Frequently Asked Questions

We’ve tried to provide answers to the issues that Pelamis are frequently asked about here. It may also be that the answer to a question can be found elsewhere on the website: the search bar at the top of the page can locate key words to help with specific queries. The ‘Key Features’ of Pelamis technology are also highlighted below:

Key Features

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.

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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.

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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.

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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.

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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.

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The Pelamis is designed to stay at sea throughout the year – that means it must be able to withstand the worst storms. Pelamis Wave Power designs the Pelamis and its anchoring system to be able to operate in the ‘100 year storm.’ We do this by first measuring the wave climate at the site using measurement buoys and satellite data. This data is then used to verify and refine wave models used to calculate the 100 year extreme conditions – the largest sea you would expect to see at the site in a 100 year period. Using these extreme conditions we then carry out tests in wave tanks and run state-of-the-art computer simulations to model the machine in the storm environment. These tests are not just for the biggest individual waves (approaching 30m high!) but over extended periods in the most extreme storms and current combinations. We design the machine and its moorings to withstand these events with a factor of safety. Lastly, we bring in external, independent experts to check the calculations and tests and verify that our design meets offshore oil & gas standards. This means the question is similar to asking how engineers know that aeroplanes, wind-turbines, or bridges can survive the worst storms. Like generations of engineers before us we have to accept that our knowledge can be incomplete and we have therefore followed a progressive testing programme to complement our design process. Read more on the 'Survivability' page.
The Pelamis is named after Pelamis Platurus, a species of sea snake because of its appearance and the way it moves in the water. It also just sounds ‘right’ and can be pronounced easily in most languages.
The machines are brightly coloured to ensure they are easily visible to other sea users. For projects in Scottish waters, the colour scheme of the machines is decided in consultation with the Maritime and Coastguard Agency (MCA) and the Northern Lighthouse Board (NLB), who are responsible for navigational safety in Scotland. For more information see our 'Visual Impact' page.
Electricity is generated inside the machines, so there is minimal requirement for onshore infrastructure and any associated environmental impact. Each project will require a building near to where the electrical cable comes onshore for the grid connection switchgear and transformer (known as a substation, such facilities are often hidden around our towns and cities). Depending on the site and capacity, there may also be a need to upgrade the local grid network for the additional electricity. For maintenance of machines we also require a modest operations & maintenance base. We carry-out all maintenance inshore in sheltered conditions, as there is no man access to the machine at sea. This base can consist of a small quay (we don’t need the full machine length) or marina pontoons to provide machine access. We also require some storage and vehicular road access.
Electricity generated by the machine is fed back to shore by an underwater electrical cable. Several machines can be linked together to share one cable back to shore. Subsea cabling is widely used to connect island communities and to connect floating structures in the oil & gas industry.
All emerging technologies require a degree of support to get them to market – whether that is private backers or public funding. The subsidies and capital support given to the wave power sector are crucial to allow this new technology to enter the highly competitive energy market where existing technologies could ‘lock-out’ emerging ones. The support enables the technology to mature and grow to a stage that it is cost competitive with other established technology, such as nuclear or coal. Pelamis has already secured supply contracts with two major utilities, showing not just that there is confidence in the technology but that there is real belief that wave will become a substantial new form of energy generation and a new industry. Pelamis machines are manufactured in Scotland creating highly skilled employment and much of our supply chain is also UK based. The UK and Scottish governments are committed to increasing the amount of renewable energy in the current electricity mix. This aim is driven by the need to increase security of supply and reduce polluting emissions. Read more in our pages about 'The Market' and 'Wave Power'.
Pelamis is firmly of the view that the aggressive offshore environment is incompatible with any requirement for access to the machine while offshore. We take a different approach from that of offshore wind, never boarding machines at sea but instead bringing them back to sheltered waters for maintenance. To facility this approach we have designed a unique quick, remotely activated, connection and disconnection system, allowing the Pelamis to be removed from its subsea infrastructure in under 15 minutes and in a range of weather conditions. Read more on our 'Operations & Maintenance' page.
During the project development process we carry out a navigational risk assessment. This process includes consulting with local sea users, such as fisherman, ferry operators and boating clubs, and with the government agencies responsible for navigational safety. We use the information from this assessment to choose a site which has low vessel traffic and to assess what navigational aids are most appropriate. Typically a wave farm will be marked at each corner with navigational marker buoys, which have lights and radar reflectors. Sites will also be marked on navigational charts and notices issued to mariners. Each Pelamis machine is brightly coloured to enhance visibility to sea users, the machines are also marked with lights and radar reflectors. For more information see our 'Visual Impact' page.
The Pelamis is anchored to the seabed by a slack, chain catenary system, similar to how a vessel moors when at sea. The moorings are attached at the front of the machine and the machine can weather-vane (or yaw) around this mooring point to face the wave direction – something the machine does naturally, like a flag weather-vanes into the wind around a flag pole. The machines in Orkney are anchored by drag anchors which bury into the seabed. For more information about the offshore infrastructure see our 'Wave Farm Infrastructure' page.
Marine growth is not such a big problem for the Pelamis, as surface roughness or very slight changes in shape do not affect the function, unlike a propeller blade for example. Corrosion in the marine environment is a well understood problem. All generating equipment is housed inside the machine in the dry. The machine structure is painted with marine grade paint, as used as standard in the oil & gas and shipping industries. We follow the offshore oil & gas codes and recommended practices for corrosion protection.
Like most renewable sources the amount of electricity generated will fluctuate with the resource but the variations in renewable sources are much slower than variations in electricity demand that happen every day (for an extreme example, think of the half-time kettles during a world-cup football match). As waves are generated over hundreds of miles of ocean and travel, not only can we forecast them more accurately than local winds but they are often out of sync with the wind conditions, such that wave power can provide a good balance to wind generation. Read more on our page 'Wave power'.