Q. Where does the name Pelamis come from?
A. The machine was named after Pelamis Platurus, a species of sea snake.
Q. Who invented Pelamis?
A. Richard Yemm together with Dave Pizer and Chris Retzler
Q. Who owns the IP?
A. All Intellectual Property is owned by PWP.
Q. Who do you think will be your customer base?
A. Energy companies and utilities.
Q. How much does Pelamis weigh, how long is it, how wide is it?
A. Pelamis machines weigh ~750 tonnes including ~350 tonnes of sand ballast, are 140m long and 3.5m wide - about the size of five train carriages.
Q. What makes Pelamis better than the other devices?
A. The Pelamis concept offers three times the power capture per unit weight than other devices. This is closely related to capital cost and hence Pelamis offers the potential for the lowest c/kWh generating cost.
Q. What is your Availability, Capacity factor, rating etc?
A. Depends on resource at location but typically 25-40% of rated power over the course of the year.
Q. Do you need different versions for different parts of the world?
A. Not necessarily but there are elements of the design which may be optimised according to site and resource criteria.
Q. How uniform is the basic design?
A. The design is uniform in that elements are modular and replicated throughout the machine facilitating maintenance, and reducing spares holdings, as well being able to benefit from economies of scale.
Q. Why does Pelamis use hydraulics?
A. Hydraulic rams are well matched to the application – high forces and low velocities. Hydraulics also offer the ability to store energy from wave to wave and produce high quality power.
Q. How is Pelamis moored?
A. Slack moored – a common misunderstanding is that the machine reacts against the mooring (rather than against itself). Mooring only becomes taut in extreme 100 year wave.
Q. How do you install the mooring system? How does it work?
A. The mooring system can be installed using an anchor handler or a barge system. The mooring is a slack moored compliant system, similar to that used for oil industry FPSOs, used to keep the machine on station. The mooring is designed to cope with the '100 year' wave with a two times factor of safety on the mooring line's breaking strength in these conditions.
Q. How does one get the power to shore from an array?
A. A single subsea cable at high voltage, step up transformer on the machine to minimise losses. Larger projects would likely have two cables for redundancy
Q. What controls and communications are used?
A. Fibre optic, high bandwidth wireless and low bandwidth wireless (ie triple redundant). Control will be done centrally (ultimately) and automatic with exception reporting.
Q. How do you stop boats hitting it?
A. The sites are delineated with navigational markers with lights and radar reflectors. Portugal and Orkney both have four cardinal markers delineating the site and project site will be marked on charts and notices to mariners. Wave Farm sites are obviously not located in shipping lanes. In comparison to offshore wind we occupy ~4-5 times less area – eg round one offshore wind farms sites were 10km2 and typically 60-90MW. In the same space, albeit different locations we’d be 300MW.
Q. What happens if Pelamis gets loose?
A. System has GPS and is monitored 24/7 so any apparent ‘out of position’ event would be immediately investigated.
Q. How does Pelamis deal with confused seas?
A. Machine self references into the dominant swell (or vector of this). This is because the machine is long and self references down its length. We wouldn’t put the machine in the Pentland Firth where you get wind over tide for example and very confused seas. The dominant swell is a long period wave and takes hundreds or thousands of miles to build up so a little bit of local wind chop short waves superimposed will not have any impact on the predominant swell.
Q. Have you considered using other materials particularly for the floats?
A. Yes, concrete and GRP both offer significant cost saving potential. However volume production will be needed to justify tooling up to do this. In the meantime steel is readily available, well understood, and very suitable for a marine environment.
Q. Why is the Pelamis Red?
A. The machine is red because red is visually intense in close proximity but becomes duller (closer to grey) when viewed from a distance. In the future we will review the colour being used, including where it may be necessary to be compliant with local or prevailing maritime legislation or regulation.
Q. What is the life expectancy of a Pelamis machine?
A. Pelamis is designed to last life of project , which is normally in the order of 20 years.
Q. How many do you have working/deployed?
A. One since 2004, with a further three entering service in Portugal in 2007. We anticipate this to rapidly increase throughout 2008 and beyond.
