The Pelamis absorbs the energy of ocean waves and converts it into clean, green electricity.
The Pelamis is an offshore wave energy converter that uses the motion of waves to generate electricity. The machine operates in water depths greater than 50m and is typically installed 2-10km from the coast. The machine is rated at 750kW with a target capacity factor of 25-40 per cent, depending on the conditions at the chosen project site. On average one machine will provide sufficient power to meet the annual electricity demand of approximately 500 homes.
Pelamis Wave Power have produced six full-scale Pelamis machines to date, including two of the latest ‘P2’ design machine, built for utility customers E.ON and ScottishPower Renewables. For more information see our ‘Development History’.
How the Pelamis works
The Pelamis machine is made up of five tube sections linked by universal joints which allow flexing in two directions. The machine floats semi-submerged on the surface of the water and inherently faces into the direction of the waves. As waves pass down the length of the machine and the sections bend in the water, the movement is converted into electricity via hydraulic power take-off systems housed inside each joint of the machine tubes, and power is transmitted to shore using standard subsea cables and equipment.
Each of the power take-off units at the joints of the machine are identical, and operate independently from each other with redundancy of all main components.
The power take-off system is driven by hydraulic cylinders at the joints, which resist the wave-induced motion and pump fluid into high pressure accumulators, allowing generation to be smooth and continuous.
Control of the resistance applied by the hydraulic cylinders allows generation to be maximised when waves are small, and the machine response to be minimised in storms.
Pelamis technology has been designed with survivability in mind.
The Pelamis hides from big waves by diving through them, just like a surfer heading out to sea.
The long, thin, streamlined shape of the machine means forces of drag and slamming are minimised.
Pelamis responds to wave curvature not height.
Since waves naturally get longer as they get higher, this inherently limits the range of motion the machine must move through.
The Pelamis has the highest power capture for a given volume of any type of wave energy machine.
The Pelamis is a ‘line-absorber’, where waves are absorbed by a long structure perpendicular to the wave front. This type of configuration has the highest power capture potential available for a given volume.
The Pelamis is ‘tuneable’ to sea conditions to maximise power capture.
This selective resonant response ensures that power capture is maximised in small waves while remaining minimised in heavy seas.
In developing and manufacturing the Pelamis wave energy converter, we have utilised established and proven technology wherever possible.
The Pelamis is a novel assembly of ‘off the shelf’ proven technology, including elements used in the offshore oil and gas industry, and also in established technology such as construction vehicles and other generation technologies.
This use of existing technology widens the supply chain options and increases component reliability.
Pelamis is firmly of the view that the aggressive offshore environment is incompatible with any requirement for access to the machine while on-site.
For this reason, we believe one of the most important and innovative aspects of the Pelamis technology is our ability to remotely install and remove the machine from its anchoring and electrical systems when required for maintenance or testing.
The Pelamis connection system is cost effective, quick to use, operable in a wide range of weather conditions, and most importantly, significantly safer than other installation techniques.
Pelamis Wave Power uses a modular manufacturing method.
Each Pelamis machine is made up of a number of similar sections, each containing an identical joint assembly and power take off equipment. The high-tech generation systems of each joint can be consolidated into a compact ‘skid’ that can be assembled and factory tested independently and on an open frame before attachment in the main tube section.
This method of manufacture minimises the time that large structural components are required in the assembly area, considerably reducing required factory size and lifting requirements. A further benefit is that the entire commissioning joint power take off system is easier to transport to final assembly sites around the world.
Pelamis technology is considered to have one of the lowest forms of environmental impact on the marine environment.
Being environmentally benign is of high importance to Pelamis Wave Power. We are working with our customers and academic institutes to develop an environmental work programme for wave power technologies.
The appearance of the Pelamis at sea is carefully considered, to maximise safety of passing vessels while minimising aesthetic effects on the seascape.
The strength of these key features are what we believe make Pelamis the optimal wave energy converter, and the reason we’re working with customers and partners to develop commercial-scale wave farms using Pelamis technology. For more information about those projects, visit ‘Our Projects’ pages.
The Pelamis and its infrastructure are optimised for mass production for multiple-machine wave farms. As with every previous generating technology, Pelamis Wave Power expects costs to significantly fall with continued deployment into the market. Our onward development programme will focus on driving down the cost of energy produced by the Pelamis machine in order to make the Pelamis fully competitive with offshore wind energy and other marine technologies.
In the longer term it is believed that wave power projects using Pelamis machines have the potential to become one of the lowest cost forms of generation, particularly if the cost of conventional generation continues to rise.
Key areas for development will include:
- Optimisation of the device configuration
- Reduction of capital costs by exploring the use of alternative structural materials
- Development of structures and systems suitable for volume production
- Further development of control systems to maximise energy capture
With the installation of a significant number of Pelamis devices, Pelamis Wave Power foresees the continued development of specialist hydraulic components and power conversion systems by a dedicated supply chain. This will in turn allow further economies of scale and reductions in cost.