Overview of UK & Wave/Tidal
The UK is geographically well positioned to take advantage of wave and tidal energy.
This article summarises recent developments.
Wavegen's Limpet 500 system has been generating electricity from the western Scottish
Isle of Islay shoreline since 2000 while the company and project developer npower
renewables have continued to move forward with plans to develop the Siadar Wave
Energy Project, potentially the first under the Scottish government's Marine Supply
Marine Current Turbines is getting ready to fully commission a grid-connected 1.2-
megawatt (MW) Seagen tidal turbine-based system in Northern Ireland's Strangford
Narrow, while elsewhere in the EU, project developers and the marine renewables
community await the commissioning of Pelamis's serpent-like wave power system off the
northern Portuguese coast.
Scotland is seen as a prime candidate for developing wave and tidal power generation
systems. Barriers to this include the need for large amounts of capital, coupled to the
requirement to build large-scale wave and tidal power systems that can connect to the
It has been suggested that marine renewable power systems built along Scotland's west
coast and outer islands can produce more than 20GW/80TWhrs of power per year. This is
roughly 20% of the UK consumption. The islands of Orkney and Shetland, and the west
coast areas of Galloway, Kintyre, Pentland Firth and West Scotland were identified as
particularly promising sites in a recent study undertaken by the Energy Systems Research
Unit at Glasgow's University of Strathclyde.
While installed renewable power capacity increased 12% (from 2,357 to 2,629 MW) in
Scotland in 2007, wave and tidal power accounted for less than 1% of that increase.
The focus on wind and bio-fuels has resulted in a relatively small number of developers
able to build, test and demonstrate the viability of system designs rated at 1 MW or more.
The Seagen system in Northern Ireland's Strangford Lough, is already connected to
Northern Ireland's grid, as well as that of its southern neighbor, the Republic of Ireland
via interconnections recently completed by the Irish republic's grid operator, ESB
(Electricity Services Board) and Northern Ireland Electricity. Shareholders in the Seagen
project include ESB, EDF Energy and Guernsey Electricity, which is interested in
bringing tidal and wave power to the UK's Channel Islands.
The system's rated power is based on 2.4 meters/second current or more with kinetic
energy conversion efficiencies of 45-50% which is comparable to modern wind turbines.
The technology of choice is the pitch-controlled, variable speed axial flow rotor. One of
the advantages of the rotors used in the installation is the ability to pitch them through
180 degrees allowing the system to work with both incoming and outgoing tides.
Marine Current Technologies is moving ahead with plans to use its latest SeaGen tidal
turbine system in an npower renewables-led project off the coast of Anglesey in northern
Wales. The tidal array is being designed to generate 10.5 MW. npower and Marine
Current Turbines are moving the project forward through a jointly held development
company, SeaGen Wales. Commissioning may come as early as 2011 or 2012 subject to
successful planning consent and financing, according to the project partners.
The companies believe that there is significant scope at the site for future expansion to a
much larger scale of generation, up to around 120 MW. The consenting project, including
EIA (environmental impact assessment) and initial studies commenced in the
spring/summer of 2008, and a planning application is expected to be submitted in early-
mid 2009. If consented, the scheme could be commissioned by late 2011-early 2012.
Wave power: from coastal to offshore
Inverness-based Wavegen, part of Voith Siemens Hydro Power Generation division, is
using its near-shore experience and applying it offshore at Siadar Bay on the Outer
Hebrides' Isle of Lewis, where its oscillating water column technology will be the
centerpiece of an active breakwater power system that includes a 4MW wave power
generating plant. Forty Wavegen 100kW turbines are to be used in the Siadar Wave
Energy Project, which will be located about 350 meters offshore in water depths of
around 7 meters.
Project Development Choke Points
While nearly all the technical problems related to building viable tidal and wave power
facilities have been addressed, access to capital, as well as grid connectivity, have not.
Capital expenditures typically make up more than 90% of a wave power systems'
development and production costs.
This situation contrasts with fossil fuel plants where the input fuel is a high proportion of
cost. A successful wave energy device will therefore have a minimum capital expenditure
and a maximum electrical output. This rather obvious fact creates a dilemma for the
designer of a wave energy plant: striking the correct balance between surviving the worst
sea or shore conditions and minimizing the capital investment and design required to do
The above issues also raise the question of whether to go through a step-wise, multi-
phase progression from test to large-scale systems, or to move directly from small
demonstrator to commercial-sized.