Q. How long does it take to build a Pelamis?
A. This depends upon PWP's order book but PWP expects to deliver orders within 12-18 months from receipt of order initially with this reducing over time depending on the order book and production capacity.
Q. How long does it take to commission a Pelamis?
A. PWP normally pre-commission each element of the machine during build (eg the 250kW electrohydraulic power pack contained in each power module). Once fully assembled the machine undergoes a full systems and commissioning check on the quayside, and finally a full functional test during sea-trials prior to installation on site. Timing will vary according to project logistics but our aim is to complete the commissioning and sea-trialling for each unit in no more than four weeks.
Q. How do you maintain the unit?
A. The machine is towed back to sheltered water for all maintenance activities to be carried out in safety on a quayside. The Pelamis has been deliberately designed this way as maintenance offshore can be extremely costly as well as being difficult to manage safely. In addition work offshore can be restricted by only being able to work in available weather windows (The period of time that sea states are forecast to be within an acceptable range for any particular operation). However with the Pelamis, only short weather windows of a few hours are required to retrieve and install the machine and are statistically quite frequent, even during the winter months.
Q. What onshore maintenance facilities are required?
A. Only modest facilities are required: a quayside or pontoon that the Pelamis can be moored to, shed storage and a small crane for lifting modular components out of the machine should they require replacement.
Q. Do you need to use divers?
A. No there is no need for divers for the main installation work, operations, or maintenance activities. No personnel are ever required to get onto the machine whilst on site. However there are sometimes small pieces of work that require diver intervention during the initial installation, and during the quayside commissioning process.
Q. How do you transport Pelamis?
A. Pelamis machines are towed or components are shipped by land or sea, for local assembly.
Q. How long does it take to tow and what sea conditions are required?
A. This depends upon how close the maintenance base is. Tow speed is typically 6kts with target sea state <2m Hs.
Q. What are the Operating and Maintenance costs typically?
A. The Operation and Maintenance costs will be competitive with other sources of renewable energy, but they are tailored to each specific project, and site, and will often take into account customers specific requirements, and their own resources.
Q. What are the environmental impacts?
A. The Pelamis is one of the most environmentally benign forms of electricity generation, both in terms of the energy required to create the machines themselves, and in terms of emissions during their operational lifetime. We have no greases or fluids in direct contact with the water, and the quantity of hydraulic fluid quantity is limited. If there is a leak it will be contained within the machine, but if the worst comes to the worst the fluid that we use is BP Biohyd (certified with the German Blue Angel mark) which is non toxic to marine organisms and rapidly biodegradable.
Paints are epoxy paints to offshore standards
Q. What are the effects of marine growth?
A. Marine growth does not affect us like a ship, as unlike a ship we do not need to be hydrodynamically efficient (we move with the water rather then through the water). We have a copper anode system to protect the oil cooler which gradually dissolves copper into the water around the cooler (there’s copper in water in any case). Other than this we have no anti-fouling on the machine.
Q. Have you taken any noise readings outside the machine when it is in operation?
A. No, although given the relatively thick walls of the machine (compared with ships for example) and the relatively noisy environment of waves, PWP believes noise is not likely to be significant.
Q. Will it interfere with fish or aquatic mammals sonar systems?
A. PWP believe this will not be an issue to be concerned about, but does recognise that different locations will have different issues that will need to be reviewed and it is fully committed to ensuring that all such matters are very carefully considered in any deployment of Pelamis machines.
Q. Has PWP carried out any impact studies on whales etc?
A. No, but wave farms should be able to be located well away from routes taken by whales, which are generally well known.
Q. What targets do you have for your cost saving programs?
A. Initially to be competitive with offshore wind energy, then onshore wind and ultimately with conventional generation.
Q. Where is the best wave resource?
A. Coastlines with a long ‘fetch’; Northern and Southern latitudes; ie W.coast of Europe, North America, South America, South Africa, New Zealand, Australia – ie most of the developed world (and with green targets and policies).
However it is very unlikely that suitable and economic sites to locate a Pelamis Wave Station can be located offshore in a large number of different environments and localities.
