What are Attenuators?
Attenuators are the type of wave energy devices placed on the surface of the water, moving along with the waves. They are placed parallel to the direction of a wave. They work by bending along with the waves. The motion of the device by the crest and trough of the wave, rotates the turbine which is used to generate power. To restrict the drifting, they are typically moored in place. They are connected to the shore grid through underwater cables.
Pelamis Wave energy converter
One of the most successful designs of the attenuator type wave maker is the Pelamis Wave maker. Pelamis works on the 'line absorber' principle, where waves are absorbed by a long structure perpendicular to the wave front. It consists of 4 to 5 cylinders linked by hinged joints. As the wave passes along the machine, it takes the shape of the wave, with the cylinders moving relative to each other. This motion is resisted by hydraulic pistons which drive hydraulic motors which are eventually used to generate electricity. This is fed to the umbilical cable at the sea bed. Most of the energy available from the waves during the year comes from those that are small compared to the storm waves.
The Pelamis Wave energy converter is the first working commercial scale prototype that was able to successfully generate electricity to the grid. So far there have been six such machines build and operated. It was first connected to UK grid in 2004. 3 first generation Pelamis machines were tested in a farm off the coast of Portugal in 2009. 2 second generation Pelamis, an improved version of the first one, was installed in Orkney, UK and are undergoing tests since 2010.
The Pelamis Wave energy converter is the first working commercial scale prototype that was able to successfully generate electricity to the grid. So far there have been six such machines build and operated. It was first connected to UK grid in 2004. 3 first generation Pelamis machines were tested in a farm off the coast of Portugal in 2009. 2 second generation Pelamis, an improved version of the first one, was installed in Orkney, UK and are undergoing tests since 2010.
Power rating
The power produced by a Pelamis system is calculated using a complicated mathematical model. However, knowing the significant wave height and the dominant wave period and using the power matrix derived by the marine power engineers at Pelamis Wave Power, you can arrive at the power produced by the system. The power matrix is shown below. The Power period in the matrix is the dominant wave period.
The story so far!
Pelamis Ocean Power was a company started in 1998 with the view of commercializing the concept of Pelamis wave energy converter. Despite the company’s founding date the technology for the Pelamis project was started in the early 1980s and has continued development for more than two decades.
A full-scale, four-section production prototype rated at 750kW was sea tested for 1000 hours in 2004. This successful demonstration was followed by the first order in 2005 of a commercial system from a consortium led by the Portuguese power company Enersis SA. The first stage was completed in 2006 and consists of three Pelamis machines of type P1, which is made up of three power conversion sections per machine, each rated at 250 kW with a combined rating of 2.25 MW sited about 5 km off the coast of northern Portugal near Povoa de Varzim. This wavefarm, called the Agucadoura wave farm, was the world’s first commercial wave farm and it first generated electricity in July 2008. However, the wave farm was shut down in November 2008,
as a result of financial issues.
The order for the initial phase was worth €8.2m, funded by a Portuguese consortium led by Enersis. The project was expected to bring power ashore at Agucadoura, and provide electricity to 1,500 homes using the national state run electricity grid system. On completion of both the phases, the project was expected to meet the average electricity demand of more than 15,000 Portuguese households and displace above 60,000 carbon dioxide emissions tons per year.
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. The first Pelamis P2 was installed off the coast of Orkney, Scotland in 2010, followed by the second one in 2012. These machines have demonstrated the safe and efficient operation of the system over more than 90 percent of wave conditions. During its two-year testing period P2-001 provided 15,000 hours’ worth of valuable data, which Wave Energy Scotland is now analysing. This extensive test program has delivered a range of valuable operational experience and performance data.
A full-scale, four-section production prototype rated at 750kW was sea tested for 1000 hours in 2004. This successful demonstration was followed by the first order in 2005 of a commercial system from a consortium led by the Portuguese power company Enersis SA. The first stage was completed in 2006 and consists of three Pelamis machines of type P1, which is made up of three power conversion sections per machine, each rated at 250 kW with a combined rating of 2.25 MW sited about 5 km off the coast of northern Portugal near Povoa de Varzim. This wavefarm, called the Agucadoura wave farm, was the world’s first commercial wave farm and it first generated electricity in July 2008. However, the wave farm was shut down in November 2008,
as a result of financial issues.
The order for the initial phase was worth €8.2m, funded by a Portuguese consortium led by Enersis. The project was expected to bring power ashore at Agucadoura, and provide electricity to 1,500 homes using the national state run electricity grid system. On completion of both the phases, the project was expected to meet the average electricity demand of more than 15,000 Portuguese households and displace above 60,000 carbon dioxide emissions tons per year.
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. The first Pelamis P2 was installed off the coast of Orkney, Scotland in 2010, followed by the second one in 2012. These machines have demonstrated the safe and efficient operation of the system over more than 90 percent of wave conditions. During its two-year testing period P2-001 provided 15,000 hours’ worth of valuable data, which Wave Energy Scotland is now analysing. This extensive test program has delivered a range of valuable operational experience and performance data.
Trivia
Pelamis platurus is a yellow-bellied sea snake that lives in tropical and subtropical waters. It prefers shallow inshore waters. That's where our converter gets its name from!