m diameter and approximately 1350 tonnes in weight. Consisting of five tube sections and four flexible joints, the design is longer and fatter than the previous P1 design.
In 2010, Pelamis Wave Power began tests of the first Pelamis P2 machine at the European Marine Energy Centre, Orkney, Scotland. The machine is owned by the German utility company, E.ON, and was the UK's first commercial supply contract in the marine energy sector. In March 2010 Pelamis Wave Power announced a second order for a P2 machine, from ScottishPower Renewables, part of Iberdrola Renovables. This second machine was installed for the first time at EMEC in May 2012. The two utility companies have announced that they will work together to share and collaborate in testing of the P2 Pelamis technology.
Projects in Development
E.ON and ScottishPower Renewables have announced plans to build larger projects using Pelamis machines in the waters off Orkney's west coast. Both companies won leases in 2010 from The Crown Estate, who own the seabed around the UK, for projects of up to 50MW. The 'Pentland Firth and Orkney Waters Leasing Round' was the world's first commercial scale wave and tidal energy leasing opportunity. Pelamis Wave Power were also awarded a lease in this round to independently develop a project of up to 50MW on the north coast of Scotland at Farr Point, Sutherland.
In October 2010, Pelamis Wave Power were secured a second agreement for lease from The Crown Estate to develop a 10MW project off Bernera, Isle of Lewis, Scotland. The farm, planned for construction in 2015-2016, will consist of up to 14 Pelamis machines.
In December 2009, Pelamis Wave Power announced a joint venture with Swedish utility Vattenfall to develop the Aegir wave farm off the southwest coast of Shetland. The joint venture company, named Aegir Wave Power, is planning to install a 10MW farm using around 13 Pelamis machines and was awarded an Agreement for Lease from The Crown Estate in May 2011.
Pelamis Wave Power has also expressed an interest in installing Pelamis devices at the Wave hub development off the north coast of Cornwall, in England, and in the Pacific ocean off the coast of Tillamook, Oregon.
Prototype Pelamis Machine
Pelamis Wave Power tested their first full-scale prototype at the European Marine Energy Centre in Orkney, Scotland between 2004 and 2007. The machine, which was rated at 750 kW, was the world's first offshore wave power machine to generate electricity into the grid system.
The prototype was 120m long and 3.5m in diameter. It consisted of four tube sections linked by three, shorter, power conversion modules
Aguçadoura Wave Farm
In 2008 Pelamis tested three first generation, P1 Pelamis waves at the Aguçadoura Wave Farm. Located off the northwest coast of Portugal near Póvoa de Varzim, the farm had an installed capacity of 2.25MW and was the world's first multiple machine wave power project. The project was part funded by Portuguese utility Enersis, at the time owned by Australian global investment company Babcock & Brown. The farm first generated electricity in July 2008 but was taken offline in November 2008 at the same time as Babcock & Brown encountered financial difficulties.
- The Aguçadoura Wave Farm was featured in the Yann Arthus-Bertrand documentary "Home".
- Pelamis was featured in the 2008 television documentary "Man-Made: Aqua Power".
- BBC's Bang Goes the Theory explored inside the Pelamis P2 in Episode 4 of Series 3.
- Pelamis Wave Power was featured on James May's Big Ideas.
The front of the Pelamis machine bursting through a wave at the Aguçadoura Wave Park
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- Pelamis Wave Power Ltd.
- Aegir Wave Power
- The European Marine Energy Test Centre
- The Power Technology website
- Pelamis Secures Wave Energy Order from E.on
- Pelamis at Aguçadoura video